chris hocknell - bsc quantity surveying dissertation 2010
TRANSCRIPT
SOLID WALL HOUSING: PUSHING THE ENVELOPE
BY
CHRIS HOCKNELL
Submitted in partial fulfilment of the requirements for the degree BSc (Hons) Quantity Surveying
Leeds Metropolitan University
April 2010
Abstract
The UK has committed to reducing carbon dioxide (CO2) emissions by 80% by 2050 compared to 1990 levels. UK housing currently accounts for 27% of all UK emissions and estimates state that 86% of existing housing will still be standing by 2050. Of the 22.19 million homes in England, 20.2 million would benefit from cost effective refurbishment measures to make them more energy efficient and therefore reduce their CO2 emissions. However, there are 6.6 million solid wall dwellings that cannot incorporate cost‐effective energy efficiency measures. These are categorised as Hard to Treat dwellings.
The aim of this dissertation was to address this problem and evaluate the specified solution of refurbishing the building envelope and heating system in order to ascertain whether an 80% reduction in CO2 emissions can be feasibly and cost‐effectively achieved in solid wall housing. The study was based on two refurbishment case studies that achieved significant reductions in their carbon emissions. It involved a quantitative analysis of the energy consumption of dwellings through the use of the domestic energy model DEMScot. The energy model was utilised to substantiate the claims of the two case studies and to simulate incremental improvements to investigate an optimum point of refurbishment.
The work builds on previous reports and studies that identify refurbishment as the solution, but have not overcome the barriers to its implementation. It also considers some of the further barriers to refurbishments, such as the currently limited uptake rate of refurbishment measures, the disruption caused to occupants and items other than those included in SAP analyses. Solutions were specified for each of these barriers.
The main findings were; firstly, the case studies are applicable to other dwellings and with the utilisation of innovative materials, reductions of up to 70% in CO2 emissions are possible. Secondly, for both dwellings there was a point where the cost to carbon saving relationship deteriorated and only minor carbon savings were achieved for high costs. Thirdly, the cost of refurbishment could be reduced by developing a mass market, either by encouraging the occupants that are willing to pay or by targeting homes in fuel poverty. Finally, an amendment of policy and Building Regulations could increase the currently low uptake rate of refurbishment measures, by ensuring that opportunities to carry out work are maximised and that inefficient appliances are removed from the market.
The conclusion drawn from this study was that solid wall housing can contribute significantly to the 80% reduction target. The evidence suggests that providing home owners accept refurbishment, reductions of up to 53% could be made for minimal costs. However, refurbishment of solid wall housing must be supplemented by other means to achieve an 80% reduction in CO2 emissions.
Following the findings, one of the key recommendations was that an appropriate body develops a method for maximising value in refurbishment, therefore ensuring that high carbon savings are delivered for optimum costs. Furthermore, the government should swiftly amend current policy in order to maximise refurbishment opportunities and focus on encouraging the public to accept energy efficiency works. Finally, comprehensive research should be carried out that investigates how and to what extent, solid wall housing can be supplemented by other means in order to develop an overall strategy for dealing with solid wall dwellings.
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Acknowledgements
I would like to thank the many people who have assisted me during this dissertation and
throughout my studies. Firstly, thank you to my dissertation tutor Robert Hayes for his time
and guidance. Secondly, I am extremely grateful for the support and encouragement given to
me by Judith and Steve Hocknell throughout my studies. Finally, I would like to thank Sandy
Cowling for her valuable opinion and Katherine Cowling for her endless encouragement
throughout my time at university.
I would also like to express my gratitude to the people at United House who provided me with
the research data, and the individuals I contacted throughout the research that endeavoured
to assist me.
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Contents
Abstract i
Acknowledgements ii
Contents iii
List of tables and figures v
Abbreviations vi
Chapter one: introduction 1
Problem specification 1
Literature review 2
Methodology 5
Chapter two: the UK housing stock 9
Climate change 9
Dwelling emissions 9
Chapter three: improvement case studies 12
Aubert Park 12
Midmoor Road 19
Chapter four: DEMScot, Scotland’s domestic energy model 24
DEMScot configuration 24
DEMScot and SAP outputs ‐ Aubert Park 26
DEMScot and SAP outputs ‐ Midmoor Road 28
Evaluation of the model’s outputs 29
The Ecogen unit 31
Chapter five: cost, Value Carbon and other limitations 33
iii
Total cost and value 33
Value Carbon ‐ Aubert Park 34
Value Carbon ‐ Midmoor Road 36
Optimum refurbishment 39
The willingness‐to‐pay and reducing costs 40
Solid wall insulation 41
Occupant disruption and occurring opportunities 43
Items other than those included in the Standard Assessment Procedure 43
Evaluation of key barriers 44
Chapter seven: conclusion and recommendations 46
Conclusion 46
Recommendations 48
Bibliography 49
iv
List of tables and figures
Table Title Page
1 Average SAP, CO2 and percentage of English housing by construction date 10
2 Aubert Park improvement measures 13
3 Midmoor Road improvement measures 20
4 Aubert Park before refurbishment, SAP and DEMScot outputs 27
5 Aubert Park after refurbishment, SAP and DEMScot outputs 28
6 Midmoor Road before refurbishment, SAP and DEMScot outputs 28
7 Midmoor Road after refurbishment, SAP and DEMScot outputs 29
8 Aubert Park refurbishment measures, Value Carbon 34
9 Aubert Park incremental improvements 35
10 Midmoor Road refurbishment measures, Value Carbon 36
11 Midmoor Road incremental improvements 37
Figure Title Page
1 Cross section of Spacetherm Aerogel insulation board 16
2 Aubert Park Value Carbon Analysis graph 35
3 Midmoor Road Value Carbon Analysis graph 38
v
Abbreviations
BRE – Building Research Establishment
CHP – Combined heat and power
CO2 – Carbon dioxide
DCLG – Department of Communities and Local Government
EST – Energy Saving Trust
HTT – Hard to treat
IPCC ‐ Intergovernmental Panel on Climate Change
kWh – Kilowatt Hour
Pa – Per annum
SAP – Standard assessment procedure
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1
Chapter one: introduction
Problem specification
The UK has committed to reducing carbon dioxide (CO2) emissions by 34% by 2020, and by
80% by 2050 compared to 1990 levels (OPSI, 2010). UK housing currently accounts for 27% of
all UK emissions and it is estimated that 86% of that existing in 1996 will still be standing by
2050 (Boardman, et al., 2005). From these statistics, it is clear that the existing housing stock
presents a substantial obstacle to achieving the UK Government’s emission reduction targets.
The English House Condition Survey 2007 (DCLG, 2009) stated that of the 22.19 million homes
in England, 20.2 million would benefit from improvement measures to make them more
energy efficient. However there is a certain sector that is problematic. This is those
categorised as Hard to Treat (HTT) dwellings. A HTT dwelling is defined as a dwelling that
cannot incorporate token or cost‐effective energy efficiency measures, such as insulating
currently un‐insulated or poorly insulated cavity walls or lofts. Four categories of HTT
dwellings have been identified by the Building Research Establishment (BRE): solid wall
dwellings, dwellings that are off the gas network, dwellings with no loft space and high rise
flats. Older dwellings are more likely to be HTT, 65% of the HTT stock was built before 1945
(BRE, 2008a). Dwellings built before this time are predominantly of solid wall construction as
cavity wall construction only became increasingly common after 1930 (EST, 2006c).
There are 9.2 million dwellings in England alone that can be considered HTT, comprising 43%
of the total stock (BRE, 2008a). Solid wall dwellings make up the biggest proportion with 6.6
million dwellings. There is still no strategy for dealing with HTT homes and there is a clear
divergence of opinion regarding the ability of the HTT housing stock to contribute to the 80%
emission reduction target. Recent reports suggest that greatly increasing demolition levels of
inefficient dwellings and replacing them with efficient new builds would offset the CO2 that
would have been generated by these inefficient dwellings (Boardman, et al., 2005). Other
reports have suggested that a nationwide refurbishment programme must be implemented, in
the form of building envelope renovation and in applicable cases, the installation of renewable
energy generation technologies (Immendoerfer, et al., 2008). These conflicting solutions have
resulted in disagreements between various organisations. Because of the restraints of this
dissertation, the focus will be on refurbishment of the building envelope and heating systems
in solid wall dwellings. Renewable energy generation technologies will not be included as they
are site specific (Mackay, 2009) and would require an extensive study of the geography and
environment of the specific housing site, which is beyond the remit of this dissertation.
The key to a dwelling being energy efficient is the thermal performance of the building
envelope, coupled with an efficient energy source (Green Building Press, 2006). In the context
of solid wall housing, refurbishment to improve the energy efficiency of the envelope would
take the form of external or internal wall insulation, insulation to the ground floor and loft (if
possible), replacement of windows and external doors and draught proofing (EST, 2006c).
These solutions would drastically improve the energy efficiency of the dwelling and therefore
significantly reduce its CO2 emissions (EST, 2006c). However, they are not without their
drawbacks. Insulating a solid wall externally, using a render or cladding system is expensive
and alters the dwelling’s appearance (Immendoerfer, et al., 2008). Alternatively, internal
insulation is generally cheaper than external insulation, but disrupts the occupants, reduces
internal room sizes, increases the risk of thermal bridges and loses thermal mass benefits from
the solid wall (Immendoerfer, et al., 2008). Ground floor and loft insulation is only feasible in
certain solid wall dwellings. Replacement of windows and doors is expensive so offers little
payback to the home owner, and may not be possible in some areas with conservation
interests. Draft proofing is generally cheap and effective, but it can be difficult to access air
leakage points (EST, 2006c). Furthermore, the estimated installation costs of these measures
can vary considerably, which leads to difficulty when trying to assess the cost‐effectiveness
and feasibility of these measures. If an 80% reduction in CO2 emissions is to be achieved by
2050 the solid wall housing stock must be addressed and an appropriate solution specified.
The aim of this dissertation therefore, is to evaluate the proposed solution of refurbishing the
building envelope and heating system. It will ascertain whether an 80% reduction in CO2
emissions can be feasibly and cost‐effectively achieved in solid wall housing.
Literature review
A sizable amount of literature has been generated in recent years regarding solid wall
dwellings. The literature focuses on three main research methods which have examined the
potential of solid wall housing and the merit given to its preservation. These are: the use of
computer modelling software, case study analyses and consultations with specialists.
Literature covering all these approaches will be appraised in this review.
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All sources examine the case for refurbishment, but there is a range of opinion as to the best
solutions. The majority of reports that recommend strategies for solid wall housing have used
The English House Condition Survey (DCLG, 2009) as a data base. The English House Condition
Survey is the largest and most comprehensive data source with regards to the demography of
the UK housing stock; it details the quantities and condition of over 22 million dwellings. The
limitation of this data is that surveys are not conducted for every home in the country; the
quantities are derived from large sample surveys. As a result, there will inevitably be a small
margin of error in the data.
The primary source that highlights the inadequacy of solid wall housing is The Environmental
Change Institute. This is demonstrated by the extensive report; 40% House (Boardman, et al.,
2005). This work describes transforming the existing housing stock as an enormous challenge
in terms of scale and cost, and states that there are limits to the improvements a building can
incorporate. As a result, the proposed strategy to achieve 80% emission reductions specifies
demolishing 3.2 million of the worst houses i.e. solid wall dwellings and replacing them with
efficient new builds. Refurbishment is included in the strategy, but only for newer houses
with superior building fabric performance. The report was carried out by the Environmental
Change Institute in collaboration with a number of universities and was funded by the Tyndall
Centre for Climate Change Research. The shortcomings of this report are that it does not
calculate the additional CO2 emissions generated by demolition and replacement new builds,
and no detailed analysis of the solid wall housing stock to accept refurbishment measures is
included in the report. This is essential when considering the trade‐off between demolition
and refurbishment.
The BRE report; Reducing carbon emissions from the UK housing stock (Shorrock, et al., 2005)
provides a credible examination of the potential of solid wall housing. The report estimates
the potential CO2 savings of refurbishment measures and their cost‐effectiveness by using
energy modelling software. It also models future emission scenarios and concludes that
insulative measures alone will not achieve the original UK Government target of a 60%
reduction. A significant take‐up of emerging technologies is also required. The report
estimates future uptake rates for refurbishment measures by using historic trends. It
concludes that refurbishment measures will require an unprecedented uptake rate in order to
achieve 60%. Although this is a very important issue, the report does not examine this further.
An examination of how to increase uptake rates is essential having established such a
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significant limitation. As with all future forecasts there is inevitably much scope for divergence
and the report acknowledges this. The report also lacks conclusiveness because high and low
capital costs are used to represent outright purchase costs and marginal costs. The result is a
large variance in what is actually deemed to be cost‐effective
Another study using energy modelling software was conducted in the report Thermal
Improvement of Existing Dwellings (Clarke, et al., 2005). The report includes an extensive
breakdown of the Scottish housing stock and features test studies of improvements to two
solid wall dwellings. The software was used to estimate the total CO2 reductions for a specific
dwelling type and was applied to the rest of that house type and ultimately the entire Scottish
housing stock. The conclusion was that a 50% reduction in CO2 emissions and energy use
would be possible. The strength of this work lies in the comprehensive analysis of the
dwellings’ construction, which leads to seemingly robust results; providing that the software
used is accurate. The limitation of this work is that the energy reduction figures stated may
not necessarily translate to English houses, because of the difference in climate between
Scotland and England (Met Office, 2010).
