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Future Challenges for Air-Quality and Health in Housing

New Horizons Project DO3Technical Report

Prepared for: Office of the Deputy Prime Minister,New Horizons Programme

Prepared by: C H Sanders, M C Phillipson and C A HunterCentre for Research on Indoor Climate and Health School of Engineering, Science and DesignGlasgow Caledonian UniversityCowcaddens RoadGlasgow G4 0BA

Tel 0141 331 8821Fax 0141 331 3690

Glasgow Caledonian UniversityApril 2004

Future Challenges for Air-Quality and Health in Housing: Technical Report

Summary

Glasgow Caledonian University were commissioned in February 2004 by the Office of the Deputy Prime Minister (ODPM) to undertake an assessment of “Future Challenges for Air Quality and Health in Housing” under the Department's New Horizons programme. This is the technical report of this project, which seeks to describe fully the study’s findings; an accompanying Final Report will summarise the findings of this study in a more concise and readily digestible form.

The four key drivers which will affect the air quality and the health of occupants within housing over the next century have been identified as:

climate change; demographic and social changes; changes in construction practice; legislation and regulations.

The effect of these drivers on ten important hazards to air quality in housing has enabled a classification of the hazards in terms of their likely change over the next century. It is felt that, given the current direction of the drivers, most of these hazards will get worse, especially high internal summertime temperatures, radon and other ground contaminants, and fungal growth and mite and cockroach infestations. Only accidents within the house and problems with tobacco smoke and other particulates, are expected to reduce in severity.

Quantitative modelling of the winter temperatures and mould risk, using the monthly values of the climate changes expected in the London, Plymouth and Newcastle areas, suggests that the changes are similar in all parts of England with only small variations between different regions. The most important impact of climate change is summertime overheating; it is not possible to model this without simulated future hourly data, which preserve the interrelationships between the variables; this is not currently available. Also, quantitative relationships are needed linking release of Volatile Organic Compounds (VOCs) from furniture and fittings with internal temperature and release of ground contaminants with ground temperature.

There is a danger that air conditioning and mechanical cooling systems will become widely installed in housing as a response to rising summer temperatures. These are energy inefficient and will add to the Carbon Dioxide from housing, unless strict measures are taken to control their use. Also unless they are properly maintained there is a serious risk of infections, such as Legionella developing in cooling systems.

The Department's current policies are responsive to likely future changes in the drivers relevant to the internal environment of housing however there are risks from some measures that may cause problems in the internal environment:

The drive to save energy due to air leakage by improving sealing of housing, being discussed in the current revision of Approved Document L1 of the



Building Regulations, may cause the indoor air quality to deteriorate unless compensating measures are taken within Approved Document F.

The increased building on brownfield sites that was recommended in the recently published Barker Report as a solution to the current problems in the housing market, will increase the risk of contaminants entering houses unless appropriate protection measures are taken.



Contents

1 INTRODUCTION 12 AIR QUALITY 23 DRIVERS FOR CHANGE 43.1 Climate Change 43.2 Demographic and social changes 63.3 Construction Practice 83.4 Regulations and Legislation 9

4 HAZARDS TO INDOOR AIR QUALITY 124.1 The hazards considered 124.2 Internal temperatures and humidities 124.3 Fungal growth, dust mites and cockroaches 154.4 Volatile Organic Compounds 194.5 Radon and other ground contaminants 214.6 Toilets, waste disposal and sewerage 244.7 Noise 264.8 Tobacco smoke and particulates 274.9 Lighting 304.10 Fire 314.11 Falls and other accidents 33

5 QUANTITATIVE ASSESSMENT OF HAZARDS 355.1 Possible quantitative analysis 355.2 Climate changes 355.3 Internal temperatures 375.4 Internal humidity 405.5 Risks of mould growth 42

6 RISK MAPPING 446.1 Introduction 446.2 Estimated future change of hazards 45



6.3 Mapping future risk priorities 486.4 Implications for particular sectors of society 50

7 IMPLICATIONS FOR POLICY DEVELOPMENT 517.1 Building Regulations 517.2 Housing 527.3 Neighbourhood Renewal Unit 537.4 Social Exclusion Unit 537.5 Sustainable Communities 547.6 Urban Policy 54

8 GAPS IN KNOWLEDGE AND IMPLICATIONS FOR FURTHER RESEARCH 56

9 DISCUSSION AND CONCLUSIONS 58References 59


1 Future Challenges for Air-Quality and Health in Housing: Technical Report

1 Introduction

Glasgow Caledonian University were commissioned in February 2004 by the Office of the Deputy Prime Minister (ODPM) to undertake an assessment of “Future Challenges for Air Quality and Health in Housing” under the Department's New Horizons programme. This is the technical report of this project, which presents the analysis that lead to the study’s findings. The Final Report contains a more concise presentation of the conclusions and indicators for future research needs.

This report presents an overview of the current state of the art for indoor air quality and health in housing. It seeks to highlight the issues that are driving research, and the issues that are important to future performance.

Through a process of risk assessment informed by expert opinion, and consideration of the interplay between future drivers, the change in risk for current hazards is mapped onto an assessment of the health impacts of a series of risks. The study is therefore able to prioritise these in terms of their potential consequences for UK health.

Work has been carried out to evaluate the extent of potential change, and the results for a number of issues are presented.

Section 2 describes the factors that make up the air quality within housing and affect the health of the occupants.

Sections 3 details the four drivers that we consider will have the most effect on the air quality and health in housing over this century.

Section 4 covers the ten 'hazards' that have been identified as having the most impact on air quality and health in housing.

Section 5 presents some quantitative modelling that has been undertaken to assess the effect of the drivers on the hazards in different regions of England.

Section 6 maps the changes in the severity of the hazards that have been identified earlier onto an assessment of the health consequences of each. This enables the impacts of each of these onto the health of the nation to be ranked in order of importance.

Section 7 discusses the implication for the current and future policies of the ODPM, which are relevant to the internal air quality in housing.

Section 8 discusses the areas that have been identified where further work is needed to clarify issues or establish the likely risks to air quality in housing in the future.



2 Air Quality

Indoor air quality is a fundamental determinant of the health, comfort and performance of people in buildings. It is estimated that we spend approximately 90% of our lives indoors, therefore any exposure to airborne pollutants will have direct implications for health. The Department for International Development identifies indoor air pollution as one of the four major risk factors for ill health globally [1]. According to a study by the American College of Allergists 50% of illnesses are caused, or aggravated by, polluted indoor air [2].

Essentially, indoor air quality depends on a combination of factors, any of which can lead to some discomfort or cause health problems for occupants. As a result air quality cannot be quantified in absolute terms, and requires careful evaluation. Knowledge and understanding of the physiological implications of different airborne factors is continually developing and so the list of potential issues is growing. There has been considerable work by BRE looking at current performance of English housing with respect to air quality issues [3, 4]. This has included a detailed survey used to identify typical exposure levels of a range of pollutants.

The factors which influence the concentration of different pollutants vary depending on the pollutant, reflecting the different nature of the sources of contamination. Volatile Organic Compounds (VOCs) and formaldehyde concentrations are associated with materials brought into the house, and, as such, will be present in slowly declining concentrations as material sources outgas. Carbon monoxide and nitrous oxides, however, are associated with combustion processes and so their presence in indoor air will depend on the utilisation and ventilation quality of combustion appliances in the dwelling.

Volatile Organic Compounds is a general characterisation applied to a wide range of different chemicals. Usually, the total contribution of these is used to determine the health implications of exposure through the assessment of the total VOC concentration of the air. However, it is recognised that the sources of these different compounds may vary and, as a result, the affect of particular drivers will vary depending on the situation. It can therefore be dangerous to generalise with overall VOC concentrations because the emission context fundamentally determines the nature and concentration of the compounds present. BRE have undertaken an assessment of VOC concentrations in English homes, and have specifically looked at the following seven compounds, which they felt were characteristic of groups of similar substances associated with different emissions sources.

Benzene; Toluene; Meta- and para-xylene; Limonene; Undecane;



2,2,4-trimethyl-1,3-pentanediol monoisobutyrate; 2,2,4-trimethyl-1,3-pentanediol diisobutyrate.

BRE identified factors which significantly influence the concentrations of these compounds and have developed a protocol for assessing the indoor air quality [5] which examines the indoor environment for key factors, including:

temperature and humidity; non-biological particles and fibres; biological particles; radon; other inorganic gases; organic compounds methane and other landfill gases.

Different monitoring approaches for each of the above factors are identified which BRE feels have the potential to influence health, safety and comfort of occupants. These will be discussed in the analysis of hazards in Section 4. Detailed measurement regimes are available which enable indoor air quality problems associated with the above issues to be assessed and identified. Short term and long term monitoring regimes can be identified, which can help diagnose the nature of indoor air quality problems.

The affect on air quality of the key drivers discussed in Section 3 will be mixed; climate change will generally act to increase the severity of problems, whereas legislation and regulations are being formulated to try to control and reduce impacts. Because of the complexity of hazard interaction and the variability of pollutant sources it is not possible to make a general quantitative assessment of the overall impact on indoor air quality. However, it is anticipated that changes in key drivers will lead to a change in the balance and nature of future impacts from poor air quality.

Other issues, which might not be considered directly relevant to air quality as such, also have an important role in determining quality of the indoor environment and therefore the health of the occupants. The most important of these are light levels within houses and especially noise from adjoining houses and flats or from the outdoor environment. These issues have therefore been included in the analysis in this report.



3 Drivers for Change

This section discusses the four key drivers for change, which will have direct and indirect influences on the future air quality and health in housing in England and Wales. These are:

climate change; social and demographic changes; economic and business performance improvement of the construction industry

(as reflected by construction industry practice); changes in Legislation and Regulations.

3.1 Climate ChangeThere is a growing recognition that climate change will have profound implications for a many human activities, and will have major impacts on the built environment [6]. Work by the UK Climate Impacts Programme (UKCIP) has coordinated research activity in the UK and has helped to focus climate science towards providing tools and information to enable impact studies to be undertaken. In 2002 the UKCIP published four scenarios, the UKCIP02 scenarios [7], which provide the current best estimates of the future climate in the UK. The issues of most relevance to the buildings and their internal environment are:

The UK climate will warm, with the average annual temperature being between 2ºC and 3.5ºC warmer by the 2080s.

Hot summer temperatures and heat waves will occur more frequently, and extreme cold winters will become less common.

Summers will become drier, especially in the south of England, and winters will become wetter.

Solar radiation levels will increase in the summer and fall in the winter. Atmospheric vapour pressure will rise. Heavy winter precipitation events will become more frequent, increasing the

frequency of flooding. Sea levels will continue to rise, with an estimated rise for the southeast

England of between 26 and 86 cm above current levels by the 2080s. Storm surges, leading to extreme sea levels becoming more common. Wind speed, which is of particular importance to the performance and internal

environment of buildings, is not expected to change significantly, however there may be a slight increase in the frequency of severe gales.

The specific consequences for health and air-quality in housing include:



Increased external temperature and humidityRising external winter temperatures will reduce the energy demand for heating and raise internal temperatures, especially in poorly insulated and heated houses. However internal temperatures will also rise in summer and the number of occasions where houses are uncomfortable will also rise. This effect will be exacerbated by rising vapour pressures.

Changes in solar radiationThe rise in solar radiation intensity in the summer will increase the heat load on houses and may increase problems of glare. Conversely lower radiation levels, caused by increased cloud cover in the winter, may lower light levels within houses.

Increased winter rainfall A key change for buildings predicted for the future climate is the increase in the amount and intensity of winter rainfall. Dampness and moisture movement within the fabric of buildings is currently a major cause of defects in housing in the UK, the increase in winter rainfall may lead to both an increase in severity of problems, and an increase in the number of properties suffering from dampness problems.

Dampness in buildings has been linked to respiratory illnesses. Any increase in the occurrence of dampness in buildings would have health implications for people affected. It would be reasonable to assume that the increasing levels of winter rainfall will be detrimental to building performance. More dampness problems can be expected in regions of the country where buildings are not routinely designed to cope with heavier rainfall (currently the west coast of Great Britain adopts pragmatic design measures to increase the weathertightness of buildings).

Increased risk of flooding Heavier winter rainfall events and rising sea level increase the risk of river and coastal flooding. Concern about the financial implications of changing flood risk is driving the insurance industry to closely consider how it can sustain flood cover.

There is a range of health consequences resulting from flooding of properties. The immediate consequences may include risk of drowning, health problems associate with exposure to flood waters and any contaminants they carry, increased injury risk, and stress. Longer term health problems can include communicable disease associated with water and sanitation, and mental health issues. Recent studies of the health effects after flooding [8, 9] have identified significant levels of mental health problems in residents many months after the flood has passed; these include anxiety, depression and post traumatic stress.

External Sources of PollutantsThere is concern that climate change may lead to greater rates of evolution of ground gases such as radon and landfill gas, which could pose a health risk to inhabitants of dwellings in affected areas. Warmer ground temperatures combined with drier summers may lead to increased soil cracking which can provide pathways for the gas to escape to the surface, and potentially enter buildings. However, there are gaps in



understanding of the potential significance of climate change for either the rates of landfill gas evolution, or the seasonal variation in radon emissions.

