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INDOOR AIR QUALITY: INSIGHTS FOR DESIGNINGENERGY EFFICIENT BUILDINGSEDUARDO de OLIVEIRA FERNANDES aa Universidade do Porto , PortugalPublished online: 10 Jun 2010.

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INDOOR AIR QUALITY: INSIGHTS FOR DESIGNING ENERGY EFFICIENT BUILDINGS

EDUARDO de OLIVEIRA FERNANDES

Universidade do Porto, Portugal

(Received 5 July 1993)

Indoor air quality has become an issue of increasing concern. The causes were mainly associated with some energy conservation measures, particularly reductions in ventilation levels, originated by the oil crisis of the 70's meanwhile, the real causes for indoor air pollution have been identified and great scientific and technical progress towards a better knowledge of the scientific basis of indoor air quality has been accomplished in recent years.

At the European Community level, among others, the activities developed since 1986 under the Community Concerted Action "Indoor Air Quality and its impact on Man" and, more recently, also in the JOULE project "European Audit Project to Optirnise Indoor Air Quality and Energy Consumption in Office Buildings" have given a major contribution for the enhancement and transfer of that knowledge towards the practitioners. At the CEN level, the work carried out by TC1.56 while preparing the European Standard "Ventilation for Buildings: Design Criteria for the Indoor Environment" also represenis 3 decis~ve conlribution in the same~direction: to have healthy, comfomble and energy effic~ent buildings with flexible requirements according to the objectives of each type of building or pan of building.

On the other hand, the European Community has been very much committed to promoting the use of solar energy in buildings, namely under the JOULE programme, mainly through a better characterisation of the climate, the development of passive solar technologies. the relationship between architecture and buildings physics, the development of codes and design tools and the implementation of actions of information and transfer of technology from the scientific world towards the design professions.

The purpose of this presentation is precisely to highlight the aspects from the IAQ problematic that must be kept continuously in mind when approaching the energy efficiency issue in all types of buildings, in particular when designing energy efficient buildings that take into account passive and natural technologies where the consideration of IAQ is not yet current practice.

KEY WORDS: Joule project, Design, Comfort, Standards.

1 INTRODUCTION

In Europe, energy consumption in buildings represents from 20% to more than 40% of all the energy consumed depending on the climate and the socio-economical development of each country. From that, more than 50% is used for maintaining comfort conditions, including heating, cooling and ventilation. Associated with some actions for energy conservation, or, maybe more exactly, for energy economy in buildings, indoor air quality has been becoming an issue of major concern for the last twenty years. These concerns were, at first, particularly relevant in some regions or countries, e.g., the Scandinavian countries and the USA, where high levels of insulation and air tightness were required as an answer to the rigorous climatic conditions in winter and where HVAC systems were generalised. Therefore, the achievement of good IAQ conditions

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combined with energy efficiency became a significant scientific challenge (1). The need for a better knowledge of the causes of indoor pollution and its remedies is

therefore fully justified and led to a large spectrum of scientific activity around the World. The experience showed that the principal causes of indoor air pollution are the relevant contributors for the pollution load: occupants, materials and HVAC systems. Therefore, the basic strategies to control IAQ are (2): source control, through the selection of materials and products to be used indoors, as well as activity control (e.g., smoking); dilution of concentrations through ventilation; and air cleaning through filtration.

Energy efficient buildings may require or not HVAC systems (3). It depends on the design strategy adopted for each building, bearing in mind, of course, the local climatic conditions and the activities taking place indoors and the associated requirements assigned to each particular building. It is a fact that HVAC systems have been better studied until now because of the industrial and commercial stimulus. They are, in principle, better fitted to assure a more rigorous control of the indoor environment (e.g., temperature in an air conditioned room may be controlled within l.O°C while in a building without HVAC daily temperature swings may exceed 5OC). Of course, it is a matter of defining the objectives or functions of a building and the associated requirements regarding health and comfort. As a very striking example, it is always impressive that in hundreds of thousands of dwellings in USA, designed as "solar houses", the users (in general also the owners) were reported never complain against temperature swings. This must be absolutely taken into consideration when it comes to specify comfort conditions and, as it has been discussed at the CEN TC156, there must be some flexibility on the acceptance of a variety of comfort conditions. This opens the opportunity to consider a new concept of comfort based on the behaviour of the person, sometimes referred in the literature as behavioural comfort (4).

