Report on the Development of Cost Optimal Calculations and Gap Analysis for Buildings in Ireland under Directive 2010/31/EU on the Energy Performance of Buildings (RECAST) Section 1-Residential Buildings Department of Housing, Planning and Local Government Final Report Revised 07/04/2020 05 April 2018
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Report on the Development of Cost Optimal Calculations and Gap Analysis for Buildings in Ireland under Directive 2010/31/EU on the Energy Performance of Buildings (RECAST)
Section 1-Residential Buildings
Department of Housing, Planning and Local Government Final Report Revised 07/04/2020
05 April 2018
Irish Cost Optimal Report 2018 2
Prepared for: Department of Housing, Planning and Local Government
AECOM
Quality information
Prepared by Checked by Approved by
Pratima Washan David Ross David Ross
Irish Cost Optimal Report 2018 3
Prepared for: Department of Housing, Planning and Local Government
AECOM
Prepared for: Department of Housing, Planning and Local Government
This document has been prepared by AECOM Limited (“AECOM”) for sole use of our client (the “Client”) in accordance with generally accepted consultancy principles, the budget for fees and the terms of reference agreed between AECOM and the Client. Any information provided by third parties and referred to herein has not been checked or verified by AECOM, unless otherwise expressly stated in the document. No third party may rely upon this document without the prior and express written agreement of AECOM.
Irish Cost Optimal Report 2018 4
Prepared for: Department of Housing, Planning and Local Government
Prepared for: Department of Housing, Planning and Local Government
AECOM
Executive Summary
This report details work undertaken for the Department of Housing, Planning and Local Government. It describes cost-optimal calculations and a gap analysis for residential buildings in accordance with Article 5 of Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings (recast) The report has been developed in accordance with Commission Delegated Regulation (EU) No 244/2012 of 16 January 2012 supplementing Directive 2010/31/EU of the European Parliament and of the Council on the energy performance of buildings (hereinafter referred to as the Cost-Optimal Regulation) and the associated Guidelines accompanying Commission Delegated Regulation (EU) No 244/2012 of 16 January 2012
The format of this report is based upon the reporting template provided in Annex 3 of the Cost-
Optimal Regulation. This report is in a similar format to the 2013 Cost Optimal Report for Ireland.
Energy Performance Assessment and modelling
The following reference buildings were selected for new and existing single-family buildings.
Bungalow
Detached house (2 storeys)
Semi-detached house (2 storeys)
Mid-floor flat
Top-floor flat
Mid-terrace (existing only)
In addition a new and existing apartment block building was modelled in accordance with the requirements of the EPBD.
The building models used are based upon typical dwellings agreed with the Department of Housing, Planning and Local Government (DHPLG).
The selection of buildings and the baseline energy performance of the existing buildings were based on an analysis of Sustainable Energy Authority of Ireland’s (SEAI) Energy Performance Certificate or Building Energy Rating database which contained 830,952 records in Q1 2018. This represents approximately 49% of occupied dwellings.
In order to model the energy performance of dwellings to a cost optimal level, the Dwelling Energy
Assessment Procedure (DEAP) as published by Sustainable Energy Authority of Ireland (SEAI) was
used.
DEAP is Ireland’s calculation methodology and software for calculating the energy performance of
buildings and meets the requirements of the EPBD (recast) Annex I and EN 13790. The requirements
regarding the conservation of fuel and energy for dwellings are laid out in Part L of the Second Schedule
to the Building Regulations 1997 (Statutory Instrument No. 497 of 1997) as amended by the Building
Regulations (Part L Amendment) Regulations (Statutory .Instrument No. 259 of 2011 to S.I. 538 of
2017). Part L of the Building Regulations provides that the energy performance of the dwelling is such
as to limit the calculated primary energy consumption and related carbon dioxide (CO2) emissions
insofar as is reasonably practicable, when both energy consumption and carbon dioxide (CO2)
emissions are calculated using the Dwelling Energy Assessment Procedure (DEAP) published by the
Sustainable Energy Authority of Ireland. DEAP calculates whole dwelling energy and carbon emissions
performance compliance for the Irish Building Regulations Part L 2005, 2008, 2011 and 2018 for new
dwellings.
Capital Costs and Lifecycle Costs
Capital costs for measures were developed by independent economic consultants Currie and Brown.
New build cost data was based on current construction projects in the Dublin region. Existing build
cost data was validated against cost data from SEAI Better Energy Homes grant schemes.
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Discount rates used took account of public sector rates used by Department of Public Expenditure
and Reform and financial rates used by the financial sector. Future energy prices were based on
SEAI forecasts. Sensitivities were modelled to allow for different energy prices, discount rates and
capital and operational costs.
Models were run from both a societal and investor perspective. The societal model included the cost
of carbon and used lower discount rates. The investor model excluded the cost of carbon and used
higher discount rates.
Results and Gap Analysis
As the reduction of carbon emissions is a societal challenge, the societal perspective which includes
the price of carbon has been used to perform the gap analysis to inform the cost optimal level.
The results of the gap analysis for new and existing dwellings from a societal perspective are
described below. The results are based on a macro economic analysis, using a 5% discount rate and
a central energy price.
The 2018 cost optimal report compares the cost optimal level to the draft 2018 Part L of the Building
Regulations performance requirements which have completed public consultation and are due to be
signed into regulation at the end of September 2018. This 2018 Part L regulation introduces Nearly
Zero Energy Building performance requirements and Major Renovation provisions to a cost optimal
level into Ireland’s Building Regulations for Dwellings.
New Buildings
The 2018 Part L of the Building Regulations Conservation of Fuel and Energy performance
requirements for the majority of dwelling types meet the cost optimal level performance. The cost
optimal gap analysis for single family dwellings is shown in table 7.1 in the main body of the report.
There is no negative gap between the cost optimal levels and 2018 performance requirements for
the majority of dwellings. The average performance of all dwelling types is also better than the cost
optimal level.
As the average performance of all dwelling types is better than the cost optimal level and the
majority of single family dwellings and the apartment block when modelled to 2018 Part L Building
Regulations performance requirements achieve the cost optimal level there is no gap between
these performance requirements and the cost optimal level.
Existing Buildings - Major Renovation (Analysis of packages)
In the majority of dwellings modelled, the current requirement of 125kWh/m2/yr is within 15% of the
cost optimal primary energy level as required by the cost optimal guidance. The cost optimal levels
are set out in Tables 7.6 to 7.9 in the main body of the report. In some cases where the cost optimal
level is more than 15% lower than the 2018 Part L requirements, this is achieved through the
installation of photovoltaics as part of the major renovation package on specific dwelling types.
From an economic perspective, the installation of photovoltaics may present an unintended barrier
to the retrofit of dwellings and it may not be functionally feasible to install photovoltaics due to
available space.
The Part L 2018 performance requirements are within 15% of the cost optimal level for the major renovation of the majority of dwellings inso far as they are technically, functionally and economically feasible.
Existing Buildings - Elemental replacement
For the heating systems, window and hollow block/solid wall elements analysed, there is no gap
between 2018 Part L requirements and the cost optimal level. The cost optimal levels are set out in
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Tables 7.3 to 7.5 in the main body of the report. In the case of roofs with insulation between joists,
cavity walls and floors there are functional reasons why it may not be possible to install additional
insulation to achieve the cost optimal level such as available space in existing rooms or roof spaces,
or cavity widths in walls. The Part L 2018 requirements are at the cost optimal level for elemental
replacement insofar as they are technically, economically and functionally feasible.
Irish Cost Optimal Report 2018 4
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1. Introduction
This report details work undertaken for the Department of Housing, Planning and Local Government. It describes cost-optimal calculations and a gap analysis for residential buildings in accordance with Article 5 of Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings (recast) The report has been developed in accordance with Commission Delegated Regulation (EU) No 244/2012 of 16 January 2012 supplementing Directive 2010/31/EU of the European Parliament and of the Council on the energy performance of buildings (hereinafter referred to as the Cost-Optimal Regulation) and the associated Guidelines accompanying Commission Delegated Regulation (EU) No 244/2012 of 16 January 2012
The format of this report is based upon the reporting template provided in Annex 3 of the Cost-
Optimal Regulation. This report is in a similar format to the 2013 Cost Optimal Report for Ireland.
.
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2. Reference Buildings
2.1 New buildings
According to Annex 1 of Cost Optimal Regulation, member states should establish reference buildings
for the following two residential building categories: single-family buildings and apartment blocks/
multifamily buildings. For each building category, at least one reference building shall be established
for new build.
The following five reference buildings have been selected for single-family buildings.
Bungalow
Detached house (2 storeys)
Semi-detached house (2 storeys)
Mid-floor flat
Top-floor flat
The following reference building has been selected for apartment blocks/ multifamily buildings.
Apartment building: This is analysed as a whole apartment block1. It comprises three types of apartment units: the top and mid-floor apartments (as adopted for single-family buildings) and a ground floor apartment based on the same geometry. The apartment building comprises six floors with 4 apartment units on each floor. It is assumed that all communal spaces (e.g. corridors, stairways) are unheated.
The building models used are based upon typical dwellings agreed with the Department of Housing, Planning and Local Government (DHPLG). The justification for adopting these dwellings is that they are based on a review undertaken of new build dwelling construction. Sources included the Department of Housing, Planning and Local Government Housing Statistics, the Central Statistics Office Construction and Housing Statistics, DKM Economic Consultants Ltd Annual Review of the Construction Industry, and Sustainable Energy Authority of Ireland’s Energy Consumption and CO2 Emissions in the Residential Sector.2
A summary of the floor areas for these buildings is shown in Table 2.1. The floor areas are calculated
by taking linear measurements between the finished internal faces of the walls. New buildings are
assumed to be of cavity wall construction. As per DHPLG advice, that this is the most common new
build construction type in Ireland.
Table 2.1: Reference Building Details – Floor Areas
Building Category Reference Building Floor Area
Single-family buildings
Bungalow 104m²
Detached house 160m²
Semi-detached house 126m²
Mid-floor flat 81m²
Top-floor flat 81m²
Apartment blocks and
multifamily buildings Apartment building
1944 m2
(total area for all apartments in the building)
1 The results for this building type aggregate the results for the individual apartment units. The results do not include energy use within communal spaces (e.g. corridors, stairways) as these are typically unheated spaces. National energy efficiency standards for communal spaces are determined by the national non-residential building regulations which are assessed separately within the cost-optimal studies. 2 UCD ERG Study for Department of Environment Heritage and Local Government, Energy Efficiency Regulations for New Dwellings and Options for Improvement, 2007.
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For the purpose of this work, it has been assumed that the buildings are constructed in Dublin. The
Greater Dublin area contributes to a significant proportion of newly constructed dwellings in the
Ireland and is also the focus of current construction activities. Hence, climate and cost data relevant
for the Dublin geographical area been taken into consideration for the analysis.
Table 2.2 provides a more detailed summary of the Reference Buildings using the template provided
with the Cost Optimal Regulations. The component level requirements that set the proposed minimum
performance standards under draft Building Regulations 2018 for new residential buildings are
Ventilation system Air permeability at 50Pa 5 m³/m².hr
Heat recovery efficiency - %
Heating system
Fuel Gas -
Generation 91.3 %
Distribution / Control 100 %
Secondary Heating Efficiency none %
Secondary Heating Proportion - %
DHW system Generation 91.3 %
Distribution / Control 100 %
Lighting Luminaire efficacy 94 Lumens/cW
Power 4 W/m2
Setpoints and
Schedules
Temperature setpoint Winter
21 (living area)
18 (rest of
dwelling)
ºC
Operation schedules All schedules are defined by the DEAP v4.1. The heating schedule is
07.00h to 09.00h and 17.00h to 23.00h daily, Oct. - May
Total water demand 125 litres/person/day
Hot water demand Based on 1 bath plus showers with 6 litres/min flow restrictor
Energy Use
Energy contribution of main
passive strategies Natural ventilation
These energy savings are not
reported separately.
Heating energy 18 kWh/m²/yr
Cooling energy - kWh/m²/yr
DHW energy 29 kWh/m²/yr
Lighting energy 2 kWh/m²/yr
Auxiliary energy 0.6 kWh/m²/yr
Energy
Generation Generated energy (photovoltaic panels) 8 kWh/m²/yr
Delivered energy
Fossil fuel 47 kWh/m²/yr
Electricity 3 kWh/m²/yr
Other (PVs) 8 kWh/m²/yr
Primary energy 43 kWh/m²/yr
Irish Cost Optimal Report 2018 13
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2.2 Existing Buildings
According to Annex 1 of Cost Optimal Regulation, member states should establish at least two
reference buildings for each building category for existing buildings subject to major renovation -
taking into account the characteristics of the national building stock. Hence, two variations have been
considered for each of the dwelling types considered for new buildings in Section 2.1, plus a mid-
terraced building. Each of the reference buildings has been modelled with two different wall
constructions. Pre-1978 uninsulated cavity wall and uninsulated hollow block wall have been
considered for existing build, as representing two common construction types within Ireland which
would be expected to have significantly different baseline energy performances, and different options
available for energy efficiency upgrades.
The floor areas of the buildings are shown in Table 2.9. For those building types evaluated under new
buildings, we have chosen to adopt the same building models (i.e. same size and geometry). The
principal reason for this is that it provides a useful comparison with the new-build results.
Furthermore, it would be expected that the new-build floor areas selected are not significantly different
to existing building floor areas and that the floor area is much less significant in determining the cost
optimum level than the initial energy efficiency values assumed in the base case (i.e. current) existing
building models.
Table 2.9: Reference Building Details – Floor Areas
Building Category Reference Building Floor Area
Single-family buildings
Bungalow 104m2
Detached house 160m2
Semi-detached house 126m2
Mid-terrace 96m2
Mid-floor flat 81m2
Top-floor flat 81m2
Apartment blocks and
multifamily buildings Apartment building
1944 m2 (total area for all apartments in the
building)
Baseline energy performance for the existing buildings has been modelled based on Ireland’s energy performance certificate database, on the Irish data gathered as part of the Intelligent Energy Europe TABULA project (https://episcope.eu/fileadmin/tabula/public/docs/brochure/IE_TABULA_TypologyBrochure_EnergyAction.pdf), and on the NSAI SR 54:2014 Code of practice for the energy efficient retrofit of dwellings (https://www.nsai.ie/certification/agrement-certification/s.r-54-energy-efficiency-standard/).
The TABULA project ran from 2009-2012 and identified common residential building typologies for
participating member states. The energy performance certificate database contains the data used to
produce energy performance certificates for existing buildings required under Article 7 of the original
Energy Performance of Buildings Directive. There are currently c.831,000 records, with large datasets
for each of the building types considered for this study (https://ndber.seai.ie/pass/ber/search.aspx).