3.2 Demographic and social changesThe demographic composition of the UK is in a continual state of change. Some of the predicted future changes will have implications for the way in which housing is used and for the health of individuals in these buildings. As with the other key factors identified in this report, there are numerous cross cutting issues, which need to be considered in combination rather than in isolation. There are a number of key authoritative sources of information, including the Office for National Statistics [10] and the British Council [11].

Impact studies have been undertaken based on changing demographics and social behaviour to investigate the consequences of future change in specific sectors. One such study has looked at the changing demands of health service provision, this was undertaken by The Nuffield Trust who published a report “The Future of Health – Health of the Future” in 2003 [12] considering the potential influences and driving factors on health care provision which are relevant to policy making towards 2015. The study identifies a number of key issues with relevance for the indoor environment of housing and which are strongly linked to the general trends from changing demographic patterns.

The following trends have been identified as having relevance to the indoor environment of buildings:

Population ChangesThe total UK population is forecast to grow modestly from 59.2 million in 2002 to 62.4 million in 2021. In 2002 there were some significant regional population movements affecting the south east of England, south west England, the east of England and London. In general there has been a significant net movement out of London. The location and sufficiency of good quality dwellings will therefore be a challenge in some areas, avoidance of urban decline will be a challenge in other areas.

Ageing PopulationThe UK has an estimated 19 million people aged over 50, this is expected to rise to 22 million by 2020. This will place specific demands on housing need and health requirements for buildings. An ageing population has social implications and will present challenges to society to provide and maintain adequate support services. The internal environment of buildings, and dwellings in particular, will be a crucial factor in determining the level of social problems that will be experienced.

There is variation in the age structure of the population by ethnic background. In general the age structure of ethnic minority groups is younger than that of the white population. This suggests that the initial implications of the ageing population will be focussed predominantly on the white population.



Although many older people live full and active lives, the increase in life expectancy will be generally associated with an increase in illness and disability. In addition, there will be a smaller working population in the UK available to support and assist this older age group. Strategies will need to be formulated to maximise the quality of life for the elderly, and help reduce future reliance on care provision. The indoor environment of buildings is an important factor in ensuring that this is achieved and for avoiding specific health issues for the elderly (for example hyperthermia and hypothermia).

Increasing DependencyDependency is defined as the ratio of dependent people (pensioners and children) to the working population; it is estimated as 63% in 1991 and is predicted to rise to 79% by 2031. There is anticipated to be an increase in the level of dependency in the population as a whole, which will have implications for the type of accommodation required in the future and the design requirements necessary for achieving a healthy indoor environment. Increasing levels of dependency will put strain on existing support networks, which if overstretched will have implications for health within the indoor environment.

Disability and Frailty There are estimated to be 8.5 million people in the UK with some disability, in addition to the growing number of elderly people, leading to a rise in the number of people with some level of frailty, and therefore a specialist requirement for housing need. There will be a need to develop pragmatic ways of facilitating people to continue to use their homes as their mobility and health decline. Flexibility of service provision can be achieved through design and technological development.

Growing Household RequirementAlthough the UK population grew by only 6% between 1971 and 2002, there has been a 31% increase in the number of households. This reflects a trend to smaller household sizes, and in particular the proportion of single person homes, which has grown from 18% in 1971 to 29% in 2003. This trend towards single person households is particularly associated with major cities.

Increasing Dwelling SizesSomewhat counter to the trend for single person households has been a trend towards new housing developments focussing on dwellings with a growing number of bedrooms. This reflects the aspirational nature of housing produced by commercial house builders. However, it also suggests that there is likely to be housing in some sectors which is only partially used, this can itself have implications for occupant health where the building is only partially heated or has a proportion of the rooms that are not ventilated properly.

Dwelling ConditionIt has been estimated from the English House Conditions Survey [13] that there are 7 million dwellings that fail to meet a decent homes standard (which is approximately one third of the total dwelling stock). To achieve a decent standard a dwelling needs to: be in a reasonable state of repair; have reasonably modern facilities; and provide a reasonable standard of thermal comfort. This has implications for health and air quality



in the indoor environment, and consequently for the sustainability and social acceptability of the poorest quality housing.

IT and CommunicationsThe recent increase in IT and communications infrastructure in the UK has given a wide proportion of the populations access to global information about a variety of issues including health. This has had the effect of increasing expectations for the standard of service provided and introduced greater scrutiny to public decision making. This has a dimension beyond the UK, with international resources and databases likely to see growing access from the UK public. This will have the effect of making health policy increasingly global and as a response make health care infrastructure change to provide more remote accessed services.

Provision of sufficient good quality housingThis is associated with the regional population movements, and the provision of dwellings that meet a decent homes standard. Air quality and indoor health are some of the core issues associated in ensuring the long term sustainability of any solution to the changing housing need.

The housing requirement of the population is changing in terms of both size and demand for larger amounts of accommodation appropriate for the needs of the elderly. In general the utility of accommodation should meet the changing needs, which will include more robust and controllable environmental controls for heating, cooling and ventilation.

Alongside the changing needs of housing are the associated changes in service provision and infrastructure, which are required in response. The service levels needed for an elderly population are quite different, and there are particular issues associated with health in buildings.

3.3 Construction PracticeRecent trends in construction have tended to move away from traditional masonry house building, towards novel, innovative techniques. This has largely been due to the influence of the Egan Report “Rethinking Construction” published in July 1998 by the Construction Task Force, which investigated the performance of the construction industry in the UK [14]. The report found that UK construction needed to concentrate on becoming more efficient, improving the quality of its output and improving the satisfaction of construction clients. This suggested that industry needed to:

Drive down construction costs (annual target of 10% reduction in capital costs). Increase the quality of construction (annual target of 20% reduction in defects

and accidents). Move towards sustainable construction with an emphasis on prefabrication and

off-site assembly.



Become more innovative to streamline the construction process (annual targets of 10% increase in productivity and profitability, and a 20% increase in the predictability of project performance).

Develop partnering between contractors and suppliers to move towards a dispute free industry.

The Egan Report led to a range of initiatives that have had a major impact on the construction industry, these include the Movement for Innovation (M4I) and the Construction Best Practice Programme. In particular, prefabrication has been identified as a major way forward in delivering these required improvements. The Government produced a Housing Green Paper “Quality and Choice: A Decent Home for All” in April 2000 [15] which identified prefabrication as a way forward in providing affordable housing, and have considered ways in which more resources could be used in schemes that use prefabrication. The paper states that:

“We expect to see progressive take-up of the technique over the next few years, for both social and private house building, as the benefits are more clearly demonstrated.”

The work of Rethinking Construction has helped to drive through changes and encouraged the construction industry to examine and measure its performance. This work is now being taken forward by Constructing Excellence [16], which will drive further improvements and change in the industry.

Many of the innovative techniques being developed use relatively lightweight products, which tend to give the finished dwelling a relatively low thermal mass. This results in little thermal storage in the building, which will consequently respond quickly to heating and cooling. This leads to a greater tendency for the indoor environment to overheat in the summer, which could cause problems given the direction of climate change. Low thermal mass buildings can function perfectly well with an appropriate building service strategy, however, there needs to be an awareness of this, and action taken through appropriate design and specification to avoid unnecessary problems.

3.4 Regulations and LegislationBuilding Regulations seek to ensure the health and safety of building users, promote energy efficiency, and enable buildings to be accessible to those with disabilities. They do this by providing functional performance requirements for building design and construction. Many of the parts to the Building Regulations have relevance to the indoor environment of buildings and the health of occupants, these include:

Approved Document B: Fire Safety Approved Document C: Site Preparation and Resistance to Moisture Approved Document D: Toxic Substances Approved Document E: Resistance to the Passage of Sound Approved Document F: Ventilation



Approved Document G: Hygiene Approved Document H: Drainage and Waste Disposal Approved Document J: Combustion appliances and fuel storage systems Approved Document L: Conservation of Fuel and Power Approved Document M: Access to and Use of Buildings

Development of the Building Regulations seeks to keep pace with changing construction practice and tackle particular risks or hazards that are identified and has the intention of improving the safety and performance standards of buildings. Consequently future developments should seek to counter risk factors as they arise. In recent years the issue of climate change has been included in the review process of parts of the Building Regulations to determine how it may affect the performance requirements.

In particular, climate change has acted as the major driver for the revision of Approved Document L of the Building Regulations, concerning the conservation of fuel and power. This is due to the opportunity for meeting greenhouse gas emissions which the building stock offers. Recent amendments to this Approved Document have increased insulation requirements and introduced new requirements for increasing the air tightness of buildings. Whilst this should provide more energy efficient buildings, there is potential for conflict with problems of air quality and health in buildings, particularly in the context of the changing climate. Warmer dwellings with poorer ventilation conditions are likely to suffer from a range of problems, which will have health consequences for building uses.

The World Health Organisation (WHO) produces guidelines for protecting human health against a range of 35 air pollutants [17]. These include pollutants from both indoor and outdoor sources. The guidance offered by the WHO seeks to protect public health from the adverse effects of air pollutants by setting standards for pollutant exposure levels below which there is no significant risk to public health. These standards are intended to be used within the basis of a risk assessment or risk management process to inform and guide decisions.

The European Commission have developed the General Product Safety Directive (GPSD), 2001/95/EC, to provide a ‘broad-based, legislative framework of a horizontal nature’ to ensure the sale of safe products [18]. The scope of the GPSD is not limited to consumer products and also includes ‘products which are designed exclusively for professional use but have subsequently migrated to the consumer market.’ The provision of housing is considered a product in the terms of this Directive. The GPSD has come into effect as of 15 January 2004.

The key provisions of the GPSD require manufacturers and importers ‘to place only safe products on the market.’ According to the GPSD a ‘safe product’ shall mean any product which, under normal or reasonably foreseeable conditions of use including duration (and, where applicable, putting into service, installation and maintenance requirements) does not present any risk or only the minimum risks compatible with the



product's use. Further, the product should be considered to be acceptable and consistent with a high level of protection for the safety and health of persons.

An important aspect of consumer protection is to prevent or reduce exposures to environmental agents. For example, high enough levels of exposure to some VOCs, alone or in combination in housing, can lead to short-term or long-term health impacts. Therefore, a consequence of the GPSD is the development of the European Information System on Chemical Risks (EIS-CHEMRISKS) [19], which is being designed as a European-wide expert network to systematically exchange and assess information on risks from chemicals released from consumer products and articles.



4 Hazards to indoor air quality

4.1 The hazards consideredThe BRE publication ‘Building regulation, health and safety’ [20] identified twenty seven ‘hazards’ to health and safety in and around buildings that should be taken into consideration in the formulation of Building Regulations. Those that are of most relevance to the internal environment and the health of occupants have been grouped into the ten categories shown below.

Internal temperature and humidity. Fungi, dust mites and cockroaches. Volatile Organic Compounds. Radon and other ground contaminants. Toilets, waste disposal and sewerage. Noise. Tobacco smoke and particulates. Lighting. Fire. Falls and other accidents.

It is evident that, while some of these hazards bear directly on indoor air quality, the main topic of this report, others, such as lighting and noise, are less directly relevant. It was decided, however, that these factors are important determinants of the quality of the indoor environment and affect the health and safety of the occupants. They have therefore been discussed in the sections below, although this discussion will inevitably be briefer than that for the more important issues.

4.2 Internal temperatures and humidities

4.2.1 The nature of the hazardHuman temperature regulation, thermal comfort and health are affected by the environmental temperature in buildings taking account of air temperature, radiant temperature, humidity and air movement. Indoor air temperatures of 18–24 °C normally cause no real discomfort or threat to health. Outside this range, thermal stress increases progressively and defence mechanisms (eg shivering, sweating) come into play. Humidity, usually expressed as relative humidity (RH), has little direct effect on comfort except in hot conditions, but damp clothing or bedding increases the cooling effect of low temperatures. Low RH can dry the eyes, nasal passages and skin and cause problems with static electricity. The main effects of air movement are discomfort from localised cooling (draughts) and drying, both of which increase with air velocity and turbulence.



Temperature requirements vary with an individual’s physiological and psychological characteristics. The most important single factor is age since the elderly may suffer from a number of disadvantages related to impaired thermoregulation, mental or physical health and low socio-economic status. Infants’ high ratio of surface area to volume entails more rapid heat loss and they have a more immature thermoregulatory system. Infants, however, are more likely to be given special protection from serious risks from the thermal environment. One other factor of importance is the amount of time a person spends at home, especially in cold weather when the indoor temperature may be colder than normal and space heating inadequate.

4.2.2 Climate Changes in external climate will have a significant effect on internal climate, and will lead to the following consequences for the health of occupants:

Increased Risk of Summer OverheatingThere is expected to be an increase in problems with summer overheating of housing, which in extreme circumstances can lead to hyperthermia in vulnerable sections of the population. The summer of 2003 saw extreme health problems for mainland Europe, with an extra 14,800 deaths in France alone being associated with the excessively hot spell [21]. The French health service was largely overwhelmed by the scale of the problems, the elderly were particularly affected by hyperthermia, as lack of mobility restricts options for finding cooler places away from excessive heat.