The previous reports have taken an academic perspective when evaluating refurbishment of
the solid wall housing stock. An additional method of research is beneficial (Knight, Ruddock,
2008) as it will provide a more robust appraisal of the potential of solid wall housing. As an
alternative to the theoretical framework used by the previous sources, Evidence on tackling
Hard to treat properties (Roaf, et al., 2008) is of particular use as it tackles solid wall housing in
a practical manner. It includes case studies, which are of significant value, as they represent
actual examples of refurbishment projects as opposed to hypothetical scenarios. The case
studies in this report demonstrate that substantial CO2 savings are available; however, certain
improvement measures are expensive so the payback period for the owner can be significant.
The work was produced for the Scottish Government by Heriot Watt University and SISTech
Ltd which is a not‐for‐profit research institute. As with Thermal Improvement of Existing
Dwellings the limitation of this work is that it was modelled around Scottish housing so energy
consumption and therefore the associated savings may be higher than possible in English
dwellings.
With the exception of work produced by the Environmental Change Institute, the previous
sources have demonstrated reasonable confidence in solid wall housing contributing to
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significant reductions. However, all have fallen short of 80%. The primary problem stated
throughout all the literature is uncertainty regarding the cost‐effectiveness of refurbishment
measures, and subsequently the feasibility of implementing a UK wide refurbishment
programme. This is further highlighted by Affordable Warmth in Hard to Heat Homes:
Progress report (Pett, 2004). This report is mostly concerned with Fuel Poverty, which is
predominantly caused by excessive heating costs because of poor performance of the building
fabric in solid wall homes (Pett, 2004). The report conducts a consultation with a wide variety
of experts and itemises the key barriers to treating solid wall homes and consequently
alleviating Fuel Poverty. The most significant barriers are: the cost of solutions, lack of
dedicated government funds and the awareness and disruption of homeowners and
occupiers.
The literature reviewed indicates that for the most part it is possible to decrease CO2
emissions by refurbishing solid wall housing. However, the most consistently stated problems
are the cost‐effectiveness of refurbishment measures and the feasibility of applying these
measures to the entire solid wall housing stock. Problems such as disruption to the occupants
and the lack of government funds have also been specified, although to a lesser extent.
It is these problems that have so far dictated the role that solid wall housing can play in
reducing CO2 emissions by 80%, and it is these problems that will ultimately decide the fate of
solid wall housing. This dissertation will explore these highlighted issues in greater depth. It
will also incorporate consideration of some new and generally untested technologies that
could offer a great step toward the 80% target. It must be noted that this dissertation will not
engage in the demolition versus refurbishment debate; it will aim to build on previous reports
and studies that identify refurbishment as the solution, but have not overcome the barriers to
its implementation. It will attempt to surmount the current barriers of high expense for little
carbon saving, and will consider solutions to increasing the uptake of refurbishment measures,
in order to determine what is required to achieve 80% emission reductions so to answer the
question; what role can solid wall housing feasibly play in reducing CO2 emissions by 80%?
Methodology
This dissertation will aim to answer the question, ‘What role can solid wall housing feasibly
play in reducing CO2 emissions by 80%?’ This question has been addressed by drawing from
the theoretical frameworks of Quantity Surveying and Building Surveying. It involved a
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quantitative analysis of the energy consumption of dwellings, i.e. how refurbishment
measures would affect the energy efficiency of dwellings and how the value of these measures
could be improved by lowering costs. The answer to this question was investigated through a
number of research methods. Modelling was employed by using an energy model in order to
substantiate the claims of existing case studies, and to simulate the different contributions
that solid wall housing could make to the Government’s reduction targets. There was also a
strong element of problem solving as it was necessary to consider systematically the main
barriers to implementing refurbishment of solid wall housing and specify solutions based on
the simulation outputs and existing secondary research in the form of academic reports,
surveys and technical literature.
The research starts with chapter two: the UK housing stock. This involves investigating the
amount of CO2 emissions that HTT housing currently contributes and the reductions that could
be achieved by the improvement measures currently considered to be cost‐effective. This
provides a basis of comparison which is required to place solid wall housing in context with
the rest of the housing stock.
Chapter three: improvement case studies, details the refurbishment case studies on which the
research is based. The case study method is particularly suited when testing a unique case or
concept, so is appropriate in this circumstance (Yin, 2003). All the measures that were applied
in the refurbishments were examined individually in order to determine how replicable they
are to other dwellings of that type. Additionally, underlying assumptions were specified and
justified. The case studies used were secondary data. The use of secondary data was
appropriate, as it provided a detailed in‐depth analysis of the problem (Naoum, 2009).
Furthermore, the data was generated and quality controlled by reliable sources; it would
make sense to utilise this data (Baxter, et al., 2006).
The weakness of case study based research is that the results of such investigations will to
some extent always be treated with a degree of circumspection because they rely on data
from a single case. It may be questionable how they can be generalised to other cases (Knight,
Ruddock, 2008). Consequently the relationships demonstrated can only be discussed
intellectually, as opposed to statistically when the sample is large (Naoum, 2009). However, in
order to limit the degree of circumspection and therefore promote a good theoretical starting
point i.e. if solid wall housing can effectively be refurbished to achieve CO2 reductions, a
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theory can be corroborated by repeatedly testing it, and finding that it is valid for a large
number of cases (Knight, Ruddock, 2008). Clearly, repeatedly renovating dwellings to
establish whether they can be effectively refurbished would not be practical or financially
viable. Consequently a legitimate alternative is to use simulation of a case, or concept to
validate theoretical predictions, where experimentation on the system under study would be
prohibitively expensive (Fellows, Liu, 2003).
The model chosen to simulate and confirm the results of the refurbishments was the domestic
energy model DEMScot which is introduced in chapter four DEMScot: Scotland’s domestic
energy model. The DEMScot model substantiates the assertion that the refurbishment
measures achieved the stated reductions, which achieves objective evaluation of the data
(Fellows, Liu, 2003). Furthermore, using DEMScot to simulate the refurbishments provided an
opportunity to verify the model’s outputs with reality (Fellows, Liu, 2003). This was essential
to provide confidence in the model. This chapter consists of a critique of the BREDEM
methodology and details the information and parameters that were applied to the model.
The CO2 reductions stated by the DEMScot model are also presented in comparison with the
original stated reductions in order to establish the differences that occur.
The cost of refurbishing dwellings was then considered in chapter five; cost, Value Carbon and
other limitations. The DEMScot model was also utilised as a tool to investigate the concept of
diminishing returns and an optimum level of refurbishment. This investigation was
experimental and quantitative in nature. An experiment is a situation in which an
independent variable is carefully manipulated by the investigator under known, tightly defined
and controlled conditions, with respect to a control point (Baxter, et al., 2006). The
refurbishment measures were the independent variable in this scenario and the CO2 emissions
were the dependent variable. The control point was the dwelling before refurbishment. This
method was the most suitable as a quantitative experiment is the only research design which
can in principle, yield causal relationships (Baxter, et al., 2006). Additional consideration was
also given to reducing costs, as cost is seen as one of the most substantial barriers to the
implementation of refurbishment programmes. This chapter also targets some of the
additional barriers associated with refurbishment. Solutions to these barriers were sought
from existing secondary research such as academic reports and surveys. Consideration of
further barriers was required as there are factors other than cost and technicality that affects
the feasibility of solid wall housing to contribute to the 80% emission reduction target. 7
Following this, the final chapter: conclusion begins with a reflection of the evidence presented
in the previous chapters. The individual objectives of each chapter were drawn upon to
provide an overall conclusion regarding the role that solid wall housing can play in the CO2
emission reduction target for 2050. The study was then completed by a collection of
recommendations that were deemed to be beneficial to the role of solid wall housing.
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Chapter two: the UK housing stock
Climate change
In 2004, the UK Government’s chief scientific advisor Sir David King stated that climate change
is the most severe problem the world faces today (King, 2004). International scientific
consensus states that changes to the global climate are taking place primarily because of the
increasing levels of anthropogenic greenhouse gases (IPCC, 2001). Greenhouse gases are
produced by burning fossils fuels to produce energy, the single most abundant greenhouse gas
being CO2 (Sturges, 2006). Greenhouse gases present in the earth’s atmosphere absorb
outgoing infrared radiation and cause additional heat to be retained in the atmosphere. This
greenhouse property of the atmosphere causes the surface of the earth to be warmer than it
would otherwise be and causes a change in the global climate (IPCC, 2001). In 2007, total
energy use by the UK amounted to 229.4 million tonnes of oil equivalent. Of this energy,
93.3% was derived from fossil fuels (Office of National Statistics, 2010).
In order to mitigate the effects of climate change, the UK Climate Change Bill aims to have
reduced total CO2 emissions by 80% in 2050. Currently there has not been a definitive target
allocated specifically to domestic energy; only an approximate figure of a 15% reduction in
CO2 emissions by 2020 for the total stock has been suggested (DirectGov, 2010). However, as
housing currently accounts for 27% of all UK emissions, a significant contribution to the overall
80% target must be made by improving the energy performance of housing.
Dwelling emissions
The Government’s Standard Assessment Procedure (SAP) is the tool used to monitor the
energy efficiency of homes. It is based on a home’s energy costs per m2 of floor area for
standard occupancy of a dwelling and a standard heating regime. It does not incorporate
geographical location; this allows buildings to be compared with others across the UK. The
energy costs take into account the costs of space and water heating, ventilation and lighting,
less cost savings from energy generation technologies. The rating is expressed on a scale of 1‐
100 and is presented in a banding system of G to A for Energy Performance Ratings. A
dwelling with a rating of 1 (band G) has poor energy efficiency and therefore high costs and a
dwelling with a rating of 100 (band A) represents zero net energy cost per year.
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Energy performance is strongly related to the age of a dwelling because of the development of
the Building Regulations (DCLG, 2010). Approximately 22% of the current housing stock was
built pre 1919; these dwellings have an average SAP rating of 40 and emit 9.0 tonnes of CO2 a
year. This can be compared with post 1990 homes which have an average SAP rating of 65
and emit 4.5 tonnes of CO2 a year, as demonstrated in table 1.
Total CO2 emissions for
the whole tenure (%)
% of housing
stock
% of housing
age that is HTT
Average SAP
Average CO2
per dwelling (tonnes/pa)
Total CO2 emissions for the
whole tenure (million
tonnes/pa) Pre 1919 40.4 9 43 29% 22% 89%
1919 ‐ 1944 45.5 7.2 27.8 19% 17% 47%1945 ‐ 1964 49.5 6.2 26.9 18% 20% 26%1965 ‐ 1980 52.4 5.7 27.3 19% 22% 27%1981 ‐ 1990 56.6 5.1 9.5 7% 9% 24%Post 1990 64.7 4.5 11.3 8% 11% 19%
All tenures 49.8 6.6 145.8 100% 100% 43%Table 1: Average SAP, CO2 and percentage of English housing by construction date (DCLG, 2009) (BRE, 2008b)
It is older housing which is most likely to be HTT. Of the 9.2 (43% of total stock) million HTT
homes in England, 5.91 million (65%) were built pre 1945 and a further 2.11 million (22%)
were built between 1945 and 1975 (BRE, 2008a). Solid wall dwellings make up the biggest
proportion with 6.6 million dwellings (31% of the total stock and 72% of the HTT stock). Off
the gas network dwellings make up the next biggest proportion with 2.8 million dwellings
(13% of the total stock and 30% of the HTT stock). There are also approximately 1.8 million
(8% of the total stock and 19% of the HTT stock) dwellings that have more than one HTT
characteristic so can be considered particularly problematic (BRE, 2008a). Dwellings of solid
wall construction suffer from high fabric heat loss which leads to high energy consumption.
It has been established that 20.2 million homes (91% of the total stock) in England could have
their emissions reduced cost‐effectively by refurbishment measures. Cost‐effective measures
alone would benefit 81% of HTT housing and would leave 1.7 million HTT dwellings unable to
receive any cost‐effective reductions (BRE, 2008a). Measures that are considered to be cost‐
effective are; installation or upgrade of loft insulation, installation of cavity wall insulation,
installation or upgrade of hot water cylinder insulation, upgrading central heating controls,
upgrading to a class A condensing boiler, upgrading storage radiators, installation of hot water
cylinder thermostats and replacement of warm air units where the original units are pre‐1998
(DCLG, 2009).
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The greatest scope for improvement is housing built between 1919 and 1980. This is because
of the highest numbers of unfilled cavity walls and in which loft insulation top‐ups and heating
control upgrades still have high potential. The least scope for improvement is in the most
recently built homes which already include more efficient measures in their design and
construction so already operate at a higher level of performance. HTT homes (predominantly
pre 1919) show relatively modest improvement potential because of the difficulty of applying
cost‐effective measures. As these dwellings have very high CO2 emissions to begin with,
reductions of 1.6 tonnes/year; from 9.0 to 7.4 tonnes/year are possible on average (DCLG,
2009). However, a HTT dwelling emitting 7.4 tonnes/year post refurbishment is still
unacceptable given that post 1990 dwellings currently emit 4.5 tonnes/year.