The Energy Performance Certificate database is analysed by the Central Statistics Office3 on a
quarterly basis. The majority (circa 80%) of Energy Performance Certificates analysed for dwellings
were for dwellings constructed between 1950-2009 and typical construction types for this period were
Operation schedules All schedules are defined by the DEAP v4.1. The heating schedule is 07.00h to 09.00h and 17.00h to 23.00h daily, Oct - May
Energy Use
Energy contribution of main
passive strategies Natural ventilation
These energy savings are not
reported separately.
Main Heating energy 62 kWh/m²/yr
Secondary Heating energy 11 kWh/m²/yr
DHW energy 41 kWh/m²/yr
Lighting energy 7 kWh/m²/yr
Auxiliary energy 0 kWh/m²/yr
Energy
Generation Generated energy 0 kWh/m²/yr
Delivered energy Fossil fuel 0 kWh/m²/yr
Electricity 121 kWh/m²/yr
Primary energy 225 kWh/m²/yr
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3. Measures and packages
3.1 New buildings
A list of potential measures has been compiled using the European Commission Cost Optimal
Guidelines document and design experience. Since it is impractical to evaluate every permutation of
the selected measures, we have grouped the measures into packages. These packages are listed in
Table 3.1. The packages represent five different components of a building design (fabric, heating
system, hot water demand, photovoltaics (PV), and lighting), so that selecting one package from each
component forms a complete building design. In total, 432 alternatives have been considered for each
reference building model. The values selected for each of the measures (e.g. the fabric u-values, type
of heating system or lamp efficacy) within the packages have been chosen to give a large spread of
primary energies and lifecycle costs. This helps to obtain a clear cost optimal curve and identification
of the optimum point. It includes solutions that together might comprise a building model that performs
more poorly than the primary energy target set by the current regulations.
It should be noted that some possible measures have been omitted from these packages. There are a number of reasons for this:
Site specific measures: Various measures are particularly dependant on site constraints. For example, building orientation and feasibility of wind turbines are all likely to depend on the site and the surrounding context. Our assumption is that the cost optimal point should be based on measures that any designer can typically adopt, if not the cost optimal point may be unrealistic to achieve in many real cases.
Design measures: Some measures impact on design constraints that are not incorporated in the building primary energy requirement. In particular, our concern is that by modifying the percentage of glazing or introducing shading to optimise primary energy, it may result in inadequate daylight levels. Furthermore, this is building dependent – a particular percentage of glazing may provide appropriate day lighting in one building design but not another. Therefore we have not considered these two measures in the list of packages.
Default measures: There are other measures that are likely to be included in new buildings by default, for example, thermostatic control for hot water cylinders. These have not been included in the packages - they will simply be added into the base building models assumed in all cases. Since these measures do not vary, there is no need to identify separate costs for them.
Table 3.1: Measures to be included in analysis – New Buildings
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Fabric (4 options) 1 2 3 4
Wall U-value (W/m²K) 0.2 0.17 0.15 0.13
Sheltered Wall U-value (W/m²K) 0.3 0.18 0.15 0.13
Roof U-value (W/m²K) House 0.16 0.13 0.10 0.10
Apartment unit 0.19 0.13 0.11 0.11
Floor U-value (W/m²K) House 0.18 0.16 0.13 0.13
Apartment unit 0.2 0.18 0.13 0.13
Window U-value (W/m²K) 1.6 1.3 0.9 0.8
Window g-value 0.65 0.65 0.55 0.55
Thermal Bridging y-
value
House 0.08 0.08 0.04 0.04
Apartment unit 0.15 0.08 0.05 0.05
Air Tightness (m³/m².hr @ 50 Pa) 5 5 3 1
Extract fans Yes Kitchen only Kitchen only Kitchen only
Ventilation type Natural ventilation Whole-house
extract ventilation
Whole-house
extract
ventilation
Balanced whole-
house mechanical
ventilation with heat
recovery
Specific Fan Power (W/l/s) - 0.2 0.2 0.7
Heat Exchanger Efficiency (%) - - - 85
Thermal Mass parameter Medium Medium Low Low
Heating (4 options) 1 2 3 4
Space Heating Source Gas boiler;
91%efficient
Biomass
boiler(bulk
pellets); 80%
efficient
Air source heat
pump; 396%
efficient
District heating
(waste fired co-
generation)
Communal option for flats (all
heating systems are individual for
houses)
No Yes No Yes
Controls
Time and
temperature
zone control;
weather
compensation;
boiler interlock
Time and
temperature
zone control;
weather
compensation;
boiler interlock
Time and
temperature
zone control
Time and
temperature
zone control;
charging linked
to use
Emitters Radiators Radiators Low temperature
radiators Radiators
Domestic Hot Water Source From main
system
From main
system
From main
system;
200% efficient
From main
system
DWH tank volume (L) 120 250 250 120
DWH tank losses (kWh/day) 1.6 2 2 1.6
PV (3 options) 1 2 3
PV Installation (percentage of foundation area) 0% 10% 20%
Installed kWp
Semi-detached 0 1.27 2.53
Bungalow 0 2.09 4.18
Detached 0 1.61 3.21
Apartment units 0 0.27 0.54
Orientation East/West
Tilt 30°
Overshading None
Lighting (3 options) 1 2 3
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Luminaire efficacy (lm/cW) 65 65 95
Power (W/m2) 8.6 4.0 2.0
Hot water (3 options) 1 2 3
Shower flow rate (l/min) 12 6 6
Waste Water Heat Recovery No No Yes
Waste Water Heat Recovery unit
Efficiency - - 45.3%
Utilisation
factor - - 0.93
3.2 Existing Buildings – Elemental analysis
A list of potential measures has been compiled using the EU Commission Cost Optimal Guidelines document and design experience. For the elemental analysis, each measure has been assessed separately. The measures which have been assessed are listed in Table 3.2. The measures selected are those most commonly applied when renovating the building fabric and heating system. The values selected for each of the measures (e.g. the fabric u-values and heating options) have been chosen to give a spread of primary energy values and lifecycle costs. It includes some fabric options which might perform more poorly than the limiting standards set for individual elements under the proposed Part L 2018.
Table 3.2: Measures included in analysis – Existing Buildings
Fabric - Cavity Walls Wall U-value
(W/m²K) Insulation
Option 1 0.31 Fully filled cavity (100mm)
Option 2 0.16 Fully filled cavity and 100mm external EPS
insulation
Option 3 0.11 Fully filled cavity and 200mm external EPS
insulation
Fabric – Hollow Block Walls Wall U-value
(W/m²K) Insulation
Option 1 (for houses only) 0.37 50mm internal PIR insulation
Option 2 0.22 100mm external EPS insulation
Option 3 0.13 200mm external EPS insulation
Fabric – Roof Roof U-value
(W/m²K) Insulation
Option 1 0.13
Pitched roof: 150mm mineral wool insulation
quilt between joists plus 150mm mineral wall
above joists
Flat roof: 160mm PIR insulation above
concrete slab
Option 2 0.11
Pitched roof: 150mm mineral wool insulation
quilt between joists plus 200mm mineral wall
above joists
Flat roof: 200mm PIR insulation above
concrete slab
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Fabric – Floor Floor U-value
(W/m²K) Insulation
Option 1 0.22 20mm of Vacuum insulated Panel (thermal
conductivity of 0.007)
Option 2 0.28 40mm PIR
Option 3 0.22 60mm PIR
Option 4 0.14 120mm PIR
Fabric – Windows
Window
U-value
(W/m²K)
Window
g-value Type
Option 1 1.6 0.65 Double glazed uPVC windows
Option 2 1.4 0.65 Double glazed uPVC windows
Option 3 0.9 0.55 Triple glazed uPVC windows
Heating (3 options)
Space heating source Gas boiler; 91%
efficient
as boiler; 91%
efficient
Air source heat
pump; 260%
efficient
Communal for flats No No No
Controls
Time and
temperature zone
controls; weather
compensation;
boiler interlock
Time and temperature
zone controls;
weather
compensation; boiler
interlock
Time and
temperature zone
control
Emitter Radiators Radiators
Larger replacement
radiators based on a
flow temperature of
55°C
DWH source From main system From main system From main system ;
200% efficient
DWH cylinder volume (L) 120 120 + 25 litres/m2 of
solar panel 250
DWH cylinder losses
(kWh/day)
As per existing
reference building
(25mm factory
insulation)
2 2
SWH No
Yes
60% of hot water
demand
No
3.3 Existing Buildings – Analysis of Packages
In addition to the elemental analysis, existing building measures were assessed on a package basis (i.e. with more than one measure implemented at a time). The analysis of packages is carried out in order to inform the cost optimal performance levels for Major Renovation works.
The measures which have been assessed for residential buildings are listed in Table 3.3. The measures selected are those most commonly applied when renovating the building fabric and heating system. The values selected for each of the measures (e.g. the fabric u-values and heating options)
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have been chosen to give a spread of primary energy values and lifecycle costs. Fabric, heating, PV, hot water and lighting packages have been tested in combination.
Table 3.3: Packages included in analysis – Existing Buildings Fabric (6 options)
1 2 3 4 5 6
Roof, wall and window improvement packages Roof and wall packages for houses
Wall and window packages for apartment units
Cavity Wall U-value
(W/m²K) 0.31 0.31 0.16 0.31 0.31 0.16
Sheltered Wall U-value
(W/m²K) 0.59 0.32 0.32 0.59 0.32 0.32
Solid Wall U-value
(W/m²K) 0.37 0.22 0.13 0.37 0.22 0.13
Roof U-
value
(W/m²K)
Houses 0.13 0.10 0.10 0.13 0.10 0.10
Apartments 0.13 0.11 0.11 0.35 0.35 0.35
Window
U-value
(W/m²K)
Houses 1.4 1.0 0.8 2.8 2.8 2.8
Apartments 1.6 1.4 0.8 1.6 1.4 0.8
Window
– g-
value
Houses 0.65 0.65 0.55 0.72 0.72 0.72
Apartments 0.65 0.65 0.55 0.65 0.65 0.55
Air Tightness (m³/m².hr
@ 50 Pa) 10 5 3 10 5 3
Ventilation
type
Houses Natural
ventilation
Natural
ventilation
cMEV
(SFP = 0.2)
Natural
ventilation
Natural
ventilation
cMEV
(SFP = 0.2)
Apartmen
ts Natural
ventilation
Natural
ventilation
cMEV
(SFP = 0.2)
Natural
ventilation
Natural
ventilation
cMEV
(SFP = 0.2)
Thermal bridging Y-
value 0.15 0.11 0.08 0.15 0.11 0.08
Heating (3 options for houses and 4 options for apartment units)
1 2 3 4
Space
Heating
Houses gas boiler; 91% efficient
Air source heat pump;
396% efficient
biomass boiler; 80%
efficient -
Apartment
s gas boiler; 91% efficient
Air source heat pump;
396% efficient
biomass boiler; 80%
efficient
High heat retention
storage heaters
Communal for flats No No Yes No
Controls
Time and temperature
zone controls; weather
compensation; boiler
interlock
Time and temperature
zone controls; weather
compensation
Time and temperature
zone controls; weather
compensation
Time and temperature
zone controls; weather
and load
compensation
Emitter Radiators
Low temperature
radiators
Low temperature
radiators Panel radiators
DWH source From main system
From main system;
200% efficient From main system Electric immersion
DWH cylinder volume
As per existing
reference building
(25mm factory
insulation)
250 250
As per existing
reference building
(25mm factory
insulation)
DWH cylinder losses - 2 2 -
PV (3 options) 1 2 3
PV Installation (percentage of foundation area) 0% 10% 20%
Installed kWp
Semi-detached 0 1.27 2.53
Bungalow 0 2.09 4.18
Detached 0 1.61 3.21
Mid-terrace 0 0.96 1.93
Apartment units 0 0.27 0.54
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Orientation East/West
Tilt 30°
Overshading None
Hot water and lighting (3 options) 1 2 3
Luminaire efficacy (lm/cW) 65 95 95
Shower flow rate (l/min) 12 6 6
Waste Water Heat recovery (WWHR) No No Yes
WWHR unit
Efficiency - - 45.3%
Utilisation factor - - 0.93
Irish Cost Optimal Report 2018 36
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4. Calculation of primary energy demand for the measures
4.1 New Buildings
4.1.1 Energy Performance Assessment
This section outlines the procedure for determining the primary energy for each package of measures.
Each of the reference buildings was modelled in the DEAP calculation spreadsheet for the draft
Technical Guidance Document (TGD) L 2018 provided by SEAI that implements the Dwelling Energy
Assessment Procedure (DEAP). DEAP is Ireland’s response to the requirement of the EPBD to develop a methodology for calculating the energy performance of buildings.
DEAP is Ireland’s calculation methodology and software to the requirements of the EPBD (recast)
Annex I and EN 13790 for calculating the energy performance of buildings. The requirements
regarding conservation of fuel and energy for dwellings are laid out in Part L of the Second Schedule
to the Building Regulations 1997 (Statutory. Instrument. No. 497 of 1997) as amended by the Building
Regulations (Part L Amendment) Regulations 2011 (Statutory. Instrument No. 259 of 2011 to S.I.
538 of 2017). Part L of the Building regulations provides that the energy performance of the dwelling
is such as to limit the calculated primary energy consumption and related carbon dioxide (CO2)
emissions insofar as is reasonably practicable, when both energy consumption and carbon dioxide
(CO2) emissions are calculated using the Dwelling Energy Assessment Procedure (DEAP) published
by Sustainable Energy Authority of Ireland. DEAP calculates whole dwelling energy and carbon
emissions performance compliance for the Irish Building Regulations Part L 2005, 2008, 2011 and
2018 for new dwellings.
This cost-optimal study identifies the gap (if any) between current whole dwelling energy performance
as defined in Part L of the Building Regulations and the cost optimal level as calculated in DEAP.
To test each package of measures, the DEAP building model input files were updated accordingly
and run through the DEAP calculation spreadsheet. The energy end uses (e.g. space heating, water
heating, lighting, pumps and fans) were recorded directly from the DEAP output files. The end use
energy consumption values were then summed for each energy carrier to find the delivered energy
requirement. Any on-site generated energy was also determined at this stage. The primary energy
factors were then applied to the delivered energy and on-site generated energy. The latter was
subtracted from the former to give the net primary energy.
Annex 1 of the Cost Optimal Regulation state that “Member States shall use a calculation period of 30
years for residential and public buildings”. A calculation period of 30 years for all of the buildings has
therefore been used in this report.
All Residential reference buildings were designed to comply with mandatory overheating/ summer comfort criteria in line with the current version of TGD (Technical Guidance Document) L. This includes compliance with solar overheating requirements in Appendix P of DEAP and is in line with Paragraph 1.3.5 of TGD L 2019 Conservation of Fuel and Energy – Dwellings.