For the UK, at present the Central England Temperature reaches or exceeds 31ºC on average one day per year, climate change predictions suggest that by the 2080s this will happen on ten days per year, or conversely that on one day per year the temperature will reach 38.5ºC. This anticipated reduction in return periods of hot weather, and the associated increase in the levels of extremes will have serious consequences for the population and will necessitate adaptation of behaviour and the built environment to cope. Without adaptation this would translate into an extra 2,000 deaths per year by the 2050s from hyperthermia and up to 200,000 extra days of NHS treatment [22].

Excessively hot weather can be linked to reductions in productivity for workers in businesses, and absenteeism rates have been strongly correlated to excessively hot weather. The Centre for Economics and Business Research suggested that the heat wave of August 2003 could have cost the British economy up to £280 million per day [23].

There will be some regional variation in this problem, and the problems will be significantly worse in large urban environments where the urban heat island effect will exacerbate the situation.

LegionellaOne of the potential responses to hotter summers may be a wider uptake of air conditioning systems in housing. HEVAC systems in public buildings and offices must



be regularly maintained and there should be procedures in place to ensure this. This will not be the case in housing, where maintenance will be left to individual householders; this could lead to an increased risk of Legionella problems unless systems are appropriately designed.

Decreased Risk of HypothermiaClimate change predictions suggest that, along with warmer summers, average winters will also become warmer, effectively reducing hypothermia problems amongst vulnerable sections of society. It has been estimated [22] that the increase in winter temperatures will result in a reduction in winter mortality by the 2050s of some 20,000 deaths.

Changes in humidityApart from the risk of fugal growth, discussed in Section 4.3, increased humidity in housing can have adverse affects on the occupants by increasing heat loss through bedding and clothes. This effect is, however, likely to be offset by the increased winter temperatures noted above.

4.2.3 Demographic and social changesThe trend towards smaller household sizes, with more people living alone, and especially the higher proportion of households made up of the elderly, will have significant affects on the temperatures and humidities within housing. More people living alone will mean lower internal temperature and humidities, this will be offset to some extent by the increased density of housing leading to more terraced houses and flats with smaller exposed envelopes.

4.2.4 Construction changes The improved levels of insulation necessary to reduce the output of greenhouse gasses from the building stock, will further reduce the impact of cold temperatures in the winter. However, improved insulation may, without changes in other design factors, increase internal temperatures in the summer. This may be made worse by increased use of lightweight structures with little thermal storage to limit high temperature peaks, if offsite construction is used more widely.

Increased use of shading, reduced window sizes and incorporation of thermal mass within building will limit summertime overheating, avoiding the need for the use of air conditioning, which would significantly add to the energy consumption and may lead to the problems of legionella noted above.

4.2.5 RegulationsThe main impacts of Building regulations will be the improved insulation standards contained in Approved Document L and the more specific guidance for ventilation provision based on the risks of condensation that will be contained in Approved Document F.



4.2.6 Vulnerable Sections of SocietyThe elderly will be particularly at risk from overheating due to a combination of factors including impaired thermoregulation, lack of mobility, and other mental and physical health issues. Infants may also have a higher risk to health as a result of immature thermoregulatory systems, however, they are also likely to be given special protection from serious risks from the thermal environment.

Summer overheating effects are likely to be worse in large urban centres where the urban heat island effect will exacerbate the situation. In addition there is likely to be a divide between householders who can afford to install comfort cooling and those that cannot. The lower economic status associated with the elderly may also inhibit their ability to afford appropriate comfort cooling.

4.3 Fungal growth, dust mites and cockroaches

4.3.1 The nature of the hazardThe growth of fungi and the occurrence of mites in buildings are dependent primarily upon the humidity of the indoor environment. Humidity is usually measured relative to the level which would represent saturation with moisture, and this varies with temperature. The important factor is the relative humidity (RH) at the locations where moulds and mites will grow; this is determined by the moisture content of the air (usually expressed as the vapour pressure) and the surface temperature.

MouldsSome species of moulds (e.g. Penicillium spp. and Cladosporium spp.) can grow when the substrate is relatively dry; others are associated with moderate condensation (e.g. Cladosporium spp.) and yet others (Ulocladium spp., Stachybotrys spp., Phoma spp.) with very wet situations (e.g. water penetration, spillage, severe condensation). They can grow on a range of materials including wall coverings, bedding materials, shoes, carpets, masonry and furnishings. Common locations are behind beds and furniture on walls with condensation and around window frames. Mould growth in homes typically occurs during the winter, when there is often less ventilation, more moisture generation and cooler surfaces, and thus a greater potential for condensation.

Much higher spore concentrations are carried in the air of buildings in which there is actively growing mould than where indoor mould growth is absent. Where there is no indoor mould growth, the indoor air spore content is determined entirely by that outdoors. Indoor spore content ranges from 10 to 50% of that outdoors, and increases transiently with an increase in human activity (e.g. vacuum cleaning). Mould growth is less common in homes which have better insulation, good ventilation and heating and a generally good state of repair. It is therefore less common in newer homes.

MitesThe principal mite species in British homes is Dermatophagoides pteronyssinus, although Euroglyphus maynei can account for up to one third of mites and may be the predominant species in some homes. D. pteronyssinus grows optimally at around 25 °C



and 80% relative humidity (RH), and feed on human skin scales (possibly requiring primary colonisation by fungi). They are found in carpets and soft-furnishings in homes throughout the world.

Seasonal fluctuations occur in live mite counts, following the humidity inside the home: high numbers in mid- to late summer, dropping dramatically in a heated home during the winter. Although the mites themselves die from desiccation, the allergen containing faecal pellets they produce persist throughout the year although they are present at somewhat higher levels in the autumn.

CockroachesCockroaches have long been acknowledged as pests in the UK with records dating back many centuries. They are much more frequent in cities and the built-up environment, although a significant percentage of rural authorities in England reported infestations. In the late nineties, just over 16,000 properties were treated for cockroaches in England and Wales.

Because they are often associated with unsanitary conditions and flourish on virtually anything we grow, store, consume, discard and excrete. Many species of bacteria, fungi, protozoa, worms and viruses pathogenic to man have been isolated from cockroaches. The commonest cockroaches in the UK (German, Oriental and American) are all capable of picking up food poisoning bacteria from food and excreting them in the faeces. They have been shown to be capable of transmitting the bacteria to other cockroaches as well as to foodstuffs, clean water sources and their general environment.

Vector-borne DiseasesBecause insects and other invertebrates are cold-blooded and heavily dependent on the environment, climate plays a major role in their behaviour, development, and reproduction. In addition, pathogen development is regulated by temperature. Thus, human diseases that are spread by these invertebrates may also be more affected by climate change than some other diseases. Vector-borne diseases result from transmission of infectious agents by arthropod vectors as they feed on human blood. Some vector-borne diseases such as malaria, termed anthroponoses, may be uniquely human infections in which an arthropod is able to transmit the microbe to another human only after first acquiring it from a human. Alternatively, many other vector- borne diseases of humans, termed zoonoses, involve infectious agents that normally are found primarily in animals, with occasional and accidental transmission to people.

AllergyIn the UK as in the rest of the developed world, the incidence of allergic asthma has risen in recent years; symptoms vary in intensity from mild occasional respiratory discomfort to serious respiratory failure. About 2 million adults and more than one child in 7 are now affected in the UK.

Asthma attacks are often induced by exposure to particular allergens, which are specific materials to which the individual is especially sensitive. House dust is known to contain a number of allergens including those associated with the faecal pellets of



house dust mites, cockroaches and mould spores which can induce allergic reactions when the suspended dust is inhaled. In addition to those individuals who exhibit asthmatic conditions, it is estimated that about 5-10% of the population has a hereditary tendency to asthma. Such individuals can be triggered into developing a clinical condition if sensitised by regular exposure to air in which significant quantities of allergens are present. The severity of clinical symptoms suffered by an individual is significantly reduced by limiting exposure to the allergen(s) to which he/she is particularly sensitive.

Other health effects identified with moulds are carcinogenic, toxic and psychological reactions, and fungal infections.

4.3.2 ClimateAs indicated above the changes in external climate are expected to cause both internal temperatures and vapour pressures to rise. Assuming that no other changes occur the net effect of these changes on the internal relative humidities that determine the risks of mould growth and mite infestation is discussed in Section 5.5. It is unlikely that the predicted slight drop in internal RH will have any significant effect on the occurrence of mould growth or mites. There is the potential that with warmer winters, the incidence of mould growth will increase since the rate of mould hyphal growth increases at temperatures approaching the optimum.

Due to the buffering effects of the carpets and soft-furnishings in which mites live, it is unlikely that the predicted climate change will have any effect of the level of mites in UK properties.

The spread of cockroaches from building to building is partially limited by the external temperature and therefore with a progression to warmer summers there is an increased likelihood of infestations occurring in properties unconnected to the source.

The animals act as reservoirs for the disease, serving as hosts for the reproduction of disease agents in between human outbreaks. Should climate change improve longevity, increase reproduction, enhance biting, or increase the ranges of these vectors, an increase in the number of people infected could result. Likewise, similar effects on the vertebrate animals that serve as reservoirs for agents associated with viral diseases, leptospirosis (a bacteria disease characterized by jaundice and fever), rabies, or vector-borne diseases could also result in greater human risk. The complex and multiple impacts of climate on the various factors that determine transmission of vector-borne diseases, however, make it extremely difficult to generalize about the mechanisms, much less predict in what direction changes may take place.

4.3.3 DemographyThe higher proportions of single occupant households will reduce internal humidity loads, reducing the risks of mould growth and mite infestation, assuming that house-sizes remain constant. If the occupied space per person decreases there will be an additional risk of condensation on cool surfaces.



Many of the factors which encourage cockroach infestation are most likely to be features of multi-occupancy dwellings, including ducted services, stud partitions and large panel construction. Historically multi-occupancy dwellings equated to tower blocks, however an increasing requirement for households in the UK may lead to more linked properties (e.g. terraced or starter homes) and thus an increase in the spread of cockroaches.

It is unlikely that vector-borne diseases will be affected by the predicted change in demography.

4.3.4 Construction changesThe improved insulation standards in new houses that will come into force over the next century and the progressive upgrading of insulation in the existing stock will raise internal surface temperatures closer to the internal air temperature and reduce the risks of mould growth.

Again, due to the buffering effects of the carpets and soft-furnishings, it is unlikely that forthcoming construction changes will have any effect of the level of mites in UK properties.

As noted previously, features that provide potential harbourage for cockroaches (for example stud partitions) encourage cockroach infestation and with the move towards off-site construction there is the increased potential for voids to result as part of this process.

As the source for many of the vector-borne diseases is the external environment, it is unlikely that they will be affected by any forthcoming changes in construction practice.

4.3.5 RegulationsThe main impacts of Building Regulations will be the improved insulation standards contained in Approved Document L and the more specific guidance for ventilation provision based on the risks of condensation that will be contained in Approved Document F. Thus while the building may become drier, any allergens released or produced within the property have an increased chance of remaining in the internal environment for longer and therefore having an effect on the health of the occupant.

4.3.6 Vulnerable Sections of SocietyThere may be some risk of increased problems for the elderly due to poorer mobility reducing the ability to properly ventilate housing and to clean as thoroughly. However this is an accessibility issue, which is likely to be considered by future Regulations and legislation. It is difficult to generalise about particular health concerns, however, there has historically been an increased level of problem with cockroaches in urban centres, and this is likely to be exacerbated by rising temperatures.



4.4 Volatile Organic Compounds

4.4.1 The nature of the hazardThe term 'Volatile Organic Compounds' (VOCs) covers a wide range of chemicals that produce vapours at room temperature. There can be a wide range of potential sources of VOCs in housing, but the following are typical:

natural metabolic processes; household consumables (particularly cleaning products); the building fabric (particularly adhesives, solvents and treatments); furniture and finishes (for example carpets, paints, etc); building services; integral garages; outdoor pollutants.

Exposure to individual VOCs can have adverse health effects, however, there are also synergistic effects between different VOCs. This means that the effect of a mixture of VOCs, where all are individually within a safe concentration threshold, can still have health consequences as a result of the combined effect. The range of different VOCs and these synergistic effects mean that generally the total VOC (TVOC) level needs to be considered along with the particular effects of individual chemicals.

VOCs can have a variety of health effects, the thresholds shown in Table 1 have been suggested [20].



Table 1 - Health consequences of exposure to VOCs

Total VOC Concentration (mg/m3) Health Consequence

Below 0.2 No irritation or discomfort

0.2 to 3.0 Risk of some discomfort or irritation

3.0 to 25.0 Irritation and headaches possible

Over 25.0 Risk of neurotoxic effects

4.4.2 ClimateThe presence and mobility of VOCs in the indoor environment is related to the climate. Internal VOC sources associated with materials and cleaning agents will be released into the air more quickly in warmer conditions, however, they will also be used up more quickly and cease to be a problem sooner. Climate change will have a direct effect on this. This may have a positive or negative effect on the occupants’ health, depending upon the specific circumstances.