If all the cost‐effective improvement measures described previously were fully implemented,
CO2 emissions would fall on average by 1.5 tonnes/year for every home (DCLG, 2009). This
would result in an estimated total saving of 33 million tonnes of CO2; 22% of total English
housing stock emissions (DCLG, 2009). The approximate cost of carrying out these
improvements is £30 billion (2009 prices) which equates to an average expenditure of £1,500
for each of the 20.2 million homes that would benefit (DCLG, 2009). Although a 22% reduction
in emissions from housing is a considerable step towards the total overall UK reduction of
80%, it is insufficient. Reductions which are not made in housing will have to be made
elsewhere in the transport, industry, agriculture and service sectors. If an 80% reduction from
the housing sector is to be achieved, measures beyond those currently considered to be cost‐
effective must be implemented.
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Chapter three: improvement case studies
Cost‐effective improvement measures alone will only achieve a 22% CO2 reduction;
consequently refurbishment measures that achieve higher reductions are required. HTT
dwellings constitute 43% of the total housing stock and are responsible for emitting over half
of UK domestic emissions (BRE, 2008b). In order to establish what emission reductions can be
achieved by refurbishment of the solid wall stock and the associated cost, two refurbishment
case studies have been selected for analysis. The objective of this chapter is to consider each
of the refurbishment measures individually and evaluate how replicable they are to other
dwellings. Any assumptions that have been made will also be identified and justified. Both
projects have utilised similar, relatively innovative materials and equipment to achieve
substantial savings.
Aubert Park
The first solid wall refurbishment is 70a Aubert Park, Islington, London. This dwelling is a
Victorian ground floor terrace flat with 13" and 9" solid brick external walls, single glazed
timber sash windows and a floor area of 47m2. The property is not in a conservation area but
was not suitable for external insulation or replacement double glazed windows. The project
participants were United House and BRE. United house carried out the works and BRE were
utilised to independently assess the CO2 reduction results using SAP.
BRE and United House differ in their conclusion of the total CO2 savings for this refurbishment.
The difference in CO2 reductions is because of a lack of test data for the micro Combined Heat
and Power (CHP) unit that was newly installed, consequently BRE based their modelling
around a condensing boiler instead. As a result BRE calculated that CO2 reductions were 60%
and United House calculated that they were 70%. In order to maintain absolute neutrality the
data generated by BRE, the independent participant would preferably be used. However, the
BRE data will not used for three reasons. Firstly, considerably robust results by the Carbon
Trust relating to micro CHP test data suggests that United House’s calculations are very
realistic, this is discussed in depth later. Secondly, the opportunity to investigate innovative
technology should be maximised in order to break new ground. It would be unproductive to
repeat conventional practices and reiterate what has already been established by past
refurbishments. Thirdly, the differences between United House and BRE affect various
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calculations so results from both sources cannot be pooled, analysis is only possible if data
from one source is used. Consequently, the United House data will be used.
There was no CO2 reduction target for this refurbishment. Instead, a contractor‐led Value
Engineering approach was taken, which focused on maximising the carbon saving for every £
spent; this method has been given the name Value Carbon. This involved an extensive survey,
detailed analysis of the data and careful selection of the improvement measures. Value
Carbon is a suitable unit of measurement because it includes cost; therefore an element of
value is incorporated. Cost is a substantial barrier to improvement measures and therefore
must be considered (Pett, 2004); focusing on CO2 reductions alone would not provide this. No
renewable technologies were used, and the project also featured some innovative materials
and equipment that were used for the first time in the UK. The improvement measures are
displayed in table 2.
Measures
1) Low energy lighting
2) Draught proofing
3) Micro CHP gas boiler
4) Double glazing (vacuum)
5) Insulate external walls
6) Insulate floors
7) Mechanical Ventilation with Heat Recovery (MVHR)
8) Rainwater harvesting
9) Insulate thermal bridges
Table 2: Aubert Park improvement measures
Each of the measures listed in table 2 will now be expanded upon and analysed using technical
literature. The aim of this is to critically assess how replicable these measures are and
consider any irregularities in this project that would limit the ability of applying these
measures to other dwellings.
1) Low energy lighting
• Before refurbishment: incandescent throughout.
• After refurbishment: CFL low energy lighting installed throughout.
CFL bulbs can be used in almost all light fittings and significant savings can be made quickly
(Boardman, 2007). This improvement measure is applicable to all dwellings.
13
2) Draught proofing
• Before refurbishment: air tightness of 9.08 m3/hr/m2.
• After refurbishment: design air tightness of 5.0 m3/hr/m2.
Five individual air tightness tests were carried out to quantify individual leakage paths around
the flat. Cracks and gaps around service penetrations, windows and doors and floors were
sealed. Part L1A 2006 requires that new builds have a Maximum Air Permeability of < 10
m3/hr/m2 and best practice is considered to be 3 m3/hr/m2 (EST, 2005). Existing dwellings
have no requirement but can reach up to 25 m3/hr/m2 (EST, 2005).
The comprehensive draught proofing measures carried out on this flat were very effective; a
recent study showed that of 100 new dwellings tested for air tightness; only 3 achieved
5m3/hr/m2 (EST, 2005). The level of air tightness will obviously vary from dwelling to dwelling;
however, the benefits of draught proofing are significant across to all dwellings. Energy loss
due to ventilation accounts for approximately one fifth of space heating demand in older
dwellings and approximately one third of space heating demand in newer well insulated
dwellings (EST,2006a); a greater proportion of energy loss occurs from air leakage as insulation
increases (Jennings, 2006). Indicative average costs and associated CO2 savings for draught
proofing to a 3 bedroom semi detached dwelling were stated to be £100 for a 43kg CO2 saving
(DCLG, 2006). Based on the data that states very few dwellings achieve the best practice level
of air tightness, and therefore have scope for significant improvement, this improvement
measure will be considered to be as effective and applicable on other dwellings.
3) Micro CHP gas boiler
• Before refurbishment: Ideal Sprint F rated combination boiler (65% efficiency),
programmer and room thermostat, room sealed fanned flue.
• After refurbishment: Baxi Ecogen micro CHP (82% efficiency).
A micro CHP system produces both heat and electricity. This system is heat led so only
produces electricity when the heating system is in operation. This was the first unit to be used
commercially in the UK and as a result test data was not available at the time of assessment.
This resulted in two different sets of results being produced by BRE and United House. Data
determining the efficiency of the Ecogen is discussed further in chapter four: DEMScot,
14
Scotland’s domestic energy model. The Ecogen is wall hung and providing the system is
adequately sized for the dwellings heating demands, could be successfully integrated into all
dwellings (Baxi, 2010a).
4) Double glazing (vacuum)
• Before refurbishment: single glazed sash windows, U‐value 4.91 W/m2K
• After refurbishment: vacuum glazing to front facade only, average glazing U‐value 3.49
W/m2K (U‐value 1.19 W/m2K for windows with vacuum glazing, including frame)
Pilkington Energikare Legacy vacuum glazing is the first example of vacuum glazing that is
commercially available in the UK. The glazing was installed in the two living room windows to
the front of the dwelling. Sash windows usually cannot accommodate double glazed units as
the rebates in the glazing bars are not deep enough (Taylor, 1996). Pilkington Energikare is
intended for this application as the thermal performance can be improved whilst maintaining
a building’s historic façade. Replacement units like these may only be unacceptable in the
exceptional circumstance of the building being listed (Taylor, 1996). It is estimated that there
are 300,000 residential buildings listed as architecturally important (Boardman, et al., 2005).
Therefore, unless the dwelling is listed this measure will be applicable to all dwellings. The
box frame was retained and new sashes were installed to hold the glazing. Although BRE
states the old sashes could have been retained no allowance will be made to adjust the cost.
5) Insulate external walls
• Before refurbishment: solid brick, 225mm and 330mm thicknesses plus internal
partitions to unheated basement/corridor, average U‐value 1.19 W/m2K
• After refurbishment: Spacetherm Aerogel, 37mm to internal surfaces and Sempatap
flexible thermal lining magic wall paper to communal basement/corridor partition,
average U‐value 0.33 W/m2K
15
Figure 1: Cross section of Spacetherm Aerogel insulation board (Balson, 2009)
Lengths of 25mm battens were fixed to the internal surfaces of all exposed walls and
Spacetherm Aerogel insulation board with three layers of matting was fixed to the battens, a
25mm air gap was left between batten runs; figure 1. This was the first project in the UK to
use this material. Spacetherm is particularly appropriate for dwellings of smaller floor size
where the reduction of internal space must be minimal. Other insulation types may require a
layer up to 120mm thick to achieve the same thermal performance, therefore making internal
wall insulation impractical because of the loss of internal space (EST, 2006c). Internal wall
insulation would not be applicable to dwellings where the disruption to occupants and fixtures
would be too great, excessive thermal bridging would be difficult to avoid and in the
exceptional instance that the interior of the building is protected under a listed building order
(EST, 2006c). However, these exemptions are rare and theoretically internal wall insulation
could be applied to the vast majority of dwellings (BRE, 2008b). Although practically possible
in all dwellings, in reality there are other factors that limit its applicability. Further
consideration to the number of applicable dwellings will be discussed in chapter five Cost,
Value Carbon and other limitations. BRE states that because of a lack of experience in cutting
this material, wastage and therefore cost was high, however no attempt will be made to
adjust the cost for wastage, because the quantity is not known.
16
6) Insulate floors
• Before refurbishment: suspended timber floor, U‐value 0.72 W/m2K and concrete floor
in kitchen extension, U‐value 0.70 W/m2K
• After refurbishment: fully insulated timber floor, U‐value 0.45 W/m2K and no work
done to concrete floor.
Heat loss and air leakage were reduced by sealing off the cellar below the timber floor which
was too small to be used as a living space. The floor boards were removed and 100mm of
plaster was hacked off from the bases of the walls. A breathable airtight barrier was laid
across and between the joists and lapped up the base of the walls, the voids between the
joists were then filled with Warmcell fibre insulation and the floor boards were replaced. The
bases of the walls were re‐plastered with the airtight barrier sealed into the plaster, the new
skirting boards were then laid and gaps sealed.
BRE commented that this improvement measure was time consuming and it would also not be
possible to carry out while there were occupants present in the house because of health and
safety reasons relating to the fibre insulation. If the cellar had allowed freer access, an
alternative solution suggested by the BRE would be to leave the floor boards intact, board the
underside of the joists, and inject spray foam insulation between the joists. This method
would achieve comparable air tightness with less disruption, and a consistent fill between the
joists would offer significantly higher thermal performance. If access from above were the
only option, an alternative that would be possible with the occupants present would be to lift
the floor boards, drape a support netting over the joists and lay board or roll insulation on top
of the netting (EST, 2006c). Although the air tightness would be inferior, draughts from the
floorboards could be reduced by fixing large area boards over the top or replacing them with
moisture resistant chipboard with glued tongue and grooved joints. As demonstrated by the
above, suspended timber floors can be improved in practically all circumstances (EST, 2006c);
therefore improvement of the floors is deemed applicable in the vast majority of
dwellings.
7) Mechanical Heat Recovery Ventilation (MVHR)
• Before refurbishment: two extract fans
17
• After refurbishment: Vent Axia HRE‐350 MVHR system (89% efficiency)
The design air tightness of 5.0 m3/hr/m2 meant that mechanical ventilation could provide CO2
savings. The MVHR unit was installed in the kitchen, and a boxed in section was added to the
kitchen and living room, a lowered ceiling was installed in the hallway to distribute the
ductwork through the dwelling. BRE stated that the significant amount of labour involved in
installing the unit and the associated ductwork meant that it would be unfeasible to carry out
the work with the tenant in place. There were also additional air leakage paths created by the
installation of the ductwork in the kitchen that required sealing. This measure would only be
applicable to dwellings where a major refurbishment takes place because the costs are high
and an exceptional rate of air tightness must be reached in order for MVHR to provide carbon
savings (EST, 2006a).
8) Rainwater harvesting
• Before refurbishment: standard taps, bath and WC.
• After refurbishment: rainwater harvesting, Twyford Galorie Flushwise 4/2.6 litre dual
flush WC, Tapmagic inserts for taps, bath unchanged.
The water saving measures on this refurbishment were regarded as giving no carbon saving.
However, all the measures installed resulted in a 24% saving in water use. Although water
efficiency is a major goal in refurbishment as approximately 23% of CO2 emissions are from
hot water use (EST, 2010b), only the tap inserts would reduce the consumption of hot water.
Consequently because of the minor reduction in CO2, this measure will not be considered
when applying measures to other dwellings.
9) Insulate thermal bridges
• Before refurbishment: full assessment not undertaken, assumed Y‐value of 0.15
W/m2K.
• After refurbishment: full assessment not undertaken, retained Y‐value of 0.15 W/m2K.
The project scope did not allow for a detailed technical assessment of thermal bridging.
Without dedicated modelling, the affect on thermal bridging by improvement measures could
not be accurately assessed. Consequently no credit could be gained in SAP as a Y‐value of 0.15 18
W/m2K was used in both before and after models. However, effort was still made to reduce
bridging by targeting the party walls and bedroom windows reveals. A disadvantage of
internal wall insulation is that at the junction of the party wall with the external wall, cold
spots can occur. Internal insulation was returned along the party wall from its intersection
with the external wall, therefore reducing the temperature gradient. Voids behind the
window reveals were filled with mineral wool. Because of the complex nature and the
detailed data required to conduct thermal bridge modelling (Abdullatiff, 2003), there will be
no reductions made in the Y‐value when modelling other dwellings. Consequently the cost of
carrying out this work will not be included in other refurbishments.