A separate study4 was carried out to assess the overheating risk in dwellings using dynamic thermal simulation software and future weather dataset. It concluded that reference buildings with current fabric standards do not present a high risk of summer overheating.
Prepared for: Department of Housing, Planning and Local Government
AECOM
4.1.2 Energy demand calculation
Tables 4.1a – 4.1f summarise the results of the energy performance calculation for the most cost-
optimal packages in each of the reference buildings5. These tables include the energy breakdown by
end use and the total energy requirement per fuel carrier. The primary energy factors used to
calculate the total primary energy requirement and the primary energy reduction over the reference
case are listed in Table 2.3 to Table 2.8. The delivered energy per carrier has been incorporated into
Tables 4.1 as this allows the values to be seen alongside the primary energy figures rather than
producing separate tables.
Table 4.1a: Energy Demand Output Table
Building: Bungalow
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass DH Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
4 ASHP 20% 3 3 4 0 3 11 2 0 19 -28 0 0 -17 132%
3 ASHP 20% 3 3 7 0 1 11 2 0 21 -28 0 0 -14 126%
1 ASHP 20% 3 2 12 0 0 12 2 0 26 -28 0 0 -5 109%
3 Gas 20% 3 2 31 0 1 25 2 56 3 -28 0 0 15 72%
2 Gas 20% 3 2 43 0 1 25 2 67 3 -28 0 0 27 48%
1 Gas 20% 3 2 50 0 0 25 2 75 3 -28 0 0 34 35%
1 Gas 10% 3 2 50 0 0 25 2 75 3 -14 0 0 60 -16%
1 Gas 10% 3 1 49 0 0 32 2 81 3 -14 0 0 67 -29%
1 Gas 0% 3 2 50 0 0 25 2 75 3 0 0 0 87 -67%
1 Gas 0% 3 1 49 0 0 32 2 81 3 0 0 0 94 -80%
Table 4.1b: Energy Demand Output Table
Building: Detached
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass DH Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
4 ASHP 20% 3 3 3 0 2 7 2 0 14 -14 0 0 0 99%
3 ASHP 20% 3 3 6 0 1 7 2 0 16 -14 0 0 4 91%
1 ASHP 20% 3 2 10 0 0 8 2 0 20 -14 0 0 11 74%
3 Gas 20% 3 2 28 0 1 17 2 44 3 -14 0 0 27 35%
2 Gas 20% 3 2 36 0 1 17 2 53 3 -14 0 0 36 13%
1 Gas 20% 3 2 43 0 0 17 2 60 2 -14 0 0 43 -3%
1 Gas 10% 3 2 43 0 0 17 2 60 2 -7 0 0 57 -35%
1 Gas 10% 3 1 43 0 0 22 2 64 2 -7 0 0 61 -46%
1 Gas 0% 3 2 43 0 0 17 2 60 2 0 0 0 70 -66%
1 Gas 0% 3 1 43 0 0 22 2 64 2 0 0 0 74 -78%
5 Note that the tables currently show the packages that deliver the highest primary energy savings. The tables will be updated once the cost optimal analysis is complete.
Irish Cost Optimal Report 2018 38
Prepared for: Department of Housing, Planning and Local Government
AECOM
Table 4.1c: Energy Demand Output Table
Building: Semi-Detached
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass DH Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
4 ASHP 20% 3 3 2 0 3 9 2 0 16 -14 0 0 3 93%
3 ASHP 20% 3 3 6 0 1 9 2 0 17 -14 0 0 6 86%
1 ASHP 20% 3 3 9 0 0 9 2 0 20 -14 0 0 11 74%
1 ASHP 20% 2 2 9 0 0 10 2 0 21 -14 0 0 13 69%
3 Gas 20% 3 2 24 0 1 21 2 45 3 -14 0 0 28 32%
2 Gas 20% 3 2 31 0 1 21 2 52 3 -14 0 0 36 13%
1 Gas 20% 3 2 38 0 0 21 2 59 2 -14 0 0 42 -1%
1 Gas 10% 3 2 38 0 0 21 2 59 2 -7 0 0 55 -33%
1 Gas 0% 3 2 38 0 0 21 2 59 2 0 0 0 69 -65%
1 Gas 0% 3 1 37 0 0 27 2 64 2 0 0 0 75 -79%
Table 4.1d: Energy Demand Output Table
Building: Mid-floor Flat
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass DH Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
4 ASHP 20% 3 3 1 0 3 13 2 0 19 -5 0 0 26 35%
3 ASHP 20% 3 3 4 0 1 13 2 0 20 -5 0 0 29 29%
1 ASHP 20% 3 3 6 0 1 13 2 0 22 -5 0 0 32 20%
4 Gas 20% 3 3 4 0 3 27 2 31 5 -5 0 0 34 14%
3 Gas 20% 3 2 16 0 1 30 2 46 3 -5 0 0 48 -20%
2 Gas 20% 3 2 19 0 1 30 2 49 3 -5 0 0 52 -29%
1 Gas 20% 3 2 27 0 1 30 2 57 3 -5 0 0 59 -48%
1 Gas 10% 3 2 27 0 1 30 2 57 3 -2 0 0 64 -59%
1 Gas 0% 3 2 27 0 1 30 2 57 3 0 0 0 68 -70%
1 Gas 0% 3 1 26 0 1 39 2 65 3 0 0 0 77 -91%
Irish Cost Optimal Report 2018 39
Prepared for: Department of Housing, Planning and Local Government
AECOM
Table 4.1e: Energy Demand Output Table
Building: Top-floor Flat
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass DH Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
4 ASHP 20% 3 3 2 0 3 13 2 0 20 -5 0 0 29 38%
3 ASHP 20% 3 3 6 0 1 13 2 0 22 -5 0 0 32 32%
4 Gas 20% 3 3 10 0 3 27 2 37 5 -5 0 0 41 12%
4 Gas 20% 3 2 10 0 3 30 2 40 5 -5 0 0 45 5%
3 Gas 20% 3 2 24 0 1 30 2 54 3 -5 0 0 57 -21%
2 Gas 20% 3 2 31 0 1 30 2 60 3 -5 0 0 64 -36%
1 Gas 20% 3 2 46 0 1 30 2 76 3 -5 0 0 80 -70%
1 Gas 10% 3 2 46 0 1 30 2 76 3 -2 0 0 84 -80%
1 Gas 0% 3 2 46 0 1 30 2 76 3 0 0 0 89 -89%
1 Gas 0% 3 1 45 0 1 39 2 83 3 0 0 0 97 -107%
Table 4.1f: Energy Demand Output Table
Building: Apartment block
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass DH Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
4 ASHP 20% 3 3 2 0 3 13 2 0 19 -5 0 0 27 36%
3 ASHP 20% 3 3 4 0 1 13 2 0 21 -5 0 0 30 30%
4 Gas 20% 3 3 6 0 3 27 2 33 5 -5 0 0 37 13%
4 Gas 20% 3 2 6 0 3 30 2 36 5 -5 0 0 40 6%
3 Gas 20% 3 2 19 0 1 30 2 49 3 -5 0 0 51 -20%
2 Gas 20% 3 2 23 0 1 30 2 53 3 -5 0 0 56 -32%
1 Gas 20% 3 2 34 0 1 30 2 63 3 -5 0 0 66 -55%
1 Gas 10% 3 2 34 0 1 30 2 63 3 -2 0 0 71 -66%
1 Gas 0% 3 2 34 0 1 30 2 63 3 0 0 0 75 -76%
1 Gas 0% 3 1 32 0 1 39 2 71 3 0 0 0 84 -96%
Irish Cost Optimal Report 2018 40
Prepared for: Department of Housing, Planning and Local Government
AECOM
4.2 Existing Buildings
4.2.1 Energy Performance Assessment
The same process was followed as for new domestic buildings outlined in section 4.1.
4.2.2 Energy demand calculation – Elemental analysis
Tables 4.2a – 4.2n summarise the results of the energy performance calculation for the most cost-optimal packages in each of the reference buildings. These tables include the energy breakdown by end use and the total energy requirement per fuel carrier. The primary energy factors used to calculate the total primary energy requirement and the primary energy reduction over the reference cases are listed in Table 2.12 to Table 2.25. The delivered energy per carrier has been incorporated into Tables 4.2a – 4.2n as this allows the values to be seen alongside the primary energy figures rather than producing separate tables.
Table 4.2a: Energy Demand Output Table – Bungalow, Cavity Wall
Prepared for: Department of Housing, Planning and Local Government
AECOM
4.2.3 Energy Demand Calculation – Analysis of Packages
Table 4.3 (a–n) summarises the results of the energy performance calculation for the most cost-optimal packages in each of the seven reference buildings respectively. It includes the energy breakdown by end use and the total energy requirement per fuel carrier. The primary energy factors used to calculate the total primary energy requirement are listed in Table 2.12 to Table 2.25.
Table 4.3a: Energy Demand Output Table
Building: Bungalow Cavity Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 11 8 2 11 2 0 26 -28 0 0 5 96%
2 ASHP 20% 3 3 14 10 1 11 2 0 28 -28 0 0 11 91%
5 ASHP 20% 2 2 17 12 1 12 2 0 33 -28 0 0 22 83%
4 ASHP 20% 2 2 19 13 1 12 2 0 35 -28 0 0 28 78%
2 Gas 20% 2 2 59 9 1 28 2 87 3 -28 0 0 60 52%
5 Gas 20% 2 2 72 11 1 28 2 100 3 -28 0 0 77 38%
4 Gas 20% 2 2 82 13 1 28 2 110 3 -28 0 0 90 28%
4 Gas 10% 1 1 80 13 1 36 3 116 4 -14 0 0 125 0%
4 Gas 0% 2 2 82 13 1 28 2 110 3 0 0 0 143 -14%
4 Gas 0% 1 1 80 13 1 36 3 116 4 0 0 0 151 -21%
Table 4.3b: Energy Demand Output Table
Building: Detached Cavity Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 8 6 1 7 2 0 19 -14 0 0 15 88%
2 ASHP 20% 3 3 11 8 1 7 2 0 21 -14 0 0 22 82%
5 ASHP 20% 2 2 15 10 1 8 2 0 25 -14 0 0 33 74%
4 ASHP 20% 2 2 17 11 1 8 2 0 27 -14 0 0 38 70%
2 Gas 20% 2 2 48 8 1 19 2 67 2 -14 0 0 61 51%
5 Gas 20% 2 2 62 10 1 19 2 81 2 -14 0 0 79 37%
4 Gas 20% 2 2 70 11 1 19 2 89 2 -14 0 0 90 28%
4 Gas 10% 2 2 70 11 1 19 2 89 2 -7 0 0 103 18%
4 Gas 0% 2 2 70 11 1 19 2 89 2 0 0 0 116 7%
4 Gas 0% 1 1 69 11 1 24 2 93 3 0 0 0 122 3%
Irish Cost Optimal Report 2018 50
Prepared for: Department of Housing, Planning and Local Government
AECOM
Table 4.3c: Energy Demand Output Table
Building: Semi-Detached Cavity Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 7 5 2 9 2 0 20 -14 0 0 16 87%
2 ASHP 20% 3 3 9 6 1 9 2 0 22 -14 0 0 22 83%
5 ASHP 20% 2 2 13 9 1 10 2 0 26 -14 0 0 33 74%
4 ASHP 20% 2 2 15 10 1 10 2 0 28 -14 0 0 38 70%
2 Gas 20% 2 2 40 6 1 24 2 64 3 -14 0 0 57 55%
5 Gas 20% 2 2 55 9 1 24 2 79 3 -14 0 0 76 39%
4 Gas 20% 2 2 63 10 1 24 2 86 3 -14 0 0 86 31%
4 Gas 20% 1 1 61 10 1 30 3 92 4 -14 0 0 93 26%
4 Gas 0% 2 2 63 10 1 24 2 86 3 0 0 0 112 10%
4 Gas 0% 1 1 61 10 1 30 3 92 4 0 0 0 120 4%
Table 4.3d: Energy Demand Output Table
Building: Terraced Cavity Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 6 4 2 12 2 0 22 -14 0 0 20 84%
2 ASHP 20% 3 3 9 6 1 12 2 0 24 -14 0 0 25 80%
5 ASHP 20% 2 2 12 8 1 13 2 0 29 -14 0 0 37 70%
4 ASHP 20% 2 2 14 10 1 13 2 0 31 -14 0 0 42 67%
2 Gas 20% 2 2 36 6 1 30 2 66 3 -14 0 0 59 52%
5 Gas 20% 2 2 51 8 1 30 2 81 3 -14 0 0 79 36%
4 Gas 20% 2 2 59 9 1 30 2 89 3 -14 0 0 89 29%
4 Gas 10% 2 2 59 9 1 30 2 89 3 -7 0 0 102 18%
4 Gas 0% 2 2 59 9 1 30 2 89 3 0 0 0 116 7%
4 Gas 0% 1 1 57 9 1 38 3 96 4 0 0 0 125 0%
Irish Cost Optimal Report 2018 51
Prepared for: Department of Housing, Planning and Local Government
AECOM
Table 4.3e: Energy Demand Output Table
Building: Mid-floor Flat Cavity Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 4 0 2 14 2 0 21 -5 0 0 31 75%
2 ASHP 20% 3 3 6 0 2 14 2 0 24 -5 0 0 35 72%
2 ASHP 20% 2 2 6 0 2 15 2 0 25 -5 0 0 38 70%
1 ASHP 20% 2 2 9 0 2 15 2 0 28 -5 0 0 42 66%
3 Gas 20% 3 3 15 0 2 31 2 46 4 -5 0 0 50 60%
3 Gas 20% 2 2 15 0 2 34 2 49 4 -5 0 0 53 57%
2 Gas 20% 2 2 26 0 2 34 2 61 4 -5 0 0 65 48%