In certain areas external sources of VOCs could become more of a problem in the future during the summer as improved ventilation of homes will become more important to control overheating problems.

Natural ventilation of homes is an essential mechanism for dispersing and removing high VOC concentrations from within the internal environment. Changes in wind speed are an essential component to any future change in natural ventilation capacity, however, there is low confidence in the accuracy of current predictions for future wind behaviour. There is therefore a gap in the ability to predict future requirements.

4.4.3 DemographyChanges in national demographics are only weakly linked to the presence of VOCs in housing. Single person, working households have less opportunity to benefit from natural ventilation by opening windows during the day to air the property. Security concerns amongst elderly people have been linked to a reluctance to open windows, again to air the property. A general reduction in the level of natural ventilation within properties will have negative consequences due to the reduced dispersal of internally generated VOCs, but could benefit exposure risks to external VOC sources.

4.4.4 Construction changesPotential changes towards innovative and lightweight construction techniques may well be associated with increased solvent and adhesive use in construction, which would be a greater source of VOCs for the internal environment. This need not be the case, and careful specification and technology can provide alternative construction options, although there may be additional costs associated with this. Regulation, best practice



and client awareness will all have a part to play in controlling the levels of potential VOC sources used in buildings and their contents.

4.4.5 RegulationsEuropean Legislation detailed in Chapter 3 will strongly influence the concentration of VOCs within dwellings. Ongoing research work is informing the development of future performance guidelines, such as the World Health Organisation guidelines which look at a range of airborne pollutants, including VOCs. It is anticipated that regulations and legislation will continue to strengthen requirements for protecting public health, and will in the future be a key driver in controlling any hazards.

4.4.6 Vulnerable Sections of SocietyVOCs are unlikely to effect any specific part of society to a greater extent than any other. As discussed previously, a reluctance or difficulty amongst the elderly to open windows for natural ventilation may result in a slower rate of dispersal for VOCs released in such dwellings. However, this may be dealt with through developments in technology to promote accessibility and usability of housing for frail and infirm members of society.

4.5 Radon and other ground contaminants

4.5.1 The nature of the hazardLand can be contaminated as a result of industrial processes (eg gasworks, metal manufacturing, dockyards, etc), landfill activities and agricultural uses. Land can also be defined as contaminated as a result of naturally occurring contaminants. The main contaminants are:

radon from the underlying igneous rocks in certain areas; heavy metals (eg lead, cadmium and mercury); organic compounds (eg halogenated volatiles, pesticides and polychlorinated

biphenyls); inorganic compounds (eg asbestos, chlorides, sulfates); vapours (eg petrol/diesel fumes) and gases (eg landfill gas).

Building on contaminated sites raises a number of health issues because many of the contaminants are toxic or carcinogenic. Occupiers of such sites can be exposed to these contaminants through a number of pathways such as inhalation of airborne dust and vapours, absorption through the skin, ingestion of produce grown on the site and, in the case of small children eating soil, direct ingestion of the contaminated material.

If radon and its decay products are inhaled, they irradiate tissues in the body. By far the largest dose is delivered to the lungs and in particular to the epithelium (lining) of the



bronchi. Alpha particles cause a high level of ionisation in the sensitive cells of the epithelium. This in turn brings about changes in the cells and may eventually lead to lung cancer.

Landfill gas is a contaminant of particular concern. It arises from the degradation of organic material deposited at landfill sites and consists primarily of methane and carbon dioxide, but a large number of other gases and vapours are present including hydrogen, carbon monoxide, saturated and unsaturated hydrocarbons, halogenated compounds, hydrogen sulfide and organosulfur compounds. Methane and carbon dioxide can also arise from disused mine workings, and methane can also leak from gas mains.

Many of the chemicals found on contaminated sites are aggressive and may attack building materials such as concrete and plastics. As a result this may open up more pathways for occupiers to be exposed to the effects of contaminants.

Risk reduction can be achieved by:

removal of the material generating the gases; construction of barriers to prevent the entry of gases into the building; containment to reduce emissions of gases from the ground outside of the footprint

of the building.

4.5.2 Climate Where the contamination is left in place the following effects resulting from climate change could affect the mobility of the contamination.

rising groundwater levels; flooding; increased temperatures; atmospheric pressure changes; very dry summers; increased wind speeds.

Rising groundwater levels at a site could mobilise soluble contaminants and raise the elevation of non-aqueous phase fluids, and increase the hydraulic pressure on a ground floor slab. Rising groundwater is known to have caused migration of contaminants into the basement of buildings. There is also the possibility that service trenches, backfilled with clean granular fill, constructed above historic groundwater levels could become migration pathways for contaminated liquids.

Flooding could have similar impact to rising groundwater depending on the time scale of the flood. Flooding would result in a downward flow through any contamination. Flooding may have a positive effect on radon exposure as generally radon levels are lower in areas with a high water table.



Hot dry summers could result in desiccation cracking of clay soils used for clean cover systems over contaminated soil and decrease the effectiveness of the cover. Additional desiccation caused by vegetation would also exacerbate the shrinkage.

Increase in wind speeds during gales would increase the occurrence of windthrow of trees on cover layers over contaminated land and increase the risk of exposure to any contaminants.

Meteorological effects on the generation, migration and emission of landfill gas have been discussed by Hartless [24].

Generation of landfill and other gases could be increased as soil temperature and moisture content rise. Methane and carbon dioxide generation rates increase under warm moist conditions, and rising groundwater levels in particular could enhance gas production as previously dry material moves into the saturated zone. The composition of landfill gas may also be altered as carbon dioxide is more water-soluble than methane.

Migration pathways for landfill gas off site could also be affected by rising groundwater. The exact effect can only be predicted on a site by site basis though since higher groundwater levels may block previously open pathways and, conversely, they may enhance migration as the gas tries to find an alternative route. Also, increases in flooding may cause gases to migrate further.

Gas emissions from the ground (as opposed to lateral migration off site) could also be influenced by climate change. More water logged ground conditions could lead to increased emissions of soil gas from drier areas, i.e. beneath buildings. (A fatal landfill gas explosion occurred in Denmark following heavy rainfall). On the other hand, hot dry summers could result in desiccation cracking of clay soils thereby leading to an increase in gas emissions through cover layers. Another effect of climate change will lead to an increase in the frequency and intensity of storms. The associated weather fronts could bring more pronounced falls in atmospheric pressure, which in turn can increase emissions of landfill gas from the ground. One of the key landfill gas explosions in the UK followed a significant fall in atmospheric pressure [24].

Finally, increases in wind speed may well help reduce the likelihood of accumulations of landfill gas in that it could improve the dispersion of landfill gas by passive gas control systems.

Overall, it is suggested that the risks from landfill gas and other gaseous contaminants may well increase as a result of climate change. The degree to which this will happen is difficult to predict and will probably have to be assessed on a site by site basis using the principles of risk assessment. Tools for assessing the impacts of meteorological effects on gas emissions are described in reference [25].



4.5.3 DemographyThe increasing need for more dwellings in parts of the country, especially the South East of England, in which building land is already at a premium, will lead to further use of brownfield sites, that may contain contaminants. This will lead to a greater need for either ground remediation, or effective protection measures, which can withstand the increased climate stresses that have been identified above.

4.5.4 ConstructionRobust guidance for protection of houses from the ingress of contaminants already exists. Provided that this is taken into account in any novel designs, it is not felt that changes on construction will affect the risks of air quality in housing from ground contaminants.

4.5.5 RegulationsApproved Document C has recently been fully revised, and will be published within the next month to come into force later this year. This revision took full account of the present knowledge on climate change and the latest requirements for protection of houses from ground contaminants. It is felt that the guidance contained will be valid for the foreseeable future, but should be reviewed as better information about contaminant behaviour becomes available.

4.5.6 Vulnerable Sections of SocietyRisk from this hazard is constrained by geographical location and dwelling design. There are no clearly susceptible subgroups of society.

4.6 Toilets, waste disposal and sewerage

4.6.1 The nature of the hazardThe potential for infectious organisms to occur, and the mechanism by which these organisms can infect people present a health hazard associated with bathrooms and toilets. It needs to be noted, however, that the presence of people infected with a diarrhoea or other infective agent is a precondition of any risk.

There are up to 20,000 notified cases of dysentery in the UK each year (this may increase to over 100,000 if viral gastroenteritis is included), however it is unclear how many of these are associated with infections derived from sanitary ware. The greatest risks to health occur in sanitary accommodation in multiple use, e.g. in houses in multiple occupation: old peoples homes, schools and public places.

The most likely disease associated with toilets and sanitary in the UK is dysentery caused by Shigella sonnei (shigellosis). This organism can survive outside the body for varying lengths of time, according to conditions, however to become infected humans



need to ingest material contaminated by faeces. Other diseases include gastroenteritis caused by viruses or protozoa.

Viral gastroenteritis, inflammation of the stomach and small and large intestines resulting in vomiting or diarrhoea is caused by a variety of viruses including rotaviruses, adenoviruses, caliciviruses, astroviruses, Norwalk virus, and a group of Noroviruses. Some enteroviruses are transmitted in conditions of poor hygiene and sanitation, and can survive in the environment away from human hosts. Other viruses like rotavirus and calcivirus appear to be spread directly from person to person contact (and possibly also by respiratory droplets) in addition to the faecal-oral route.

Cryptosporidium is a protozoan parasite found in man and in many other mammals, the most newsworthy species is Cryptosporidium parvum. This species has been responsible for a number of outbreaks of cryptosporidiosis in England over the last twenty years. The means of dispserion of this protozoa is via tiny spore-like structures (oocysts), four to six micrometres in diameter, which carries the infective form, the sporozoites. When ingested by another host the sporozoites “hatch” from the oocysts and set up a new cycle of infection. The oocysts are very resistant to adverse conditions in the environment and can survive dormant but viable for months in clean water or moist cool soil.

4.6.2 ClimateAs noted in the introduction, the precondition of any risk is the occurrence, within the property, of people infected with diarrhoea or other agents. The predicted warmer weather during the summer period has raised concerns about bacterial contamination of food. Food-borne infections generally are more common in the warm summer months, probably due in part to the fact that summertime is when most outdoor dining takes place in the UK, with associated storage of food outside of refrigerators. Higher ambient temperatures are likely to increase the risk of bacterial growth sufficient to cause human infection. Therefore, the potential for cross-infection of other members of the household will be increased as a result of the predicted climate change.

4.6.3 DemographicsFor our aging population, gastroenteritis is a serious illness, since they are among those at greatest risk of dehydration from loss of fluids as a result of vomiting or diarrhoea. In addition, diarrhoea and faecal incontinence are very common in older people especially in the frail and disabled and while the reasons behind this occurrence are often unclear, the potential that this is linked to food poisoning or faecal contamination can not be ruled out.

Immune compromised persons (eg AIDS suffers) are also at risk from dehydration as a result of gastroenteritis because they may get a more serious illness, with greater vomiting or diarrhoea. They may need to be hospitalised for treatment to correct or prevent dehydration.



4.6.4 Construction practiceThe changes envisaged in construction practice are unlikely to affect the health risk associated with sanitary linked infections.

4.6.5 Regulations and LegislationsRecent legislation, aimed at reducing water use, has encouraged a move away from older-style toilets, which use between 7.5 and 13 litres per flush, to low flush toilets using only 6 litres per flush. This, and the use of partially treated waste water (greywater) from washbasins and showers for flushing toilets, have the potential to permit the build-up of biological biofilms. The droplets formed by flushing toilets can contain bacteria, viruses and oocysts which remain as aerosols for long enough to settle on surfaces in the lavatory or bathroom. In addition, current flushing rates do not completely remove the microorganisms, which may become absorbed into the porcelain surfaces and reappear in further flushes.

It is important to note that the conventional WC and sewage system presents negligible risk of infection if they are in good repair and if lavatories are regularly cleaned. However, with an aging population and the potential for an increased chance of poor personal and building-linked hygiene, the risk of infections may increase. This factor coupled with a warmer climate increasing the chance of food-poisoning does imply a serious risk to the health of occupants.

4.6.6 Vulnerable Sections of SocietyThe elderly are particularly vulnerable to the consequences of ill health associated with poor sanitation. In addition, the increased difficulty of achieving adequate cleaning as mobility decreases in an ageing population may increase the risks of such health problems.

4.7 Noise

4.7.1 The Nature of the HazardIt is unlikely that noise within the home will ever be loud enough to cause damage to the hearing of occupants. However noise from neighbours, traffic, children playing outside etc. is a major cause of annoyance to occupants and is associated with psychological symptoms such as headaches, irritability, loss of sleep and feeling tense. Between 10 and 20 cases of suicide per year have been attributed to noise from neighbours [20]. Assaults on neighbours (and occasionally homicide) are also occasionally attributed to noise but actual numbers are not available. There has been a rise in domestic noise complaints to Local Authorities from just over 200 per million population in 1971 to over 5000 per million population in 1997/98. The most common noise sources were recorded as being amplified music, voices, children, barking dogs, and neighbours’ vehicles. Studies have shown that most sources of disturbance were



inside the neighbouring building, and that the evening and night were the most vulnerable times.

