Assessing the potential for reductions in Irish local authority residential energy consumption: A case study of the efficacy of thermal envelope upgrades in a sample of Wicklow County Council’s housing stock. Robert Wyse MSc Climate Change and Sustainable Development Institute of Energy and Sustainable Development De Montfort University September 2012
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Assessing the potential for reductions in Irish Local Authority residential energy consumption
A case study of the efficacy of thermal envelope upgrades in a sample of Wicklow County Council's housing stock.
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Assessing the potential for reductions in Irish
local authority residential energy
consumption:
A case study of the efficacy of thermal envelope upgrades in
a sample of Wicklow County Council’s housing stock.
Robert Wyse
MSc Climate Change and Sustainable Development
Institute of Energy and Sustainable Development
De Montfort University
September 2012
ii
Abstract
It is recognised that the energy performance of the Irish housing stock is poor, with ambitious
retrofitting targets seen as essential to achieving legally binding energy consumption and CO2
emissions reductions targets. Local authorities are retrofitting their housing stocks, and are not only
subject to stringent energy reduction targets, but are expected to play the role of market maker and
encourage the uptake of retrofitting measures in their area.
This research focuses on Wicklow County Council. Based on the analysis of a sample of 718 dwellings
from their stock, it is evident that the energy performance of an average Wicklow County Council
dwelling is considerably worse than the average dwelling in Co. Wicklow or Ireland. In the absence of
an overarching strategy for retrofitting, the retrofitting interventions employed by Wicklow County
Council are considered on a per-dwelling basis and are driven by external energy assessors. An
analysis of the efficacy of the thermal envelope in Wicklow County Council dwellings, coupled with
an analysis of recommended retrofit interventions, reveals a failure to address significant areas of
heat loss, and hence energy consumption.
Using a purpose built Excel based model, the impact of upgrading the thermal envelope to differing
thermal standards on energy consumption and CO2 emissions in the sample of dwellings was
investigated. Reductions in primary energy consumption of between 23% and 50% and in CO2
emissions of between 24% and 52% are deemed achievable, with potential Government funding of
between €2.3 million and €7.8 million available depending on the thermal standard adopted.
iii
Acknowledgements
And now, after so many months of working on a piece that must be structured ‘just so’, I shall write
freely of my thanks to those who have helped me complete this body of work.
From De Montfort University, I thank my supervisor, Dr. Andrew Wright. What I have produced I’m
sure is quite different to what you had originally envisaged when you suggested retrofitting as a
research topic for one of your students (Lessons learned from Retrofitting, anyone?), and I thank you
for granting me free reign to craft this dissertation as I saw fit. Your advice over the last year or so
has been of immense benefit to me. I’m not quite sure it is the norm for someone to command over
an hour of your time on the phone, yet I did on several occasions, and it was most helpful. Your
understanding and swift actions when I requested a short extension were most appreciated for the
peace of mind they afforded me.
From Wicklow County Council, I thank Breege Kilkenny for agreeing to let me carry out this research
in the first place, and Alan Martin for providing the plethora of source materials that enabled it. Al, it
is staggering to think that this work stemmed from our chance meeting on the Long Hill waiting for a
bike race! Our frequent discussions gave me the insight I needed to complete this report, and I truly
hope it is of some benefit to you. I’m fairly sure the next cuppa is on me.
The fulfilment of this dissertation has coincided with a most difficult time in my personal life. Step
forward Mam and Dad, and my sisters Cathy, Emma, Jenny and Fiona. I may never be able to
adequately express how invaluable your support has been to me over the past few months. The
effort in trying to complete this work given my circumstances quite literally nearly broke me, but
with your help, it did not. Thank you.
William Power; you inspired me to undertake this Masters in the first place. There have been times
over the years when I couldn’t quite say I was thankful to you for that, but now that it's at a close, I
can honestly say that I am a more complete person for having done this. And for that, I am in your
debt.
Auntie Carmel; I have never forgotten your words on how, in order to complete this course, I would
draw upon the same mental and physical strength I drew upon when cycling competitively. Prescient
is not the word. And Auntie Rioghnach; when I bemoan the time and effort this course has
demanded of me, your advice on how the years would have passed anyway gives me much needed
perspective and dare I say, makes me smile. Thank you both for your encouragement over the years.
iv
Paul Price; would you believe that in the end, I never got to use WUFI or Therm in anger!! Not to
worry. I truly enjoy our 'sustainability rants' which have played no small part in shaping this work.
The best of luck over the next month or so as you work towards completing your own dissertation
and please, call on me to review as I called on you.
And last, but absolutely by no means least; Mike Clarke. You are a Gent. Please take a bow, Sir. I
cannot thank you enough for your patience and guidance as I endured the painstaking process of
constructing the model used in this study (which, absurdly, was never even included in my original
plan!). I hope you'll agree it was worth it. Forgive me, but I simply cannot resist;
Dim NumPintsOwed As Integer
NumPintsOwed = 1
And now to rest
And now to heal
And get my life
Back to even keel
v
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Table of Contents
Table of Figures ...................................................................................................................................... ix
Table of Tables ....................................................................................................................................... xi
Abbreviations ........................................................................................................................................ xii
Table 17 Allocation of funding according to energy reductions achieved ........................................... 75
Table 18 Funding available for each scenario ....................................................................................... 76
Table 19 Overview of reductions achieved for all scenarios ................................................................ 77
xii
Abbreviations
ac/h Air changes per hour
BEH Better Energy Homes
BER Building Energy Rating
CO2 Carbon Dioxide
DEAP Dwelling Energy Assessment Procedure
DECLG Department of the Environment, Community and Local Government
DCENR Department of Communications, Energy and Natural Resources
EC European Commission
EP European Parliament
EPA Environmental Protection Agency
EPBD Energy Performance of Buildings Directive
ETS Emissions Trading Scheme
EU European Union
GDP Gross Domestic Product
GHG Greenhouse Gas
GWh Giga-Watt hour
kgCO2 Kilo-gram
kWh Kilo-Watt hour
LZC Low to Zero Carbon
m2 Meters squared (area)
m3 Meters cubed (volume)
MPEPC Maximum Permitted Energy Performance Coefficient
MPCPC Maximum Permitted Carbon Performance Coefficient
MtCO2eq Mega tonnes of Carbon Dioxide equivalent
MVHR Mechanical Ventilation and Heat Recovery
NBERRT National BER Research Tool
NERP National Energy Retrofit Program
Pa Pascals
RET Renewable Technologies
xiii
SAP Standard Assessment Procedure
SEAI Sustainable Energy Authority of Ireland
SEI Sustainable Energy Ireland
sqm Square Meter (area)
TGD Technical Guidance Document
WCC Wicklow County Council
yr Year
1
Section 1. Introduction
1.1 Context
In 2010, the Irish residential sector was responsible for 27% of total final energy consumption and
12.7% of greenhouse gas (GHG) emissions. Given these sizeable contributions, the residential sector
is seen as an important contributor towards the achievement of Irish obligations regarding GHG
emissions under the Kyoto protocol and European Climate and Energy packages.
