Tracking the improvement in the energy performance of the Irish housing stock – lessons learned from the EU EPISCOPE project

Author: Michael Hanratty, BE, MEI, energy consultant

The Intelligent Energy Europe EPISCOPE (2013-2016) project is seeking to develop mechanisms to track the rate of energy refurbishment of housing stocks against the background of energy saving and climate protection needs. In addition, projections to 2020, 2030 and 2050 are made within EPISCOPE based on currents trends with regard to the 80 per cent CO2 reduction target by 2050 (compared to 1990 levels), and the necessary scenarios to meet those targets are identified.

During the project different residential building stocks are analysed in 16 European countries – from local housing portfolios to regional or national housing stocks – in order to gather learnings from a range of alternative methodologies leading to recommendations for a uniform approach to longer term tracking of the energy refurbishment of housing stocks.

Energy Action Limited, based in Dublin 8, with over 20 years’ experience in EU building energy research programmes, is the Irish EPISCOPE partner. Energy Action selected the housing stock of the northside of Dublin City for its EPISCOPE pilot action project consisting of 133,431 dwellings [Census 2011] and a population of 307,000. It includes the Dublin postal districts 1, 3, 5, 7, 9, 11, 13 and 17 and the stock contains approximately 96,183 houses (72 per cent) and 37,248 apartments (28 per cent). 14,060 dwellings are owned by Dublin City Council and a further 2,000 to 3,000 dwellings are owned by housing associations. Thus, approximately 12.5 per cent of the stock is social/public housing.

Current status of tracking the energy performance of housing stocks

While data is available from multiple sources on the Irish housing stock (explored further below), there is no comprehensive tracking system in Ireland comparable to specially designed processes such as the English House Condition Survey or the Scottish House Condition Survey. In the case of the latter for example, a random sample of 3,000 dwellings are surveyed each year to give a continuous evaluation of that stock including energy performance along with building condition, household income levels and fuel affordability.

For the Irish EPISCOPE project, data from multiple sources was pieced together to try to complete a jig-saw of the current energy performance trends of the housing stock. Where gaps were found, modelling assumptions were made.

Data sources for tracking

Three key data sources were used to analyse the energy performance of the building stock and its refurbishment status and rates.

    • National BER database: The national BER database, managed by the Sustainable Energy Authority of Ireland, provides a key data source. Out of a national housing stock of 1.6 million dwellings, over 600,000 dwellings (37.5 per cent) now have BER certificates. BER certificate data for 40,797 dwellings published on the SEAI BER database on February 11, 2015 provided valuable data on the selected pilot action stock. While BER data is not statistically representative, it nevertheless provides a rich and growing data source with a further 100,000 dwellings in Ireland obtaining BER certificates annually;
    • EPISCOPE field survey: A field survey was conducted to cross-check the refurbishment rates that emerged from the BER database analysis. 200 dwellings addresses were visited in order to successfully complete 100 surveys;
    • Energy efficiency upgrade programmes: Data on the number of energy efficiency measures carried out in the pilot action area under SEAI’s Better Energy Homes and Better Energy Warmer Homes was obtained as both of these national energy efficiency programmes have been in operation for more than five years. Data for large scale local authority roof and cavity wall insulation upgrade programmes which began in late 2013 was also assessed. The combined activity from both of these programmes showed refurbishment rates of less than 1 per cent per annum for all types of measures.

State and trend indicators

The EPISCOPE project involves identifying state indicators (i.e. proportion of the stock that has been refurbished to date) and trend indicators (i.e. annual refurbishment rates of the stock).

The BER database was analysed to establish the state indicators. This was done by setting a range of qualifiers for key building energy characteristics. For example, in the case of exposed walls, the qualifiers listed in Table 1 were applied to all available BER data. The U-value is defined as the rate at which thermal energy is conducted through unit area, per kelvin temperature difference between its two sides. Essentially it indicates the rate of heat loss through building elements such as wall, roofs, windows, floors etc. The default U-value bands in Table 1 reflect the introduction of Draft Building Regulations in 1976 and subsequent revisions thereafter. The default U-values of uninsulated walls range from 1.78 (cavity construction) to 2.4 (hollow block walls). If walls have been insulated to a reasonable standard, they will have achieved U-values of 0.6 or better. So, by applying the qualifiers in Table 1, it is possible to estimate the percentage of dwellings with BER certificates that have had their walls insulated or have had additional insulation added since they were originally constructed.