4.7.2 Climate Changes in climate will not impact directly on noise levels within buildings. However the associated social changes such as increased use of gardens for barbecues in warm summer weather and changes in window opening habits to provide better ventilation, will lead to increased nuisance from noise outside the house.

4.7.3 DemographyThe increased density of housing necessary to meet demand for accommodation in certain areas of the country, especially the South East of England, will lead to more construction of terraced houses and flats. This will lead to more risk of sound transmission between dwellings with consequent annoyance to occupants.

4.7.4 Construction changesSound insulation of buildings is essentially dependant on the total mass of material present. This means that if lightweight off site construction becomes more widely used, there is a risk that sound transmission between dwellings, and between rooms in the same dwelling may increase, unless steps are taken to mitigate this in design.

4.7.5 RegulationsMeasures to control sound transmission from outside to within buildings and between rooms within a building are included in Approved Document E. The recent revisions of AD E and AD L1 and L2 have demonstrated that there can be conflicts between effective sound and thermal insulation. It will be important to coordinate future revisions of these documents to minimise future problems.

4.7.6 Vulnerable Sections of SocietyNoise is likely to be an increasing problem for people living in high density urban environments, compared to those living in rural or surburban areas.

4.8 Tobacco smoke and particulates

4.8.1 The nature of the hazardParticles in buildings frequently originate from external sources although tobacco smoke is an important indoor source. They may be natural, such as pollen grains or they may be man induced, for example emissions from vehicles or smoke from fires. A number of fibrous materials used within the building envelope can release dust on



handling or when damaged, these include mineral silicates (eg asbestos) and man-made mineral fibres produced from molten glass or rock (glasswool and rockwool).

The use of asbestos for most building products ceased by the mid- 1980s, however, considerable amounts of old asbestos cement building products still remain in situ, and are a potential source of fibre release. Inhalation of airborne asbestos fibres in sufficient quantity can cause asbestosis, lung cancer and mesothelioma (a cancer of the lining of the pleural cavity). The first two illnesses are only associated with occupational exposure, however mesotheliomas have been documented in wives of asbestos workers, only exposed to fibres when handling contaminated clothes.

As man-made mineral fibres do not split into extremely fine fibres, few of the airborne fibres will be inhaled into the lung. The bulk of these molten glass or rock products pose a low risk to health, they can however cause skin and upper respiratory tract irritation.

Tobacco smoke contains over 3800 different chemical components, both gaseous and particulate. The smoke given off from the burning end of the cigarette is known as ‘sidestream’ smoke and environmental tobacco smoke (ETS) consists mainly of this type of smoke. In theory ETS could cause any of the health effects normally associated with active smoking but at a lower level of risk. Between 5% and 10% of all lung cancers occurring among non-smokers are linked to ETS exposure (potentially several hundred extra deaths per year in Britain). Also about 5% of coronary heart disease deaths (between 5000 and 10 000 extra deaths per year) are related to passive smoking.

4.8.2 ClimateIn the UK, smog is normally associated with wintertime, the classic example of this was the pollution episode that effected London in December 1952 which was thought to be responsible for up to 4000 deaths. However, summer smog is very common in cities in a number of countries around the world (for example Mexico City) and is produced by the action of sunlight on a number of pollutants such as hydrocarbons and oxides of nitrogen causing these pollutants to react chemically. The resultant photochemical smog contains secondary pollutants such as ozone, aldehydes and fine particles.

Exposure to high concentrations of ozone, the principal constituent of summer smog, may cause eye irritation. People suffering allergic disorders, such as asthma and hay fever, or chronic disorders, such as bronchitis, or cardiac conditions, are at risk when ozone concentrations exceed acceptable levels. Whether the increase in summer temperatures predicted for the UK will increase the likelihood of summer smog is unclear since large reductions in polluting emissions from vehicles and industry have been achieved since 1990. Therefore there is the potential that such episodes become less frequent.

The ultimate impact of climate on pollen-induced disease is difficult to predict, but will depend in part on whether local allergenic species increase or decline in response to climate changes. Since the start of the twentieth century, the length of the growing season has increased in much of the world, and further increases are likely with



continued warming. A longer growing season would lead to greater cumulative exposures to pollens from weeds and grasses that tend to pollinate until the first annual frost. Longer-term changes in climate may lead to altered plant distributions and increases or declines in the numbers of allergen producing species. Additional factors, including ultraviolet radiation and air pollutant concentration, may change levels of pollen produced by plants or alter the allergenicity of pollen grains.

4.8.3 DemographyThere are about 12 million adult cigarette smokers in Great Britain and in 2002 it was estimated that 24% of women and 26% of men smoked, reflecting a steady decline since the mid 1970s. This decline has been more pronounced in male than female smokers. Smoking is significantly higher among people employed in routine or manual occupations compared to those in managerial and professional employment.

How the shift away from manual occupations in the next few decades and the steady decline in the number of smokers will affect the levels of ETS exposure is unclear. However, exposure is likely to decline especially if a ban on smoking in public places is implemented.

There is a close historic linkage between population growth, traffic congestion and economic growth. The UK government forecast that congestion will grow faster than previously assumed, by 2010 congestion levels on all roads could be up by at least 11%. (Transport Ten Year Plan 2000: Delivering better transport - progress report). The increased congestion coupled with continued concentration of the UK population in the South East of the country could lead to an increase in the incidence of summer smogs.

4.8.4 Construction changesThe changes envisaged in construction practice are unlikely to affect the health risk associated with particulates.

4.8.5 RegulationsLaws banning smoking in public places, including bars and restaurants have been introduced in a number of European countries including Italy, the Netherlands, Sweden and Greece. At this moment the UK Government has shown no signs of committing to such a law. However public pressure is growing and such legislation would cut exposure to ETS resulting in a significant number of lives being saved.

There is now good evidence that short-term increases in particle levels are associated with increases in mortality and morbidity rates. Cardiopulmonary impairment appears to be the predominant effect and the elderly and infirm appear to be especially at risk. In addition asthmatics, irrespective of age appear to suffer symptoms and increased risk of acute attack. Other short-term effects include altered pulmonary function and for children, increases in upper respiratory tract symptoms. Long-term effects of exposure



to airborne particles include cardiopulmonary disease, reduced lung function, respiratory illness, and, possibly cancer.

4.8.6 Vulnerable Sections of SocietyThere is a demonstrable correlation between social class, gender and the likelihood of being a smoker. Generally there are higher numbers of manual/unskilled workers who currently smoke than in other classes. There are also generally changes with age group with statistics for young adults showing an increase in the rate of smoking offsetting some of the decline in smoking in other age groups. Legislation and taxation may well have a complex effect on the future social and gender balance of smokers.

4.9 Lighting

4.9.1 The nature of the hazardVisual acuity increases with the level of illuminance, and hazardous situations can be created by inadequate lighting. This includes insufficient light sources, glare, gloom and shadows. For certain tasks (for example walking down stairs), an adequate level of illuminance is required for users to avoid slip, trip and fall accidents. Low lighting is also likely to increase the likelihood of collision with obstacles or buildings features. Studies indicate that inadequate lighting may be a significant contributory factor in domestic industrial accidents. Inadequate lighting may also affect the behaviour of people in buildings. If individuals cannot identify a hazard, they may not be able to evaluate the potential harm.

Studies of animals show that light can have physiological effects, as distinct from simply being the vehicle for seeing (although it is not known whether these effects have health significance). Depression in patients with seasonal affective disorder (SAD) can be reduced if they are given bright light as therapy. Lighting can induce complex changes in the production of hormones and other biochemical indices.

4.9.2 ClimateIt is expected that there will be increased sunshine in the summer, especially in the south of England, leading to higher light levels, this may increase problems of glare in houses. However winter sunshine will decrease, due to increased cloudiness; this will lower light levels within housing, especially if designs are changed to improve shading, increasing the risks of accidents and depressive illness noted above.

4.9.3 DemographyIt is felt that changes in demography will not have significant effects on light levels in housing.



4.9.4 Construction changesOne method of preventing excessive solar gain and limiting the high summer temperatures that may result within housing is to construct buildings that make effective use of natural shading, or incorporate shading devices and smaller windows. This may have the advantage of reducing glare in summer but may make houses darker in the winter increasing the risks of accidents and depressive illness.

4.9.5 RegulationsThe current Building Regulations make no requirements for daylight provision in domestic buildings, however some guidance in given in CIBSE and similar Guides. This situation should be reviewed and consideration given to incorporation of this issue in future revisions to the regulations.

4.9.6 Vulnerable Sections of SocietyGood lighting and construction design should be independent of particular sectors of society. Good practice may become more important for urban developments where higher densities of housing could lead to compromises on the provision of natural daylighting; care should be taken in urban planning to avoid this.

4.10 Fire

4.10.1 The nature of the hazardAccording to Home Office data, there are about 70,000 fires a year in dwellings; 80% of these are accidental, the remainder being malicious in origin. According to other surveys, many minor fires go unreported to the fire service and, hence, the numbers given may represent only a small proportion of all fires, in dwellings. However, they will include those fires giving rise to serious casualties. In 1998, of the 524 deaths in building fires, 497 (95%) occurred in dwellings; similarly of the 16,669 recorded non-fatal casualties, 14,929 (90%) occurred in dwellings. Fire deaths are not evenly spread among the whole population, rising steadily above average with increasing age beyond 65.

The physiological and psychological effects of exposure to toxic smoke and heat from a fire result in varying degrees of harm, which include either death or permanent injury. The effects (or potential harms) include:

impaired vision resulting from the optical opacity of smoke and from the painful effects of irritant smoke products and heat on the eyes;

respiratory tract pain and breathing difficulties or even respiratory tract injury resulting from the inhalation of irritant smoke which may be very hot. In extreme cases this can lead to collapse within a few minutes from asphyxia due to laryngeal spasm and/or bronchoconstriction. Lung inflammation may also occur,



usually after some hours, which can also lead to varying degrees of respiratory distress;

narcosis from the inhalation of toxic gases resulting in confusion and loss of consciousness;

pathological changes in the brain that can lead to long term behavioural and psychological problems; and

pain to exposed skin and the upper respiratory tract followed by burns, or hyperthermia, due to the effects of heat preventing escape and leading to collapse.

4.10.2 ClimateThe only effect of climate change on fires within homes is felt to be the possible increased risk of scrub or woodland fires, occurring in summer drought conditions, spreading into the house. This risk should be taken into account in the planning process for new housing.

4.10.3 DemographyStatistics show that there is an increased risk of fire affecting elderly people as a consequence of an increased susceptibility to accidents in the home. In addition the reduced mobility and increased confusion of this age group will act to impede safe evacuation of the building in the event of a fire occurring. The ageing population will therefore face an increased overall risk of fire and be less able to survive it. This is a key demographic change for this hazard.

4.10.4 Construction changesInnovation in construction, and in particular the increased use of lightweight composite construction technology could increase the potential rate of fire spread in buildings. Care is needed to ensure that service runs in modular components are appropriately compartmentalised to avoid offering a pathway for fire to spread. This requires an awareness and understanding by both designers and site workers. Techniques and solutions to control fire risk in these structures exist, and in theory are being implemented. However, there is concern that poor standards of workmanship are leaving some buildings in the UK exposed to unnecessary risk of fire; a recent investigation identified this specific issue for timber frame housing.

4.10.5 RegulationsThere is an extensive regulatory and legislative framework (including Approved Document B of the Building Regulations) acting to reduce the risks of fires occurring, to control any fire spread in the event of fires occurring, and to reduce the consequences to any occupants. It is anticipated that regulations and legislation will continue to be developed in future to address serious fire risk issues as they are identified. The net effect of future Regulations is therefore assessed as a positive one, and will counter changes in other drivers.



4.10.6 Vulnerable Sections of SocietyThere is a link between fire risk and the elderly which results from a reduced awareness of potential hazards. An ageing population may result in larger numbers of such incidents unless the risk is countered. There is a greater risk for the elderly and children to be killed in fires due to physical mobility limitations and increased mental confusion impeding escape. Statistics from the United States show that the Fire Death Risk increases significantly with age over 65.

The move towards planning for higher density urban developments may result in fire incidents affecting greater numbers of people. Regulations and legislation make requirements for controlling this risk; these requirements need to be integral to an innovation in urban space design.

4.11 Falls and other accidents

4.11.1 The nature of the hazardSlips, trips and falls are a major cause of accidents in and around buildings. Contributory factors to accidents occurring on the level include surface contamination, surface condition (including the efficacy of drainage), user and task characteristics, footwear, lighting, noise and ambient temperature, and exposure of the building to adverse weather. A key feature within buildings is the nature and condition of flooring and its affects upon the safe circulation of users. Slipping and tripping probabilities relate to a number of aspects including inherent slipperiness, overall construction, unevenness, and the level of maintenance or cleanliness. Many devices and test methods have been used to assess slip resistance and investigations to date have not found a simple means of determining the relationships between footwear and floors; one reading from a single instrument cannot currently be used to predict the suitability of a floor surface under all conditions. Uneven and badly maintained floors are also known to be important causal factors in accidents in the workplace [26]. Wetness is a particular problem; for example, in the catering industry, 77% of accidents are related to wet surfaces [26]. The severity of injuries resulting from a fall is also, in part, determined by the type of flooring.