The stated goal of the National Energy Retrofit Program (NERP) is to reduce the energy consumption
of dwellings in Ireland by an average of 42% by 2020. The NERP is essential to the success of the
National Energy Efficiency Action Plan (NEEAP), itself devised to achieve Ireland’s obligations under
the European Climate and Energy Package. As part of the NEEAP, local authorities are obliged to
increase energy efficiency by 33% by 2020, far in excess of the 20% required for the nation as a
whole (DCENR, 2009, p. 8). As custodians of 6% the national housing stock, Irish local authorities are
undertaking widespread residential retrofits in an effort to meet such targets.
Studies such as that carried out by Wardell & Shanks (2005) suggest that the efficacy of the thermal
envelope in Irish dwellings is poor, with high levels of ventilation heat loss and widespread
deficiencies in insulation. Poor workmanship and regulatory non-compliance are deemed
contributing factors to this situation which has resulted in the energy consumption of Irish dwellings
exceeding European norms. It is understood that reductions in CO2 emissions in the region of 90%
are achievable in the Irish residential sector, however retrofitting measures employed to date in
Ireland are insufficient to deliver such reductions.
Taking Wicklow County Council (WCC) as a case study, this research investigates the reductions in
energy consumption and CO2 emissions achievable across a sample of dwellings should the
principles of the fabric first approach be implemented, and a focus be placed solely on the thermal
envelope whilst retrofitting.
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1.2 Background
1.2.1 Energy Performance of Buildings Directive
The EU Directive on the Energy Performance of Buildings (EPBD) was adopted into Irish law in 2006.
Two principle aims of this directive are to provide a common methodology for calculating the energy
performance of a building and to provide a system of certification that makes the energy
consumption of a building readily available to the public (EC, 2003). Based on IS EN 13790, and
drawing heavily on the UK Standard Assessment Procedure (SAP), the Dwelling Energy Assessment
Procedure (DEAP) is the official Irish procedure for calculating and assessing the energy performance
of a dwelling and is fully compliant with the methodology framework set out in the EPBD (SEAI a,
2008). The main steps carried out as part of a DEAP survey are described in section 3.3.1.
A DEAP assessment results in the issuance of a Building Energy Rating (BER) certificate, which
indicates the annual primary energy consumption and CO2 emissions of the building. As shown in
Figure 1 (below), ‘A’ rated dwellings (consuming less than 75 kWh/m2/yr) are the most energy
efficient, with ‘G’ rated ones (consuming more than 450 kWh/m2/yr ) the least;
3
Figure 1 A sample Building Energy Rating (BER) Certificate (SEAI, 2007)
4
1.2.2 The Fabric First Approach
Energy consumption in houses is complex, depending on building geometry, the thermal
characteristics of the building envelope and therefore by extension, the external climate. The
ultimate aim of retrofitting dwellings in Ireland must be to create a housing stock which provides a
healthy and comfortable environment for occupants and whose energy consumption is greatly
reduced relative to present levels and largely independent of the vagaries of the Irish climate.
A distinction is made between the thermal and building envelopes; the physical components of the
building envelope – the planar elements such as doors, floors, roof, walls and windows - combine to
form the thermal envelope, which is the enclosure that holds warm or cold air in a structure (Energy
Vortex, n.d.). The fabric first approach emphasises reducing space heating demand to the minimum
possible level by optimising the thermal envelope in terms of air-tightness and heat retention. The
principles underlying this approach are discussed further in section 2.5
The fabric first approach clearly underlies Irish building regulations for new dwellings (DECLG, 2011),
is championed by the Energy Savings Trust in the UK (EST a, 2010) and is the foundation for both
Code for Sustainable Homes (BRE Trust, 2010) and Passivhaus (Schnieders & Hermelink, 2006)
standards.
The fabric first approach is equally applicable to retrofits, with Davies & Osmani (2011, p. 1694)
noting its widespread adoption in the UK. In recognition of the fact that achieving the Passivhaus
standard whilst retrofitting is extremely challenging primarily owing to the difficulties in achieving
low levels of thermal bridging heat loss and high levels of air-tightness with an existing structure
(Hearne, 2012), the Passivhaus Institute have devised the EnerPHit standard for retrofits, the central
tenet of which is a fabric first approach (Feist, 2010).
For several reasons, the fabric first approach should be of interest to local authorities in general and
WCC in particular.
Wardell & Shanks (2005, p. VI) note how local authority tenants have the highest occupancy ratio,
and therefore the highest energy consumption of all tenure types, thus reductions in space heating
demand achieved through retrofitting will be most fully exploited by this occupant type. As outlined
in section 2.5, optimising the thermal envelope should minimise space heating demand, tackle fuel
poverty, ensure good indoor air quality is maintained and eliminate issues relating to mould growth
arising from thermal bridging and surface condensation, where present. Upgrading heating systems
as part of a retrofit will reduce space heating demand and CO2 emissions (particularly where a solid
fuel system or inefficient boiler is replaced) and may alleviate instances of fuel poverty. However,
5
replacing heating systems at the expense of optimising the thermal envelope means current and
future heating loads are not minimised, and health benefits accruing from envelope optimisation are
not realised; an approach not strictly aligned with WCC’s aim to improve the quality of life of its
tenants (Sheehy, 2004, p. 17).
A failure to capitalise on the benefits afforded by the fabric first approach necessitates that the
building fabric be revisited at a later date to upgrade its performance. Given the potentially long lead
time in revisiting dwellings for a second retrofit, health issues and unnecessarily high space heating
related energy consumption and CO2 emissions may persist for some time to come, as noted in (EST
b, 2010, p. 4). This approach is not aligned with Irish government policy to maximise energy savings
to clients and avoid the necessity of undertaking further costly energy upgrade works at a later stage
(DEHLG a, 2010, p. 2).
The expectation has been set that local authorities should lead by example, and act as market
makers and exemplars in the promotion of the energy performance of buildings (Neary, n.d.). In
Wicklow, a county where the average dwelling energy consumption is 14.8% above the national
average (see section 4.2.1 for further details) and that ranks 20th out of 26 counties for retrofitting
grant applications (SEAI a, 2012, p. 1), this is a vital role for WCC to fulfil.