Midmoor Road
The second solid wall refurbishment that achieved substantial savings was 46 Midmoor Road,
Balham, London. The dwelling is a Victorian 3 bedroom mid terrace with 225mm solid brick
walls. It is not in a conservation area and has a floor area of 99 m2. The project was carried
out by Family Mosaic housing association. It must be noted that SAP calculations for the
dwelling before the refurbishment were not available, only SAP data was available for the
dwelling after the refurbishment. Consequently, a SAP assessment was carried out using the
SAP manual (BRE, 2009) and the data that was available. U‐values before refurbishment for
some of the building elements have been assumed based on technical literature (BRE, 2001).
The default ventilation rates and electrical use have been taken from the SAP manual (BRE,
2009) and the English Building Regulations (DCLG, 2010). Furthermore, an assumption has
also been made for the specification of the heating system before refurbishment.
This is one of the weaknesses in study; the pre refurbishment data for Midmoor Road should
to some extent, be treated as indicative because of the assumptions that had to be made.
However, Family Mosaic achieved a 63% reduction in CO2 emissions from a refurbishment of
an identical dwelling on the same road the following month. The only difference between the
two dwellings was that 46 Midmoor achieved a less airtight envelope. Consequently, the CO2
savings were lower in 46 Midmoor Road because of a higher space heating requirement (EST
2006a).
This dwelling is unique in that it was converted into two 1 bedroom flats several years ago;
Family Mosaic converted the dwelling back to a 3 bedroom terrace in 2009. Consequently
19
there were works other than the energy efficiency measures involved in the project, such as
minor demolition and construction of partitions, and re‐joining of services. It must be noted
that the incorporation of other works would most likely result in a reduction in the cost of the
energy efficiency measures (BRE, 2001). The measures aimed at improving the energy
efficiency of the dwelling are displayed in table 3:
Measures
1) Low energy lighting
2) Draught proofing
3) Loft insulation
4) Micro CHP
5) Insulate external walls
6) Insulate timber floor
7) Insulate concrete floor
8) Mechanical Ventilation with Heat Recovery (MVHR)
Table 3: Midmoor Road improvement measures
Each of the measures listed in table 3 will be expanded upon and analysed using technical
literature to critically assess how replicable these measures are and any assumptions will be
detailed and justified.
1) Low energy lighting
• Before refurbishment: incandescent throughout.
• After refurbishment: CFL low energy lighting installed throughout.
CFL bulbs can be used in almost all light fittings and significant savings can be made quickly
(Boardman, 2007). This improvement measure is applicable to all dwellings.
2) Draught proofing
• Before refurbishment: air tightness unknown.
• After refurbishment: air tightness of 7.5 m3/hr/m2.
The draught proofing measures carried out achieved a good level of air tightness. However
the degree of improvement in not known as the air tightness before refurbishment is
unknown. The air change rate in this dwelling is higher than could have been achieved as two
chimneys and open flues were left vented after refurbishment. The redundant fire places
were bricked up and then vented; these vents contribute significantly to the air changes per
20
hour figure. The exact reason why these vents were left unsealed is unknown. However,
because the moisture levels in sealed chimneys increase rapidly, it is therefore recommended
that ventilation remains in redundant flues (Taylor, 2009). This may have been the rationale
when refurbishing this dwelling, although as a result, the space heating requirement was
increased because of these remaining ventilation points. As with Aubert Park, this
improvement measure will be considered to be as effective to other dwellings.
3) Loft insulation
• Before refurbishment: 50mm insulation, U‐value 0.22 W/m2K assumed
• After refurbishment: 270mm insulation, U‐value 0.14 W/m2K.
Sheets of 100mm insulation were laid between joists and a blanket of 170mm was laid above
joists. The thickness of insulation before refurbishment is unknown, although the price in the
bill of quantities is for 270mm. The assumption of 50mm has been made for two reasons.
Firstly, houses owned by housing associations such as Family Mosaic are much more likely to
have cost‐effective measures such as loft insulation utilised (DCLG, 2009); it would be very
rare for a housing association to let properties with no insulation in the loft. Secondly, the U‐
value of a loft with no insulation is 1.14 W/m2K (BRE, 2001); if this U‐value were included in
the model, a pre and post refurbishment comparison would show significant improvement in
energy consumption and, this would skew the actual CO2 savings resulting from the
refurbishment. This measure would be applicable to most other dwellings as 46% of all mid
terraces, including both HTT and non HTT would benefit from additional loft insulation (DCLG,
2009). Furthermore, only 6% of all solid wall houses have no loft to insulate (BRE, 2008b).
Consequently the measure will be deemed applicable to the majority of other dwellings.
4) Micro CHP gas boiler
• Before refurbishment: standard combination boiler (70% efficiency), assumed.
• After refurbishment: Baxi Ecogen micro CHP (82% efficiency), assumed.
A full replacement of the hot and cold water system was carried out on this dwelling.
Although the boiler present before refurbishment is unknown; an assumption of 70%
efficiency has been made based on the base case for solid wall dwellings (EST, 2006c). A
21
conventional gas boiler (87.3% efficiency) with hot water storage was specified for the
refurbishment as a solar panel was installed on the roof of the dwelling. As outlined
previously; renewable energy generation technology is beyond the remit of this dissertation.
This presents a difficult scenario as the specification of the heating system may be quite
different without the solar panel being included. Given that an entire boiler replacement was
required, an assumption has been made that without the solar panel in the specification, the
most likely replacement would have been a micro CHP. This assumption has been made based
on the current refurbishment project of 84 Midmoor Road where Family Mosaic have
specified a Baxi Ecogen micro CHP. The Ecogen unit was not commercially available when this
refurbishment originally took place (Baxi, 2010b), Family Mosaic suggest this may be the
future preference for their refurbishments. The Ecogen could be integrated into all dwellings
(Baxi, 2010a).
5) Insulate external walls
• Before refurbishment: 225mm solid brick, U‐value 2.1 W/m2K
• After refurbishment: Kingspan Kooltherm K17 dry lining board 32.5mm, U‐value 0.55
W/m2K
Boards of Kingspan Kooltherm were fixed to internal surfaces of exposed walls and chimney
breasts. Kooltherm, like Spacetherm, minimises internal space intrusion due to its minimal
thickness. Further consideration to the number of applicable dwellings will be discussed in
chapter five: cost, Value carbon and other limitations.
6 & 7) Insulate floors
• Before refurbishment: suspended timber floor; U‐value 0.72 W/m2K, and concrete
floor in kitchen extension; U‐value 0.70 W/m2K
• After refurbishment: fully insulated timber floor; U‐value 0.20 W/m2K, new concrete
slab laid on insulation; U‐value 0.24 W/m2K.
Floor boards were removed and netting was draped over the joists. New Rockwool insulation
was laid on top of the netting and new chipboard flooring was laid. The concrete floor in the
kitchen extension was completely broken out, a layer of insulation was then laid and a new
slab was poured. As with Aubert Park the suspended timber floor improvement is considered
22
to be applicable to other dwellings. However, the removal of the concrete slab would only be
possible in dwellings with an extension and cellar. Moreover, it is a considerably disruptive
process and would most likely not be possible if the occupants were present (EST, 2010b).
7) MVHR
• Before refurbishment: natural ventilation
• After refurbishment: Vent Axia MVHR system (86% efficiency)
The after‐refurbishment air tightness of 7.5 m3/hr/m2 meant that mechanical ventilation
would most likely not provide CO2 savings (EST, 2006a). Specifying MVHR was a poor decision
by the project team. This measure would only be applicable to dwellings where a major
refurbishment takes place because the costs are high and an exceptional rate of air tightness
must be reached in order for MVHR to provide carbon savings (EST, 2006a).
The refurbishment measures that were applied to both dwellings have been reviewed in order
to establish how applicable they would be to others. The majority of these measures could be
applied to all other dwellings of the same type, with the exception of the internal wall
insulation in some circumstances, the MVHR and the concrete floor insulation. The internal
wall insulation is an essential component of these refurbishments and without it the CO2
reductions would be much lower. This presents a significant barrier which will be fully
considered in chapter five: cost, Value Carbon and other limitations. The MVHR and concrete
floor insulation have a less significant bearing on the CO2 reductions which is demonstrated in
chapter five: cost, Value Carbon and other limitations. With the exception of the above, these
refurbishments are very applicable to others of that type. The next chapter will model these
case studies in order to verify the stated CO2 reductions.
23
Chapter four: DEMScot, Scotland’s domestic energy model
DEMScot configuration
Having established the applicability of the chosen case studies to other dwellings, the next
step is to strengthen reliability in the case studies using DEMScot. Furthermore using the
DEMScot model in comparison with SAP will give an opportunity to view where DEMScot
differs in its outputs. Any differences will be considered when using the model to generate
Value Carbon scenarios in chapter five: cost, Value Carbon and other limitations.
DEMScot was developed to allow the Scottish Government to see the impact of different
policy interventions aimed at reducing CO2 emissions from housing (Scottish Government
Social Research, 2010). The model was created in Microsoft Excel and draws heavily on
research from Scottish housing, CO2 emissions and economic determinants of carbon
emissions. The literature reviewed to develop the tool was extensive; 134 separate
references, all produced since 1999, the majority being released during the past two years.
The manual for DEMScot critiques the existing modelling tool used to determine emissions
and energy use from UK dwellings: BREDEM‐12. The DEMScot team state there are several
shortcomings in the BREDEM 12 methodology which is used for SAP that the DEMScot model
aims to address. These are: the difference in Scottish climate data, incorporating the latest
fuel cost data and accurate future energy costs, behavioural aspects such as chosen internal
temperature etc, accurate estimates of energy use by lighting, cooking and appliances and the
performance of renewable technologies. The following are the shortcomings stated by
DEMScot that are of particular relevance to the study of HTT dwellings.
The first critique is that the BREDEM method does not provide accurate and realistic estimates
of energy consumption, and carbon and other environmental emissions from lighting, cooking
and appliances. Despite minor modifications, algorithms for hot water consumption date
from the 1980’s; since then overall use has been affected by changes in equipment and
behaviour i.e. power‐showers and dishwashers etc. Although algorithms for lighting have
been updated in the 2005 revision of SAP, algorithms for electrical appliances in SAP also date
from the 1980’s, when the type and use of these appliances was much different i.e. low
ownership of PCs, no internet and plasma TVs (Scottish Government Social Research, 2010).
This stance is somewhat supported by literature that suggests electricity and lighting use has
risen sharply over the last 30 years, although, the same data states that this rise has been
24
partially offset by a fall in energy use from cooking (Shorrock, Utley, 2003). Recent research
has shown that SAP 2005 may under estimate overall CO2 emissions for lights and appliances
by up to 15% (Lowe, 2007). Additionally, this point was also picked up in technical papers
supporting SAP 2009, which recommended updating the equations for lights, appliances and
associated gains, and water heating (Henderson, 2009).
Secondly, the method does not accurately model badly heated homes by the fuel poor i.e. HTT
dwellings. BREDEM uses the two‐zone model with a temperature difference in the main living
area and the rest of the dwelling. It also assumes that dwellings are adequately heated and
that the heating system is adequately sized. DEMScot states that these assumptions can be
considerably inaccurate, and can have a significant impact on the dwellings’ energy
consumption. In respect of the outputs from BREDEM; space heating energy use in older
dwellings can be overestimated because old dwellings are often heated to a lower
temperature than modern ones; a compromise between running costs and thermal comfort
on the part of the occupants of older dwellings (Scottish Government Social Research, 2010).
The DEMScot model has three components that were adjusted to model the refurbishments: a
Building stock database, a Building physics model and Factors under occupant control. The
building stock database contains the physical parameters considered to have the most impact
on the performance of dwellings i.e. dwelling age, wall construction, building form, dwelling
size, heating system and the number of floors. The model also allows for specific selection
and modelling of HTT dwellings. Two solid wall dwellings were added to the database for
Aubert Park and Midmoor Road with all the characteristics and physical parameters of the
dwellings.
The building physics model contains extensive data and formulae to calculate energy
consumption and emissions. The DEMScot team updated the methodologies for calculating
lighting, small power, cooking and water consumption in respect of the inadequacies
previously highlighted in the BREDEM model. The updated methodology accounts more
realistically for the number of occupants, behaviour and increased use of power over time.
The building physics model also contains climate data, allowing required consumption of
energy for space heating and lighting to be derived more accurately. The default mean
external temperatures, annual heating degree days, monthly solar radiation and declination
25
were based on averages for East Scotland. In order to model the refurbishment case studies
accurately the climate data had to be adjusted. The DEMScot model has the option to select
mean external temperatures for the Thames area, so these were selected. Annual heating
degree days were adjusted to the 20 year averages for Greater London obtained from the
Oxford Environmental Change Institute (Oxford Environmental Change Institute, 2010).
Consideration was given to the fact that mean annual temperatures in South East England
have increased by 0.78°C based on 1961 – 1990 and 1991 – 2004 averages, and annual heating
degree days have decreased by 13.9% since 1961 (Perry, 2006). However, a year to year
analysis of climate data demonstrated that there can be a significant variance in temperatures
and degree days. To avoid the risk of distorted outputs from the model, data for a 20 year
average was chosen.
Monthly solar radiation data for London was obtained from NASA’s Atmosphere Science Data
Centre (NASA, 2010). Monthly solar declination data for London was obtained from the US
Department of Commerce, National Oceanic & Atmospheric Administration: Earth System
Research Laboratory (National Oceanic & Atmospheric Administration, 2010). In order to
evaluate the accuracy of the data collected for the London climate, the Scottish climate data
present in the DEMScot model was compared with the outputs for the Scottish climate from
the above sources. The data was found to be accurate to one decimal place.