1 Gas 20% 2 2 37 0 2 34 2 71 4 -5 0 0 76 39%
1 Gas 0% 2 2 37 0 2 34 2 71 4 0 0 0 85 32%
1 Gas 0% 1 1 35 0 2 44 3 79 5 0 0 0 95 24%
Table 4.3f: Energy Demand Output Table
Building: Top-floor Flat Cavity Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 6 0 2 14 2 0 24 -5 0 0 36 72%
6 ASHP 20% 3 3 9 0 2 14 2 0 27 -5 0 0 41 67%
5 ASHP 20% 3 3 12 0 2 14 2 0 30 -5 0 0 46 63%
5 ASHP 20% 2 2 12 0 2 15 2 0 31 -5 0 0 49 61%
6 Biomass 20% 2 2 35 0 1 33 2 0 3 -5 68 0 72 42%
5 Biomass 20% 2 2 48 0 1 33 2 0 3 -5 81 0 85 32%
5 Gas 20% 2 2 52 0 2 34 2 86 4 -5 0 0 93 26%
4 Gas 20% 2 2 64 0 2 34 2 99 4 -5 0 0 107 15%
4 Gas 0% 2 2 64 0 2 34 2 99 4 0 0 0 116 8%
4 Gas 0% 1 1 62 0 2 44 3 106 5 0 0 0 125 0%
Irish Cost Optimal Report 2018 52
Prepared for: Department of Housing, Planning and Local Government
AECOM
Table 4.3g: Energy Demand Output Table
Building: Apartment Block Cavity Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 5 0 2 14 2 0 23 -5 0 0 34 84%
5 ASHP 20% 3 3 9 0 2 14 2 0 26 -5 0 0 39 82%
5 ASHP 20% 2 2 9 0 2 15 2 0 27 -5 0 0 42 81%
4 ASHP 20% 2 2 11 0 2 15 2 0 30 -5 0 0 47 78%
3 Gas 20% 3 3 21 0 2 31 2 53 4 -5 0 0 57 74%
6 Gas 20% 2 2 24 0 2 34 2 58 4 -5 0 0 63 71%
5 Gas 20% 2 2 36 0 2 34 2 70 4 -5 0 0 75 65%
4 Gas 20% 2 2 47 0 2 34 2 81 4 -5 0 0 87 60%
4 Gas 0% 2 2 47 0 2 34 2 81 4 0 0 0 96 55%
4 Gas 0% 1 1 45 0 2 44 3 89 5 0 0 0 106 51%
Table 4.3h: Energy Demand Output Table
Building: Bungalow Solid Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 11 8 2 11 2 0 26 -28 0 0 5 96%
2 ASHP 20% 3 3 13 9 1 11 2 0 28 -28 0 0 9 92%
5 ASHP 20% 3 3 16 11 1 11 2 0 31 -28 0 0 18 86%
4 ASHP 20% 2 2 20 13 1 12 2 0 35 -28 0 0 29 77%
2 Gas 20% 2 2 56 9 1 28 2 84 3 -28 0 0 56 55%
5 Gas 20% 2 2 69 11 1 28 2 97 3 -28 0 0 73 41%
4 Gas 20% 2 2 84 13 1 28 2 112 3 -28 0 0 92 26%
4 Gas 10% 1 1 82 13 1 36 3 118 4 -14 0 0 127 -2%
4 Gas 0% 2 2 84 13 1 28 2 112 3 0 0 0 145 -16%
4 Gas 0% 1 1 82 13 1 36 3 118 4 0 0 0 154 -23%
Irish Cost Optimal Report 2018 53
Prepared for: Department of Housing, Planning and Local Government
AECOM
Table 4.3i: Energy Demand Output Table
Building: Detached Solid Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 8 5 1 7 2 0 19 -14 0 0 15 88%
2 ASHP 20% 2 2 10 7 1 8 2 0 21 -14 0 0 21 83%
5 ASHP 20% 2 2 14 9 1 8 2 0 24 -14 0 0 30 76%
4 ASHP 20% 2 2 17 12 1 8 2 0 28 -14 0 0 39 68%
4 ASHP 10% 2 2 17 12 1 8 2 0 28 -7 0 0 53 58%
5 Gas 20% 2 2 58 9 1 19 2 77 2 -14 0 0 74 41%
4 Gas 20% 2 2 73 12 1 19 2 92 2 -14 0 0 93 26%
4 Gas 20% 1 1 72 11 1 24 2 96 3 -14 0 0 99 21%
4 Gas 0% 2 2 73 12 1 19 2 92 2 0 0 0 119 5%
4 Gas 0% 1 1 72 11 1 24 2 96 3 0 0 0 125 0%
Table 4.3j: Energy Demand Output Table
Building: Semi-Detached Solid Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 7 5 2 9 2 0 20 -14 0 0 16 88%
2 ASHP 20% 3 3 9 6 1 9 2 0 21 -14 0 0 20 84%
5 ASHP 20% 2 2 12 8 1 10 2 0 26 -14 0 0 31 75%
4 ASHP 20% 2 2 15 10 1 10 2 0 28 -14 0 0 39 69%
2 Gas 20% 2 2 37 6 1 24 2 61 3 -14 0 0 53 58%
5 Gas 20% 2 2 52 8 1 24 2 76 3 -14 0 0 72 42%
4 Gas 20% 2 2 64 10 1 24 2 88 3 -14 0 0 88 29%
4 Gas 10% 2 2 64 10 1 24 2 88 3 -7 0 0 102 19%
4 Gas 0% 2 2 64 10 1 24 2 88 3 0 0 0 115 8%
4 Gas 0% 1 1 63 10 1 30 3 93 4 0 0 0 122 3%
Irish Cost Optimal Report 2018 54
Prepared for: Department of Housing, Planning and Local Government
AECOM
Table 4.3k: Energy Demand Output Table
Building: Terraced Solid Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 6 4 2 12 2 0 22 -14 0 0 20 84%
2 ASHP 20% 3 3 8 5 1 12 2 0 23 -14 0 0 23 81%
5 ASHP 20% 2 2 12 8 1 13 2 0 28 -14 0 0 35 72%
4 ASHP 20% 2 2 14 10 1 13 2 0 31 -14 0 0 43 66%
2 Gas 20% 2 2 33 5 1 30 2 64 3 -14 0 0 56 55%
5 Gas 20% 2 2 49 8 1 30 2 79 3 -14 0 0 76 39%
4 Gas 20% 2 2 61 10 1 30 2 91 3 -14 0 0 91 27%
4 Gas 10% 2 2 61 10 1 30 2 91 3 -7 0 0 105 16%
4 Gas 0% 2 2 61 10 1 30 2 91 3 0 0 0 118 6%
4 Gas 0% 1 1 59 9 1 38 3 97 4 0 0 0 127 -1%
Table 4.3l: Energy Demand Output Table
Building: Mid-floor Flat Solid Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 4 0 2 14 2 0 21 -5 0 0 31 75%
2 ASHP 20% 3 3 6 0 2 14 2 0 23 -5 0 0 35 72%
2 ASHP 20% 2 2 6 0 2 15 2 0 25 -5 0 0 37 70%
3 Gas 20% 3 3 14 0 2 31 2 46 4 -5 0 0 50 60%
3 Gas 20% 2 2 14 0 2 34 2 49 4 -5 0 0 53 58%
2 Gas 20% 2 2 25 0 2 34 2 59 4 -5 0 0 64 49%
1 Gas 20% 2 2 38 0 2 34 2 72 4 -5 0 0 77 38%
1 Gas 10% 2 2 38 0 2 34 2 72 4 -2 0 0 82 34%
1 Gas 0% 2 2 38 0 2 34 2 72 4 0 0 0 86 31%
1 Gas 0% 1 1 36 0 2 44 3 80 5 0 0 0 96 23%
Irish Cost Optimal Report 2018 55
Prepared for: Department of Housing, Planning and Local Government
AECOM
Table 4.3m: Energy Demand Output Table
Building: Top-floor Flat Solid Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 6 0 2 14 2 0 24 -5 0 0 35 72%
6 ASHP 20% 3 3 9 0 2 14 2 0 27 -5 0 0 41 67%
5 ASHP 20% 2 2 12 0 2 15 2 0 31 -5 0 0 48 61%
4 ASHP 20% 2 2 16 0 2 15 2 0 34 -5 0 0 55 56%
6 Biomass 20% 3 3 34 0 1 30 2 0 3 -5 65 0 69 45%
6 Gas 20% 2 2 38 0 2 34 2 72 4 -5 0 0 78 37%
5 Gas 20% 2 2 50 0 2 34 2 85 4 -5 0 0 91 27%
4 Gas 20% 2 2 65 0 2 34 2 100 4 -5 0 0 108 14%
4 Gas 0% 2 2 65 0 2 34 2 100 4 0 0 0 117 7%
4 Gas 0% 1 1 63 0 2 44 3 107 5 0 0 0 126 -1%
Table 4.3n: Energy Demand Output Table
Building: Apartment Block Solid Wall
Package Energy Use Fuel Use Primary Energy
Fabric Heating PV Light DHW Heat
Sec
Heat Aux DHW Light Gas
Grid
Elec.
Gen.
Elec. Biomass
Smoke-
less
fuel
Total
Reduction
over
Reference
kWh/m² kWh/m² kWh/m² %
3 ASHP 20% 3 3 5 0 2 14 2 0 23 -5 0 0 34 84%
5 ASHP 20% 3 3 8 0 2 14 2 0 26 -5 0 0 39 82%
5 ASHP 20% 2 2 8 0 2 15 2 0 27 -5 0 0 41 81%
4 ASHP 20% 2 2 11 0 2 15 2 0 30 -5 0 0 47 78%
6 Gas 20% 2 2 23 0 2 34 2 58 4 -5 0 0 62 71%
5 Gas 20% 2 2 34 0 2 34 2 69 4 -5 0 0 74 66%
4 Gas 20% 2 2 48 0 2 34 2 82 4 -5 0 0 89 59%
4 Gas 10% 2 2 48 0 2 34 2 82 4 -2 0 0 93 57%
4 Gas 0% 2 2 48 0 2 34 2 82 4 0 0 0 97 55%
4 Gas 0% 1 1 46 0 2 44 3 90 5 0 0 0 107 50%
Irish Cost Optimal Report 2018 56
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5. Global cost calculation
5.1 New Buildings
The following cost data and modelling variables have been used for the analysis.
The capital and maintenance cost data is based on 2018 prices. The costs for the various
measures considered to improve building energy performance are shown in Tables 5.1a – 5.1c.
The costs for each measure include both material and labour costs. For the purpose of this
work, no learning rates have been applied when any of the measures are replaced. In practice,
some of the newer technologies will reduce in cost over time. However, given that the
calculation period being considered is similar to the lifetime of the technologies, replacements
are limited and any benefits from learning are uncertain and will be significantly discounted in
the calculated Net Present Value (NPV). Where components have a lifetime of less than 30
years their replacement costs are included in the global cost calculation. Residual values are
accounted for in accordance with the Cost Optimal Guidance
A social discount rate of 5% has been assumed for the macroeconomics calculation (as used
for Government policy Impact Assessments in Ireland). A figure of 3% has been used for the
sensitivity analysis as required by the Commission.
A real discount rate of 7% has been used for the financial calculation with 10% for the
sensitivity analysis.
Energy prices used in the analysis are as shown in Table 5.2a. Sensitivity analysis has been
carried out using low and high values of +/- 30% of these prices for gas and biomass and +/-
20% for electricity. As gas is the most significant primary energy source for electricity, the low
scenario has been modelled to include both the low gas and electricity prices and the high
scenario to include both the high gas and electricity prices.
o The central energy prices for electricity and gas are derived from wholesale electricity
prices forecasted for the next 30 years by SEAI using difference between retail price
(SEAI, 2018) and wholesale price in 2018. Electricity retail prices for Band DC
(>=2,500 <5,000 kWh per annum) and gas retail prices for Band D2 (>=5,556
<55,556 kWh per annum) have been used for the analysis.
o To derive the energy price for heat supplied by district heating, a 90% efficient gas
boiler has been used as a proxy.
o The biomass price has been provided by SEAI based on a range of prices identified
in a study on the cost benefit analysis of district heating (AECOM and SEAI, 20156).
This is assumed as a fixed price over 30 years.
The primary energy (PE) and CO2 factors for grid supplied electricity are based on projections
provided by SEAI (SEAI, 2016). This gives an average PE factor of 1.86 over the next 30 years.
This has been developed based on future scenarios of electricity generation mix. A figure of 1.6
has been used for the sensitivity analysis assuming a move away from fossil fuel generation in
future years. For district heating, a PE factor of 1.1 and a CO2 factor of 0.11kgCO2/kWh have
been used as provided by SEAI. The PE and CO2 factors for all other fuels are from the DEAP
tool.
The social cost of carbon for the macroeconomic calculations is shown in Table 5.2b. These
values have been provided by SEAI and are based on projected emissions trading system
(ETS) carbon prices for the traded sector and on carbon taxes for the non-traded sector.
Sensitivity analysis assumes a 2% increase in carbon prices year on year.
In accordance with Annex I of Commission Delegated Regulation No. 244/2012 the global cost for the macroeconomic calculation of a measure/ package/ variant, i.e. the relevant prices which have been taken into account, exclude all applicable taxes, VAT, charges and subsidies.