Finally, the approved re-cast of the EPBD (EP, 2012) states that by 2018, all new buildings owned or
occupied by local authorities will need to consume ‘nearly zero’ energy, with extant energy
consumption met via renewable sources. Though no target is explicitly set for existing buildings
becoming ‘near zero’, there is a clear indication that this may occur in the future, with local authority
buildings likely leading the way. An optimised thermal envelope provides the ideal platform for
renewable energies and hence the adoption of the fabric first approach puts in place a strong
foundation for such an eventuality.
1.2.3 Wicklow County Council
Wicklow County Council is one of 4 local authority housing providers in the administrative area of
County Wicklow, which is located on the east coast of Ireland. Perhaps reflective of the level of
construction activity in Ireland in the opening decade of the 21st century, WCC’s housing stock grew
from 1,740 units in 2004 (Sheehy, 2004, p. 10) to between 2,297 (WCC, 2008) and 2,334 (WCC a,
2011) units by 2008, with 90% of dwellings deemed to be in ‘Good’ or ‘Reasonable’ condition
(Sheehy, 2004, p. 24). This however refers to the general, maintained condition of the stock and
bears no relation to its energy performance.
6
In response to government directives, WCC are now placing a strong emphasis on energy efficiency,
and commenced a widespread retrofitting effort in 2010. The first phase of this was to establish the
baseline energy performance of their stock, with Building Energy Rating (BER) Assessors invited to
carry out dwelling energy assessments (WCC b, 2011). A total of 15 assessors were chosen for the
first tranche of assessments which considered 1,973 dwellings, with each assessor being assigned
circa 131 dwellings (WCC c, 2011).
Like other Irish local authorities, WCC receive partial funding for retrofitting work from central
government as part of the Social Housing Investment Program (SHIP), with the amount allocated per
dwelling based on reductions in energy consumption achieved (DEHLG b, 2010). Sheehy (2004, p. 36)
notes that where retrofitting work is carried out, it must meet the standard defined by the building
regulations currently in force. As per government guidance, the retrofitting interventions
implemented by WCC are not confined to the building fabric, and can relate to space and water
heating systems also (WCC d, 2011).
Crucially, and unlike other local authorities such as Tipperary or Carlow/Kilkenny County Councils for
example, WCC do not enjoy the support of a local energy agency with which they can devise an
overall retrofitting strategy. From private communications with Mr. Alan Martin, a representative of
the Housing department in WCC, it is further understood that;
• There is a lack of understanding of how energy is consumed across the stock
• There is an shortage of knowledge and expertise regarding building physics and thermal
envelope optimisation
• Techniques such as thermal bridging analysis, condensation analysis, thermal imagery and
air-tightness testing are not routinely used during retrofits
• In the absence of an overall retrofitting specification, the interventions implemented for any
of the dwellings vary based on recommendations provided by BER Assessors
• With specific reference to the thermal envelope, it is unclear to WCC how effective
recommended interventions are at mitigating heat loss, and hence energy consumption,
across the stock
• There is a preference for internal insulation over external insulation, primarily as this can be
undertaken by internal staff
7
1.3 Aims and Objectives
Given the acknowledged absence of assistance from any external agency, and the general lack of
knowledge of energy consumption across the stock, this research aims to profile the energy
performance of WCC’s dwellings, highlight the impact that the adoption of the fabric first approach
could have on energy consumption and CO2 emissions, and ultimately, contribute to the
development of an overarching retrofitting strategy.
To achieve these aims, several objectives have been identified;
1. Profile the physical characteristics, energy performance and thermal envelope efficacy of a
sample of WCC’s housing stock
2. Analyse a sample of the retrofitting interventions performed by WCC
3. Model the impact of various thermal envelope retrofit strategies on the primary energy
requirement and CO2 emissions of the sample
4. Extrapolate the impact on stock-wide primary energy requirement and CO2 emissions
1.4 Research Questions
To meet the aims and objectives, several research questions have been compiled;
1. What are the physical attributes of dwellings in WCC’s housing stock?
2. In terms of energy consumption and CO2 emissions, how does the average WCC dwelling
compare to the average dwelling in Co. Wicklow or Ireland?
3. How well does the thermal envelope of WCC dwellings perform – what are the areas of
significant heat loss?
4. Are the retrofit interventions being suggested to WCC addressing these areas of significant
heat loss?
5. If the fabric first approach was fully embraced, what is the scale of reductions in energy
consumption and CO2 emissions achievable?
8
1.5 Methodology
This will be a desk based study taking as input a sample of Dwelling Energy Assessment Procedure
Survey reports supplied by Wicklow County Council.
1.6 Dissertation Structure
This report is divided as follows;
Literature Survey; an overview of the drivers for and status of retrofitting in Ireland is presented,
alongside an overview of the state of the Irish housing stock. The principles underlying the fabric first
approach are discussed.
Methodology; an outline of the methodology employed for this research is presented, along with a
description of the model used to facilitate scenario analysis.
Model Output & Data Analysis; a detailed analysis of the energy performance of the sample and
recommended retrofitting interventions is presented.
Scenario Analysis; the impacts of upgrading the thermal envelope in dwellings across the sample to
differing standards are discussed.
Conclusions: concluding remarks are presented along with suggested topics for further research.
9
Section 2. Literature Survey
2.1 Introduction
This section discusses the drivers for retrofitting in an Irish context and describes retrofitting
Interventions typical to Ireland. The principles of the fabric first approach, and its relevance to
retrofitting, are discussed. Irish and European policy is drawn upon, with statistics on energy
consumption and CO2 emissions obtained from authoritative sources such as the Sustainable Energy
Authority of Ireland (SEAI) and the Environmental Protection Agency (EPA). Detailed reports on the
energy performance of the Irish housing stock are used to provide further context.
2.2 Drivers for retrofitting in the Irish context
When considering the drivers for retrofitting in an Irish context, it is useful to begin with the
contribution of the residential sector to overall Irish energy consumption and GHG emissions.
2.2.1 Contributions to energy consumption and CO2 emissions
As illustrated in Figure 2 (below), the residential sector is a major energy consumer, second only to
the transport sector, and in 2010 was responsible for 22% of total primary energy requirement and
27% of total final consumption (SEAI a, 2011, p. 15);
10
Figure 2 Energy Flow in Ireland, 2010
The sector’s contribution to GHG emissions is less significant at 12.7% (7.42 MtCO2eq), with only the
waste sector contributing less (EPA a, 2012, p. 2).
Overall Irish GHG emissions were 0.7% lower in 2010 than in 2009, an artefact of the on-going
economic recession (ibid, p. 1). The harsh winter of 2010 led to an increase in residential related
GHG emissions of 5.3% (ibid, p. 8) and an increase in residential related energy use of 5.9% (SEAI a,
2011, p. 4). However, climate corrected residential energy consumption reduced 2.9% on 2009
figures (ibid, p. 4), something which serves to highlight the impact of climate on Irish residential
energy consumption.