The Factors under occupant control component involves modifications to ventilation rates, hot
water and electricity use. This accounts for lifestyle and habits of the occupiers. The model
can also be manipulated to account for changes in behaviour as occupants become more or
even less conscious of their CO2 emissions. Occupants are divided into low, medium and high
users; the split is 30%, 40% and 30% respectively. This element was adjusted to 100% medium
users; the assumptions made by the Scottish Government for medium use behaviour remain.
DEMScot and SAP outputs ‐ Aubert Park
Detailed data for the Aubert Park dwelling before refurbishment such as the construction
materials, areas of the building elements, U‐values, plan shape efficiency, ventilation and air
infiltration rates and the heating system were entered into the DEMScot housing database and
a simulation was run. The results of the simulation are shown in table 4.
SAP (BRE & United House)
DEMScot DEMScot Energy requirements (kWh pa)
(1 occupant) (2 occupants)
26
Space heating* 11,912 10,531Hot Water* 4,310 5,205Cooking 544 635Gas consumption SAP items 18,096 16,222 15,736
Gas consumption from all items 16,766 16,371
Appliances 1,772 2,152Cooking 310 362Lighting* 259 314Pumps and fans* 196 196Electric consumption SAP items 596 455 510Electric consumption all items 2,537 3,024 CO2 emissions from SAP items (tonnes pa) 3.80 3.34 3.27CO2 emissions from all items (tonnes pa) 3.80 4.32 4.45
* SAP items
Table 4: Aubert Park before refurbishment, SAP and DEMScot outputs
Table 4 demonstrates a definite divergence between both DEMScot outputs and SAP in gas
and electric consumption. The DEMScot outputs are lower than SAP. Gas consumption is
lower by 10% and 13%, and electric by 14% and 24% depending on the number of occupants.
SAP calculations are based on standard occupancy and climate data, and regulated use of
heating, hot water, lighting and ventilation systems (DECC, 2010b). As SAP does not account
for behavioural savings, outputs can be compared across the UK. Conversely, DEMScot
requires defining the number of occupants per dwelling; this dictates the amount of
consumption as demonstrated by table 4. Data for Aubert Park after refurbishment were
entered into the model and a simulation was run. The results of the full refurbishment are
shown in table 5.
SAP (BRE)
SAP (United House)
DEMScot DEMScot Energy requirements (kWh pa)
(1 occupants) (2 occupants)
5,248 4,626Space heating* 1,789 2,498Hot Water* 544 635Cooking
6,710 7,500 7,037 7,124Gas consumption SAP items 7,581 7,759Gas consumption from all items 1,772 2,152Appliances 310 362Cooking 65 78Lighting* 284 284Pumps and fans*
484 484 349 362Electric consumption SAP items 2,431 2,876Electric consumption all items
n/a 900 844 845Electric generated by micro CHP*
1.51 1.14 1.03 1.06CO2 emissions from SAP items (tonnes pa) 2.01 2.24CO2 emissions from all items (tonnes pa)
27
* SAP items only
**Deducted from CO2 emissions
Table 5: Aubert Park after refurbishment, SAP and DEMScot outputs
Table 5 demonstrates that again there is a definite divergence for gas and electric
consumption between both DEMScot and the United House SAP estimates. The DEMScot
outputs are lower than SAP. Gas consumption is lower by 6% and 5%, and electric by 28% and
25%, depending on the number of occupants. There is also a significant variation in the gas
consumption and associated CO2 emissions between the two SAP analyses. This is because of
the Baxi Ecogen CHP unit. The Ecogen is a new product that is not commercially available till
spring 2010; Aubert Park was the first project to use the unit in a dwelling. Because of the test
data for the Ecogen not being available at the time of the BRE SAP analysis, BRE based their
SAP calculations on a class A condensing boiler (91% efficiency) and overall CO2 reductions
were calculated to be 60%. BRE stated that Baxi have since provided indicative data that
suggests overall CO2 reductions could have been 70% with the micro CHP. United House
included the micro CHP unit based on Baxi’s indicative data and consequently their
calculations produced a 70% reduction in overall CO2. DEMScot calculates CO2 reductions at
69% and 68% for one and two occupants respectively.
DEMScot and SAP outputs ‐ Midmoor Road
The full details of Midmoor Road were entered into DEMScot and a simulation was run, the
results are shown in table 6.
DEMScot (2 occupants)
DEMScot (3 occupants)
DEMScot (4 occupants)
Energy requirements (kWh pa) SAP
Space heating* 28,573 26,670 24,974 23,876Hot Water* 3,507 3,851 4,676 5,502Cooking 631 721 811Gas consumption SAP items 32,080 30,521 29,650 29,378Gas consumption from all items n/a 31,152 30,371 30,189 Appliances 2,964 3,755 4,546Cooking 359 410 462Lighting* 932 437 554 671Pumps and fans* 214 214 214 214Electric consumption SAP items 1,146 651 768 885Electric consumption all items n/a 3,974 4,933 5,893 CO2 emissions from SAP items (tonnes pa) 6.71 6.20 6.08 6.07CO2 emissions from all items (tonnes pa) n/a 7.71 7.97 8.34 * SAP items only
28
Table 6: Midmoor Road before refurbishment, SAP and DEMScot outputs
Similarly to Aubert Park, table 6 demonstrates a definite divergence between both DEMScot
outputs and SAP in gas and electric consumption. The DEMScot outputs are lower than SAP.
Gas consumption is lower by 5% to 8% and electric by 43% to 23%, depending on the number
of occupants. Data for Midmoor Road after the refurbishment were entered in DEMScot and
a simulation was run, the results of the full refurbishment are shown in table 7.
DEMScot (2 occupants)
DEMScot (3 occupants)
DEMScot (4 occupants)
Energy requirements (kWh pa) SAP
Space heating* 11,501 10,532 9,737 9,000Hot Water* 2,994 2,480 3,184 3,889Cooking 631 721 811Gas consumption SAP items 14,495 13,012 12,921 12,889Gas consumption from all items n/a 13,643 13,642 13,700 Appliances 2,964 3,755 4,546Cooking 359 410 462Lighting* 441 109 138 168Pumps and fans* 488 488 488 488Electric consumption SAP items 929 597 626 656Electric consumption all items n/a 3,920 4,791 5,664 Electric generated by micro CHP* 1739 1561 1550 1546 CO2 emissions from SAP items (tonnes pa) 2.22 1.89 1.89 1.90CO2 emissions from all items (tonnes pa) n/a 3.41 3.79 4.01
* SAP items only
**Deduction from overall figure Table 7: Midmoor Road after refurbishment, SAP and DEMScot outputs
Again similarly to Aubert Park, table 7 demonstrates that there is a marked divergence of gas
and electric consumption between both DEMScot and the United House SAP estimates. The
DEMScot outputs are lower than SAP. Gas consumption is lower by 12% to 11%, and electric
by 36% to 29%, depending on the number of occupants. SAP calculates the overall CO2
reduction to be 67% and DEMScot calculates the overall reduction to be 70% and 69% for two,
three and four occupants respectively.
Evaluation of the model’s outputs
For both dwellings, the DEMScot outputs are lower than SAP for gas consumption, both before
and after refurbishment. However the lower outputs are markedly lower before
refurbishment. This supports the DEMScot comments that SAP overestimates heating in badly
heated HTT homes owing to the effects of fuel poverty, as after refurbishment the owners
29
would no longer suffer fuel poverty so presumably their heating requirements would not be in
effect capped. The primary reason for the overall lower outputs in gas consumption appears
to be because of the climate data. DEMScot’s climate data was changed from the default
settings of East Scotland to Greater London in order to model Aubert Park and Midmoor Road
accurately. SAP’s climate data is based on mean external temperatures for all of the UK. The
mean external temperature in Greater London is lower than East Scotland (Met Office, 2010)
(Scharmer, Greif, 2000), therefore the internal heating demand would be decreased
(Mavrogianni, 2009).
In order to test this, a sensitivity analysis was carried out by modelling both case studies with
climate data for East Scotland; this is the default climate setting for the model. The result was
that the overall percentage of CO2 reduction was the same as when the climate data for
London was used. However, the space heating requirements increased so that the gas
consumption was higher than in the SAP estimates. This suggests that the reason for the
overall lower outputs is primarily because of the climate data being changed to Greater
London.
One significant difference in the modelling results concerns lighting. DEMScot’s estimate of
electricity use after low energy lighting has been installed, is significantly lower than that of
SAP. The greater reduction produced by the DEMScot model is supported by data from the
Energy Saving Trust, which states that low energy lighting can save up to 80% of the electricity
used by standard lighting (EST, 2010a). However, the difference in electric use has a
substantial impact on the average CO2 reduction; if the DEMScot lighting consumption
calculation was substituted, the overall CO2 reductions in SAP for the Midmoor Road
simulation would increase from 67% to 70%. With the exception of lighting, the DEMScot
outputs are very close to SAP’s.
Overall, the SAP and DEMScot simulations calculated a CO2 reduction of 68% to 70% for
Aubert Park, and 67% to 70% for Midmoor Road. Although this differs from SAP slightly, the
DEMScot model was designed to account for inadequacies in the SAP methodology, so by
virtue of its purpose the outputs would differ to some extent. The major contributor to these
savings is the Baxi Ecogen micro CHP. Its influence is demonstrated in the Aubert Park
simulation where the incorporation of the Ecogen resulted in an additional 10% CO2 reduction.
30
The Ecogen unit
Such a reduction in CO2 is significant and therefore must be examined and verified. The
Carbon Trust is currently conducting one of the most comprehensive field trial assessments of
micro CHP systems, with interim results released in 2007. The Ecogen unit was not included in
the trial; however the report contained two important factors relating to the overall carbon
performance of micro CHPs when compared with condensing boiler systems. Firstly, as the
heat the demand increases, the likelihood of CO2 savings increases because more electricity is
generated. At low heat demands of less than 6000 kWh pa micro CHPs and condensing boilers
are generally indistinguishable. However, with heat demands of more than 12,000 kWh pa
there is a statistical likelihood that micro CHP systems will outperform condensing boilers.
Consequently micro CHP units are most appropriate and beneficial for houses with higher heat
demands of over 20,000 kWh, such as larger houses with 3 bedrooms or more and older
houses i.e. solid wall houses. In this capacity typical savings are expected to range from 5% to
10% (Carbon Trust, 2007). The BRE referred to the results of the Carbon Trust’s trial and
implied that the Ecogen unit may not be fully utilised in a dwelling of lower heat demand like
Aubert Park. The second factor is that current micro CHP units typically need to operate for a
minimum cycle of over one hour to provide an overall CO2 saving benefit relative to a
condensing boiler (Carbon Trust, 2007). If appropriate use was adopted benefits could be
realised.
In Aubert Park’s case, the heating demand had been significantly reduced by improvement
measures to the building envelope, resulting in space heating and water demand reducing
dramatically to approximately 6000 kWh pa. In spite of this, the Ecogen is a new product that
claims unprecedented efficiency, and production of 1 kWh of electricity during a period of
heat demand (Baxi, 2010b). Allowing for this exceptional efficiency and the new heating
controls that were installed in the dwelling, it is conceivable that the Ecogen could be capable
of producing an increased saving relative to a condensing boiler. United House used an
efficiency figure of 82% in their calculations. Baxi now state an efficiency of 92% (Baxi, 2010a).
To provide a basis for comparison and to avoid a potentially optimistic efficiency figure, an
efficiency of 82% was used in the DEMScot model.
The Ecogen’s influence is increased further because of the carbon bonus for electricity
generated and returned back to the grid. The carbon intensity for gas and electric used in
31
dwellings is 0.194 kg CO2/kWh and 0.422 kg CO2/kWh respectively. The current SAP
methodology allows micro‐generated electricity to displace grid emissions at 0.568 kg
CO2/kWh, while grid electricity consumption has a carbon intensity of 0.422 kg CO2/kWh (Cole,
2008). The 0.422 kg CO2/kWh figure is based on the Government’s long‐term projections for
the average mix of grid electricity from 2005 to 2010. The 0.568 kg CO2/kWh figure is based
on the 1998–1999 marginal mix of generating plant plus a factor to account for new build
from 2005 to 2010, assuming that it would be combined cycle gas turbines (Bergman, et al.,
2010). Because of this, the figure is contentious and has been challenged (Bergman, et al.,
2010). It is likely that the 0.568 kg CO2/kWh will revised in later editions of SAP (Bergman, et
al., 2010)
This is a potential weakness in the study. Because of the carbon bonus for electricity returned
to the grid, refurbishments can claim high savings. If the long term average grid‐mix
assumption of 0.43 kg CO2/kWh is used instead, the relative CO2 benefits of CHP would reduce
accordingly (Carbon Trust, 2007). The DEMScot model avoids the possibility of inflated
reductions as the carbon intensity of CHP generated and returned electricity is the same as
the grid; 0.422 kg CO2/kWh, consequently the actual carbon savings generated by the
DEMScot model for Aubert Park are 1.16 and 1.18 tonnes of CO2 pa for 1 and 2 occupants
respectively. However, in order for a direct comparison to the SAP data, the 0.568 kg
CO2/kWh figure has been used in the DEMScot outputs shown in tables 5 and 7.
It has been confirmed that with the correct types of materials and heating systems utilised,
savings of up to 70% can be made from two types of solid wall dwellings. The next chapter
will consider the costs that are incurred in order to achieve savings of this magnitude.