4.11.2 ClimateThe only important relationship between climate change and accidents in buildings is the lower possible light levels discussed in Section 4.9. This could lead to an increased risk of falls on stairs, especially by the elderly with poor eyesight.

4.11.3 DemographyThe ongoing demographic trend of an ageing population is likely to have a serious effect on this hazard. The DTI Home Safety Network reports that currently 80% of all home fatalities, that are as a result of falls, occur to people in the over 65 age group. Furthermore, 300,000 pensioners require hospital treatment each year as a result of



falls. The trend towards single person households, if replicated in the older age group, will increase the consequences of such falls because of the increased delay in treatment.

4.11.4 Construction changesChanges in construction practice are unlikely to have a significant impact on this hazard as they reflect the way in which the building fabric is erected rather than the quality of the internal finishing.

4.11.5 RegulationsThere are requirements already within the Building Regulations, the Housing Fitness Standard, and within other legislation for measures to control the risk of these accidents occurring. It is anticipated that these requirements will be maintained and where appropriate strengthened in the future. Future development of Approved Document M of the Building Regulations “Access to and Use of Buildings” may have a role to play in facilitating the safety of the ageing population in their own homes. Overall, Regulations should be a positive driver for this hazard in future and act to further reduce its level of impact.

4.11.6 Vulnerable Sections of SocietyLack of mobility amongst the elderly puts individuals at greater risk of accidents; this is compounded by the more severe consequences of falls and other accidents in the elderly.



5 Quantitative assessment of hazards

5.1 Possible quantitative analysisTo supplement the qualitative discussion of the drivers and hazards to air quality, it had been hoped to provide specific quantitative guidance as to the possible changes in as many areas as possible. Some of the hazards discussed, indoor temperatures and risk of mould growth for example, lend themselves naturally to quantitative analysis, others like lighting and noise levels are much more difficult to quantify. Similarly, of the drivers analysed, the effects of climate change are easily quantifiable, while changes in regulations are not.

This exercise has identified areas where quantitative analysis might be expected to be both feasible and valuable, but at present is not possible because the background information is not available. The most important of these areas are:

the occurrence of high internal temperatures in summer; the variation of the release of ground contaminants as ground temperature rises;

and, the variation in the release of VOCs from furniture and fittings and internal

temperatures increase.

The sections below discus the quantitative changes to the climate, that have been taken into account in the analysis and the consequent changes to indoor air temperature, humidity and risk of mould growth within houses.

5.2 Climate changes The UKCIP02 scenarios are based on new global emissions scenarios published in 2000 by the Intergovernmental Panel on Climate Change (IPCC) in their Special Report on Emissions Scenarios [27], and are based on a series of climate modelling experiments completed by the Hadley Centre using their most recently developed models. The scenarios describe four alternative future climates for the UK labelled, respectively, Low Emissions, Medium-Low Emissions, Medium-High Emissions and High Emissions. No probabilities can be attached to these four climate futures and it is not possible to suggest that one is more likely than another. While they represent a wide range of possible future climates, the UKCIP02 scenarios do not capture the entire range of future possibilities.

As shown in Figure 1, the scenario information is available in 50km grid squares, covering the UK and Ireland. To assess the regional variability of effects, the analysis has concentrated on the grid squares covering London, Plymouth and Newcastle.



Figure 1 : Distribution of the winter and summer temperature changes from the present day to the 2080s in the UKCIP02 High emissions scenario

To gain an impression of the range of possible effects, data from the two extreme scenarios, Low Emissions and High Emissions, have been used. Table 2 summarises the changes for London, Plymouth and Newcastle in summer (June, July and August) and winter (December, January and February) temperature, relative humidity, rainfall and wind speed, contained in the Low Emissions Scenario and Table 3 shows the same information for the High Emissions scenario.

Table 2 – Changes in summer and winter conditions for London, Plymouth and Newcastle in the UKCIP02 Low Emissions Scenario

Mean TemperatureC

Mean Relative Humidity %

Total Rainfallmm

Mean Wind Speedm/s

Winter Summer Winter Summer Winter Summer Winter SummerLondon1960_90 5.0 15.8 88.1 75.4 206 148 5.7 4.7

2020 5.7 17.0 87.6 72.7 215 133 5.7 4.72050 6.2 17.8 87.2 70.6 222 122 5.8 4.72080 6.7 18.7 86.8 68.6 229 110 5.9 4.7

Plymouth1960_90 6.3 14.3 89.8 83.5 503 262 8.0 5.2

2020 6.9 15.3 89.5 81.4 523 235 8.1 5.12050 7.3 16.1 89.2 79.7 539 213 8.2 5.12080 7.7 16.8 89.0 78.0 554 192 8.2 5.1

Newcastle1960_90 4.5 14.3 84.5 76.2 164 191 6.4 4.5

2020 5.1 15.2 84.1 74.7 173 175 6.5 4.52050 5.5 15.8 83.8 73.6 179 163 6.5 4.52080 6.0 16.4 83.5 72.5 185 151 6.5 4.5



Table 3 – Changes in summer and winter conditions for London in the UKCIP02 High Emissions Scenario

Mean TemperatureC

Mean Relative Humidity %

Total Rainfallmm

Mean Wind Speedm/s

Winter Summer Winter Summer Winter Summer Winter SummerLondon1960_90 5.0 15.8 88.1 75.4 206 148 5.7 4.7

2020 5.8 17.2 87.5 72.2 217 131 5.8 4.72050 6.9 19.0 86.6 67.7 232 106 5.9 4.72080 8.3 21.3 85.5 62.1 250 75 6.0 4.7

Plymouth1960_90 6.3 14.3 89.8 83.5 503 262 8.0 5.2

2020 7.0 15.5 89.4 81.0 527 229 8.1 5.12050 7.9 17.1 88.8 77.4 560 184 8.2 5.12080 9.1 19.1 88.1 72.9 602 127 8.4 5.0

Newcastle1960_90 4.5 14.3 84.5 76.2 164 191 6.4 4.5

2020 5.2 15.3 84.0 74.5 174 172 6.5 4.52050 6.1 16.7 83.4 72.1 187 146 6.6 4.52080 7.4 18.4 82.5 69.1 204 113 6.6 4.4

The most significant changes are: a marked rise in summer temperatures, with a rather smaller rise in winter temperatures, falls in relative humidity and summer rainfall, but rises in winter rainfall, and very little change in mean wind speed.

5.3 Internal temperatures As discussed in section 4.2.1, climate change is expected to have two main effects on internal temperatures and health risks to the occupants:

warmer winter temperatures will reduce the incidence of hypothermia in the elderly;

summertime over heating will lead to increased incidence of strokes, heat disease and similar problems and will lead to more discomfort and stress.

Winter mean temperatures can be modelled reliably, using the monthly mean conditions available from the UKCIP02 scenarios. The very high temperatures that lead to problems in summer are more complex as they depend on a combination of high air temperatures, high humidity, high solar radiation and low wind speed. Therefore, to model summer overheating robustly, it will be necessary to obtain hourly data which realistically reflect the future variation of these four variables while preserving the interrelationships between them. This type of data is not available at present, however it is hoped that it will be generated by a Partners in Innovation project ‘Climate change and the internal environment of buildings’ being carried out by Arup Research and Development, due to report later this year.



5.3.1 Winter mean temperaturesThe benchmark for modelling the energy consumption in UK housing was developed by BRE in the 1980s and is referred to as BREDEM (BRE’s Domestic Energy Model) [28]. BREDEM has been used to provide the basis for the Carbon Index calculation method, and is the basis on which much of the commercially available energy rating software works. In simple terms, BREDEM balances occupant behaviour with the heating system characteristics and the building fabric composition to assess the overall energy consumption of the dwelling. As part of this process internal temperatures are calculated in two zones: Zone 1, usually assumed to be the living room, and Zone 2 usually assumed to be the rest of the house. These two zones can be heated separately.

The monthly version of BREDEM has been used to examine the affect of climate change on the internal conditions within notional houses. The monthly temperature and solar radiation for London were taken from the UKCIP02 scenarios. These climate data have been used within the model to compare and contrast the performance of the dwelling at the timeframes of: 1960 – 90, 2020s, 2050s and 2080s. The Low emissions and the High emission scenarios were used to give the potential spread of future internal climates.

The following assumptions have been made to construct the model:

Heating patternsA notional 3 bedroom semi-detached house has been modelled, with, as an extreme situation, the living room heated to a demand temperature of 21ºC in the evening, but the rest of the house left unheated. This has been done partly to reflect a ‘worst case’ situation but also to reflect the future trend for smaller households using only part of the house. The heating hours have been constructed to reflect “typical” working behaviour, ie during the week 2 hours on in the morning and 6 hours on in the evening, and at the weekend on for 12 hours each day.

Building FabricTwo different standards of fabric insulation have been assessed, as shown in Table 4. The first set of insulation standards reflects the 1995 requirements of Approved Document L, which may be still typical of many dwellings within the timescale of the assessment. The second set of insulation values looks forward to future insulation standards using the GIL 72 Best Practice standard [29].

Table 4 – Fabric U-values assumed in BREDEM modelling

1995 Standard GIL 72 Best PracticeExternal Walls 0.45 0.25Roof 0.25 0.13Ground Floor 0.45 0.20Windows 3.3 1.8



Heating SystemA modern gas fired central heating system using a hot water storage tank has been assumed.

Using this model the average monthly temperature in the living room and in the rest of the house have been calculated. The mean winter temperatures (December, January and February) in the rest of the house, effectively the bedrooms, are shown for the two climate scenarios and the two levels of insulation, in Figure 2.

Raising the insulation levels, increases the unheated bedroom temperature by about 2°C, with the effect of climate change ranging from 1.0°C to 2.5°C, depending on the scenario and insulation level. It is intended to extend this analysis to the effect on the minimum temperature that a bedroom is likely to fall to overnight, because this is the factor that may put elderly occupants at most risk. Other location in England will be examined.

10

11

12

13

14

15

16

17

60_90 2020s 2050s 2080s

Bed

room

Tem

pera

ture

: C

Low Scenario : 1995 Insulation

Low Scenario : Future Insulation

High Scenario : 1995 Insulation

High Scenario : FutureInsulation

Figure 2 – Calculated winter mean temperatures in an unheated bedroom in London, by climate scenario and insulation level

This exercise was repeated with the climate data from Plymouth and Newcastle, to assess the variability over the country. Figure 3 shows the bedroom temperatures calculated in a highly insulated house for the Low and High Scenarios, in the three locations. There is no marked difference between the changes in the three areas; they are all moving in parallel.



13.0

13.5

14.0

14.5

15.0

15.5

16.0

16.5

17.0

60_90 2020s 2050s 2080s

Bed

room

Tem

pera

ture

: C

Plymouth : Low ScenarioPlymouth : High ScenarioLondon : Low Scenario London : High ScenarioNewcastle : Low Scenario Newcastle : High Scenario

Figure 3– Calculated winter mean temperatures in an unheated bedroom in a house insulated to future standards in London, Plymouth and Newcastle by climate scenario

5.3.2 Summer peak temperaturesRising internal summer temperatures are the major threat to the health of occupants from climate change, however the monthly mean data available in the UKCIP02 scenarios do not allow an analysis of the peak summer temperatures within houses. If the necessary data become available, a draft CEN Standard procedure can be used to calculate the changes in summertime overheating likely over the next century.

5.4 Internal humidityThe long term mean internal humidity within a house depends on the water vapour generated by the normal activities of the occupants and the degree of ventilation. In the shorter term, local storage of moisture in the building fabric and furnishings, with subsequent release will modify peak values, however this effect can be neglected for most purposes.

The British Standard for control of condensation, BS5250:2002 [30], contains a procedure, based on BS EN ISO 13788:2002 [31], for estimating the excess vapour pressure with a house over the outside. Figure 4 shows the moisture load lines for five classes, ranging from 1, very low occupancy, to 5, very high occupancy. These are based on the concept that houses are better ventilated as the outside temperature rises, because occupants’ window opening behaviour is strongly associated with external temperature.



0

1200

-5 0 5 10 15 20 25Monthly mean outdoor air temperature,

1080

810

540

270

1

2

3

4

5

0

0,002

0,004

0,006

0,008

q e

D v D pPakg/m3

Co

Figure 4 – Internal climate classes for moisture loads from BS5250:2002

This methodology has been applied to the house modelled in Section 5.3.1 to generate the figures for winter bedroom vapour pressure in London, Plymouth and Newcastle shown in Figure 5.

7

8

9

10

11

12

13

60_90 2020s 2050s 2080s

Inte

rnal

Vap

our P

ress

ure

: mb


Figure 5 – Calculated bedroom vapour pressures for London, Plymouth and Newcastle by climate scenario

This shows that internal vapour pressures will be expected to rise in all locations under both scenarios. The rise is however significantly lower in London (an increase of 7% of the current value under the High scenario by the 2080s) compared to Plymouth or Newcastle (an increase of 19%). This effect will be exacerbated if steps are taken to



improve the air tightness of houses to save energy, without the use of effective ventilation systems.