Therefore, the fact that HVAC systems are one of the potential major causes for contamination of the indoor air is a reason to have their need well justified from the very beginning of the design process of each particular building. When their use is justified, special care should be taken about their design and their maintenance schedule. As a matter of principle, energy efficiency in buildings requires that the need for HVAC should always be questioned. Justification should no longer be simply a matter of economics or even the scarcity of one particular form of energy. Options must, hopefully, consider also environmental reasons: at the global level, because of the CO, and the CFCs consequences; at local level, because of the dysfunction caused to the environment associated with the use of fossil fuels; and at the indoor level, since it has been shown that there is a trend showing more IAQ problems in buildings having HVAC than in the others (5).

The environmental (indoor and outdoor) perspective that must preside over building design and energy management must encourage the development of passive solar and natural techniques (passive heating and cooling, daylighting and natural ventilation) wherever and whenever applicable, in principle and, at least, as a background environmental energy. The difficulties that their use still pose due to a lack of the adequate information about natural ventilation, critical for being able to guarantee a good IAQ, must be resolved.

If there are several ways to reconcile energy efficient use with good IAQ, passive and natural techniques can certainly give a major contribution to that. And, of course, such an objective cannot be kept away from those initiatives related to the development of the application of passive solar technologies in buildings.

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INSIGHTS FOR DESIGNING ENERGY EFFICIENT BUILDINGS 39

CEC's DG Xn has been involved with both aspects of the problem. At the European Community level, there have been related scientific activities since 1986: first, under the former Community Concerted Action "Indoor Air Quality and its impact on Man", later, through COST Project 613, now called "European Collaborative Action", with twelve working groups, centred at the Joint Research Centre in ISPRA (Italy); and, more recently, since 1992, in the JOULE programme, a project "European Audit Project to Optimise Indoor Air Quality and Energy Consumption in Office Buildings" has been funded. At the CEN level, work carried out at the TC156 while preparing the European Standard ".Ventilation for Buildings: Design Criteria for the Indoor Environment" also represents a decisive contribution in the same direction: to have healthy, comfortable and energy efficient buildings with flexible requirements according to the objectives of each type of building or part of building. A number of many other actions, workshop and meetings sponsored by IEA, NATOICCMS and others have been promoted.

On the other hand, the European Community has been very much committed to promoting the use of solar energy in buildings, namely under the JOULE programme, mainly through a better characterisation of the climate, the development of passive solar technologies, the relationship between architecture and building, physics, the development of codes and design tools and the implementation of actions of information and transfer of technology from the scientific world towards the design professions.

It is then appropriate to articulate objectives (both of good IAQ and energy efficiency), backgrounds and limitations in order to produce' more comprehensive methodologies for the whole design process. Sometimes, the focus of the innovation regarding energy use in buildings has been put on technologies (either active or passive). More recently a great deal of effort has been placed on the development of design tools, particularly computer software. None of those essential elements should hide the need for an adequate formulation of the problem of energy efficiency in buildings without regional, cultural or other types of prejudices or bias.

2 INDOOR AIR QUALITY

Indoor air quality has gradually developed into a major concern for the last twenty years. It has been suggested that energy conservation strategies or, maybe, more precisely, some energy economy measures consisting on the reduction of the ventilation rates for the buildings were its major cause. Tighter buildings with natural ventilation only, and buildings with small rates of mechanical ventilation, will have a lower capacity for diluting whatever pollutants may be produced indoors.