Moreover, given that up to a 70% reduction in CO2 can be made by employing all of the
measures in these dwellings, the next chapter will seek to examine at what reductions can be
made by employing fewer measures and at what point does the financial investment of these
measures begin to yield lower returns in terms of carbon.
32
Chapter five: cost, Value Carbon and other limitations
The previous chapter has established what reductions are practically feasible for two types of
solid wall dwellings. The objective of this chapter is to examine the additional barriers that
were highlighted in chapter 1: introduction. It will consider the barrier of cost and investigate
the optimal point of refurbishment. Furthermore, it will also consider some of the wider
issues that affect the feasibility of solid wall housing in contributing to 80% reductions. All
these issues must be examined in order to determine the true potential of solid wall housing.
Total cost and value
Aubert Park and Midmoor Road achieved CO2 savings in the order of 68% to 70% and 69% to
70% for a total capital cost of £21,190 and £18,210 respectively at 2009 prices. It must be
noted that Aubert Park does not necessarily represent the average converted flat. The
average converted flat in England produces 5.8 tonnes of CO2 pa, has a floor area is 66m2, and
an average SAP rating of 44 (DCLG, 2009). Aubert Park produced less CO2 emissions and had a
smaller floor area; although it had a higher SAP rating before refurbishment, making it harder
to achieve higher savings than other dwellings with low SAP ratings (DCLG, 2009). Additionally
the average medium to large terrace produces 5.8 tonnes of CO2 pa, has a floor area of 94m2,
and an average SAP rating of 50.4 (DCLG, 2009). Midmoor Road had higher CO2 emissions, a
larger floor area, and a lower SAP rating before refurbishment making it easier to achieve
higher savings than other dwellings with higher SAP ratings (DCLG, 2009)
It would be improvident to adopt an all‐encompassing approach and presume all of these
dwellings could achieve the same level of CO2 reductions for the same cost. However, a rough
order of magnitude case will be presented. Of the 6.599 million solid wall dwellings in
England, approximately 490,000 are converted flats and 1.094 million are mid‐terraces (DCLG,
2009). If all 490,000 flats and 1.094 million mid‐terraces were refurbished to the same
specification as Aubert Park and Midmoor Road, the cost would be £10.4 and £19.91 billion
respectively, which is clearly a substantial sum of money. There are currently a small number
of major sources of funding and loans available to homeowners and occupiers. The two most
significant are the Carbon Emissions Reduction Target scheme, which has available funding of
£1.5 billion (Jenkins, 2010), and the interest free UK Energy Efficiency Home Loan which has a
total of £700 million allocated per annum.
33
The cost of refurbishing existing dwellings is seen to be one of the key barriers to home
owners implementing refurbishments (Pett, 2004). In light of this it seems essential to
investigate the relationship between expenditure and CO2 savings in order to maximise value.
This concept was integrated into the design phase of the Aubert Park refurbishment, and is
very similar to the process of Value Engineering; the name given to this approach is Value
Carbon. Value Carbon is a unit that illustrates the cost for every kg of CO2 saved, the lower the
lower the figure, the more cost‐effective the refurbishment measure is.
Value Carbon ‐ Aubert Park
The Aubert Park refurbishment measures were simulated individually in DEMScot in order to
determine their separate carbon savings so that a Value Carbon figure could be established.
The results are presented in table 8.
Value Carbon (£/kg)
Installed cost Carbon saved (kg CO2)
Measures
0.57 1) Low energy lighting £40 70
6.23 2) Draught proofing £650 104
2.85 3) Micro CHP gas boiler £4,800 1685
11.90 4) Insulate external walls £6,100 513
28.90 5) Double glazing (vacuum) £600 21
31.32 6) Insulate floors £3,700 118
78.80 7) MVHR £6,300 80
n/a 8) Rainwater harvesting £1,000 0
n/a 9) Insulate thermal bridges £2,000 0
Table 8: Aubert Park refurbishment measures, Value Carbon
As table 8 shows, there is a large variance in the cost and effectiveness with a 79:1 difference
between the most and least effective measures. Following this, measures were grouped into
incremental improvements based on their Value Carbon figure and the ease with which they
could be applied to a dwelling. Increment 1 consists of measures 1) and 2), increment 2
consists of measures 1) to 3), increment 3 consists of measures 1) to 5), increment 4 consists
of measures 1) to 6), and increment 5 consists of all measures that had an effect on CO2
reduction. The increments were modelled as one package; the reduction in consumption is
shown in table 9.
Increment 1
Increment 2
Increment 3
Increment 4
Increment 5
Saving (kWh pa)
Space heating 385 1,947 4,803 5,422 5,905Hot Water 0 2,707 2,707 2,707 2,707Cooking 0 0 0 0 0
34
Appliances 0 0 0 0 0Cooking 0 0 0 0 0Lighting 236 236 236 236 236Pumps and fans 0 ‐20 ‐20 ‐20 ‐88 Electric generated by micro CHP 0 1,318 987 902 845Gas consumption 385 4,654 7,510 8,129 8,612Electric consumption 236 216 216 216 148 Reduction in CO2 (tonnes pa) 0.17 1.74 2.11 2.18 2.21Total % saving 5% 53% 65% 67% 68%Cost (£) £690 £5,490 £12,190 £15,890 £22,190 Overall CO2 emissions (tonnes pa) 3.09 1.53 1.16 1.09 1.05
Table 9: Aubert Park incremental improvements
Table 9 shows that for relatively low cost, substantial reductions in CO2 emissions can be
made, a total of 1.74 tonnes of CO2 (53%) for £5,490. It also shows that there are two
significant jumps in the CO2 reductions; increment 1 to 2 because of the micro CHP and
increment 2 to 3 because of the solid wall insulation. After these measures have been applied
there is severely diminished carbon saving potential. This is better illustrated by figure 2.
Value Carbon Analysis ‐ Aubert Park
Increment 1
Increment 2
Increment 3
Increment 4
Increment 5
£‐
£2,000
£4,000
£6,000
£8,000
£10,000
£12,000
£14,000
£16,000
£18,000
£20,000
£22,000
£24,000
0% 10% 20% 30% 40% 50% 60% 70% 80%
Reduction in CO2 (%)
Cost (£
)
SAP CO2
Grid CO2
Figure 2: Aubert Park Value Carbon Analysis graph
35
Figure 2 demonstrates the payback in terms of CO2 reductions for each £ spent. The curve is
similar to an exponential growth curve; after increment 2 the curve becomes dramatically
steeper, following increment 3 the carbon saved is minimal and the cost is high. The SAP CO2
curve is based on the carbon intensity of electricity returned to the grid based on the SAP
methodology of 0.568 kg CO2/kWh. The Grid CO2 is based on the carbon intensity of
electricity returned to the grid based on the long term average grid‐mix assumption of 0.43 kg
CO2/kWh. This has been added in respect of the criticism it has received and the likelihood
that it will be revised in future versions of SAP (Bergman, et al., 2010).
Value Carbon ‐ Midmoor Road
The Midmoor Road refurbishment measures were simulated individually in DEMScot in order
to determine their separate carbon savings so that a Value Carbon figure could be established.
The results are presented in table 10.
Value Carbon (£/kg)
Installed cost Carbon saved (kg CO2)
Measures
1) Low energy lighting 0.68 80 118
2) Draught proofing 1.32 310 234
3) Loft insulation 7.50 1,050 140
4) Micro CHP 2.69 6,000 2,231
5) Insulate external walls 2.38 4,300 1,805
6) Insulate timber floor 12.56 2,050 163
7) Insulate concrete floor 24.49 2,100 86
8) MVHR 2,400 ‐49 ‐48.51
Table 10: Midmoor Road refurbishment measures, Value Carbon
Table 10 shows a less dramatic variance in the cost and effectiveness in comparison with
Aubert Park, with a 25:1 difference between the most and least effective measures.
Additionally it shows that the MVHR was detrimental to the carbon reductions. The MVHR
saved energy by reducing space heating demand as a portion of the dwellings heat was
recovered. However, the electricity used in operating the ventilation system’s fans offset this
saving. Energy savings are only realised in airtight properties (<5m3/hr/m2 at 50Pa) where
almost all ventilation air passes through the heat exchanger (EST, 2006a). This dwelling had
only achieved an air tightness of 7.5m3/hr/m2 at 50Pa because the chimneys were vented.
Following the calculation of table 10, measures were again grouped into incremental
improvements based on their Value Carbon figure and the ease with which they could be
applied to a dwelling. Increment 1 consists of measures 1) and 2), increment 2 consists of 36
measures 1) to 4), increment 3 consists if measures 1) to 5), increment 4 consists of measures
1) to 7), and increment 5 is the full upgrade and consists of all measures. The increments were
modelled as one package and the reduction in consumption is shown in table 11.
Increment 1
Increment 2
Increment 3
Increment 4
Increment 5
Saving (kWh)
Space heating 1,348 5,357 13,880 15,200 15,225Hot Water 0 1,492 1,494 1,494 1,494Cooking 0 0 0 0 0 Appliances 0 0 0 0 0Cooking 0 0 0 0 0Lighting 416 416 416 416 416Pumps and fans 0 ‐75 ‐75 ‐75 ‐199
Electric generated by micro CHP 2,734 1,712 1,542 1,550Gas consumption saving 1,348 6,849 15,374 16,694 16,719Electric consumption saving 416 341 341 341 217 Reduction in CO2 (tonnes pa) 0.44 3.03 4.10 4.26 4.22Total % saving 7% 50% 67% 70% 69%Cost (£) £390 £7,440 £11,740 £15,890 £18,210Overall CO2 emissions (tonnes pa) 5.64 3.05 1.98 1.82 1.86
Table 11: Midmoor Road incremental improvements
Table 11, like table 9, shows that for a relatively low cost, substantial reductions in CO2
emissions can be made, a total of 3.03 tonnes of CO2 (50%) for £7,440. It also shows that
there are two significant jumps in the CO2 reductions; increment 1 to 2 because of the micro
CHP and increment 2 to 3 because of the solid wall insulation. After increment 3 has been
applied there is a severely diminished carbon saving potential and the cost is high. This is
better illustrated by figure 3.
37
Value Carbon Analysis ‐ Midmoor Road
Increment 1
Increment 2
Increment 3
Increment 4
Increment 5
£‐
£2,000
£4,000
£6,000
£8,000
£10,000
£12,000
£14,000
£16,000
£18,000
£20,000
0% 10% 20% 30% 40% 50% 60% 70% 80%
Reduction in CO2 (%)
Cost (£
)
SAP CO2
Grid CO2
Figure 3: Midmoor Road Value Carbon Analysis graph
Figure 3 demonstrates the payback in terms of CO2 reductions for each £ spent. Between
increments 1 and 3, the curve is almost linear, following increment 3 the gradient changes
radically and there is very little carbon saving for a relatively high cost. The difference in the
gradient between increments 1 and 3 in the two dwellings is primarily because of cost. Aubert
Park and Midmoor Road achieved 53% and 50% CO2 reductions by increment 2, and
reductions of 65% and 67% by increment 3 respectively. However, by increment 2, Aubert
Park and Midmoor Road had cost £5,490 and £7,440, and by increment 3 they had cost
£12,190 and £11,740 respectively. This difference in cost is because Midmoor Road included
£1,050 of loft insulation in increment 2, and the installation of the micro CHP cost £1,200
more because of additional plumbing work. Contrast this with Aubert Park, where in
increment 3 the solid wall insulation had cost £1,400 more and glazing had been included at a
cost of £600.
38
Optimum refurbishment
The data illustrates that for different dwellings with somewhat different refurbishment
measure requirements, the gradient of the Value Carbon curve can vary. However, in both
cases there was a critical tipping point whereby additional measures were costly and provided
little carbon saving in return. This invites the question of what might be the optimum level of
refurbishment. This issue has been given little consideration in previous reports and studies,
perhaps because most HTT refurbishments have only achieved reasonable but not exceptional
reductions (Energy Efficiency Partnerships for Homes, 2004). One report has considered this
concept and specifies costs in the region of £6,500 per dwelling (WWF, 2008). However, close
inspection reveals that the study relies on radical decarbonisation of the national grid to a
carbon intensity less than half of the current carbon intensity (Ecotricity, 2010); this is not
included in the costs. Numerous sources agree that decarbonisation of the nation grid is
essential to achieve the required CO2 reductions (EST, 2006c) (Lowe, 2007), but it is not
guaranteed to happen (EST, 2008). Consequently, the refurbishment measures specified in
this report would only achieve a 31% reduction in CO2 emissions if the nation grid was not
decarbonised (WWF, 2008).
With the introduction of micro CHPs and innovative insulation, there is the opportunity to
achieve significant reductions in solid wall dwellings beyond what has been achieved in
previous refurbishments. However, pursuing maximum reductions without considering the
obvious diminishing returns demonstrated by the previous data would not necessarily provide
the best option in terms of cost and CO2.
Given that the cost of refurbishment measures is regarded as a substantial barrier, the
opportunity cost of the finance required to refurbish dwellings must be given adequate
attention. For example, Aubert Park can achieve a 53% (1.74 tonnes) CO2 reduction for
£5,490, 65% (2.11 tonnes) for £12,190 and 68% (2.21 tonnes) for £22,190. Consequently, it
would be more cost and carbon effective to refurbish 70a, 70b and 70c Aubert Park to each
achieve a reduction of 53%, therefore resulting in total reduction of 5.22 tonnes for £16,470,
as opposed to refurbishing 70a alone to achieve a reduction of 68%, therefore resulting in a
total reduction of 2.21 tonnes for £22,190. The same principle also applies to Midmoor Road.