5.5 Risks of mould growthMoulds will grow on the internal surfaces of buildings when the relative humidity at the surface exceeds 80% for at least six hours a day. The surface relative humidity rises with increasing internal vapour pressure and decreasing surface temperature. Mould growth is commonest on ‘thermal bridges’, local areas of the envelope where, because of the geometry of the structure or the presence of high conductivity materials, such as metal reinforcement, heat flows are higher and surface temperatures are lower than elsewhere. Thermal bridges commonly occur at the junctions between plane elements and around penetrations such as doors and windows.

The thermal quality of the thermal bridge is expressed by the surface temperature factor of f-value, which is given by

Where, Ts is the surface temperature, Ti the internal air temperature and Te the external air temperature.

A well insulated structure will have a high f-value near 1.0, a severe thermal bridge will have a value close to 0.5 or even lower. The Robust Construction Details [32], developed to accompany the recent revision of Approved Documents L1 and L2, were designed to achieve a minimum f-value of 0.75, the value needed to minimise the risk of mould growth.

Three changes which will affect the risk of mould growth have been identified in this report:

internal vapour pressures are expected to rise, increasing the risk; internal and external air temperatures are expected to rise, reducing the

risk; insulation values will rise and design to avoid thermal bridges improve,

raising internal surface temperatures, lowering the risk.The effect of these changes is combined in Figure 6, which shows the calculated surface relative humidity for the unheated bedroom in London, discussed above, for the Low and High Emissions Scenarios and three different surface temperature factors.

The net effect of the changing climate in London is a small fall in the surface relative humidity and therefore a fall in the risk of mould growth.

The benefits of improved insulation and reduction in thermal bridges are shown clearly, in the sharp fall in the surface relative humidity with increasing f-value.



60

65

70

75

80

85

60_90 2020s 2050s 2080s

Surf

ace

Rel

ativ

e H

umid

ity :

%

f = 0.6 : Low Scenario f = 0.6 : High Scenario



Figure 6 – Calculated surface relative humidities for London with the Low and High Emissions Scenarios and a range of thermal bridge severitiesFigure 7 shows the calculated bedroom relative humidity for the Low and High Emissions Scenarios in London, Plymouth and Newcastle. There is only a slight difference in the trends between the different locations.

65

66

67

68

69

70

71

72

60_90 2020s 2050s 2080s

Bed

room

Rel

ativ

e H

umid

ity :

%


Figure 7 - Calculated bedroom relative humidity for London, Plymouth and Newcastle for the Low and High Emissions Scenarios.



6 Risk mapping

6.1 IntroductionThe objective of this section is to identify the relative significance of future changes in indoor hazards, and prioritise these in terms of the possible consequences for health in the UK. A risk mapping approach has been utilised to identify those issues which are anticipated to change significantly and have potential to affect the health of a significant number of people in the UK. Fundamentally, this can be expressed as:

Risk Mapping = (potential change in the hazard) combined with (current level of impact)

Most of the changes in the hazards, that have been identified and discussed in Section 4, are negative, i.e. the changes are acting to make the air quality in housing worse and increase the risks to the health of the occupants; a small number are, however, positive. Because positive impacts may also have implications for policy, no distinction between the two trends has been made in the discussion below.

The results of the risk mapping could be interpreted as follows:

Those issues identified as having the biggest current impact for health, and most potential for future change will be of most concern to future policy development.

Those issues that have a low current impact, but are anticipated to change significantly, are of some concern.

Those issues which have a high current impact, but are anticipated to change little in the future will already be being addressed through policy and so are of less concern.

Issues which have little current impact, and which are anticipated to change little in the future are of least concern.

This is summarised in Figure 8.

Current Level of Health Impact

Potential Future Change of DriversHigh

High

Low

Low

Most Concern

Least Concern Some Concern

Low Concern



High

Low

Low



High

Low

Low

Most Concern

Least Concern Some Concern

Low Concern



Figure 8 –Interpretation of Risk Mapping for Future Decision Prioritisation

In order to undertake the risk mapping for this study, the current health impact of the main hazards identified in Section 4 have been assessed from statistics [20] and classified according to Table 5. Mortalities have been used as the basis for the measure of the level of health impact of a hazard, however, it is recognised that some hazards may lead to extensive ill health whilst having a relatively low associated mortality rate. There are various levels of reported statistics associated with some of these hazards, where this has occurred, the statistic most consistent with a reasonable degree of confidence has been used.

Table 5 – Current Level of Hazard

Risk Classification Description

1 Associated with illness, rather than fatal consequences

2 Estimate to be responsible for between 1 and 9 deaths per year.



5 Estimate to be responsible for more than 1000 deaths per year.

6.2 Estimated future change of hazardsA detailed discussion of the key drivers, and their interplay, for each hazard is given in Section 4. Theses can be summarised as:

Internal temperature and humidityThis hazard has a range of health implications, some of which lead to extensive levels of ill health and mortality (for example hypothermia and hyperthermia). Climate is a key factor for this hazard and climate change will have significant implications on future health consequences. Lightweight construction techniques may increase the risk of summertime overheating. Current changes to regulations to make buildings more airtight will reduce some of the health problems but exacerbate others.

Fungi, dust mites and cockroachesThese biological hazards can lead to widespread ill health amongst vulnerable groups and may occasionally lead to mortality. Climate is a critical factor for this hazard and climate change may have a significant effect in the future. Changes in demography and construction practice may lead to a greater risk of problems in future, but Building Regulations and legislation should help counter this.

Volatile Organic CompoundsSome volatile organic compounds are associated with irritation and allergic response



which can have long term health consequences and in extreme cases lead to mortality. Climate change will cause greater problems, and a construction industry move to using more lightweight, prefabricated construction may introduce higher levels of these compounds into the internal environment. Future changes in legislation are likely to demand tighter controls on these compounds, and research work should help facilitate selective reduction of those compounds associated with health consequences.

Radon and other ground contaminantsGases emitted from the ground are associated with a range of health consequences. Radon, which has a carcinogenic effect, and is estimated to be a cause of about 5% of all lung cancer deaths in the UK, is associated with particular geological formations and is constrained to specific regions of the UK. Other ground contaminants tend to be associated with previous use by specific industrial processes, or landfill sites. Climate change will directly affect the ground conditions and will lead to a change in the rate of release of these types of contaminant from the soil. Population movement to the south east is increasing the pressure on the need to use more highly contaminated sites for housing developments, which will require appropriate technical solutions to avoid health implications. Building Regulations tackle this health hazard for new developments through the guidance detailed in Approved Document C. This guidance has recently been revised to provide greater protection, it is anticipated that this guidance will continue to evolve where necessary to provide appropriate protection in the future.

Toilets, waste disposal and sewerageMaintaining sanitary conditions in housing is important in order to avoid a range of health consequences. Climate change has the potential to increase the risk of unsanitary conditions occurring, and with an ageing population hygiene may become harder to maintain. Recent legislation to reduce the flush capacity of toilets may allow the build up of biofilms that would have been removed with older systems, and if hygiene standards fall, this could lead to health problems.

NoiseExcessive noise is associated with a range of psychological stresses. Climate change will have little direct impact on noise levels, but the increased need to open windows in summer in order to provide comfort ventilation and greater use of gardens may lead to greater noise levels being experienced in urban housing. The move to lightweight construction techniques, coupled with the demands for higher density urban developments will increase the risk of unacceptable levels of noise transfer between dwellings. The Building Regulations make specific performance requirements for new dwellings in Approved Document E, this is anticipated to evolve as performance requirements change.

Tobacco smoke and particulatesParticles and tobacco smoke have well proven links with health consequences. The existing level of problems is anticipated to be reduced in the future through changes in legislation and more stringent future performance requirements.

LightingPoor lighting provision can have a range of psychological effects on individuals,



including depression. A predicted increase in future cloudiness may lead to a deterioration in natural light levels at certain times of the year. Potential use of shading in dwelling design to reduce summer overheating, may cause additional gloominess in the same dwellings during winter. CIBSE provide design guidance for adequate daylighting of buildings, this should evolve to help provide future recommendations.

FireFire in dwellings is associated with a high level of injury and death in the UK. The ageing population, and a move towards higher density urban developments may lead to greater risk from the hazard in the future. Lightweight construction may also have greater levels of risk associated with it, although technical solutions to this should be developed. The existing regulatory framework makes stringent performance requirements, these may need to be reviewed in light of potential changes in demographics.

Burns, Falls and Other AccidentsAccidents in the home are a significant cause of injury and lead to a number of deaths each year. The biggest future challenge comes from the ageing population, with the elderly being most susceptible to the risk and effects of this hazard. Building Regulations will need to be reviewed to encourage greater usability and safety within dwellings occupied by the elderly if the need for other extensive care networks is to be avoided.

Table 6 summarises the influence of changes in key drivers on the future hazards within housing that were discussed in Section 4. Although some of the drivers are relevant to a specific hazard, changes in the driver are not anticipated to have any significant effect on the level of risk from that hazard. The final column in Table 6 provides a summation of the different drivers and gives an overview of the anticipated change in the level of hazard.

Table 6 - Potential influence of changes in key drivers on common hazards

Sec

tion

Clim

ate

Dem

ogra

phy

Con

stru

ctio

n

Reg

ulat

ions

Futu

re D

river

S

umm

ary

4.2 Internal temperature and humidity 3 + 0 2 + 2 + 7 +4.3 Fungi, dust mites and cockroaches 3 + 2 + 2 + 2 - 5 +4.4 Volatile Organic Compounds 2 + 0 3 + 2 - 3 +4.5 Radon and other ground contaminants 3 + 2 + 0 1 - 4 +4.6 Toilets, waste disposal and sewerage 2 + 1 + 0 1+ 4 +4.7 Noise 1 + 2 + 2 + 2 - 3 +4.7 Tobacco smoke and particulates 0 0 0 1 - 1 -4.9 Lighting 1 + 0 1 + 1 - 1 +4.10 Fire 0 2 + 1 + 2 - 1 +



4.11 Burns, falls and other accidents 0 1 + 0 2 - 1 -Key: 1 the driver has a minor influence on the hazard

2 the driver has a significant influence on the hazard3 the driver is central to the hazard0 change in the driver will not influence its current effect on the hazard

+ The driver will exacerbate the future hazard- The driver will reduce the future hazard

6.3 Mapping future risk prioritiesThe future change in hazard level shown in Table 6 can be can be combined through multiplication with the risk classification given in Table 5 to compare future influence and current risk. This risk mapping of relative future health consequence associated with a hazard is shown in Table 7. By comparing the relative health change associated with different hazards, the most significant future health hazards can be identified, with positive numbers indicating levels of increased risk, and negative numbers indicating levels of reduced risk.



Table 7 - Future Risk Priority

Sec

tion

Hazard

Futu

re D

river

S

umm

ary

Cur

rent

Ris

k C

lass

ifica

tion

Futu

re R

isk

Prio

rity

4.2 Internal temperature and humidity 7 + 5 354.3 Fungi, dust mites and cockroaches 5 + 2 104.4 Volatile Organic Compounds 3 + 2 64.5 Radon and other ground contaminants 4 + 5 204.6 Toilets, waste disposal and sewerage 4 + 2 84.7 Noise 3 + 2 64.8 Tobacco smoke and particulates 1 - 4 -44.9 Lighting 1+ 1 14.10 Fire 1 + 4 44.11 Burns, falls and other accidents 1 - 3 -3

Table 7 can be arranged in order of the potential significance of changing future risk, this hierarchy is illustrated in Table 8.

Table 8 - Hierarchy of Significance of Future Change in Risk

Hazard PriorityInternal temperature and humidity 35

Radon and other ground contaminants 20

Fungi, dust mites and cockroaches 10

Toilets, waste disposal and sewerage 8 Increasing riskNoise 6

Volatile Organic Compounds 6

Fire 4

Lighting 1

Burns, falls and other accidents -3 Decreasing riskTobacco smoke and particulates -4

Table 8 shows that, on the present assessment, the two most important hazards are internal temperatures and radon and other ground contaminants, both of which are expected to become greater risks in the future, unless positive steps are taken to counteract them.



6.4 Implications for particular sectors of societyTable 9 shows the sectors of society identified as being particularly vulnerable to these hazards. For some hazards the principal driver may be geographical location, and therefore there is no distinction in risk between social groups. In other cases there is one or several particular elements of society for whom the risk or consequence may be greater. Where possible, Table 9 has been developed on the basis of published statistics.

It is noteworthy that the table shows that the elderly section of population may be particularly vulnerable for half of the risks. With demographics showing a continuing trend for an ageing population, there may be an increased prominence of such problems if these are not addressed.