It is now well known that the major cause for the IAQ problems is the increasing pollution load due to the occupants and their activities, to the outgassing by the building materials and, strangely enough, to the HVAC systems themselves, which may account for as much as 30% of the pollution load in certain cases. The problem was aggravated by the fact that new materials adopted by the building industry (paints, glues, synthetic products of all kinds, carpets, furniture finishing, etc.) are usually major sources of contaminants (formaldehyde, volatile organic compounds, etc.) together with the fact that ventilation requirements used to take into account only the pollution due generated by the occupants. Definitely, occupants are not the only polluters and, therefore, the ventilation rate (in I/s.olf (5) or in air changes per hour) must take into account the total pollution load in the building which means also adding the strength of other sources, i.e., the materials and products within the building shell.

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It could, then, appear that, apparently, IAQ seems to be a hopeless problem or a fatality: buildings are made for people and occupants are a major source of contamination (smoking, CO,, odours, etc.); building technologies progress and new materials, generally with higher pollutant outgassing than the traditional ones, are brought into the scene; the HVAC systems, in their turn, while having been specifically designed to control the indoor environment, are finally recognised as being themselves potential important sources of contamination. Even though ventilation rates were decreased due to the "pressure" for adopting energy economy measures.

However, there are solutions. i.e., the problem is not as hopeless as it appears. There are three alternatives to control indoor air quality (6): a. source control; b. dilution (ventilation); and c. air cleaning (filtering).

Source control - The control at the source is the most adequate strategy: prevention rather than cure. And, when it is not possible to completely eliminate a source of contamination, there are still, at least, two other options: to reduce the source strength or to discharge the pollutants directly to outdoors. In practice, to select materials with smaller contaminant load requires the knowledge of the characteristics of the materials as pollutant sources. This type of information is recognised not yet to be widely available. The creation of a data base gathering this information and establishing protocols to determine the source strength of pollution sources by both chemical and sensory methods is thus urgently needed.

Air dilution (Ventilation) - This strategy is attained through ventilation, either mechanical or natural. As the objective is to guarantee a certain level of IAQ, there must be a minimum of ventilation, expressed in litters/s.olf or in litters/s.m2 or even in littersls. person if in the latter case the occupants are the major criterion. As it was mentioned it is necessary to know the characteristics of those sources to be able to establish a minimum ventilation rate that should control the IAQ levels. The minimum ventilation rate alone, however, does not guarantee the level of IAQ. It,is necessary to have a good ventilation efficiency in order to avoid dead zones with increased concentrations in the space.

Unfortunately, what may still be problematic for mechanical ventilation is even more complex with natural ventilation. Experience shows that buildings with natural ventilation are less prone to pollution than those mechanically ventilated. But lack of models and reliable quantification criteria make the evaluation of the potential of the naturally ventilated spaces and the anticipation of its behaviour problematic.

Meanwhile, ventilation has been suffering the blame as the cause for bad IAQ in many cases. This is not totally fair and lacks scientific objectivity. In fact there are three criteria to fix the level of ventilation in a' building: mass air flux as a thermal camer for heating or cooling the space - and, eventually, humidifying; fulfilment of the health criteria (e.g., to eliminate CO, produced by the human metabolism); and the accomplishment of comfort (IAQ) conditions (on the basis of a sensory evaluation). In principle, the ventilation rate shall correspond to the highest of these three figures. As, in general, the highest figure is determined by the last criteria, it is necessary to make sure that other strategies have.been used to reduce the pollution load in order to assure the lowest possible ventilation rate, as a requirement for energy ecqnomy.

Filtration - Through this strategy, the air that is removed from the room and is partially or totally re-injected in the room (recirculated) undergoes a filtration process. It is thus possible to understand the sensitivity of the IAQ to the maintenance programmes, namely to periodic cleaning or replacement of the filters that are supposed to fulfil a positive role but may be themselves a major source of contamination.