6 SEAI, AECOM; Cost Benefit Analysis of the potential for High-Efficiency Cogeneration and Efficient District Heating & Cooling in Ireland; Dec 2015
Cost Fabric Heating PV Light DHW Maintenance Energy
Bungalow –
30 year calc
4 ASHP 20% 3 3 -17 470 13 16 - -8 491
3 ASHP 20% 3 3 -14 425 10 22 - -7 450
1 ASHP 20% 3 2 -5 351 10 37 - -5 392
3 Gas 20% 3 2 15 377 12 3 - -10 382
2 Gas 20% 3 2 27 344 12 10 - -9 357
1 Gas 20% 3 2 34 315 12 13 - -8 332
1 Gas 10% 3 2 60 296 12 35 - -7 336
1 Gas 10% 3 1 67 295 12 40 - -7 339
1 Gas 0% 3 2 87 249 12 58 - -5 314
1 Gas 0% 3 1 94 248 12 62 - -5 317
Detached –
30 year calc
4 ASHP 20% 3 3 0 382 8 23 - -6 407
3 ASHP 20% 3 3 4 339 6 29 - -5 369
1 ASHP 20% 3 2 11 284 6 40 - -4 328
3 Gas 20% 3 2 27 300 8 15 - -7 316
2 Gas 20% 3 2 36 272 8 21 - -6 295
1 Gas 20% 3 2 43 255 8 24 - -6 281
1 Gas 10% 3 2 57 242 8 35 - -5 279
1 Gas 10% 3 1 61 239 8 38 - -5 280
1 Gas 0% 3 2 70 215 8 46 - -4 265
1 Gas 0% 3 1 74 212 8 49 - -4 265
4 ASHP 20% 3 3 3 392 11 27 - -6 425
3 ASHP 20% 3 3 6 351 8 32 - -5 387
Irish Cost Optimal Report 2018 75
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Building
Package PE
(kWh/
m²)
Initial
Investment
Cost
Annual Costs Cost of
Emissions
Residual
Value
Macro
Cost Fabric Heating PV Light DHW Maintenance Energy
Semi-
Detached –
30 year calc
1 ASHP 20% 3 3 11 303 8 40 - -4 348
1 ASHP 20% 2 2 13 290 8 44 - -3 339
3 Gas 20% 3 2 28 309 10 17 - -7 328
2 Gas 20% 3 2 36 283 10 21 - -6 308
1 Gas 20% 3 2 42 260 10 24 - -6 288
1 Gas 10% 3 2 55 248 10 35 - -5 287
1 Gas 0% 3 2 69 217 10 46 - -4 269
1 Gas 0% 3 1 75 215 10 50 - -4 270
Mid-floor
Apartment –
30 year calc
4 ASHP 20% 3 3 26 365 17 51 - -3 430
3 ASHP 20% 3 3 29 326 13 55 - -2 392
1 ASHP 20% 3 3 32 288 13 62 - -1 361
1 ASHP 20% 2 2 35 270 13 67 - -1 349
3 Gas 20% 3 2 48 264 16 34 - -5 308
2 Gas 20% 3 2 52 249 16 36 - -5 295
1 Gas 20% 3 2 59 226 16 39 - -4 276
1 Gas 10% 3 2 64 220 16 43 - -4 275
1 Gas 0% 3 2 68 215 16 47 - -4 274
1 Gas 0% 3 1 77 214 16 52 - -4 277
Top-floor
Apartment –
30 year calc
4 ASHP 20% 3 3 29 425 17 56 - -4 493
3 ASHP 20% 3 3 32 386 13 61 - -3 456
2 ASHP 20% 3 2 37 347 13 70 - -3 427
4 Gas 20% 3 2 45 346 19 35 - -7 393
3 Gas 20% 3 2 57 307 16 39 - -6 355
2 Gas 20% 3 2 64 285 16 43 - -6 337
1 Gas 20% 3 2 80 254 16 52 - -5 316
1 Gas 10% 3 2 84 249 16 56 - -5 315
1 Gas 0% 3 2 89 243 16 59 - -5 313
1 Gas 0% 3 1 97 242 16 64 - -5 317
Apartment
block – 30
year calc
4 ASHP 20% 3 3 27 384 17 53 - -3 451
3 ASHP 20% 3 3 30 345 13 57 - -3 413
2 ASHP 20% 3 3 32 328 13 61 - -2 399
1 ASHP 20% 3 2 38 286 13 71 - -1 368
4 Gas 20% 3 2 40 317 19 32 - -6 362
3 Gas 20% 3 2 51 278 16 36 - -6 323
2 Gas 20% 3 2 56 260 16 39 - -5 309
1 Gas 20% 3 2 66 235 16 44 - -5 290
1 Gas 10% 3 2 71 230 16 47 - -4 289
1 Gas 0% 3 2 75 225 16 51 - -4 287
Irish Cost Optimal Report 2018 76
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5.2 Existing Buildings – Elemental Analysis
The capital costs for the various measures that we have considered in this work are shown in Tables
5.5a – 5.5b. Maintenance costs are as set out in Section 5.1. As for new build, the costs for each
measure include both material and labour costs. For the purpose of this work, no learning rates have
been applied when any of the measures are replaced. In practice, some of the newer technologies will
reduce in cost over time. However, given that the calculation period being considered is similar to the
lifetime of the technologies, replacements are limited and any benefits from learning are uncertain and
will be significantly discounted in the calculated Net Present Value (NPV). Note that these costs do
not include the total costs of measures, only the cost of the elements which vary between
measures/packages (e.g. removal costs are excluded).
The energy prices, cost of carbon, discount rates and other variables are the same as for new buildings,
set out in Section 5.1.
Table 5.5a: Elemental Capital Costs per m² of Fabric – Existing build, Elemental analysis
(varying components only) (EUR/m²)
Building Part Value Cost (EUR/m²)
Cavity wall 0.31 €14.7
Cavity wall 0.16 €130.4
Cavity wall 0.11 €158.2
Solid wall 0.37 €76.2
Solid wall 0.22 €116.7
Solid wall 0.13 €127.3
Semi exposed wall 0.32 €72.1
Pitched roof 0.13 €20.0
Pitched roof 0.10 €79.5
Flat roof 0.13 €131.0
Flat roof 0.11 €137.0
Solid floor 0.22 €202.5
Solid floor 0.28 €327.0
Solid floor 0.22 €332.9
Solid floor 0.14 €351.6
Window 1.6 €298.9
Window 1.4 €307.5
Window 1.1 €337.7
Window 0.9 €364.9
Window 0.8 €384.3
Air Permeability (m³/m².hr) @50Pa
EUR/m2
Thermal Bridging (y-value)
EUR/linear m
5 3 1 0.15 0.11 0.08
External insulation €5.4 €8.6 €13.7
0 €2.5 €58.7
Internal insulation 0 €2.5 €4.5
Table 5.5b: Elemental Capital Costs per Building – Existing build, Elemental analysis (varying
components only) (EUR) Heating system:
Building Type
Gas Boiler with
radiators
(EUR/system)
Gas Boiler with
radiators, plus solar hot
water system
(EUR/system)
ASHP with low
temperature radiators
(EUR/system)
Irish Cost Optimal Report 2018 77
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Package 1 Package 2 Package 3
Bungalow €3,100 € 12,000 €8,314
Detached €3,525 € 13,025 €9,847
Semi-detached €3,250 € 12,750 €8,526
Terraced €3,100 € 12,000 €8,314
Mid-Floor Flat €2,685 € 10,985 €7,205
Top-Floor Flat €3,000 € 11,300 €8,102
Apartment building
(costs per unit)
€2,790 € 11,090 €7,504
Controls:
Time and temperature
zone control,
weather compensation,
interlock
Time and temperature
zone control,
weather compensation,
interlock
Time and temperature
zone control
Package 1 Package 2 Package 3
€1,000 €1,000 €650
Hot water cylinder:
Package 1 Package 2 Package 3
€0 €1,450 €1,450
The following tables summarise the results of the cost calculations for the most cost-optimal packages in each of the seven reference buildings. Table 5.6 relates to the macroeconomic calculations and Table 5.7 relate to the financial calculations.
Table 5.6a / Table 5.7a: Central energy price, central discount factors
Table 5.6b / Table 5.7b: Low energy price, central discount factors
Table 5.6c / Table 5.7c: High energy price, central discount factors
Table 5.6d / Table 5.6d: Central energy price, alternative discount factors
Table 5.6e: Central energy price, central discount factor, alternative primary energy factor Table 5.6e: Central energy price, central discount factor, alternative cost of carbon
The sensitivity analysis shows the following.
Discount rate and Energy Price: Low energy prices, reduce the cost of energy over the
calculation period. The main impact of this is that it makes solutions with higher primary
energy demand relatively more attractive. The reverse is true when increasing the energy
prices and reducing the discount rate. However, none of these changes affects the cost
optimal solution.
Primary emission factor (PEF): The reduced PEF in the sensitivity case changes the cost
optimum primary energy without changing the optimum technology for the lowest cost
solution.
Price of carbon: The sensitivity case for the price of carbon has minimal impact on the overall
macroeconomic costs and does not impact on the cost optimal level.
Prepared for: Department of Housing, Planning and Local Government
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Dwelling
Type
Wall
Type Package Value
PE
(kWh/m²)
Initial
Investment
Cost
Annual Costs Cost of
Emissions
Residual
Value
Macro
Cost Maintenance Energy
Floor U-value 0.22 211 230 0 214 - -7 437
Floor U-value 0.22 211 378 0 214 - -12 580
Floor U-value 0.28 215 371 0 218 - -12 577
Window U-value 0.9 208 89 0 212 - 0 301
Window U-value 1.4 212 75 0 215 - 0 290
Window U-value 1.6 214 73 0 217 - 0 290
Heating Source ASHP 128 131 10 193 - -4 330
Heating Source Gas + SWH 160 181 19 114 - -5 309
Heating Source Gas 179 51 12 123 - -1 186
Detached Cavity
Wall U-Value 0.11 154 181 0 157 - -6 333
Wall U-Value 0.16 158 150 0 160 - -5 305
Wall U-Value 0.31 168 17 0 170 - -1 186
Roof U-value 0.1 173 44 0 175 - -1 218
Roof U-value 0.13 174 11 0 176 - 0 187
Floor U-value 0.14 170 205 0 172 - -6 370
Floor U-value 0.22 173 118 0 175 - -4 289
Floor U-value 0.22 173 194 0 175 - -6 362
Floor U-value 0.28 175 190 0 177 - -6 361
Window U-value 0.9 162 93 0 164 - 0 257
Window U-value 1.4 165 79 0 167 - 0 246
Window U-value 1.6 168 77 0 170 - 0 246
Heating Source ASHP 101 97 7 152 - -3 253
Heating Source Gas + SWH 129 126 12 91 - -3 226
Heating Source Gas 142 37 8 98 - -1 141
Detached Solid
Wall U-Value 0.13 156 146 0 158 - -5 300
Wall U-Value 0.22 162 134 0 164 - -4 294
Wall U-Value 0.37 172 87 0 174 - -3 259
Roof U-value 0.1 184 44 0 185 - -1 228
Roof U-value 0.13 185 11 0 186 - 0 197
Floor U-value 0.14 181 205 0 182 - -6 380
Floor U-value 0.22 184 118 0 185 - -4 299
Floor U-value 0.22 184 194 0 185 - -6 372
Floor U-value 0.28 186 190 0 187 - -6 371
Window U-value 0.9 173 93 0 174 - 0 268
Window U-value 1.4 176 79 0 178 - 0 256
Window U-value 1.6 179 77 0 180 - 0 257
Heating Source ASHP 106 97 7 160 - -3 261
Heating Source Gas + SWH 137 126 12 96 - -3 231
Heating Source Gas 150 37 8 103 - -1 146
Semi-
detached Cavity
Wall U-Value 0.11 155 122 0 159 - -4 278
Wall U-Value 0.16 157 101 0 162 - -3 259
Wall U-Value 0.31 164 11 0 168 - 0 179
Roof U-value 0.1 165 45 0 169 - -1 212
Roof U-value 0.13 166 11 0 170 - 0 181
Floor U-value 0.14 163 200 0 167 - -6 360
Floor U-value 0.22 165 115 0 169 - -4 281
Floor U-value 0.22 165 189 0 169 - -6 352
Floor U-value 0.28 167 186 0 171 - -6 351
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Dwelling
Type
Wall
Type Package Value
PE
(kWh/m²)
Initial
Investment
Cost
Annual Costs Cost of
Emissions
Residual
Value
Macro
Cost Maintenance Energy
Window U-value 0.9 152 97 0 156 - 0 254
Window U-value 1.4 156 82 0 160 - 0 242
Window U-value 1.6 159 80 0 163 - 0 243
Heating Source ASHP 99 110 8 151 - -3 266
Heating Source Gas + SWH 121 157 16 88 - -4 257
Heating Source Gas 137 44 10 97 - -1 150
Semi-
detached Solid
Wall U-Value 0.13 156 98 0 160 - -3 255
Wall U-Value 0.22 160 90 0 164 - -3 252
Wall U-Value 0.37 167 59 0 171 - -2 228
Roof U-value 0.1 172 45 0 176 - -1 219
Roof U-value 0.13 173 11 0 177 - 0 188
Floor U-value 0.14 170 200 0 174 - -6 367
Floor U-value 0.22 173 115 0 176 - -4 288
Floor U-value 0.22 173 189 0 176 - -6 359
Floor U-value 0.28 175 186 0 178 - -6 358
Window U-value 0.9 159 97 0 164 - 0 261
Window U-value 1.4 164 82 0 168 - 0 250
Window U-value 1.6 167 80 0 170 - 0 250
Heating Source ASHP 103 110 8 156 - -3 271
Heating Source Gas + SWH 127 157 16 92 - -4 261
Heating Source Gas 143 44 10 100 - -1 153
Terraced Cavity
Wall U-Value 0.11 163 114 0 170 - -4 281
Wall U-Value 0.16 166 94 0 172 - -3 263
Wall U-Value 0.31 172 11 0 178 - 0 188
Roof U-value 0.1 172 45 0 178 - -1 221
Roof U-value 0.13 173 11 0 179 - 0 190
Floor U-value 0.14 170 200 0 176 - -6 369
Floor U-value 0.22 173 115 0 178 - -4 290
Floor U-value 0.22 173 189 0 178 - -6 361
Floor U-value 0.28 175 186 0 180 - -6 360
Window U-value 0.9 157 104 0 164 - 0 268
Window U-value 1.4 162 87 0 169 - 0 256
Window U-value 1.6 165 85 0 171 - 0 256
Heating Source ASHP 103 141 11 159 - -4 308
Heating Source Gas + SWH 122 196 21 91 - -5 303
Heating Source Gas 142 56 13 102 - -2 169
Terraced Solid
Wall U-Value 0.13 164 92 0 171 - -3 260
Wall U-Value 0.22 168 84 0 174 - -3 256
Wall U-Value 0.37 175 55 0 180 - -2 234
Roof U-value 0.1 179 45 0 184 - -1 228
Roof U-value 0.13 180 11 0 185 - 0 196
Floor U-value 0.14 177 200 0 182 - -6 376
Floor U-value 0.22 179 115 0 185 - -4 296
Floor U-value 0.22 179 189 0 185 - -6 368
Floor U-value 0.28 181 186 0 187 - -6 366
Window U-value 0.9 164 104 0 171 - 0 274
Window U-value 1.4 169 87 0 175 - 0 262
Window U-value 1.6 172 85 0 178 - 0 263
Irish Cost Optimal Report 2018 117
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Dwelling
Type
Wall
Type Package Value
PE
(kWh/m²)
Initial
Investment
Cost
Annual Costs Cost of
Emissions
Residual
Value
Macro
Cost Maintenance Energy
Heating Source ASHP 107 141 11 165 - -4 313
Heating Source Gas + SWH 127 196 21 94 - -5 306
Heating Source Gas 147 56 13 105 - -2 172
Mid-Floor
Flat Cavity
Wall U-Value 0.11 183 54 0 307 - -2 359
Wall U-Value 0.16 185 44 0 310 - -1 353
Wall U-Value 0.31 190 5 0 319 - 0 324
Window U-value 0.9 154 101 0 258 - 0 359
Window U-value 1.4 164 85 0 275 - 0 361
Window U-value 1.6 169 83 0 284 - 0 367
Heating Source ASHP 84 150 13 140 - -4 299
Heating Source Gas + SWH 93 216 25 76 - -6 311
Heating Source Gas 116 59 16 88 - -2 161
Mid-Floor
Flat Solid
Wall U-Value 0.13 184 43 0 308 - -1 350
Wall U-Value 0.22 187 40 0 314 - -1 352
Wall U-Value 0.37 192 26 0 323 - -1 348
Window U-value 0.9 159 101 0 267 - 0 369
Window U-value 1.4 170 85 0 285 - 0 370
Window U-value 1.6 175 83 0 294 - 0 377
Heating Source ASHP 85 150 13 143 - -4 302
Heating Source Gas + SWH 96 216 25 77 - -6 312
Heating Source Gas 118 59 16 89 - -2 163
Top-Floor
Flat Cavity
Wall U-Value 0.11 244 54 0 410 - -2 462
Wall U-Value 0.16 246 44 0 413 - -1 456
Wall U-Value 0.31 252 5 0 422 - 0 427
Roof U-value 0.11 228 155 0 382 - -5 533
Roof U-value 0.13 231 149 0 388 - -5 532
Window U-value 0.9 214 101 0 360 - 0 461
Window U-value 1.4 225 85 0 377 - 0 463
Window U-value 1.6 230 83 0 386 - 0 469
Heating Source ASHP 101 164 13 170 - -5 343
Heating Source Gas + SWH 122 221 25 94 - -6 333
Heating Source Gas 145 64 16 105 - -2 183
Top-Floor
Flat Solid
Wall U-Value 0.13 245 43 0 411 - -1 453
Wall U-Value 0.22 248 40 0 417 - -1 455
Wall U-Value 0.37 254 26 0 426 - -1 451
Roof U-value 0.11 234 155 0 392 - -5 543
Roof U-value 0.13 237 149 0 398 - -5 542
Window U-value 0.9 220 101 0 370 - 0 471
Window U-value 1.4 231 85 0 387 - 0 473
Window U-value 1.6 236 83 0 397 - 0 479
Heating Source ASHP 103 164 13 173 - -5 346
Heating Source Gas + SWH 125 221 25 95 - -6 335
Heating Source Gas 148 64 16 107 - -2 185
Apartment
block Cavity
Wall U-Value 0.11 205 54 0 345 - -2 397
Wall U-Value 0.16 207 44 0 348 - -1 391
Wall U-Value 0.31 213 5 0 357 - 0 362
Roof U-value 0.11 214 26 0 360 - -1 385
Roof U-value 0.13 215 25 0 361 - -1 385
Irish Cost Optimal Report 2018 118
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Dwelling
Type
Wall
Type Package Value
PE
(kWh/m²)
Initial
Investment
Cost
Annual Costs Cost of
Emissions
Residual
Value
Macro
Cost Maintenance Energy
Floor U-value 0.14 213 67 0 358 - -2 422
Floor U-value 0.22 215 38 0 360 - -1 398
Floor U-value 0.22 215 63 0 360 - -2 421
Floor U-value 0.28 216 62 0 363 - -2 422
Window U-value 0.9 176 101 0 295 - 0 396
Window U-value 1.4 186 85 0 313 - 0 398
Window U-value 1.6 192 83 0 321 - 0 404
Heating Source ASHP 90 155 13 151 - -4 314
Heating Source Gas + SWH 104 218 25 82 - -6 319
Heating Source Gas 126 61 16 94 - -2 169
Apartment
block Solid
Wall U-Value 0.13 206 43 0 346 - -1 388
Wall U-Value 0.22 209 40 0 351 - -1 390
Wall U-Value 0.37 215 26 0 360 - -1 386
Roof U-value 0.11 220 26 0 370 - -1 395
Roof U-value 0.13 221 25 0 371 - -1 395
Floor U-value 0.14 219 67 0 368 - -2 432
Floor U-value 0.22 221 38 0 370 - -1 407
Floor U-value 0.22 221 63 0 370 - -2 431
Floor U-value 0.28 222 62 0 372 - -2 432
Window U-value 0.9 182 101 0 305 - 0 406
Window U-value 1.4 192 85 0 322 - 0 408
Window U-value 1.6 197 83 0 331 - 0 414
Heating Source ASHP 92 155 13 154 - -4 317
Heating Source Gas + SWH 106 218 25 84 - -6 320
Heating Source Gas 129 61 16 96 - -2 171
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5.3 Existing Buildings – Analysis of Packages
The costs and underpinning assumptions are the same as those in Section 5.2. Additional data on costs
for specific measures included in the packages is summarised in Table 5.8.