Historically, through the retrofitting of dwellings and other measures, the residential sector “strongly
influenced” (Odyssee, 2011, p. 1) a 9% improvement in the Irish energy efficiency index between
2000 and 2008. Alongside a growing stock of more efficient new dwellings, these measures partially
contributed to a decline of 24.4% in overall climate corrected energy consumption per dwelling
during the period 1990 – 2010 (SEAI a, 2011, p. 69), however this reduction occurred against the
backdrop of an increase in total dwelling numbers from 1,019,723 in 1991 (CSO, 1997, p. 40) to
2,004,175 in 2011 (CSO, 2011, p. 17), resulting in a long term climate corrected increase of 21.1% in
residential energy consumption (SEAI a, 2011, p. 67), and a 12.1% increase in GHG emissions (ibid,
p.68).
11
Through sustained retrofitting, the increased implementation of Low to Zero Carbon (LZC)
technology and the decarbonisation of the electricity grid, 90% reductions in CO2 emissions are
deemed achievable in the residential sector by 2050 (SEAI, 2010, p. 5).
Curtain (2009, p. 24) and Dineen et al. (2010, p. 2) note how retrofitting building fabric is one of the
most effective and cost efficient ways to achieve energy savings in the Irish economy, a view
reinforced by Motherway & Walker (2009, p. 4) in Figure 3 (below), which illustrates how this
abatement opportunity incurs a negative societal cost;
Figure 3 Ireland's GHG Abatement Cost Curve, 2030
2.2.2 Legally binding emission reductions targets
Given its potentially significant contribution and evident cost effectiveness, residential retrofitting is
seen as a key contributor in achieving compliance with legally binding obligations to reduce overall
GHG emissions under the Kyoto protocol and the European Climate and Energy Package.
Irish obligations under the Kyoto protocol are to limit GHG emissions to no more than 13% above
1990 levels by 2012 (DEHLG, 2007, p. 7). The National Climate Change Strategy illustrates how
increased penetration of renewable heating, enhanced building regulations and energy efficiency
12
improvements in local authority housing are the primary contributors from the residential sector
towards Kyoto compliance (ibid, p. 9).
Emissions reductions owing to the economic recession, the permitted inclusion of the impact of
forest sinks and governmental purchase of credits under the European Union Emissions Trading
Scheme (EU-ETS) (EPA b, 2012, p. 3), mean this target, once seen as “extremely challenging” (DEHLG,
2006, p. 8), and first breached in 1998 (SEAI a, 2011, p. 29), now appears likely to be met.
EC (2010) notes three legally binding targets central to the Climate and Energy Package agreed by
the European Parliament and Council in December 2008;
1. A reduction in EU GHG emissions to at least 20% below 1990 levels
2. 20% of EU energy consumption to come from renewable resources
3. A 20% reduction in primary energy use compared with projected levels, to be achieved
by improving energy efficiency
Ireland’s obligations under the Effort Sharing Decision implemented to achieve agreed GHG
reductions is for emissions in sectors of the economies not covered by the EU-ETS to be reduced to
20% below 2005 levels by 2020 (EP, 2009). Crucially however, the contribution of forest sinks is not
permitted (EPA b, 2012, p. 12), thus the proportional reductions required from other participating
sectors, including the residential sector, are increased. It should be noted that Irish local authorities
manage 6% of the national housing stock (DECLG a, 2012).
The National Energy Efficiency Action Programme (NEEAP) (DCENR, 2009) outlines Ireland’s plan of
action to fulfill the agreed 20% reduction in primary energy use.
From a requirement of 32GWh, this plan identifies savings of circa 24GWh, with circa 10.4GWh
(44%) of these being identified in the residential sector alone. Long term trends indicate that as a
result of the NEEAP, energy consumption in the residential sector could be 22.5% lower than
projected levels in 2020 (SEAI b, 2011, p. 30). The 8GWh shortfall in energy savings is expected to be
filled by way of the National Energy Retrofit Program (NERP), a central aim of which is to deliver
energy efficiency upgrades to 1 million residential, public and commercial buildings by 2020 (DCENR,
n.d., p. 8).
It is anticipated that residential related GHG emissions will decrease by 33.8% between 2010 and
2020 as a result of NEEAP & NERP activity (EPA b, 2012, p. 17), yet overall compliance with EU 2020
13
emissions targets for non-ETS sectors is nonetheless expected to be missed by 4.1 – 7.8 MTCO2eq
(ibid, p.4).
Residential retrofitting is also seen as a way to tackle issues other than energy consumption and
GHG emissions.
2.2.3 Import Dependency
Irelands energy import dependency was 86% in 2010 (SEAI a, 2011, p. 4), with imports costing the
exchequer approximately €6 billion in 2008 (DCENR, 2009, p. 8). SEAI (2010) highlights how
retrofitting can contribute greatly to our energy independence and reduce Irish exposure to oil price
volatility.
2.2.4 Employment
The construction sector once generated 24% of Irish GDP (Curtain, 2009, p. 14) and provided 20% of
all jobs in the economy (DKMEC, 2010, p. iii). The recent economic contraction has seen employment
in the sector return to 1998 levels (ibid). A sustained retrofitting programme could sustain 10,000
jobs over a 10 year period (SEAI, 2010, p. 5).
2.2.5 Fuel Poverty
Clinch & Healy (2001, p. 114) define fuel poverty to be an inability to heat the home to an adequate
(safe and comfortable) temperature, owing to low household income and poor household energy
efficiency. This is a widespread issue in Ireland, with over 20% of Irish households affected in 2009
(DCENR, 2011). Fuel poverty is associated with serious respiratory illnesses, with research suggesting
that for every euro invested in energy poverty measures, 42 cents are returned in savings from
health expenditure on all householders (ibid p. 32). Clinch & Healy (2001, p. 114) note how Ireland
suffers from one of the highest rates of excess winter mortality in northern Europe, and link this with
the poor thermal efficiency of the housing stock.
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2.3 Energy performance of the Irish housing stock
Based on an analysis of 286,793 DEAP surveys, made accessible through the National BER Research
Tool (NBERRT) (SEAI b, 2012), the average primary energy consumption for an Irish dwelling is 262.9
kWh/m2/yr., yielding a D2 rating. Thus, on average, the energy consumption of Irish dwellings must
decrease 42% to achieve a C1 energy rating, the target rating for NERP and local authority related
retrofitting work (Armstrong & Dowling, 2012, p. 1). Average CO2 emissions for an Irish dwelling are
estimated to be 62.6 kgCO2/m2/yr.