The strategy of source control is, certainly, the most interesting one. However, it asks

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INSIGHTS FOR DESIGNING ENERGY EFF'ICIENT BUILDINGS 4 1

for a @at deal of work in order to characterize the pollution sources: the types and the conditions of all the emissions must be identified. The occupants are quite well known as sources of contaminants. But that is not yet the case, in a reliable and systematic way, neither for current construction materials, nor for the HVAC systems. In principle, if the potential and the nature of the emissions of a given material are known, it will be possible to anticipate the level of contamination @at can be expected from that type of source. It is also necessary to know the potential of emissions from HVAC systems, when they exist. and which maintenance must be performed to assure that such potential will not be reached.

Having done all that is possible to control the sources, the next step to be considered is dilution. Dilution can be obtained either by natural ventilation, including air infiltration, or by mechanical ventilation. The latter may be associated with some heatinglcooling and humidification/dehumidification measures. It is necessary to make clear that HVAC may not necessarily represent "the solution" in what regards the control of comfort and IAQ problems. There are indoor environmental conditions that necessarily require HVAC systems. However, an appropriate approach to any problem must admit two alternatives as always open: HVAC or mechanical ventilation systems; and natural ventilation. If a mechanical ventilation system is installed, filtration is always possible and, of course. desirable. With natural ventilation, that possibility is more problematic.

In such a context and looking at the new buildings, one has to identify all the available options to design and build buildings with more respect for natural resources. This must be the criterion for the definition of the energy strategy for a given building taking into account not only the IAQ but also the pollution that may be generated outdoors at both global and local levels.

3 ENERGY EFFICIENT BUILDINGS

Buildings represent the major single demanding sector in the World energy balance. As around 90% of the energy consumed comes from fossil fuels, buildings are, certainly, a major contributor for one of the most important environmental concerns of today: the CO, production. In addition, air conditioning makes buildings responsible for about one third of the CFC emissions. Several energy uses inside buildings (cooking, fireplaces, boilers, etc.) are responsible for indoor pollution and outdoor pollution as well. Therefore, energy conservation or energy efficiency in buildings has become a very important political issue not just because of the economical aspects but because energy efficiency must meet the policies for a more rational management of natural resources.

The objective of rational use of energy in buildings may be attained in practice through several different strategies: there are several basic different assumptions that can be adopted, concerning the climate, the cost, etc., and there is also a diversity of objectives concerning the types of buildings and comfort and energy requirements. That is why the assumption of three levels of comfort, as it is considered by CEN TC156 in its draft of new ventilation standards, is perfectly justified (7). Such a perspective, which deserves applause, opens the way to a gradual scale of agreed comfort conditions and it will lead to a wiae spectrum of energy strategies including the acceptance of the passive solar technologies for some of them.

Through the last decades the energy problem has been severely marked by economic and political parameters or conditions, with all their conjunctural consequences. That may partially explain why there are levels of consumption of energy per capita quite diverse in

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different countries, even if the comparison is made among countries with the saine stage of development and, sometimes, irrespectively of their climatic conditions. That may also explain also why some countries with an advanced development in science and technology ended up by somehow influencing the rest of the World, imposing, in the process, with more or less subtle techniques of marketing, their own perspectives and, finally, the same type of problems for which they, in fact, already had found the solutions. That is the case of air conditioning now under an explosive expansion in Southern European countries. The fact that the climate is warm does not justify such large diffusion of air conditioning since there are other techniques that can respond to the needs of summer comfort. These, in particulai, are more in tune with the traditional ways of building (e.g., massive constructions in the Mediterranean rim versus wooden buildings in Scandinavia) and of living (e.g., open spaces in Southern countries versus tight envelopes in Northern latitudes). .

After the Rio Conference, concerns with the environment will, hopefully, contribute somehow to streamline, harmonise and give more coherence to the energy use as far as externalities of the energy conversion systems may progressively been taken into consideration. Otherwise, as we have seen in the past, a t r u e dialogue energy- environment becomes almost impossible. Following that path, it is essential to distinguish the primary forms of energy that need to be converted before they can be used in buildings, and those primary forms that can be used as final energy. This is the case of solar energy under passive and natural techniques. It presents a great potential for both daylighting and heating and for cooling purposes. Experience has demonstrated that the rush in the 80's to some type of solar equipment did not work. The logic was still too much the logic of the oil. Solar was asked to be a direct substitute for oil. Buildings very often became more like assemblies of components and they did not look like being architecture.