Table 9 - Vulnerable Sectors of Society

Section HazardAge Groups

Urban / Rural

Wealth / Social Background

4.2 Internal temperature and humidity Elderly & Children Urban Poor

4.3 Fungi, dust mites and cockroaches Elderly Urban -4.4 Volatile Organic Compounds Elderly? - -

4.5 Radon and other ground contaminants - - -

4.6 Toilets, waste disposal and sewerage Elderly - -

4.7 Noise - Urban -

4.8 Tobacco smoke and particulates Young Adults - Unskilled

Workers4.9 Lighting - Urban -4.10 Fire Elderly - -4.11 Burns, falls and other accidents Elderly - -



7 Implications for Policy Development

This section seeks to highlight the particular implications of this report for policy development within the context of the key areas of interest within the ODPM discussed below. The theme of providing decent homes is common to several of these areas of policy.

7.1 Building RegulationsAs discussed more fully in Section 3.4, Building Regulations seek to ensure the health and safety of building users, promote energy efficiency, and enable buildings to be accessible to those with disabilities. The particular areas of the Building Regulations which are likely to be affected by future changes to the factors that affect the internal environment of housing include:

Approved Document B: Fire Safety Approved Document C: Site Preparation and Resistance to Moisture Approved Document D: Toxic Substances Approved Document E: Resistance to the Passage of Sound Approved Document F: Ventilation Approved Document G: Hygiene Approved Document H: Drainage and Waste Disposal Approved Document J: Combustion appliances and fuel storage systems Approved Document L: Conservation of Fuel and Power Approved Document M: Access to and Use of Buildings

Changes to the demographics of the UK, specifically the ageing population, and the changing climate are the two key factors that future Building Regulations must take into account. Future revision of the Building Regulations should therefore make appropriate consideration of these issues.

One part of the Building Regulations that needs particular consideration in its future development to avoid unforeseen blind siding is Approved Document L (L1) Conservation of Fuel and Power. Recent development of this AD has been driven by the need to reduce greenhouse gas emissions associated with the housing stock. As a result, dwellings are becoming more highly insulated, and improved performance standards for air tightness discussed. Warmer, less well ventilated housing may lead to particular health problems, including hyperthermia, hygiene and internal pollution problems. Care needs to be taken when developing AD L to ensure that changes do not cause these problems, and appropriate ventilation requirements are made through AD F to compensate for the loss of infiltration through the fabric.



7.2 Housing

The stated aim of the Housing Unit is:

“… to give everyone the opportunity of a decent home, and so promote social cohesion, well-being and self-dependence.”

Future changes in air quality and health in housing may provide particular challenges for the provision of a decent home.

Two particular issues relevant to departmental activity in this area have been identified as follows:

7.2.1 Review of Housing Supply “Delivering Stability: Securing our Future Housing Needs

A report by Kate Barker was published in March 2004 as a response to a review of housing supply initiated by the Chancellor and the Deputy Prime Minister. The increasing demand for housing in certain regions is set against a significant decline in the construction of new houses. This report explores the issues surrounding the stability and responsiveness of the housing market and the affordability of housing. It concludes that, in order to improve the responsiveness of the market, a step change is needed in the level of new house building.

The consequences of any response to the findings of the report should result in greater levels of urban development, particularly in the south-east of England where pressures for housing are highest. To meet these needs the availability of land for development will be an issue alongside the environmental concerns associated with utilising existing greenbelt land. This may lead to an emphasis on developers considering the use of higher housing density levels in developments than has been traditional, and, where feasible, considering the use of brownfield sites for new developments.

Higher density housing has particular health consequences for the indoor environment, namely:

Exacerbation of the urban heat island effect and increased pressure on summer overheating risk.

Increased risk of biological pests spreading between dwellings (eg cockroaches).

Potential noise issues between dwellings. Possible reduction in natural daylighting.

Use of brownfield sites has an associated risk of contaminants entering the home unless appropriate clean up and barrier technologies have been applied. Technological solutions exist for developing such sites, however, with increased pressure for land in some regions, sites that may not have previously been used for housing redevelopment may have to be considered, and so remedial technologies may face greater demands in future.



7.2.2 Housing Health and Safety Rating System (HHSRS)The Housing Health and Safety Rating System (HHSRS) has been developed to replace the housing fitness standard and to form a basis for action against unacceptable housing conditions and will be included in Regulations as a means for determining the severity of housing problems.

The hazards to the indoor environment and health in housing, outlined in Section 4, should therefore be implicit to the intended use of HHSRS. Future development of HHSRS, and any future successor, must take note of these changing hazards to ensure that future assessments are based on a complete understanding of the state of the art.

7.3 Neighbourhood Renewal UnitIn January 2001 the Prime Minister launched its vision for neighbourhood renewal in the form of “New Commitment to Neighbourhood Renewal: A National Strategy Action Plan”. This set the following aims:

delivering economic prosperity; encouraging safer communities; offering high quality education; providing decent housing; promoting better health in the poorest parts of the country.

Clearly, indoor air quality and health in housing is particularly relevant to the last of these two aims. There is therefore a clear link between the future of air quality and health in housing and the continuation of the current strategy into the future.

7.4 Social Exclusion UnitThe Social Exclusion Unit sets out in its report “Tackling Social Exclusion: Taking stock and looking to the future” the issues that it sees as relevant for future development of its activities. These include:

The increasing premium on skills; The ageing population and associated care needs; Greater ethnic diversity; A growing proportion of single person households.

Clearly, there is some commonality between those issues affecting the future of indoor air quality and health in housing and those affecting social exclusion. As a result, some of the health hazards associated with the future of air quality in housing may become more strongly linked with social exclusion. Currently, exposure to mould and dampness problems is the most important problem associated with low income households. More work is needed for a complete consideration of potential factors, however, in the future,



summer overheating, and an inability to control internal temperatures may become equally important in low income households, who live in poorly insulated structures and cannot afford the sophisticated ventilation systems that will become necessary.

7.5 Sustainable CommunitiesThe Deputy Prime Minster launched the Communities Plan “Sustainable Communities: Building for the Future” in February 2003. This plan sets out a long term strategy for delivering sustainable communities by tackling housing demand and housing supply issues throughout the country. It identifies a series of key elements to be addressed in achieving this, the most relevant to this report being associated with delivering decent homes. The following requirements are identified for decent homes.

“The Plan sets out an action programme to ensure that all social housing is brought up to a decent standard by 2010, alongside targeted action to improve conditions for vulnerable people in private housing.”

The Decent Homes Standards puts forward commitments for improving social housing to a decent standard:

“Ensure that all social housing meets set standards of decency by 2010, by reducing the number of households living in social housing that does not meet these standards by a third between 2001 and 2004, with most of the improvement taking place in the most deprived local authority areas.”

For a home to be considered to meet the decent homes standard, it must: Be above the minimum standard (fitness standard); Be in a reasonable state of repair; Have reasonably modern facilities; Provide a reasonable degree of thermal comfort.

This report shows that in future there will be a series of issues that will start to affect the quality of the internal environment of housing, and which could lead to a deterioration in the fitness of housing. Although winter thermal comfort may improve in housing, summer overheating will introduce a thermal stress for housing occupants which until now has been relatively rare. The dimension of thermal comfort therefore could be extended to consider summer and winter comfort. All of the hazards outline in Section 4 could be relevant to housing sustainability, and the priorities established in the Risk Mapping in Section 6 could be a guide to where appropriate consideration may be given in future.

7.6 Urban PolicyThe urban policy unit was established in 2002 following the White Paper “Our towns and cities: the future”. This paper identifies five key challenges for urban life in the UK:



Changing demographics and ageing population leading to social changes. As a result the UK will need to accommodate up to an estimated 3.8 million extra households by 2021.

Counteracting the trend for people to move away from urban centres, and encourage people to remain and move back to urban centres in the future.

Tackling quality of life and lack of opportunities associated with some urban centres.

Improving the economic performance of some urban areas that have performed relatively weakly previously.

Reducing the environmental impact of urban centres and facilitating sustainable options.

Future hazards for air quality and health identified as being particularly associated with urban housing will have a direct impact on targets associated with the above challenges. Aside from reducing the sustainable value of housing in urban centres, these hazards will have a direct impact on the quality of life of individuals in these environments, and as a result will have a detrimental effect on the quality of life and economic performance of these communities. The particular hazards identified in Section 6 as being of concern specifically for urban centres are:

internal temperature and humidity; fungi, dust mites and cockroaches; noise; lighting.



8 Gaps in Knowledge and Implications for Further Research

The analysis and discussion in the preceding sections of this report has identified a number of areas in which knowledge is currently lacking and in which further research should be undertaken. These are discussed below in terms of the relevant drivers and hazards.

Climate change data

The most important climate parameter which determines the ventilation of buildings, and therefore the internal air quality, is the wind speed. Unfortunately this parameter is the one which is most difficult to predict in the future. The present best estimate in the UKCIP02 scenarios [7] is that mean wind speeds will not change over the present century, however it is recognised that there is considerable uncertainty in this prediction. Further research is needed to improve the predictions of future wind speeds.

High internal temperatures and humidities during hot spells in the summer have been clearly identified as the most significant risk to the health of buildings. Unlike, for example, cold winter internal temperatures, which depend simply on the external air temperature, high internal temperatures depend on the coincidence of high external temperature, solar radiation and humidity and low wind speed. Currently available future climate data cover only individual variables and do not take account of the necessary interrelationships between variables. Work is needed to generate future climate data which represents the all the interactions between variables in a realistic way.

It is expected that release of potentially hazardous gasses from the ground and from materials with buildings will increase as the ground and internal temperatures rise. It is not, however, possible to quantify these effects at present. Work is needed to establish the relationships between temperature and the release of gas from materials.

Demographic and social changes

In future increasing numbers of households will consist of single elderly people. This will increase the chance of accidents in the home and similar problems, unless buildings are designed accordingly. Consideration of appropriate strategies and technical solutions to facilitate safe housing for the elderly is required.

Construction Practice

Excessively high indoor temperatures in summer have been identified as one of the most significant impacts on the internal environment. At present the installation of cooling by air conditioning in housing, is very unusual in the UK. There is, however, evidence that these systems are becoming the latest 'fashion accessory' in housing, comparable to double glazing in the eighties and conservatories in the nineties and are



being installed at the top end of the housing market. Manufacturers are anticipating substantial sales in the future as the demand spreads to cheaper houses.

This situation will lead to a number of problems. Current air conditioning systems are energy inefficient and their widespread use will add significantly to CO2 production from the housing stock. Cooling systems are not currently included in the SAP rating procedure, which is the basis of the Carbon Index, which is referenced in Approved Document L1. Inclusion of these systems in the SAP procedure, would make their impact clear and drive research towards the development of more efficient systems or methods of avoiding their use altogether by the more effective use of natural ventilation or thermal mass.

Regulations and Standards

Building Regulations are reviewed regularly, and recent reviews (for example the review of AD A (structures) completed in 2002 and the revision of AD C completed in 2004) have taken climate change into account. One issue where care needs to be taken that improved regulations in one area do not cause problems in another is the reduction in ventilation of housing that might be caused by the improved sealing measures being specified in the current revision of AD L. It is important that compensating changes are included in the ventilation provisions on AD F to ensure that air quality within houses is not adversely affected.

A more complex area is the role of British and European Standards that are widely referred to in Regulations. Because the standardisation process is based on consolidation of past knowledge, it is very difficult for it to take account of future changes.



9 Discussion and conclusions

The four key drivers which will affect the air quality and the health of occupants within housing over the next century have been identified as:

climate change; demographic and social changes; changes in construction practice; legislation and regulations.

The effect of these drivers on ten important hazards to air quality in housing has enabled a classification of the hazards in terms of their likely change over the next century. It is felt that, given the current direction of the drivers, most of these hazards will get worse, especially high internal summertime temperatures, radon and other ground contaminants, and fungal growth and mite and cockroach infestations. Only accidents within the house and problems with tobacco smoke and other particulates, are expected to reduce in severity.

Quantitative modelling of the winter temperatures and mould risk, using the monthly values of the climate changes expected in the London, Plymouth and Newcastle areas, suggests that the changes are similar in all parts of England with only small variations between different regions. The most important impact of climate change is summertime overheating; it is not possible to model this without simulated future hourly data, which preserve the interrelationships between the variables; this is not currently available. Also, quantitative relationships are needed linking release of Volatile Organic Compounds (VOCs) from furniture and fittings with internal temperature and release of ground contaminants with ground temperature.

There is a danger that air conditioning and mechanical cooling systems will become widely installed in housing as a response to rising summer temperatures. These are energy inefficient and will add to the Carbon Dioxide from housing, unless strict measures are taken to control their use. Also unless they are properly maintained there is a serious risk of infections, such as Legionella developing in cooling systems.

The Department's current policies are responsive to likely future changes in the drivers relevant to the internal environment of housing however there are risks from some measures that may cause problems in the internal environment:

The drive to save energy due to air leakage by improving sealing of housing, being discussed in the current revision of Approved Document L1 of the Building Regulations, may cause the indoor air quality to deteriorate unless compensating measures are taken within Approved Document F.

The increased building on brownfield sites that was recommended in the recently published Barker Report as a solution to the current problems in the housing market, will increase the risk of contaminants entering houses unless appropriate protection measures are taken.



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