By way of international comparison, Irish dwellings in 2006 consumed 27% and 36% more energy
than the average UK and European counterparts respectively. Similarly, the average Irish dwelling
emitted 47% more CO2 than the average UK dwelling and 104% more than the average dwelling in
the EU27 block of nations (SEAI b, 2008, p. 2). Several reasons are proffered for this poor
performance;
• Larger dwelling size
• Fuel use mix for space heating
• Losses in the electricity grid
Both Scheer et al. (2012, p. 2) and DEHLG (c, 2010, p. 4) note rising expectations of internal
temperatures as a factor while regulatory non-compliance has recently been identified as a
significant driver in Irish dwelling energy consumption.
2.3.1 Regulatory non-compliance
Building regulations were first considered in Ireland in 1972 (Curtain, 2009, p. 20). It was only after
the enactment in 1991 of the Building Control Act 1990 that mandatory regulations incorporating
thermal standards came into effect. The Irish building regulations comprise a set of Technical
Guidance Documents, each concerned with a different aspect of building control, with TGD Part L-
Conservation of Fuel and Energy, the most relevant here. TGD Part L has been revised several times.
Changes made in 2002 included reductions in the permitted thermal transmittance (U-value) of the
building fabric planar elements (doors, floors, roofs, walls and windows) while more radical
amendments in the 2008 and 2011 revisions mean dwellings built to standard should consume
between 40% and 60% less energy than their 2005 counterpart, respectively.
15
Headline revisions to Part L of the 2011 Building Regulations (DECLG, 2011) include;
• Acceptable air permeability reduced from 10m³/h/m² to 7m³/h/m²
• Required efficiency for Biomass boilers set at 77%, all other boilers increased to 90%
• The Maximum Permitted Energy Performance Coefficient (MPEPC) set at 0.4
• The Maximum Permitted Carbon Performance Coefficient (MPCPC) set at 0.46
It is understood that merely complying with minimum values of air permeability and meeting default
U-values will not be sufficient to achieve required MPEPC and MPCPC values, thus at least some of
the ‘backstop values’ will need to be exceeded to ensure regulatory compliance (Antonelli & Colley
a, 2012).
In 2011, the national housing stock numbered 2,004,175 dwellings (CSO, 2011, p. 17), with 52.9% of
these constructed prior to 1991 (DECLG b, 2012). Daly (2007) asserts that the large proportion of
dwellings built in a non-regulated context is a significant factor in the poor performance of the Irish
residential sector and in doing so, infers that the presence of building regulations will guarantee
more efficient housing. Indeed, as much is assumed in (EPA, 2010, p. 12), which suggests enhanced
building regulations will contribute a 20% reduction in residential sector GHG emissions by 2020.
However, the efficacy of building regulations is clearly linked with their enforcement, which in
Ireland, falls under the remit of the City and County Councils. Inspections are only required for 12% –
15% of commencement notices, i.e. 85% of newly constructed homes are not required to be
inspected under the issued guidelines (NCA, 2008, p. 3). Local government statistics indicate average
nationwide rates of inspection varied from 23% to 33% over the period 2004 to 2010 (Power, 2012,
p. 27).
Based on data from the NBERRT, Antonelli & Colley (b, 2012) claim that 21% of homes built under
the 2005 regulations failed to meet its main requirements, while 67.7% of homes built under the
2008 regulations fail to meet all of its main requirements, indicating widespread non-compliance
with regulations.
In a study of 150 residential units representative of national trends of dwelling age, built form and
tenure of occupancy, Wardell & Shanks (2005) calculated a 41% reduction in theoretical energy
rating for dwellings constructed between 1997 – 2002 compared with those constructed between
16
1961 and 1980 (pre-regulation era), a reduction attributable to successive improvements to Irish
Building Regulations since 1979. However the study notes this theoretical reduction is not met with
a corresponding reduction in actual energy consumption, which reduced by only 13%.
Figure 4 (below) illustrates how, for the sample as a whole, an increasing difference between
Purchased Heat Energy (actual energy consumption) & Home Energy Rating (theoretical energy
consumption) was noted amongst newer dwellings (ibid, p. 14);
Figure 4 Purchased Heat Energy and Home Energy Rating over time
While this phenomenon is partially attributed to occupant behaviour, it is further noted that, of the
52 dwellings in the study constructed between 1997 – 2002, no dwelling was fully compliant with
Part L (Conservation of Fuel and Energy), Part F (Ventilation) and Part J (Heat Producing Appliances)
of the Irish building regulations. Only 1 dwelling was fully compliant with Part L in every respect, 29
dwellings fully complied with Part F in every respect (ibid, p. 61) and 27 complied fully with Part J
(ibid, p. 63).
2.3.1.1 Thermal envelope performance
With specific reference to the efficacy of the building fabric, the report notes that based on a visual
inspection, 87% of dwellings are compliant with insulation levels, with non-compliance usually
attributed to inadequate attic insulation (ibid, p. 57). The report notes that:
17
“It was possible to measure wall insulation type and thickness accurately in
the majority of dwellings, through unsealed openings for plumbing and
electrical services, such as waste pipe openings and around the electricity
meter box.” (ibid, p. VI).
The presence of unsealed openings as mentioned, along with poor on-site practice in failing to seal
the void between dry lining and masonry walls at edges of openings such as doors, for example,
contributes to the low level (15%) of infiltration compliance (ibid, p. 57). Low levels of compliance
were also noted for pipe work insulation, with only 10% of dwellings in compliance (ibid, p. 57).
Infra-red thermography and air tightness tests were performed on a subset of 20 dwellings
constructed predominately in the period 1997-2002 to supplement the findings of the visual
inspection. This highlighted significant deficiencies (ibid, p. VII);
• 55% of dwellings had some insulation (typically roof or wall) missing
• 15% of the dwellings had extensive insulation missing
• Local thermal bridging at window sills and lintels etc. was found in 66% of dwellings
• Condensation risk mainly due to missing insulation was found in 33% of living rooms,
bedrooms and wet rooms.
• Average air permeability was recorded as being 11.8m3/hr/m2@50pa, 69% higher than good
practice value of 7.0m3/hr/m2@50pa (ibid, p.39)
• Excessive air leakage (ac/h > 0.5) was found in 37% of dwellings.
2.4 Typical Retrofit Interventions in Ireland
The findings presented thus far suggest a significant improvement in the overall energy performance
of the Irish housing stock is achievable through retrofitting. The NERP is being administered by the
Sustainable Energy Authority of Ireland (SEAI), with grant assistance for residential energy efficiency
interventions available through the Better Energy Homes (BEH) scheme.