Going to basics, one could ask: "energy in buildings" what for?" And the answer be: "Of course, the well being of man". But, well being and man is not seen here under a restrictive perspective of the occupant inside his house, with his personal history, at a given particular time and for a particular location but the well being related to the Mankind in the global environment. That underlines the importance of buildings in the environmental understanding and practice: they represent an infinity of micro- environments (indoors and outdoors at the scale of the street or of the city) with strong and decisive repercussions at the macro-scale (global).

It was not always like that. It was a time where comfort was a very restricted benefit to a small number of people and a time where heating was just a condition for survival. Nowadays, that situation is not acceptable. Even though, there are many regions where the access to energy is not yet what it should be. However, on the opposite, there are many expressions of energy waste that must be thought about: on the one hand, in the cold regions there are needs for cooling because buildings have an excess of glazed areas and/or of internal gains, originating overheating situations; and, on the other hand, a fashionable rush to air conditioning in regions where the threshold of comfort in the heating season is still far from being attained. Those situations are not normal. Science and technology has been providing the tools. What seems to be lacking is enough coherence and independence to make the appropriate choices.

Historically the progress in this field was not always very consequent as it was mainly stimulated by economicist and short term objectives. That was the case of some solar energy developments in buildings seeing solar more as a primary energy resource in competition with fossil fuels than a final energy form ready for immediate used in the

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building as passive solar for heating and for daylighting but also for natural ventilation and passive cooling.

This new and more global solar approach, in what regards the relationship buildings/energy, is more friendly with the environment in the sense that it takes as much as possible from the local environmental conditions. This has been called bioclimatic architecture or climatic responsive architecture, among many other designations. It is based on the integration of passive solar technologies and aims at satisfying the energy needs with as much natural energy as possible. Solar energy appears, then, to respond as a background energy. Its consideration at the beginning of the design process is a first and definite step towards energy efficient buildings.

4 MAKING IAQ AND EFFICIENT ENERGY BUILDINGS COMPATIBLE

Energy efficiency in buildings has been an objective throughout the World since the 70's. In the beginning, the emphasis was put on energy economy or reduction of the energy consumption. The criteria were based on cost-benefit analysis, both to install more efficient equipment using the same form of energy or to substitute one form of energy by another.

The promotion of energy conservation in areas or countries with a large tradition of mechanical systems in buildings was then economically driven, in some cases with incentives from the Administrations. In other areas or countries, the use of energy in buildings was and still is at a very low level. The less extreme climatic conditions cannot explain the differences. This has to do with the still very low level of comfort both in winter and in summer in those countries. Without the pre-existing energy consumption, the cost-benefit analysis is not possible. Therefore, other strategies should be. identified to h m o n i s e the demand of more comfort with the concept of energy efficiency.

Meanwhile, the environmental problems, mainly at the global scale, called for a series of political steps that culminated, somehow, at the Rio Conference, in June 1992. While calling for the promotion of renewable energies, the Conference favoured the perspective of internalising some costs associated with the externalities dues to the pollutants emitted when fossil fuels bum. That, definitely points to a new order on the approach to the energy issues.

The promotion of solar energy in buildings, in particular under passive and natural technologies for daylighting, passive heating and passive cooling, being a form of energy that can be used at the final stage, without any conversion, offers a great potential for reconciling energy use and environment.

In the beginning, new concerns about the quality of the indoor environment resulted from some strategies for energy conservation. Today, besides the need to adopt correct strategies to control the indoor air pollution - which still require a great deal of research and harmonisation work - there is a better knowledge of the situation and there are many options available to reconcile IAQ with energy efficiency.