Table 5.8: Elemental Capital Costs per Building – Existing build, Packages (varying components only) (EUR)
Heating system:
Building Type
Gas Boiler
with
radiators
(EUR/system)
ASHP with
low
temperature
radiators
(EUR/system)
Biomass Boiler
with radiators
(EUR/system)
High heat
retention
storage heaters
(EUR/system)
Package 1 Package 2 Package 3 Package 4
Bungalow €3,100 €8,314 €19,596 -
Detached €3,525 €9,847 €22,524 -
Semi-detached €3,250 €8,526 €20,486 -
Terraced €3,100 €8,314 €19,596 -
Mid-Floor Flat €2,685 €7,205 €6,250 €4,175
Top-Floor Flat €3,000 €8,102 €6,250 €4,175
Apartment building
(costs per unit)
€2,790 €7,504 €6,250 €4,175
Controls:
Time and
temperature
zone control,
weather
compensation,
interlock
Time and
temperature
zone control
Time and
temperature
zone control,
weather
compensation,
interlock
Time and
temperature
zone controls
with weather
and load
compensation
Package 1 Package 2 Package 3 Package 4
€1,000 €650 €1,000 €700
Hot water cylinder:
Package 1 Package 2 Package 3 Package 4
€0 €1,450 €1,450 €0
Ventilation:
Building Type Extract fans Whole house MEV
Bungalow € 0 €3,228
Detached € 0 €4,243
Semi € 0 €3,736
Terraced € 0 €3,228
Mid-Floor Flat € 0 €2,314
Top-Floor Flat € 0 €2,314
Apartment building
(costs per unit)
€ 0 €2,314
Irish Cost Optimal Report 2018 120
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Lighting:
Building Type
Luminaire efficacy
65 l/W
Luminaire efficacy
95 l/W
Bungalow € 0 € 52
Detached € 0 € 80
Semi € 0 € 63
Terraced € 0 € 48
Mid-Floor Flat € 0 € 41
Top-Floor Flat € 0 € 41
Apartment building
(costs per unit)
€ 0 € 41
Hot water demand:
Building Type
Shower flow rate
of 12l/min
Shower flow rate of
6l/min
Waste Water heat
Recovery
Bungalow € 0 €90 €2,335
Detached € 0 €270 €2,530
Semi € 0 €180 €2,530
Terraced € 0 €90 €2,530
Mid-Floor Flat € 0 €90 €2,335
Top-Floor Flat € 0 €90 €2,335
Apartment building
(costs per unit)
€ 0 €90 €2,335
Photovoltaics:
PV
Building Type 0% 10% 20%
Bungalow - € 3,784 € 5,339
Detached - € 3,303 € 4,906
Semi - € 2,963 € 4,225
Terraced €2,656 €3,623
Mid-Floor Flat - € 329 € 657
Top-Floor Flat - € 329 € 657
Apartment building
(costs per unit) - € 329 € 657
The following tables summarise the results of the cost calculations for the most cost-optimal packages in each of the seven reference buildings. Table 5.6 relates to the macroeconomic calculations and Table 5.7 relate to the financial calculations.
Table 5.9a / Table 5.10a: Central energy price, central discount factors
Table 5.9b / Table 5.10b: Low energy price, central discount factors
Table 5.9c / Table 5.10c: High energy price, central discount factors
Table 5.9d / Table 5.10d: Central energy price, alternative discount factors
Table 5.9e: Central energy price, central discount factor, alternative primary energy factor Table 5.9f: Central energy price, central discount factor, alternative cost of carbon
The sensitivity analysis shows the following.
Discount rate and Energy Price: Low energy prices, reduce the cost of energy over the
calculation period. The main impact of this is that it makes solutions with higher primary
Irish Cost Optimal Report 2018 121
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energy demand relatively more attractive. The reverse is true when increasing the energy
prices and reducing the discount rate. A key impact of this sensitivity analysis is that, in some
cases, it changes the amount of PV in the cost optimal solution.
Primary emission factor (PEF): The reduced PEF in the sensitivity case changes the cost
optimum primary energy without changing the optimum technology for the lowest cost
solution.
Price of carbon: The sensitivity case for the price of carbon has minimal impact on the overall
macroeconomic costs and does not impact on the cost optimal level.
Cost Fabric Heating PV Light DHW Maintenance Energy
Bungalow
Cavity Wall
– 30 year
calc
3 ASHP 20% 3 3 5 611 10 43 - -12 652
2 ASHP 20% 3 3 11 428 10 51 - -7 482
5 ASHP 20% 2 2 22 320 10 65 - -6 389
4 ASHP 20% 2 2 28 245 10 73 - -4 325
4 ASHP 10% 2 2 54 227 10 96 - -3 329
5 Gas 20% 2 2 77 231 12 40 - -8 275
4 Gas 20% 2 2 90 156 12 48 - -5 210
4 Gas 10% 1 1 125 134 12 77 - -5 218
4 Gas 0% 2 2 143 90 12 92 - -3 192
4 Gas 0% 1 1 151 87 12 99 - -3 196
Irish Cost Optimal Report 2018 149
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Building
Package PE
(kWh/
m²)
Initial
Investment
Cost
Annual Costs Cost of
Emissions
Residual
Value
Macro
Cost Fabric Heating PV Light DHW Maintenance Energy
Detached
Cavity Wall
– 30 year
calc
3 ASHP 20% 3 3 15 519 6 40 - -10 556
2 ASHP 20% 3 3 22 323 6 50 - -4 375
5 ASHP 20% 2 2 33 219 6 64 - -4 285
4 ASHP 20% 2 2 38 178 6 71 - -3 252
4 ASHP 0% 2 2 64 138 6 93 - -1 237
5 Gas 20% 2 2 79 151 8 46 - -5 199
4 Gas 20% 2 2 90 110 8 52 - -4 166
4 Gas 10% 2 2 103 97 8 63 - -3 165
4 Gas 0% 2 2 116 70 8 75 - -2 151
4 Gas 0% 1 1 122 65 8 80 - -2 150
Semi-
Detached
Cavity Wall
– 30 year
calc
3 ASHP 20% 3 3 16 498 8 43 - -9 541
2 ASHP 20% 3 3 22 343 8 50 - -4 397
5 ASHP 20% 2 2 33 230 8 66 - -4 300
4 ASHP 20% 2 2 38 189 8 72 - -3 267
4 ASHP 10% 2 2 51 176 8 83 - -2 266
5 Gas 20% 2 2 76 156 10 45 - -5 206
4 Gas 20% 2 2 86 115 10 51 - -4 172
4 Gas 20% 1 1 93 110 10 57 - -4 173
4 Gas 0% 2 2 112 71 10 73 - -2 153
4 Gas 0% 1 1 120 67 10 79 - -2 154
Terraced
Cavity Wall
– 30 year
calc
3 ASHP 20% 3 3 20 545 11 50 - -9 597
2 ASHP 20% 3 3 25 394 11 56 - -5 456
5 ASHP 20% 2 2 37 268 11 73 - -4 348
4 ASHP 20% 2 2 42 227 11 80 - -3 314
2 Gas 20% 2 2 59 267 13 36 - -6 311
5 Gas 20% 2 2 79 171 13 48 - -6 227
4 Gas 20% 2 2 89 130 13 54 - -4 193
4 Gas 10% 2 2 102 117 13 65 - -4 191
4 Gas 0% 2 2 116 81 13 76 - -2 168
4 Gas 0% 1 1 125 78 13 84 - -2 172
Mid-floor
Apartment
Cavity Wall
– 30 year
calc
3 ASHP 20% 3 3 31 421 13 60 - -4 489
2 ASHP 20% 3 3 35 318 13 67 - -2 395
2 ASHP 20% 2 2 38 285 13 71 - -1 368
1 ASHP 20% 2 2 42 264 13 78 - -1 354
1 ASHP 10% 2 2 47 258 13 82 - 0 353
3 Gas 20% 2 2 53 286 16 39 - -5 335
2 Gas 20% 2 2 65 183 16 45 - -3 240
1 Gas 20% 2 2 76 161 16 52 - -2 226
1 Gas 0% 2 2 85 151 16 59 - -2 224
1 Gas 0% 1 1 95 147 16 67 - -2 228
Top-floor
Apartment
Cavity Wall
– 30 year
calc
3 ASHP 20% 3 3 36 592 13 67 - -9 662
6 ASHP 20% 3 3 41 436 13 77 - -4 521
5 ASHP 20% 2 2 49 301 13 90 - -1 402
4 ASHP 20% 2 2 54 279 13 99 - -1 390
6 Gas 20% 2 2 79 291 16 54 - -5 355
5 Biomass 20% 2 2 85 264 2 54 - -5 315
5 Gas 20% 2 2 93 188 16 62 - -3 262
4 Gas 20% 2 2 107 166 16 70 - -2 250
Irish Cost Optimal Report 2018 150
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Building
Package PE
(kWh/
m²)
Initial
Investment
Cost
Annual Costs Cost of
Emissions
Residual
Value
Macro
Cost Fabric Heating PV Light DHW Maintenance Energy
4 Gas 10% 2 2 111 161 16 74 - -2 248
4 Gas 0% 2 2 116 156 16 77 - -2 247
Apartment
Block Cavity
Wall – 30
year calc
3 ASHP 20% 3 3 34 452 13 64 - -5 524
5 ASHP 20% 3 3 39 323 13 74 - -2 407
5 ASHP 20% 2 2 42 290 13 78 - -1 380
4 ASHP 20% 2 2 47 269 13 86 - -1 367
4 ASHP 0% 2 2 56 259 13 93 - 0 364
6 Gas 20% 2 2 63 287 16 45 - -5 342
5 Gas 20% 2 2 75 185 16 51 - -3 248
4 Gas 20% 2 2 87 163 16 58 - -2 235
4 Gas 0% 2 2 96 153 16 66 - -2 232
4 Gas 0% 1 1 106 149 16 74 - -2 236
Bungalow
Hollow Block
Wall – 30
year calc
3 ASHP 20% 3 3 5 608 10 42 - -12 648
2 ASHP 20% 3 3 9 518 10 48 - -10 566
5 ASHP 20% 3 3 18 436 10 59 - -10 495
4 ASHP 20% 2 2 29 299 10 75 - -6 379
4 ASHP 10% 2 2 55 281 10 97 - -5 383
5 Gas 20% 2 2 73 321 12 38 - -11 360
4 Gas 20% 2 2 92 210 12 49 - -7 264
4 Gas 10% 1 1 127 188 12 78 - -6 272
4 Gas 0% 2 2 145 144 12 94 - -4 246
4 Gas 0% 1 1 154 141 12 101 - -4 250
Detached
Hollow Block
Wall – 30
year calc
3 ASHP 20% 3 3 15 515 6 39 - -10 551
2 ASHP 20% 2 2 21 422 6 49 - -8 470
5 ASHP 20% 2 2 30 336 6 60 - -8 395
4 ASHP 20% 2 2 39 249 6 73 - -5 323
4 ASHP 10% 2 2 53 236 6 84 - -4 322
4 ASHP 0% 2 2 66 209 6 95 - -3 307
4 Gas 20% 2 2 93 180 8 54 - -6 237
4 Gas 20% 1 1 99 175 8 59 - -6 236
4 Gas 0% 2 2 119 141 8 77 - -4 221
4 Gas 0% 1 1 125 135 8 81 - -4 221
Semi-
Detached
Hollow Block
Wall – 30
year calc
3 ASHP 20% 3 3 16 496 8 42 - -9 538
2 ASHP 20% 3 3 20 422 8 48 - -7 471
5 ASHP 20% 2 2 31 309 8 63 - -6 375
4 ASHP 20% 2 2 39 237 8 74 - -4 315
4 ASHP 10% 2 2 52 224 8 85 - -4 313
5 Gas 20% 2 2 72 235 10 43 - -8 280
4 Gas 20% 2 2 88 162 10 52 - -5 219
4 Gas 10% 2 2 102 149 10 64 - -5 218
4 Gas 0% 2 2 115 119 10 75 - -3 200
4 Gas 0% 1 1 122 114 10 81 - -3 201
Terraced
Hollow Block
Wall – 30
year calc
3 ASHP 20% 3 3 20 543 11 50 - -9 594
2 ASHP 20% 3 3 23 467 11 54 - -7 525
5 ASHP 20% 2 2 35 342 11 71 - -6 417
4 ASHP 20% 2 2 43 271 11 81 - -4 359
4 ASHP 10% 2 2 56 258 11 92 - -4 357
5 Gas 20% 2 2 76 245 13 46 - -8 296
Irish Cost Optimal Report 2018 151
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Building
Package PE
(kWh/
m²)
Initial
Investment
Cost
Annual Costs Cost of
Emissions
Residual
Value
Macro
Cost Fabric Heating PV Light DHW Maintenance Energy
4 Gas 20% 2 2 91 174 13 55 - -6 237
4 Gas 10% 2 2 105 161 13 66 - -5 236
4 Gas 0% 2 2 118 125 13 78 - -4 212
4 Gas 0% 1 1 127 122 13 85 - -4 216
Mid-floor
Apartment
Hollow Block
Wall – 30
year calc
3 ASHP 20% 3 3 31 419 13 59 - -4 487
2 ASHP 20% 3 3 35 353 13 66 - -3 428
2 ASHP 20% 2 2 37 320 13 70 - -2 400
1 ASHP 20% 2 2 43 285 13 79 - -1 375
3 Gas 20% 2 2 53 284 16 38 - -5 333
2 Gas 20% 2 2 64 218 16 44 - -4 273
1 Gas 20% 2 2 77 182 16 52 - -3 247
1 Gas 10% 2 2 82 177 16 56 - -3 246
1 Gas 0% 2 2 86 172 16 60 - -2 245
1 Gas 0% 1 1 96 168 16 68 - -2 249
Top-floor
Apartment
Hollow Block
Wall – 30
year calc
3 ASHP 20% 3 3 35 591 13 67 - -9 661
6 ASHP 20% 3 3 41 435 13 77 - -4 520
5 ASHP 20% 2 2 48 336 13 88 - -2 434
4 ASHP 20% 2 2 55 300 13 99 - -1 411
4 ASHP 0% 2 2 64 290 13 107 - -1 409
6 Gas 20% 2 2 78 290 16 54 - -5 354
5 Gas 20% 2 2 91 223 16 61 - -4 295
4 Gas 20% 2 2 108 187 16 71 - -3 270
4 Gas 0% 2 2 117 177 16 78 - -3 268
4 Gas 0% 1 1 126 173 16 86 - -3 272
Apartment
Block Hollow
Block Wall –
30 year calc
3 ASHP 20% 3 3 34 451 13 64 - -5 522
5 ASHP 20% 3 3 39 358 13 72 - -3 440
5 ASHP 20% 2 2 41 325 13 77 - -2 412
4 ASHP 20% 2 2 47 290 13 87 - -1 388
6 Gas 20% 2 2 62 286 16 44 - -5 341
5 Gas 20% 2 2 74 219 16 50 - -4 281
4 Gas 20% 2 2 89 184 16 59 - -3 256
4 Gas 10% 2 2 93 179 16 63 - -3 254
4 Gas 0% 2 2 97 174 16 66 - -3 253
4 Gas 0% 1 1 107 170 16 75 - -2 257
Irish Cost Optimal Report 2018 152
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6. Cost Optimal Level for Reference Buildings
6.1 New Buildings
We have elected to undertake the gap analysis based on the macro-economic calculations. Macro-economic analysis is used by the Government for the purpose of evaluating different options for technical standards for Building Regulations. The analysis has been carried out using a discount rate of 5% to mirror that used for Government policy analysis.