Statistics relating to energy efficiency interventions undertaken as part of the BEH scheme between
March 2009 and July 2012 (SEAI c, 2012) are presented in Table 1 (below), alongside those reported
as part of a survey of housing quality undertaken during 2001 – 2002 (Watson & Williams, 2003);
18
Measure SEAI (2012) Watson & Williams
(2003)
Roof Insulation 29% 7%
Cavity Insulation 24%
Dry Lining (internal) Insulation 3% 2-3%
External Insulation 3%
Replacement Windows 22%
External Doors 19%
High efficiency Boiler with heating controls
upgrade
10%
Heating controls upgrade only 3%
Solar Heating 1%
Before / After BER 4%
Integral BER 23%
Table 1 Typical Irish Retrofitting Interventions
Dineen et al. (2010, p. 8) distinguish between ‘shallow’ measures such as roof and cavity insulation
and ‘deep’ measures such as heating controls upgrades and external insulation. SEAI (2010, p. 4)
expand upon this by citing internal and external insulation, high efficiency windows and Mechanical
Ventilation Heat Recovery (MVHR) as deep interventions.
Though both sets of data in Table 1 (above) are not directly comparable (for example, double glazing
is excluded from BEH on cost effectiveness grounds (Curtain, 2009, p. 19)), there is a clear bias
towards shallow retrofit measures that are unlikely to achieve the 90% reductions in GHG emissions
envisioned by SEAI (2010), a finding in keeping with Dineen et al. ( 2010, p. 8). A similar situation is
noted in the UK by Davies & Osmani (2011, p. 1691).
Despite administering the NERP, a scheme with an “easily achievable” (Curtain, 2009, p. 32) target
BER of C1, SEAI (2010, p. 3) conclude there is a need to encourage ‘deep retrofits’, something for
which there appears to be no single definition.
Struabe offers a generic definition, holding a deep retrofit to be one which “extends the viability of
the building 50 to 100 years into the future” (BSC, 2010, p. 6). Others define deep retrofits in terms
of energy consumption reductions, with qualifying levels ranging from to 50% to 90% (Scania, 2010).
Reductions in operating costs is also a commonly used measure, with Bloom & Wheelock (2010, p. 4)
and Curtain & Maguire (2011, p. 4) assuming deep retrofits to achieve 60% and 40% reductions,
respectively.
19
2.5 Principles of the Fabric First Approach
The fabric first approach is central to regulations governing the construction of new dwellings in
Ireland and to the EnerPHit standard for deep retrofits, and as such, can be said be central to the
achievement of the significant emissions reductions deemed possible in the Irish residential sector.
Several interrelated principles underlie the fabric first approach;
• The building envelope should be highly and continuously insulated
• Thermal bridging should be minimal
• The thermal envelope should exhibit low levels of infiltration, yet be well ventilated
• Moisture should be well managed
Given the constraints inherent in an existing structure, the achievement of these principles in a
retrofit scenario can be challenging, particularly aspects relating to thermal bridging and infiltration.
2.5.1 Insulated building envelope
In creating highly insulated building envelope, the objective is to maximise reductions in the
transmittance of heat through building envelope planar elements. The thermal transmittance of any
such planar element is defined by its ‘U-value’, and is measured in W/m2K.
Davies & Osmani (2011, p. 1692) note how, in the UK, improving thermal retention through thermal
insulation of planar elements is the preferred retrofitting approach, possibly reflective of claims that
the energy related attributes of a dwelling’s fabric have the greatest influence on space heating
energy demand and define the extent of fabric and ventilation heat loss in a dwelling (Wardell &
Shanks, 2005, p. 25).
2.5.2 Minimal Thermal Bridging
A principle consideration of the thermal envelope is that insulation levels should be as continuous as
possible, with breaks in the continuity of the level of insulation giving rise to a thermal bridge; a
localised area of reduced insulation, resulting in increased levels of thermal transmittance, hence a
lower surface temperature which can facilitate mould growth (Little & Arregi, 2011).
Aside from the health implications associated with mould growth, thermal bridge related heat loss
can contribute significantly to overall dwelling heat loss. As thermal transmittance through planar
elements decreases as a result of increasing levels of insulation, the proportion of overall heat loss
attributable to thermal bridging increases. Further to this, (Little a, 2009) graphically demonstrates
how the ill-management of thermal bridges can serve to increase the absolute thermal
transmittance through them. Furthermore, it is demonstrated that significant reductions in thermal
20
transmittance through common thermal bridges as found at the eaves, window sills and jambs can
be achieved given sufficient attention to detail. For example, where external insulation is dropped
below ground level, thermal transmittance along the thermal bridge at the junction of ground floor
and external wall (as indicated by Ψ in Figure 5 (below)1) can be reduced over 60%;
Figure 5 Reductions in thermal transmittance at ground floor / external wall junction where external insulation stopped
at ground level (left) and continued underground (right) (Little a, 2009)
Through the use of thermal imagery, Wardell & Shanks (2005) determined that 13 dwellings from a
sample of 20 contained thermal bridging in contravention of Irish building regulations, with 11 and
13 dwellings missing wall and roof insulation respectively.
A brief discussion of how thermal bridging heat loss is accounted for by DEAP and the model used in
this study is provided in Appendix B.
1 See Appendix B for further information on Ψ
21
2.5.3 Highly air-tight thermal envelope
Wardell & Shanks (2005, p. 39) note that infiltration is air exchange that occurs through cracks and
small gaps in the external fabric that are not designed in, such as spaces between window frames
and external walls and small gaps around penetrations through the external envelope. A measure of
infiltration is air permeability, which represents the volume of air passing through each square
meter of building envelope (Sinnott & Dyer, 2012, p. 270). For new dwellings in Ireland, the limiting
value of air permeability is 7m3/h/m2 (DECLG, 2011), a value far in exceedance of other European
countries (EST a, 2010, p. 44).
Table 2 (below) presents sample air permeability values for Irish dwellings derived from various
sources;
(Sedlak &
Sheward, 2008)
(Sinnott &
Dyer, 2012)
(O'Se, 2011)
Number of Tests 32 28 circa 120
Avg. m3/hr/m
2 8.1 9.1 5.0
Max. m3/hr/m
2 20.8 14.4 23.0
Min. m3/hr/m
2 2.1 5.1 0.3
Table 2 Air permeability values from various Irish sources
The maximum values noted here are far in excess of Irish best practice values, with the average
values noted by Sedlak & Sheward (2008) and Sinnott & Dyer (2012) also failing to meet current
regulations. O'Se (2011) notes the lower average and minimum values of air permeability result from
air-tightness being ‘designed in’ to the dwellings being tested. Values of air permeability of 0.82
m3/hr/m2 have been recorded for dwellings retrofitted to the EnerPHit standard (EST, 2011, p. 31), a
figure which highlights the significant scope for reductions in infiltration related heat loss in Irish
dwellings.