This trade‐off analysis would be required for each individual case, as the diversity of the UK
stock means that there is no standard refurbishment package for a dwelling. The same
39
measures could be applied to different dwellings and achieve different CO2 reductions for
different costs (Jenkins, 2010). However, the diminishing returns are evident in both the case
studies and almost certainly would apply to other dwellings.
The willingness‐to‐pay and reducing costs
Achieving high levels of reductions will rely on implementing measures that are not necessarily
deemed to be cost‐effective, in that they are unlikely to present an economic payback that is
attractive to the consumer (Peacock, et al., 2009) (Pett, 2004). A willingness‐to‐pay survey
conducted in 2008 found two key findings in relation to this. Firstly, 78% of home owners
thought it was the responsibility of the Government or Local Authorities to pay for at least half
of the cost of refurbishment measures, only 17% felt that the home owner should be
responsible for paying for most of it (Peacock, et al., 2009). Secondly, the principal motivating
factor for reducing their energy consumption was reducing their energy bills (Peacock, et al.,
2009). Not surprisingly, the occupants’ willingness to pay for measures themselves increased
with the total household income, the time that they were intending to stay in that property,
and the perceived asset value of their properties as a result of the measures. These results
suggest that the majority of respondents feel that climate change is a problem has been
caused by the wider society rather than the individual, and consequently should be paid for by
a societal agent. Delivering substantial CO2 reductions in the housing sector is fundamental to
climate change policy, and therefore motivating homeowners to adopt responsibility for
implementing energy saving measures is essential.
One way to address this problem would be make refurbishment measures more economic. To
do this the market would have to be improved (Jenkins, 2010). However, the current reliance
on market related solutions to achieve infiltration of newer technologies and refurbishment
measures into dwellings is limited, as there is a clear lack of working exemplars available. A
lack of information relating to performance and reliability of these measures makes it difficult
to encourage a mass market (Jenkins, 2010). One approach would be to focus on the willing‐
to‐pay sector; households with significant disposable income and ambitions to improve energy
efficiency and therefore reduce their CO2 emissions (Geroski, 2000). This has been
demonstrated with the capital cost of IT equipment (Jenkins, 2010). The reduction in the
capital cost of a measure as the number of units produced increases, could result in cheaper
40
measures for the mass market, and therefore encourage higher uptake rates of that measure
(Peacock, et al., 2009).
Another approach would be to focus on fuel poor social housing, as this could provide a large
number of exemplar refurbishments as well as reducing fuel poverty (Jenkins, 2010). This
would in turn stimulate the private buyer and the manufacturers, therefore improving
confidence and reducing capital costs (Jenkins, 2010). This approach would require significant
subsidies to be made available to social housing associations. However, substantial reductions
in the cost of carrying out the work could be made because of the economies of scale
associated with bulk buying and large scale projects (Plimmer, 2008). This would provide
better value for the government. Some of the wider benefits of this would be boosts in
employment and Gross Domestic Product (WWF, 2008).
Solid wall insulation
The data presented in chapter three: DEMScot: Scotland’s domestic energy model and
numerous other research reports demonstrate that solid wall insulation has a vital role to play
in reducing CO2 emissions. However, the current rate of installation is low (BRE, 2008b). The
reasons for this are the reduction in the usable floor area of dwellings (in the case of internal
insulation), change of external appearance of dwellings (in the case of external insulation),
high costs and disruption to the occupants (BRE, 2008b). These barriers must be overcome in
order to increase the uptake of this measure.
There are a variety of different solid wall types and associated finishes. The predominant wall
finish is masonry pointing (55%); the other significant proportion is a rendered finish (33%). A
further 10% has a mixture of both, and the remaining 2% has a non masonry natural finish
(BRE, 2008b). Following this, solid wall insulation can be specified according to the type of
finish and in the presence of other obstacles.
In theory external or internal wall insulation could be applied to almost any dwelling except in
the instance of listed buildings. External insulation is applied in either a wet render or a
cladding system. It offers the advantage of little disruption to the occupants, reduces the risk
of thermal bridging, can improve the look of an ageing and weathered facade, and can be
specified in order to solve rain penetration and frost damage (Sustainable Energy Ireland,
2005). A minor barrier is that external wall insulation may require planning consent as it
41
changes the appearance of a dwelling (Impetus Consulting, 2004), although this is unlikely to
apply to dwellings that are already rendered (BRE, 2008b). Another barrier may be in the case
of converted or purpose built flats, where all the occupiers would have to agree to change the
external appearance (BRE, 2008b). The primary barrier is that occupants may be averse to
changes in the external appearance of their homes (BRE, 2008b). In order to overcome this,
external wall insulation should be targeted at the 45% of dwellings that have render and non
masonry natural finishes. It can be incorporated when work to the exterior is desired or
necessary, thus eliminating the barrier as the work will be carried out anyway. Any additional
costs could be covered by government or local authority grants.
Internal insulation is applied as a rigid insulation board or insulation fitted between studwork.
One of the barriers to internal insulation is the loss of usable floor area, which has more
significance in dwellings under 60m2 (BRE, 2008b). However, this was an issue in the Aubert
Park refurbishment and was mostly overcome by utilising new materials that are much thinner
than the standard application of 80mm to 120mm of insulation. These high performance
materials could be subsidised by grants in order to make them more competitive in
comparison with the standard application. The major barrier to this measure is the amount of
disruption to the occupants. Realistically this could only be applied when a major
refurbishment takes place, or on a room by room basis when redecoration takes place
(Impetus Consulting, 2004). Internal wall insulation can also be applied on a DIY basis; this
improves its appeal to home owners (Sustainable Energy Ireland, 2005). Internal wall
insulation lends itself to dwellings with masonry pointing where the occupants are averse to
changes in the external appearance of their dwelling and in the case of flats where not all the
occupants are in agreement of external wall insulation (BRE, 2008b). It should therefore be
targeted for the other 55% of dwellings where the occupants would resist any change to the
external appearance of their homes.
This is somewhat of a simplified arrangement, and clearly the applicability of one method of
wall insulation does not preclude another. If the occupant is averse to internal disruption, but
will forego the undesired change in external appearance, then external wall insulation could
be specified. The method of selection could be approached in the manner of a flow chart that
represents an algorithm. Under the assumption that either external or internal insulation
could be applied in respect of the previous solutions, 6.3 million dwellings could be insulated
(BRE, 2008b), excepting the 300,000 residential buildings listed as architecturally important 42
(Boardman, et al., 2005). Realistically, solid wall insulation would be best if it was
incorporated into other works in order to marginalise the problems stated previously; this is
discussed subsequently.
Occupant disruption and occurring opportunities
Midmoor Road incorporated the energy efficiency measures into a major refurbishment of the
whole property. This is a common feature in demonstration refurbishment projects as both
costs and disruption are kept to a minimum (Killip, 2008). In 2005 £23.9 billion was spent on
repair, maintenance and improvement (Department for Business Enterprise and Regulatory
Reform, 2007). Work which does not incorporate energy efficiency measures represents a
major missed opportunity, as it is unlikely that further substantial refurbishment work will not
be carried out for sometime afterwards (EST, 2006c).
These naturally occurring opportunities to incorporate energy efficiency measures need to be
taken advantage of; they have been named trigger points (EST, 2008). Trigger points with the
potential to deliver CO2 savings are; moving home, building an extension, new kitchen or
bathroom, loft conversion, new windows, new heating system and new flooring. These
scenarios offer the following advantages; the home owner is already considering work so is
receptive, workpeople may already be on site so the disruption is minimal, the cost of
improvement will be less and there is scope to incorporate improvements that would not be
included after the work is complete (EST, 2008). In order to promote the uptake of these
measures it is essential that these trigger points are maximised, this can be done by three
methods. Firstly, start a programme of public engagement to encourage the public to support
technologies and policy. Secondly, modify the Building Regulations to extend the coverage of
triggers for improving the energy performance of homes in the case of extensions and loft
conversions. Finally, increase incentives and awareness raising activity that targets people’s
behaviour (EST, 2008).
Items other than those included in the Standard Assessment Procedure
The data presented in chapter 3: DEMScot: Scotland’s domestic energy model confirmed that
reductions of up to 70% are possible from solid wall housing. However, these reductions are
based on SAP items only; therefore emissions from cooking and appliances are not included.
The past four decades have seen an unprecedented increase in the use of electrical appliances
43
and time saving devices (EST, 2006d). Although the energy efficiency of these products has
greatly increased, this saving has been outstripped by a massive increase in demand. On
average, appliances and cooking account for 21% of total emissions (DCLG, 2007). If items
other than SAP items were included in the Aubert Park and Midmoor Road refurbishments,
the CO2 reductions would be reduced to 50% and 52% respectively if a full refurbishment was
implemented. Although energy use for cooking has been declining (Shorrock, Utley, 2003),
the increase in appliances is viewed as a serious threat to achieving the Government’s CO2
reduction targets (EST, 2006d). However, appliances have a high turnover and it is likely that
they will be replaced 3 to 4 times by 2050 (Boardman, et al., 2005). This presents an
opportunity for savings as appliances are traded goods and savings can be implemented by EU
and UK policy initiatives. Products with improved electrical efficiency need to be brought into
the market; however, this relies on strong policy from the EU and UK (Boardman, et al., 2005).
This could be executed by the UK Government pressing for 25% of the most electrically
inefficient products to be removed from the market every 3 to 5 years, luxury products with
disproportionately high energy use, i.e. patio heaters, should be subject to increased tax (EST,
2006d). Furthermore, the Building Regulations could be revised so that property developers
must install the most efficient appliances available (Boardman, 2007).
Evaluation of key barriers
It is clear that cost is a significant barrier to the implementation of energy efficient
refurbishment measures. This chapter has presented the most viable solutions to overcoming
this barrier and encouraging the uptake of measures. However, even accounting for
reductions in overall costs resulting from market forces, refurbishment measures will still
come at a fee, either to the home owner or the Government that has to subsidise the cost.
The attitudes presented in the willing‐to‐pay survey pose a severe threat to achieving the 80%
target. It is obviously in the Governments’ best interest to transfer as much of the costs to the
willing‐to‐pay sector. What the Government can or cannot afford is beyond the remit of this
dissertation. However, the cost of refurbishing all solid wall housing is a substantial burden
for the Government to bear. Consequently, the major UK political parties have only pledged
funding for the cost‐effective measures stated in chapter two: the UK housing stock (BBC,
2010).
44
Barriers above the technical feasibility and cost of refurbishment will also affect the potential
of solid wall housing to reduced CO2 emissions. The additional three other major barriers
other than cost (solid wall insulation, occupant disruption and opportunities and items other
than SAP), have been addressed and an appropriate solution suggested. However, for all the
barriers there was no easy or quick fix solution because they all require reinforcement from
government regulation and policy if they are to be surmounted. Having analysed the
remaining barriers to refurbishment, the study will move onto the following chapter where
conclusions and recommendations will be presented.
45
Chapter seven: conclusion and recommendations
Conclusion
The aim of this dissertation was to evaluate the proposed solution of refurbishing the building
envelope and heating system, in order to determine what is required to achieve 80% emission
reductions so to answer the question; what role can solid wall housing feasibly play in
reducing CO2 emissions by 80%?
The first objective was to assess the improvement measures that were applied to the two
chosen dwellings individually in order to ascertain the applicability of the refurbishment
package to other dwellings of that type. The outcome was that with the exception of MVHR,
concrete floor insulation and the solid wall insulation in some circumstances, the
refurbishment measures represent a package that could be applied to other dwellings without
major disruption and therefore could produce comparable results.
The second objective was to confirm that the case studies were capable of achieving the
reduction in emissions that were advocated. This was carried out by using the DEMScot
model which utilised the assumptions and methodology made by the DEMScot team relating
to occupants behaviour and the use of lights, cooking and hot water. There were minor
differences in the results for Aubert Park and Midmoor Road, as they achieved a 2% lower and
a 2% to 3% higher reduction respectively, in comparison to their SAP assessments. The results
from the modelling process suggest that it is technically feasible to achieve the claimed level
of reductions, providing the Baxi Ecogen can deliver the performance it claims.
The third objective was to investigate the main barriers to the refurbishment of solid wall
dwellings. Cost is one of the primary factors that limit the feasibility of solid wall housing in
achieving significant reductions. This was dealt with by exploring the possibility of less
comprehensive improvements and considering the Value Carbon factor thereby bridging the
disincentive of a significant capital cost. The results from this established that there is a very
clear tipping point where the diminishing returns are acute. Consequently pursing a path of
all‐out refurbishment would not necessarily be a prudent use of funds when considering the
opportunity cost of the finance available.
46
The issue of cost reduction was also explored in response to an indication that home owners
expect the costs to be heavily subsidised by Government or a Local Authority. A possible
solution was that market forces would be capable of reducing prices and therefore addressing
the issues of cost. However either the willing‐to‐pay sector had to be targeted to initiate this,
or homes in fuel poverty could be utilised to create a mass market whilst reducing fuel
poverty. The overall evidence relating to cost suggests that costs can be reduced by either
specifying less work that achieves a high Value Carbon rating, or by improving the market to
make refurbishment measures more economic.