For completeness, the macro-economic cost optimal curves for each of the reference buildings are
shown in Figures 6.1a – 6.1f. The costs are based on the central energy price and 5% discount rate.
Figure 6.1a: Results of the cost optimal analysis – Bungalow (Macro-economic costs, central
energy price, 5% discount rate)
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700
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Figure 6.1b: Results of the cost optimal analysis – Detached (Macro-economic costs, central energy price, 5% discount rate)
Figure 6.1c: Results of the cost optimal analysis – Semi-detached (Macro-economic costs, central energy price, 5% discount rate)
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600
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Figure 6.1d: Results of the cost optimal analysis – Mid-floor flat (Macro-economic costs, central energy price, 5% discount rate)
Figure 6.1e: Results of the cost optimal analysis – Top-floor flat (Macro-economic costs, central energy price, 5% discount rate)
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600
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
Irish Cost Optimal Report 2018 155
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Figure 6.1f: Results of the cost optimal analysis – Apartment block (Macro-economic costs, central energy price, 5% discount rate)
From these curves, the economic optimal energy performance level in primary energy (kWh/m2/yr) is
shown in Table 6.1. All cost optimal solutions in the main analysis comprised:
Fabric Option: 1
Lighting Option: 3
DHW Option: 2
Heating Option: Gas heating
The difference between residential building types is that the bungalow and apartment cost optimal solutions include 20% PV whereas the detached and mid-terraced properties include no PV.
We have also included a range to cover the sensitivity cases investigated in Section 5. Furthermore,
to provide some allowance for sensitivity in the price of the fabric/services/LZC measures, we have
included those primary energy values which are within 5% of the lowest macro-economic cost in the
main analysis.
Another benefit of considering a sensitivity range is that it covers other technology solutions. Whilst
we have selected options that are applicable in most cases there will be some specific issues. For
example, particular houses may be very over-shaded which may make the use of photovoltaics less
effective or not realistically feasible. Hence, by considering a sensitivity range, it allows for the fact
that the cost optimal level for a given dwelling may differ from the more general cost optimal level.
0
100
200
300
400
500
600
700
0 10 20 30 40 50 60 70 80 90
Ma
cro
eco
no
mic
Co
st (
EU
R/m
²)
Primary Energy (kWh/m²)
Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
Irish Cost Optimal Report 2018 156
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Table 6.1: Economic Optimal Energy Performance Level in Primary Energy
Reference building Primary Energy (kWh/m2/yr) Sensitivity Range(kWh/m2/yr)
Bungalow 34 34 – 94
Detached house 70 36 – 74
Semi-detached house 69 42 – 75
Mid-floor flat 59 59 – 77
Top-floor flat 80 64 – 97
Apartment buildings 66 56 – 84
6.2 Existing Buildings – Elemental Analysis
As for new buildings the cost optimal comparison has been undertaken using the macroeconomic
cost calculations. The cost optimal curves for each of the reference buildings are shown in Appendix
2. The costs are based on the central energy price and a discount rate of 5%.
From these curves, the economic optimal energy performance level in component units (e.g. U-value
for fabric elements) is shown in Table 6.2a and Table 6.2b. All cost optimal solutions comprised:
Walls: U-value = 0.31 W/m2K for cavity walls and U-value = 0.37 W/m2K for hollow block walls
Roof: U-value = 0.13 W/m2K for all buildings except for top floor apartments U-value = 0.11 W/m2K
Floor: U-value = 0.22 W/m2K (option with 20mm of Vacuum insulated Panel) Window: U-value = 1.4 W/m2K for houses and U-value = 0.9 W/m2K for apartment units and
blocks
Heating: Gas heating
We note some differences between houses and apartment units/blocks which are particularly
influenced by differences in heating systems; the apartments have electricity heating whereas the
houses are heated by oil. The primary energy factor and fuel cost for electricity is higher than that for
oil which makes energy-efficient measures more financially attractive for apartments.
We have also considered a range to cover the macro-economic sensitivity cases investigated in
Section 5. Values are only included if they differ from the optimum primary energy in the central case.
However, the macro-economic sensitivity analysis identified no change in the cost optimal solution
and hence no solutions are included in the sensitivity column.
We have not included sensitivity in the price of the fabric measures as we assume effects on the
capital cost will be similar for each scenario on a given curve. Whilst it is reasonable to consider cost
sensitivity on the heating systems given their different technologies, the gas heating solution has a
significantly lower capital cost than alternatives and it is not anticipated that cost sensitivity analysis
would affect the cost optimal heating solution.
Irish Cost Optimal Report 2018 157
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Table 6.2a: Economic Optimal Energy Performance Level, Cavity Wall Dwellings
Reference building Measure Optimum component
level
Sensitivity Range
Bungalow, Cavity Wall
Walls U-value = 0.31 W/m2K -
Roof U-value = 0.13 W/m2K -
Floor U-value = 0.22 W/m2K -
Window U-value = 1.4 W/m2K -
Heating Gas boiler (91%) -
Detached House,
Cavity Wall
Walls U-value = 0.31 W/m2K -
Roof U-value = 0.13 W/m2K -
Floor U-value = 0.22 W/m2K -
Window U-value = 1.4 W/m2K -
Heating Gas boiler (91%) -
Semi-detached House,
Cavity Wall
Walls U-value = 0.31 W/m2K -
Roof U-value = 0.13 W/m2K -
Floor U-value = 0.22 W/m2K -
Window U-value = 1.4 W/m2K -
Heating Gas boiler (91%) -
Terraced House, Cavity
Wall
Walls U-value = 0.31 W/m2K -
Roof U-value = 0.13 W/m2K -
Floor U-value = 0.22 W/m2K -
Window U-value = 1.4 W/m2K -
Heating Gas boiler (91%) -
Mid-Floor Flat, Cavity
Wall
Walls U-value = 0.31 W/m2K -
Window U-value = 0.9 W/m2K -
Heating Gas boiler (91%) -
Top-Floor Flat, Cavity
Wall
Walls U-value = 0.31 W/m2K -
Roof U-value = 0.11 W/m2K -
Window U-value = 0.9 W/m2K -
Heating Gas boiler (91%) -
Apartment Building,
Cavity Wall
Walls U-value = 0.31 W/m2K -
Roof U-value = 0.13 W/m2K -
Floor U-value = 0.22 W/m2K -
Window U-value = 0.9 W/m2K -
Heating Gas boiler (91%) -
Irish Cost Optimal Report 2018 158
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AECOM
6.3 Existing Buildings – Analysis of Packages The cost optimal comparison for packages in existing buildings is also based on the macroeconomic cost calculations. The cost optimal curves for each of the reference buildings are shown in Figure 6.2 (a–g). The costs are based on the central energy price in Section 5.1 and a discount rate of 5%. For comparison, the proposed 2018 standard required by Ireland is included.
Figure 6.2a: Results of the cost optimal analysis – Bungalow, cavity wall (Macro-economic
costs, central energy price, 5% discount rate)
0
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700
800
900
0 20 40 60 80 100 120 140 160 180
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Primary Energy (kWh/m²)
Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Figure 6.2b: Results of the cost optimal analysis – Detached, cavity wall (Macro-economic costs, central energy price, 5% discount rate)
Figure 6.2c: Results of the cost optimal analysis – Semi-detached, cavity wall (Macro-economic costs, central energy price, 5% discount rate)
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900
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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900
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Figure 6.2d: Results of the cost optimal analysis – Terraced, cavity wall (Macro-economic costs, central energy price, 5% discount rate)
Figure 6.2e: Results of the cost optimal analysis – Mid-floor flat, cavity wall (Macro-economic costs, central energy price, 5% discount rate)
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900
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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100
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800
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Figure 6.2f: Results of the cost optimal analysis – Top-floor flat, cavity wall (Macro-economic costs, central energy price, 5% discount rate)
Figure 6.2g: Results of the cost optimal analysis – Apartment block, cavity wall (Macro-economic costs, central energy price, 5% discount rate)
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Figure 6.2h: Results of the cost optimal analysis – Bungalow, solid wall (Macro-economic costs, central energy price, 5% discount rate)
Figure 6.2i: Results of the cost optimal analysis – Detached, solid wall (Macro-economic costs, central energy price, 5% discount rate)
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
0
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900
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Figure 6.2j: Results of the cost optimal analysis – Semi-detached, solid wall (Macro-economic costs, central energy price, 5% discount rate)
Figure 6.2k: Results of the cost optimal analysis – Terraced, solid wall (Macro-economic costs, central energy price, 5% discount rate)
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800
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
0
100
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Figure 6.2l: Results of the cost optimal analysis – Mid-floor flat, solid wall (Macro-economic costs, central energy price, 5% discount rate)
Figure 6.2m: Results of the cost optimal analysis – Top-floor flat, solid wall (Macro-economic costs, central energy price, 5% discount rate)
0
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800
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st (
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Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
0
100
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300
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800
900
0 50 100 150 200 250
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st (
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Primary Energy (kWh/m²)
Macroeconomic Costs (Central energy price, 5% discount rate, EUR/m²)
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Figure 6.2n: Results of the cost optimal analysis – Apartment block, solid wall (Macro-economic costs, central energy price, 5% discount rate)
From these curves, the economic optimal energy performance level in primary energy (kWh/m2/yr) is
shown in Table 6.3. All cost optimal solutions in the main analysis comprised:
Fabric Option: 4 (except for mid-floor flats which have option “1” as no roof improvement is possible)
Lighting Option: 2
DHW Option: 2
Heating Option: Gas heating
The difference between residential building types is that the bungalow and apartment (individual units
and block) cost optimal solutions include 20% PV whereas the detached, semi-detached and terraced
properties include no PV.
We have also included a range to cover the sensitivity cases investigated in Section 5. Furthermore,
to provide some allowance for sensitivity in the price of the fabric/services/LZC measures, we have
included those primary energy values which are within 5% of the lowest macro-economic cost in the
main analysis.
Another benefit of considering a sensitivity range is that it covers other technology solutions. Whilst
we have selected options that are applicable in most cases there will be some specific issues. For
example, particular houses may be very over-shaded which may make the use of photovoltaics less
effective or not realistically feasible. Hence, by considering a sensitivity range, it allows for the fact
that the cost optimal level for a given dwelling may differ from the more general cost optimal level.