In terms of reducing heat losses via infiltration during retrofits, O'Se (2011) notes that renovated
dwellings did not necessarily see significant improvements in air-tightness, though he does not
mention what interventions were undertaken during renovations. Sedlak & Sheward (2008) note
that older, renovated dwellings showed the worst performance, even with new windows installed, a
problem attributed to problems with joints between new and old constructions. Both findings are at
odds with Sinnott & Dyer (2012, p. 272), who note that values of air-tightness in dwellings which had
undergone a retrofit to be on average 35% better than for dwellings which had not, and note that
cavity wall insulation and double glazing installation have the largest effect, reducing air
permeability by 28% and 39% respectively.
22
2.5.4 Ventilation
Whereas infiltration is uncontrolled air movement through the building envelope, ventilation is
controlled air movement, and is required to ensure good indoor air quality is provided for occupants.
Both Little (b, 2009) and Dimitroulopoulou (2012, p. 110) note the health impacts of poor
ventilation, including the onset of respiratory problems such as asthma. The provision of adequate
ventilation in low energy dwellings is a delicate act, balancing the need to maintain air quality and
keep ventilation related heat losses to a minimum. For this reason, mechanical ventilation with heat
recovery is mandatory for low energy standards such as EnerPHit (Feist, 2010, p. 8).
2.5.5 Moisture management
The need for adequate ventilation is furthered by Little & Arregi (2011) who note that humidity in
Irish dwellings is higher than European norms, something which can lead to two types of
condensation; surface and interstitial.
Wardell & Shanks (2005, p. 37) note that surface moisture condensation and mould growth can
occur when the surface temperature is lower than the dew point temperature of the air in the room.
Thus, surface condensation leading to mould growth can occur where relative humidity reaches
100% around a thermal bridge in an area where ventilation is poor. The possibility of such
condensation problem arising was noted in approximately 33% of sample of 20 dwellings (ibid).
In discussing interstitial condensation, Little (a, 2010) focuses on walls, claiming them to be the
planar element most supportive of mould growth. Mould growth can occur at 80% humidity, less
than the 100% required for surface condensation (Little b, 2009). In an earlier age of high infiltration,
little or no insulation and internal heat sources such as open fires, walls could dry out over time with
little mould growth. When a wall is internally insulated, the wall structure cannot dry out, leading to
the potential failure of the insulation system and internal mould growth on the wall (Little a, 2010).
This situation can be avoided through the use of a suitable vapour control layer to limit the moisture
reaching the internal façade of the wall behind the insulation (Little b, 2009) and the suitable
impregnation of the external façade of the wall to prevent rain ingress (Little b, 2010).
Little & Arregi (2011) note how internal insulation at the party wall can lead to cold spots and
potential mould growth in adjacent properties, as shown in Figure 6 (below);
23
Figure 6 Mould risk associated with differing approaches to wall insulation
Note how in Figure 6 (left), the use of external insulation means the wall in House A remains warm,
with the temperature in the corner of House B raised locally. Note the temperature factor (fRsi),
which must be maintained above 0.75 to remove the risk of mould growth. In Figure 6 (right)
internal insulation has been used in House A, which lowers the temperature in the corner of House B
and brings the temperature factor below 0.75, introducing the risk of mould growth.
External insulation keeps materials within the thermal envelope warm and dry, preventing
condensation and mould problems (Little & Arregi, 2011). Instances of thermal bridging are also
lower with external insulation, which is mandatory for the EnerPHit standard, with Internal
insulation only permitted for 25% of wall area where external insulation is not practical or permitted
(Feist, 2010, p. 6).
2.6 Workmanship
EST (2011) and makes clear the level of detail required to achieve EnerPHit levels of air permeability.
Little (a, 2009) and EST (b, 2010) clearly emphasise the need for high levels of design and
workmanship in order to significantly reduce thermal bridging heat loss during a retrofit. Taking a
more holistic view, Sinnott & Dyer (2012, p. 273) conclude that quality workmanship, design,
detailing and construction practice are all essential to successful retrofitting, while (EST b, 2010)
highlights the importance of each team recognising the centrality of their work to the achievement
of a low energy retrofit.
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2.7 Key Findings
The residential sector is a major contributor to overall Irish energy consumption and CO2 emissions.
Regulatory non-compliance and poor enforcement have combined to create the legacy of a housing
stock where the average performance is considerably poorer than European norms. Evidence
presented in this section suggests it would be unwise to assume newer dwellings do not require
energy efficiency interventions.
Although retrofitting to date has yielded results, the widespread uptake of deep retrofits is deemed
necessary not only to achieve the magnitude of reductions in energy consumption and CO2
emissions deemed possible in the residential sector, but to the achievement of Ireland’s obligations
under internationally binding emissions agreements. The fabric first approach has been shown to
provide a suitable foundation for deep retrofits.
The need for quality workmanship across all disciplines has been identified as a requirement to the
successful achievement of low energy retrofits.
25
Section 3. Methodology
3.1 Research Strategy
Taking WCC as a case study, the strategy is to perform a desk based analysis of a sample of DEAP
survey results. A custom built excel based model will be used to analyse the input files and perform
scenario analysis.
3.2 Data Sources
Two significant sources of primary data are Wicklow County Council and the Sustainable Energy
Authority of Ireland.
3.2.1 Wicklow County Council
External, accredited assessors perform DEAP surveys for WCC, and as per WCC (b, 2011), must
provide the following documents for each survey performed;
1. A copy of the BER certificate issued
2. A detailed report of the assessment exported from DEAP, in both Excel and XML format (the
‘Dwelling Report’)
3. An Excel file containing recommendations made by the assessor on energy efficiency
interventions which could be implemented to achieve the target C1 energy rating for the
dwelling (the ‘Energy Efficiency Report’)
In total, 718 Dwelling Reports and 68 Energy Efficiency Reports provided by WCC are considered in
this study.
3.2.2 Sustainable Energy Authority of Ireland
The SEAI is responsible for the administration of the Building Energy Rating (BER) scheme in Ireland
and maintain the NBERRT, which contains the results of DEAP surveys carried out nationwide to
date. Given that the inputs to this research and the data contained in the NBERRT were collected in
an identical fashion (i.e. a standardised DEAP survey), use of this information facilitates a direct
comparison between dwellings in WCC and those in Ireland and Co. Wicklow.
At the time of use (July, 2012), this database contained 289,593 results, representing approximately
14.4% of the national stock. For comparative purposes, this study assumes the 286,793 non-
26
provisional2 entries to represent the average dwelling in Ireland, while the 8,465 non-provisional
entries for dwellings in Co. Wicklow are deemed to represent the average dwelling in Co. Wicklow.
3.3 Research Model
Key objectives of this research are to;
1) Profile the energy performance and thermal envelope efficacy of a sample of WCC dwellings
2) Model the impact on energy consumption of various thermal envelope retrofit strategies
A custom model, based on the DEAP application used to perform dwelling assessments, has been
created for this purpose.