Some of the wider limitations and issues that reduce the ability of the solid wall stock to
achieve CO2 reductions were also considered. For solid wall insulation the solution was to
specify the type on the basis of the original wall finish or by an algorithmic process. However,
the evidence shows that there is little that can be done about the disruption caused to the
occupants from internal wall insulation. The only possible solution is to ensure that on
occasions where there is work being carried out or the occupants are in transition, the
opportunity is maximised by increasing incentives and awareness, and by making
refurbishment works compulsory through the Building Regulations.
Furthermore, the CO2 emissions produced by appliances presents a serious barrier to the 80%
reduction target as they are not included in the SAP analyses which currently rates the energy
performance of dwellings. The evidence suggests that this barrier requires strong policy
intervention from the UK Government to reduce the number inefficient appliances, and to
ensure only efficient appliance are used.
Overall, the objectives have clarified the ability of solid wall housing to contribute to 80%
reductions. They have aimed to answer the question; what role can solid wall housing feasibly
play in reducing CO2 emissions by 80%? It can be concluded that the role solid wall housing
can play is certainly significant but refurbishment alone will not be enough. Considerable
emission reductions can be achieved by using innovative materials and technology. However,
home owners need to start accepting responsibility for making their homes energy efficient.
Refurbishment can be cost‐effective; reductions of 50% to 53% are possible for a reasonable
expense, and reductions of 65% to 67% are possible if the cost threshold is raised.
Nevertheless, refurbishment measures must be supplemented by other means to achieve the
80% reduction target.
47
Recommendations
Given these conclusions, a number of recommendations can be proposed that aim to address
the barriers previously highlighted and to advance this field of study. Firstly, an appropriate
body such as the Carbon Trust carries out a trial on the Baxi Ecogen unit. This technology
could greatly assist the delivery of the 80% reduction target if it can deliver what Baxi claims.
Secondly, a Value Carbon methodology should be developed by the BRE to ensure property
developers, housing associations and any other persons that are involved in refurbishment,
carry out work that delivers high carbon savings for the lowest cost. This would also
encourage the up‐take of refurbishments.
Thirdly, considerable progress is made regarding the attitudes of the public. This could be
through awareness campaigns or by heavily incentivising refurbishment work through
financial rebates. The Government needs to dismantle public resistance and progress the
refurbishment market from the research stage to mass adoption.
Fourthly, a swift and robust amendment of policy and regulation is implemented by the UK
Government. Primarily in the Building Regulations so that the opportunities to improve the
energy performance of dwellings is not lost when renovation and maintenance is carried out.
This policy should encompass white goods and appliances to ensure that the efforts to
improve energy performance of the building fabric and heating system are not offset by the
demand for electronics and appliances; this may involve working with the manufacturers
themselves.
Finally, having established that refurbishment of solid wall housing will not achieve the 80%
reduction target; extensive research is carried out that investigates how and to what extent
solid wall housing can be supplemented by other means so that an overall strategy for dealing
with Hard to treat dwellings can be specified.
48
Bibliography
Abdullatiff, E. (2003) Development of an integrated dynamic thermal bridging assessment environment. Energy and Buildings 35 (4), 375‐382.
Balson, T. (2009) T‐Zero Case Study: Green Living 70a Aubert Park, Islington, London. Watford, BRE bookshop.
Baxter, L., et al. (2006) How to research. 3rd Ed, Maidenhead, Open University Press.
Baxi. (2010a) Baxi Ecogen – FAQ’s. [Internet] Available from: <http://www.baxi.co.uk/products/frequently‐asked‐questions.htm> [Accessed 12 April]
Baxi. (2010b) Baxi Ecogen ‐ Free Piston Stirling Engine. [Internet] Available from: <http://www.baxi.co.uk/baxiecogen> [Accessed 08 April]
BBC. (2010) Where They Stand: Guide to party election policies. [Internet] Available from: <http://news.bbc.co.uk/1/hi/uk_politics/election_2010/8515961.stm#subject=environment&col1=conservative&col2=labour&col3=libdem> [Accessed 26 April]
Bergman, N., et al. (2010) UK Micro Generation Policy and Behavioural Aspects. Energy 162, 23‐36.
Boardman, B. (2007) Home Truths: A Low‐carbon Strategy to Reduce UK Housing Emissions by 80% by 2050. Research Report 34. Oxford, Environmental Change institute.
Boardman, B., et al. (2005) 40% House. Research Report 31. Oxford, Environmental Change institute.
Building Research Establishment. (2001) Energy‐efficient refurbishment of existing housing. Good practice guide 155, Watford, BRE bookshop.
Building Research Establishment. (2008a) Energy Analysis Focus Report: A Study of Hard to Treat Housing using the English House Condition Survey Part 1. Watford, BRE bookshop.
Building Research Establishment. (2008b) Energy Analysis Focus Report: A Study of Hard to Treat Housing using the English House Condition Survey Part 2. Watford, BRE bookshop.
Building Research Establishment. (2009) The Government’s standard Assessment
Procedure for Energy Rating of Dwellings. 2005 Ed, revision 3, Watford, BRE Bookshop.
Carbon Trust. (2007) Micro CHP Accelerator. Interim Report. London, Carbon Trust.
49
Clarke, J. A., et al. (2005) Thermal Improvement of Existing Dwellings. Glasgow, Energy Systems Research Unit.
Cole, C. (2008) CHP and SAP – Part II. [Internet] Available from: <http://carbonlimited.org/2008/03/20/chp‐and‐sap‐part‐ii/> [Accessed 06 April 2010]
Department for Business Enterprise and Regulatory Reform. (2007) Construction Statistics Annual 2007 [Internet] Available from: <http://www.berr.gov.uk/files/file42061.pdf> [Accessed 16 April 2010]
Department of Communities and Local Government. (2006) Review of Sustainability of Existing Buildings. London, Communities and Local Government Publications.
Department of Communities and Local Government. (2007) Building a Greener Future: policy statement. London, Department for Communities and Local Government.
Department of Communities and Local Government. (2009) English House Condition Survey 2007. London, Communities and Local Government Publications.
Department of Communities and Local Government. (2010) Building Regulations. [Internet] Available from: <http://www.communities.gov.uk/planningandbuilding/buildingregulations/> [Accessed 06 April 2010]
Department of Energy and Climate Change. (2010b) The Standard Assessment Procedure (SAP) [Internet] Available from: <http://www.decc.gov.uk/en/content/cms/what_we_do/consumers/saving_energy/std_assess/std_assess.aspx> [Accessed 06 April 2010]
Direct.Gov. (2010) How the UK will meet CO2 emissions targets. [Internet] Available from: <http://www.direct.gov.uk/en/Nl1/Newsroom/DG_179190> [Accessed 14 April 2010]
Ecotricity. (2010) UK Grid live. [Internet] Available from: <http://www.ecotricity.co.uk/about/live‐grid‐carbon‐intensity> [Accessed 14 April 2010]
Energy Efficiency Partnerships for Homes. (2004) Insulating solid walls: a challenge for local authorities and housing associations. London, Energy Efficiency Partnerships for Homes.
Energy Saving Trust (2005) Improving airtightness in dwellings. Research Report 224. London, Energy Saving Trust.
Energy Saving Trust. (2006a) Energy efficient ventilation in dwellings. Research Report GPG 268. London, Energy Saving Trust.
Energy Saving Trust. (2006b) Practical refurbishment of solid‐walled houses. Research Report 184. London, Energy Saving Trust.
50
Energy Saving Trust. (2006c) Refurbishing Dwellings – a summary of best practice. Research Report 189. London, Energy Saving Trust.
Energy Saving Trust. (2006d) The rise of the machines. London, Energy Saving Trust.
Energy Saving Trust. (2008) Towards a long‐term strategy for reducing carbon dioxide emissions from our housing stock. London, Energy Saving Trust.
Energy Saving Trust. (2010a) Lighting. [Internet] Available from: <http://www.energysavingtrust.org.uk/corporate/Corporate‐and‐media‐site/Media‐centre/Energy‐saving‐statistics‐and‐facts/Lighting> [Accessed 20 April 2010]
Energy Saving Trust. (2010b) Sustainable refurbishment. Research Report CE309. London, Energy Saving Trust.
Fellows, R., Liu, A. (2003) Research Methods for Construction. 2nd Ed, Oxford, Blackwell Publishing Ltd.
Geroski, P.A. (2000) Models of technology diffusion. Research Policy 29, 603–625
Green Building Press. (2006) The Green building bible volume 1. Volume 1. 3rd Edition. Llandysul, Green Building Press.
Henderson, J. (2009) Review of auxiliary energy use and the internal heat gains assumptions in SAP. (STP 09/AUX01), Watford, BRE.
Immendoerfer, A., et al. (2008) Fit for the future: the green homes retrofit manual. London, Housing Corporation.
Impetus Consulting. (2004) Insulating solid walls a challenge for policy makers and scheme
managers. London, Energy Efficiency Partnerships for Homes.
Intergovernmental Panel on Climate Change. (2001) Climate change 2001: the scientific basis. Technical Summary, Intergovernmental Panel on Climate Change, Geneva.
Jenkins, D.P. (2010) The value of retrofitting carbon‐saving measures into fuel poor social housing. Energy Policy 38 (2), 832‐839.
Jennings, P. (2006) The Green Building Bible Volume 1. 3rd Edition, Llandysul, Green Building Press.
Killip, G. (2008) Transforming the UK’s Existing Housing Stock. London, Federation of Master Builders.
51
King, D.A. (2004) Climate change science: Adapt, mitigate or ignore? Science 303 (5655), 176‐177.
Knight, A. (2008) Advanced Research Methods in the Built Environment. Chichester, Wiley‐Blackwell Publishing Ltd.
Lowe, R. (2007) Technical options and strategies for decarbonizing UK housing. Building Research and Information 35(4), 412–425.
Mackay, D. (2009) Sustainable Energy ‐ without the hot air. Cambridge, UIT Cambridge.
Mavrogianni, A. (2009) Space heating demand and heatwave vulnerability: London domestic stock. Building Research and Information 37 (5), 583–597.
Met Office. (2010) UK mapped climate averages. [Internet] Available from: <http://www.metoffice.gov.uk/climate/uk/averages/ukmapavge.html> [Accessed 13 April 2010]
Naoum, S.G. (2009) Dissertation research & writing for construction students. 2nd Edition, Oxford, Elsevier Ltd.
NASA. (2010) Surface meteorology and Solar Energy. [Internet] Available from: <http://eosweb.larc.nasa.gov/cgi‐bin/sse/sse.cgi?+s01#s01> [Accessed 16 March 2010]
National Oceanic Atmospheric Administration. (2010) NOAA Solar Calculator. [Internet] Available from: <http://www.esrl.noaa.gov/gmd/grad/solcalc/> [Accessed 16 March 2010]
Office for National Statistics. (2010) Industry Consumption of Energy & Output. [Internet] Available from: <http://www.statistics.gov.uk/cci/nugget.asp?id=151> [Accessed 17 January 2010]
OPSI. (2010) Climate Change Act 2008 [Internet] Available from: <http://services.parliament.uk/bills/2007‐08/climatechangehl.html> [Accessed 10 April 2010]
Oxford Environmental Change Institute. (2010) Degree Days for energy management. [Internet] Available from: <http://www.eci.ox.ac.uk/research/energy/degreedays.php> [Accessed 11 March 2010]
Peacock, A.D., et al. (2009) Market development potential of residential refurbishment package. European Council for an Energy Efficient Economy (ECEEE), Summer Study, Cote d’Azur,
Perry, M. (2006) A spatial analysis of trends in the UK climate since 1914 using gridded datasets. Climate Memorandum No.21. Exeter, Met Office.
52
53
Pett, J. (2004) Affordable Warmth in ‘Hard to Heat’ Homes: a progress report. Research Report v1.1. London, Association of the Conservation of Energy.
Plimmer, F., et al. (2008) Knock it down or do it up? Watford, BRE bookshop.
Roaf, S., et al. (2008) Evidence on Tackling Hard to Treat Properties. Edinburgh, Scottish Government Social Research.
Scharmer, K., Greif, J. (2000) THE EUROPEAN SOLAR RADIATION ATLAS Vol. 1: Fundamentals and maps. Paris, Presses de l'École des Mines.
Scottish Government Social Research. (2010) Modelling Greenhouse Gas Emissions from Scottish Housing: Manual and Model. Glasgow, Scottish Government Social Research.
Shorrock, L.D., et al. (2005) Reducing carbon emissions from the UK housing stock. Research Report 480. Watford, BRE Bookshop.
Shorrock, L.D., Utley, J.I. (2003) Domestic Energy Fact File 2003. BRE457. Watford, BRE.
Sturges, J. (2006) Planet earth: what we need to know about it. Leeds, Leeds Metropolitan University.
Sustainable Energy Ireland. (2005) A detailed guide to insulating your home. Dublin, Sustainable Energy Ireland.
Taylor, R. (1996) The Conservation and Thermal Improvement of Timber Windows. [Internet] Available from: < >[Accessed 12 April 2010]
Taylor, R. (2009) Chimneys and Flues. [Internet] Available from: <http://www.buildingconservation.com/articles/services/chimney.htm> [Accessed 05 April 2010]
WWF. (2008) How Low–Achieving Optimal Carbon Savings from the UK’s Existing Housing Stock. WWF, London, UK.
Yin, R.K. (2003) Case Study Research: Design and Methods. 3rd Edition. Thousand Oaks, CA, Sage.