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Table 6.3: Economic Optimal Energy Performance Level in Primary Energy
Reference building Primary Energy (kWh/m2/yr)
Sensitivity Range(kWh/m2/yr)
Bungalow, Cavity Wall 90 90 – 151
Detached House, Cavity Wall 116 90 – 122
Semi-detached House, Cavity Wall 112 86 – 120
Terraced House, Cavity Wall 116 116 – 125
Mid-Floor Flat, Cavity Wall 76 65 – 95
Top-Floor Flat, Cavity Wall 107 93 – 125
Apartment Building, Cavity Wall 87 75 – 106
Bungalow, Hollow Block Wall 92 92 – 145
Detached House, Hollow Block Wall 119 93 – 125
Semi-detached House, Hollow Block
Wall 115 88 – 122
Terraced House, Hollow Block Wall 118 91 – 127
Mid-Floor Flat, Hollow Block Wall 77 77 – 96
Top-Floor Flat, Hollow Block Wall 108 91 – 126
Apartment Building, Hollow Block Wall 89 74 – 107
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7. Comparison of Current Regulations and Cost Optimal Level
7.1 New Buildings
7.1.1 Single family buildings For single family buildings, Table 7.1 shows the proposed 2018 Building Regulations compared to the cost optimal sensitivity range described in Section 6.
Table 7.1: Comparison Table
Reference building Cost Optimal Range
(kWh/m2/yr)
Cost Optimal Level (kWh/m2/yr)
2018 Requirements(kWh/m2/yr)
Gap
Bungalow 34 – 94 34 52
The gap between cost optimal level
and 2018 Part L
requirements is greater than 15%
Detached house 36 – 74 43 42
There is no gap between cost optimal
level and 2018 Part L
requirements
Semi-detached house 42 – 75 42 42
Mid-floor flat 59 – 77 59 40
Top-floor flat 64 – 97 80 47
Average 47 – 83 52 45
The proposed 2018 Part L of the Building Regulations Conservation of Fuel and Energy requirements
for all new dwelling types with the exception of bungalows meet the cost optimal level performance.
There is no negative gap between the cost optimal levels and 2018 performance requirements for these
dwellings with the exception of bungalows. The average performance of all dwelling types is also better
than the cost optimal level. As the average performance of all dwelling types is better than the cost
optimal level and the majority of single family dwellings and the apartment block when modelled to 2018
Part L Building Regulations performance requirements achieved the cost optimal level there is no plan
to revise the performance.
The results would be different if the actual build mix was included rather than assuming a similar weighting for all reference buildings. However, the 2018 Part L requirements are within the cost optimal range for all but one building type. Hence, the overall outcome would not significantly change.
7.1.2 Apartment blocks and multi-family buildings For multi-family buildings, Table 7.2 shows the proposed 2018 Building Regulations compared to the cost optimal level.
Table 7.2: Comparison Table
Reference building Cost Optimal Range
(kWh/m2/yr)
Cost Optimal Level (kWh/m2/yr)
2018 Requirements(kWh/m2/yr)
2018 Part L requirements
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and cost optimal level
Apartment building 56 – 84 66 43
There is no gap between cost optimal
level and Part L 2018 Part L requirements
There is no negative gap between the cost optimal levels and 2018 Part L regulations performance
requirements for these dwellings and indeed the 2018 Part L building Regulations performance
requirements are better than the cost optimal level for some dwelling types.
The cost optimal range in Table 7.2 has been chosen to represent the range of the lowest points on the cost optimal points on the curve as described in Section 6. This facilitates the use of a variety of technical solutions for the range of new dwellings.
7.1.3 Plan to address gap for new dwellings
There is no negative gap between the cost optimal levels and 2018 Part L regulations performance requirements for new dwellings
7.2 Existing Buildings – Elemental Analysis
7.2.1 Single family buildings For each improvement measure, Table 7.3 and Table 7.4 show the proposed 2018 Building Regulations compared to the cost optimal level. Due to the different construction types, cavity and solid walls have been considered separately.
In the heating systems, window and hollow block wall elements analysed there is no gap between current requirements and the cost optimal level. In the case of roofs with insulation between joists, cavity walls and floors there are functional reasons why it may not be possible to install additional insulation to achieve the cost optimal level such as available space in existing rooms or roof spaces or cavity widths in walls. The 2018 Part L requirements are at the cost optimal level insofar as they are technically, economically and functionally feasible. There are no plans to review the elemental performance requirements prior to the next set of cost optimal calculations due by March 2023.
Terraced Hollow Block – Heating Gas boiler (91%) Gas boiler (90%)
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Reference building Cost Optimal Level 2018 Part L
requirements) Gap
Top-Floor Flat Hollow Block –
Heating Gas boiler (91%) Gas boiler (90%)
Mid-Floor Flat Hollow Block –
Heating Gas boiler (91%) Gas boiler (90%)
Average Gas boiler (91%) Gas boiler (90%)
Bungalow Hollow Block –
Windows U-value = 1.4 U-value = 1.4
There is no gap
between cost
optimal and 2018
Part L
requirements
Detached Hollow Block –
Windows U-value = 1.4 U-value = 1.4
Semi-Detached Hollow Block –
Windows U-value = 1.4 U-value = 1.4
Terraced Hollow Block –
Windows U-value = 1.4 U-value = 1.4
Top-Floor Flat Hollow Block –
Windows U-value = 0.9 U-value = 1.4
Mid-Floor Flat Hollow Block –
Windows U-value = 0.9 U-value = 1.4
Average U-value = 1.23 U-value = 1.4
7.2.2 Apartment blocks and multi-family buildings For each improvement measure, Table 7.5 shows the proposed 2018 Building Regulations compared to the cost optimal level. Due to the different construction types, cavity and solid walls have been considered separately.
In the heating systems, window and hollow block wall elements analysed there is no gap between 2018 Part L requirements and the cost optimal level. In the case of roofs with insulation between joists, cavity walls and floors there are functional reasons why it may not be possible to install additional insulation to achieve the cost optimal level such as available space in existing rooms or roof spaces or available cavity widths in walls. The 2018 Part L requirements are at the cost optimal level insofar as they are technically, economically and functionally feasible.
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Apartment Building Hollow Block – Walls U=0.37 U=0.35
There is no gap between cost optimal and 2018 Part L
requirements
Apartment Building Cavity – Windows U=0.9 U=1.4
The gap between 2018
Part L requirements
and cost optimal is greater than
15%
Apartment Building Hollow Block – Windows U=0.9 U=1.4
The gap between 2018
Part L requirements
and cost optimal is greater than
15%
Apartment Building Cavity – Roof U=0.13 U-value = 0.16
The gap between 2018
Part L requirements
and cost optimal is greater than
15%
Apartment Building Hollow Block – Roof U=0.13 U-value = 0.16
The gap between 2018
Part L requirements
and cost optimal is greater than
15%
Apartment Building Cavity – Heating Gas boiler
(91%) Gas boiler
(90%)
There is no gap between cost optimal and 2018 Part L
requirements
Apartment Building Hollow Block – Heating Gas boiler
(91%) Gas boiler
(90%)
There is no gap between cost optimal and 2018 Part L
requirements
7.2.3 Plan to address gap for existing dwellings-elemental
In heating systems, windows and hollow block wall elements analysed there is no gap between 2018 Part L requirements and the cost optimal level.
There are cases where the 2018 Part L requirements are greater than 15% from cost optimal. These are discussed below.
Cavity walls: The standard for renovated cavity walls is 0.55 W/m2K, which is equivalent to a fully insulated 50mm cavity. The dwellings were modelled with a 100mm cavity and the cost optimal U-value is 0.31 W/m2K which represents a fully filled 100mm cavity. It appears
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reasonable that for a 50mm cavity, the current standard of 0.55 W/m2K is also cost optimal. Therefore, the current requirement meets the cost optimal level for a 50mm cavity.
Roofs: The standard for renovated roofs is 0.16 W/m2K. The cost optimal U-value is 0.11 W/m2K which is equivalent to 150mm mineral wool insulation quilt between the joists plus 200mm above the joists. In practice, the cost optimal would need to take account of the impact on the usable space between the joists and the rafters and this may restrict the depth of insulation that may be practically installed. The installation of additional insulation can also create a condensation risk in the attic space and a risk assessment is required to assess if the attic is suitable for increased levels of insulation. Details of this risk assessment can be found in Annex A1 of National Standard Authority of Ireland S.R. 54 Code of Practice for the Energy Efficient Retrofit of Dwellings7. Due to this risk it may not always be technically, functionally or economically feasible to install insulation to the cost optimal level.
Floors: The standard for renovated floors is 0.45 W/m2K. The cost optimal U-value is 0.15 W/m2K which is equivalent to 120mm of insulation. For a room with a height of 2.4m, this is equivalent to reducing the room volume by 5% which is on the borderline of acceptability. Such a level of insulation may be dependent on available foundation depth to avoid such impact on room volume.
The 2018 Part L requirements are at the cost optimal level insofar as they are technically economically and functionally feasible. There are no plans to review the elemental performance requirements prior to the next set of cost optimal calculations.
7.3 Existing Buildings – Analysis of Packages
7.3.1 Single family buildings For single family buildings, Table 7.6 and Table 7.7 show the proposed 2018 Building Regulations compared to the cost optimal sensitivity range described in Section 6.
In the majority of dwellings modelled, the current requirement of 125kWh/m2/yr is within 15% of the cost optimal primary energy as required by the cost optimal guidance. Where the cost optimal level is lower than the 2018 Part L requirements, this is normally achieved through the installation of photovoltaics as part of the major renovation package. On many existing dwellings sufficient roof space may not be available to install photovoltaics due to room in the roof, roof lights and other existing roof modifications. From an economic perspective, the installation of photovoltaics may present an unintended barrier to the retrofit of dwellings. It is not considered functionally or economically feasible to set a performance requirement based on the installation of photovoltaics for major renovations.
The cost optimal level for the majority of dwellings are within 15% of the cost optimal level insofar as they are technically economically and functionally feasible
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cost optimal is greater than 15%
Average 89 – 124 105 125
7.3.2 Apartment blocks and multi-family buildings For multi-family buildings, Table 7.8 and Table 7.9 show the proposed 2018 Building Regulations compared to the cost optimal level. Regarding apartment blocks and multi-family buildings, where the cost optimal level is lower than the current requirements, this is normally achieved through the installation of photovoltaics as part of the major renovation package. On apartment blocks and multi-family buildings, sufficient roof space may not be available to install photovoltaics due to existing services installed on the roof and other existing roof modifications. From an economic perspective, the installation of photovoltaics may present an unintended barrier to the retrofit of apartment blocks and multi-family buildings. It is not considered functionally or economically feasible to set a performance requirement based on the installation of photovoltaics for major renovations.
7.3.3 Plan to address gap for existing dwellings -packages The 2018 Part L requirements are at the cost optimal level insofar as they are technically economically and functionally feasible. The elemental U-values for apartment dwellings are the same as for single family dwellings and the justification for the elemental gaps is provided in Section 7.2.3.
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Appendix 1 – Current Regulations
Table A.1: Relevant Standards for New Residential Buildings
BUILDING ELEMENT
STANDARD SOURCE
Wall Maximum average area-weighted U=0.18
Maximum for individual element U=0.6
Draft Building Regulations 2018, Technical Guidance Document L , Table 1, columns 2 and 3
Roof (pitched, insulation at ceiling)
Maximum average area-weighted U=0.16
Maximum for individual element U=0.3
Draft Building Regulations 2018, Technical Guidance Document L , Table 1, columns 2 and 3
Roof (flat) Maximum average area-weighted U=0.20
Maximum for individual element U=0.3
Ground floor Maximum average area-weighted U=0.18
Maximum for individual element U=0.6
(Note: U=0.15 advised for floors with underfloor heating)
Draft Building Regulations 2018, Technical Guidance Document L , Table 1, columns 2 and 3
Window Maximum average area-weighted U=1.4
Maximum for individual element U=3.0
Draft Building Regulations 2018, Technical Guidance Document L , Table 1, columns 2 and 3
Thermal Bridging Adopt ACDs for all key junctions Draft Building Regulations 2018, Technical Guidance Document L, section 1.3.3.2
Gas boiler Minimum 90% seasonal efficiency Draft Building Regulations 2018, Technical Guidance Document L, section 1.4.1.1
Controls Automatic control of space heating on the basis of room temperature
Automatic control of heat input to stored hot water on the basis of stored water temperature
Separate and independent automatic time control of space heating and hot water Shut down of boiler or other heat source when there is no demand for either space or water heating from that source.
Draft Building Regulations 2018, Technical Guidance Document L, section 1.4.3.1
Controls for heat pumps
External controls to include: - weather compensation or internal
temperature control) - timer or programmer for space heating
Heat pump unit controls to include: - control of water pump operation
(internal and external as appropriate) - Control of water temperature for the
distribution system. - Control of outdoor fan operation for air-
to-water units. - Defrost control of external airside heat
exchanger for air-to-water systems. - Protection for water flow failure
Draft Building Regulations 2018, Technical Guidance Document L, Table 2
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Table A.2: Relevant Standards for Existing Residential Buildings – Replacement of Individual Elements
- Protection for water high temperature - Protection for high refrigerant pressure
Protection of air flow failure on air-to-water units.
Hot water controls to include: - auxiliary heating regime to 60°C or
more for disinfection purposes
- temperature control and time control to optimise the time taken to heat the water
Insulation of pipes, ducts and vessels
All hot water storage vessels, pipes and ducts associated with the provision of heating and hot water in a dwelling should be insulated to prevent heat loss. 50mm factory applied PU-foam for hot water tanks having zero ozone depletion potential and a minimum density of 30 kg/m3 satisfies the criterion for insulation of the hot water tank when installed within the normally heated area of the dwelling.
Draft Building Regulations 2018, Technical Guidance Document L , section 1.4.4.2
MVHR Minimum Specific Fan Power of 0.6W/litre/sec for continuous supply only and continuous extract only
Minimum Specific Fan Power of 1.2W/litre/sec for balanced systems
Minimum Heat Recovery Efficiency of 70%
Draft Building Regulations 2018, Technical Guidance Document L , Table 3
All – Maximum Permitted Energy Performance Coefficient
0.3 compared to reference dwelling Draft Building Regulations 2018, Technical Guidance Document L , section 1.1.2
All - Maximum Permitted Carbon
Performance Coefficient
0.35 compared to reference dwelling
Draft Building Regulations 2018, Technical Guidance Document L , section 1.1.2
Draft Building Regulations 2018, Technical Guidance Document L, Section 2.2.2
Controls Time and temperature control for room and hot water cylinder, boiler interlock.
Draft Building Regulations 2018, Technical Guidance Document L, Section 2.2.3
Insulation of pipes, ducts and vessels
All hot water storage vessels, pipes and ducts associated with the provision of heating and hot water in a dwelling should be insulated to prevent heat loss. Equivalent to 50mm factory applied PU-foam for hot water tanks.
Draft Building Regulations 2018, Technical Guidance Document L, Section 2.2.4
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