In order to aim at that "reconciliation", it is necessary to formulate the problem of energy efficiency in a building in a broader and comprehensive way. Then, efficient use of energy is much more than substituting fuels for solar as it was one of the trends in the 70's and the early 80's. It shall represent the result of a holistic approach that comprises four main steps: a. appropriate definition of the essential requirements (hygiene, health and comfort) (8) and corresponding energy needs; b. reduction of the needs for final energy; c. justification of the need for HVAC systems, giving priority to the passive and

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natural techniques; d. good efficiency and good maintenance of the systems, naturally or mechanically driven.

5 , CONCLUSIONS AND RECOMMENDATIONS

A number. of conclusions/recommendations could be drawn from the previous considerations. The intention was not to.be exhaustive on the, assessment of the problem ; but rather to highlight t h e need for promoting passive solartechnologies without. forgetting about IAQ. Then the major points to be retained afethe following: . . .

To reconcile IAQ and energy efficiency .in buildingsi'it is necessary that each problem represented by a new building design process be'well formulated, taking into account all the objectives, conditions and means available without any prejudice or bias.

'IAQ has to be, taken into consideration from the very early stage of the design process for all types of buildings and energy .strategies is going to be adopted.

IAQ conditions can be controlled by several different means other than just ventilation. Designing a building according to the type of its utilisation is an essential first step. Architectural form and selection of materials, components and systems is a part of this step.

Energy efficiency means more than just energy economy or substituting one form of energy for another to reduce the energy consumption or to reduce the consumption of a particular form of energy, Energy efficiency must be seen as a contribution towards the management of the environmental resources: those that are used (the energy itself) and those that may be harmed by that use (fhe environment inside and outside the building envelope).

A large share of buildings could avoid completely or at least have much smaller heating or cooling systems if they were better designed according to the climatic condition.

Different comfort conditions offer many opportunities to address different building types and situations and therefore they also offer many opportunities to h m o n i s e IAQ and energy efficiency in buildings.

Natural means, such as natural ventilation, driven thermally (natural convection) and/or mechanically (dynamic pressure difference), may be asked to play a relevant role in IAQ.

There is a need to proceed with four major urgent actions:

- launching an European data base for sourcesof indoor air pollution, harmonising methods and procedures for the whole Europe; - studying comfort under transient conditions, in particular in the cooling regime of free running buildings

- studying and characterking natural ventilation and ventilation efficiency in natural ventilation conditions;

- developing and promoting the complbteness of methodologies and criteria for the design process.

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INSIGHTS FOR DESIGNING ENERGY EFFICIENT BUILDINGS 45

Acknowledgements

The author is grateful to Dr. W. Palz and Mr. Theo Steemers, of the DGXII of the Commission of the European Communities, for all the opportunities given in the context of JOULE U Programme. Thanks are also due to JNICT, Junta Nacional de Investiga@o Cientifica e Tecnol6gica and, the last but not the least. to Professor Eduardo Maldonado.

References

Roulet, C. A. : Proc Workshop on Indoor Air quality Management. Lausanne, Commission of the European Communities, Directorate General Xn for Research and Development, Swiss Federal Office of Energy, May 1991. Bluyssen, P. M.: Indoor Air Quality Management, A State of the An and Research Needs. Executive Summary. Workshop on Indoor Air Quality Management, Lausanne, October. 1991. Oliveira Fernandes, E.: The Relationship Comfort - Energy - IAQ. Workshop on Indoor Air Quality Management, Lausanne, October 1991,95-102. Baker, N.: Comfort and Passive Cooling. Workshop on Passive Cooling. pp. 15. Ispra. 1990. Fanger. P. 0. : Introduction of the olf and decipol to quality air pollution perceived by humans indoors and outdoors. Energy Buildings, 1989; 12, 1-6. Woods, J. E.,. E. Maldonado and G. Reynolds: How Ventilation Influences Energy Consumption and Indoor Aii Quality. ASHRAE Journal. 23. Sept. 1981,4043. C E N I T C I ~ ~ / W G ~ - Ventilation For Buildings: Design Criteria for the Indoor Environment (Dmft). 1993. Council Directive 89/106/EEC of 21 Dec I988 on the Approximation of Laws, Regulations and Administrative Provisions of the Member States relating to Construction Products

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