3.3.1 DEAP Calculations
A DEAP survey is performed using the ‘DEAP’ software application, which is developed and
maintained by the SEAI3. The calculations used by the DEAP application to determine primary energy
consumption and CO2 emissions for a dwelling are fully accessible in (SEI, 2007). The DEAP process
can be broken into several steps, as outlined in Figure 7 (below);
Figure 7 The 5 steps of a DEAP Assessment
Step 1: Determine the Overall Heat Loss Coefficient, which represents total dwelling heat loss by
way of ventilation heat loss, planar heat loss and thermal bridging heat loss. Key inputs here relate
2 There are 3 BER types (SEAI d, 2012, p. 5); Provisional (required for a dwelling that is not yet built but is
offered for sale “off the plans”), Final (required for a newly-built dwelling before it is occupied) and Existing
(required for any existing dwelling that is offered for sale or to let). 3 This study assumes all dwelling assessments were performed using DEAP V3.1.0, the latest version available
at the time WCC undertook their assessments.
Internal Gains(W) Solar Gains (W)
Occupants (W) Window Orientation
Heat Loss -
Doors
Heat Loss -
Floors
Heat Loss -
Roofs
Heat Loss -
Walls
Heat Loss -
Windows
Hot Water
System (W)
Glazing Transmittance
Frame Factor
Area Area Area Area Area Appliances (W) Standardised values
U-value U-value U-value U-value Adjusted
U-value
Lighting (W) of Monthly Insolation
Step 2. Determine Overall Heat Gains (W)
Thermal Bridging Factor (W/m2K)
Fabric Heat Loss (W/K)
Step 1. Determine Overall Heat Loss Coefficient (W/K)
Average Monthly External Temperature (°C)
Ventilation Heat Loss (W/K)
Number of openings (m3/h)
Structural Infiltration (ac/h)
Ventilation Method (ac/h)
Number of sheltered sides
Heating system responsiveness
Step 3. Determine Net Space Heat Demand (kWh/y)
Heat Capacity (thermal mass) of Dwelling (MJ/K)
Average Internal Temperature (°C)
Step 5. Determine total primary energy consumption (kWh/y) and
CO2 emissions (kg/y)
Space heating system(s) efficiency (%) and fuel type
Water heating system(s) efficiency (%) and fuel type
Renewable contributions
Step 4. Determine Annual Space Heating Demand (kWh/y)
Heating system controls
Presence and location of heating system(s) pumps and fans
27
to the number of openings in the dwelling, building envelope element U-values and areas and a
thermal bridging factor.
Step 2: Determine Overall heat gains. Key inputs here relate to the number of lights in the dwelling.
Step 3: Based on standardised assumptions of internal and external temperature, the thermal mass
of the dwellings and solar gains, determine the Net Space Heat Demand (NSHD).
Step 4: Accounting for the responsiveness of any heating system(s) and the presence of controls,
pumps and fans, determine the Annual Space Heating Energy Requirement.
Step 5: Accounting for space and water heating system efficiencies, fuel types used and the presence
of any renewable technologies, determine the primary energy requirements and CO2 emissions for
the dwelling.
The effect of retrofit interventions on overall energy usage can also be modelled for individual
dwellings through the DEAP application. The results of a DEAP survey can be exported to an Excel
file (the ‘Dwelling Report’) containing the following information on separate tabs;
1) Dwelling overview
information
8) Lighting and internal gains
2) Dwelling dimensions 9) Annual Heat Use
3) Ventilation details 10) Annual Space Heat Req.
4) Planar element details 11) Distribution system losses
and gains
5) Heat Loss details 12) Heating system energy
requirements
6) Water heating details 13) Summer internal gains
7) Solar water heating details 14) Dwelling energy requirements
and CO2 emissions
Table 3 DEAP Dwelling Report contents
3.3.2 Profiling Energy Performance and Thermal Envelope Efficacy
In the context of this study, that DEAP can only analyse a single dwelling at a time is a key limitation,
as this this research aims to analyse the performance of 718 dwellings. To circumvent this
limitation, the 718 separate ‘Dwelling Reports’ provided by WCC were parsed using a custom built
Excel Macro and collated into a single Excel ‘Master Spreadsheet’, which forms the basis of the
model used to perform energy profiling and retrofit analysis.
28
Information central to determining the energy consumption and CO2 emissions for each dwelling in
the sample is distilled to a single row in the master spreadsheet, thus facilitating data analysis. Table
4 (below) highlights specific energy related quantities central to profiling the energy performance of
the sample;
Assessed Quantity
Ventilation Heat Loss
Planar Element Heat Loss
Thermal Bridging Heat Loss
Fabric Heat Loss
Overall Heat Loss
Net Space Heat Demand
Total Space Heating Primary Energy Demand
Dwelling Primary Energy Demand
Dwelling CO2 Emissions
Table 4 Energy related quantities considered in this study
The analysis of these quantities is presented in section 4.
3.3.3 Modelling retrofit interventions
Upon creation, the data contained within the master spreadsheet is static, that is to say information
contained in one cell is not linked in any way with information in any other cell. To model the
impact on primary energy consumption and CO2 emissions arising from the implementation of
various retrofit interventions, the calculations performed by the DEAP application must be
incorporated into the master spreadsheet. The results of these calculations are represented by
‘modelled quantities’ which are implemented as columns in the master spreadsheet adjacent to the
corresponding ‘assessed quantity’.
Figure 8 (below) shows an extract of the master spreadsheet, with the assessed and modelled values
of Fabric heat loss (FabricHeatLoss [W/K] and MFabricHeatLoss [W/K], respectively) clearly visible;
29
Figure 8 Extract from the Master Spreadsheet
As can be seen, this approach easily facilitates a comparison of ‘before and after’ values for a
quantity, and allows reductions achieved to be determined for a quantity.
The retrofit interventions the model aims to accommodate are listed in Table 5 (below). It is clear
that the implementation of any of the listed interventions will alter the inputs to specific DEAP
calculations. This is managed in the model by associating each retrofit intervention with a ‘modelled
attribute’, also noted in Table 5 (below). The value associated with each modelled attribute can be
manually defined via an ‘attribute control’, which is implemented as a dropdown containing values
relevant to the intervention the modelled attribute represents. The values of modelled attributes
are taken as input to the DEAP calculations embedded within the master spreadsheet. For Floors,
Roofs, Walls and Windows, an attribute control is provided per element type to account for the fact
that there may be several element types per dwelling.
Intervention Modelled Attribute
Alter the number of Chimneys M#Chimneys
Alter the number of Flues M#OpenFlues
Alter the number of extract fans / open vents M#Fans/Vents
Alter the number of mobile gas appliances M#FluelessGas