Table 1: Improved Walls Qualifiers

Age Band Wall U-value (default) Wall improvement qualifier ( U=<)
1700-1977 1.78-2.4 0.6
1978-1982 1.1 0.6
1983-1993 0.6 0.45
1994-1999 0.55 0.37
2000-2005 0.55 0.27
2005-2010 0.37 0.21
2011 onwards 0.27 0.21

A similar set of qualifiers was applied to roof and floor insulation and to window upgrades.Thus, the state indicators shown in Table 2 were established for the pilot action stock.

Table 2: State indicators – BER database data

Building elements % stock refurbished to date
Walls 14.2%
Roofs 34.7%
Floors 6%
Windows 76.2%

As the trend indicators are key to tracking currents trends and making long term projections, a greater focus was placed on the trend indicators. As the BER database is not a scientific sample, it was important to conduct a field survey to cross-check the BER-based analysis. A  field survey was conducted between December 2014 and April 2015 interviewing randomly selected dwelling occupiers with an EPISCOPE retrofit questionnaire. The field survey trend data was collated and then combined BER database trend analysis.

The trend indicators results from both the BER database analysis and the field survey are shown in Table 3.

Table 3: Trend indicators (aggregate)

Aggregate trend (annual):
Element Field survey BER research tool Aggregate trend
Walls 2.2% 2.5% 2.5%
Roofs 4.5% 2.6% 3.6%
Windows 3.2% 2.2% 2.7%
Floors 0.0% 0.0% 0.0%
Boilers 4.2% 2.0% 3.1%
Controls 0.8% N.A. 0.8%

The field survey provided useful insights into energy refurbishment activity on the ground. Many homeowners reported carrying our energy upgrades themselves outside of grant  schemes. With the exception of wall insulation, the field survey shows higher annual rates of refurbishment. As many of the works were done outside of grant schemes, the upgrades would not be reflected in BERs for those dwellings, even if BERs did exist. Thus it is quite logical that the field survey would record higher refurbishment rates than the BER-based analysis.

However, given the relatively small field survey sample, it was decided to use an aggregate trend based on the average of the field survey and the BRT data, where the field survey rate is the highest. The aggregate trends provide the trend indicator values for the scenario analysis, looking to 2020 and beyond.

Trend scenarios

Trend scenarios from 2015 out to 2050 have been produced for the current trend, an improved refurbishment trend B and an optimum trend C that will achieve the 80 per cent CO2 reduction target by 2050.

All scenarios are based on the following assumptions:

  • The starting point in 2015 is the average primary energy BER value per dwelling, calibrated to reflect measured energy use, for the population of 40,797 published BERs for the pilot action area. (BER ratings are asset-based values. Typically actual measured energy usage for poorer rated dwellings is much less than the asset-based estimation.)
  • The growth to 2050 for all three scenarios is based on a prediction that 1,000 new dwellings will be built per annum out to 2050. Given the introduction of the NZEB standard by 2021 [DECLG 2012], the model assumes all new dwellings will have an average primary energy of 45 kWh/m2/year (including renewable and non-renewable primary energy).
  • The CO2 benchmark is on an estimate of 619.97 ktCO2 benchmark for the pilot action stock in 1990. A 17 per cent reduction from this benchmark had been achieved by 2013 [EPA 2015].
  • The primary energy demand benchmark is based on the reported achievement of 38 per cent of the 20 per cent energy saving targets at the end of 2012, (i.e. 7.6 per cent) [DCENR 2014].
Energy Demand Scenarios

Figure 1: Energy Demand Trends to 2050 (click to enlarge)

Figure 1 shows the trend scenarios from 2015 out to 2050 for the current trend, an improved refurbishment trend B and an optimum trend C that will achieve the 80 per cent CO2 reduction target by 2050.

The current trend A is based on aggregate shown in Table 3. The current trend estimates that the average primary energy per dwelling for all stock by 2050 will be 129.73kWh/m2/year. This will achieve a 48 per cent CO2 reduction by 2050, well short of the target.

Trend B assumes 25 per cent of the stock will have undergone a deep retrofit and that the grid will be decarbonised by 30 per cent compared to current levels by 2050. A deep retrofit assumes that an existing dwelling will achieve an A2 BER rating by adopting ambitious fabric upgrades and switching to renewable technologies including heat pumps for space and water heating.

Trend C is based on the assumption that 75 per cent of the stock will have undergone a deep retrofit by 2050 and that the grid will be decarbonised by 60 per cent compared to current levels by 2050.  While the practicalities of achieving deep retrofits on such a very large scale are highly debatable, the analysis shows the scale of the task ahead and that business as usual will not suffice if CO2 reduction targets are to be achieved.


The energy demand trend scenario results are summarised in Table 4.

Table 4:       Energy Demand Reduction Target Predictions

Energy Reduction (base 2005) Trend Scenario Scenario B Scenario C
2015 -8 % -8 % -8 %
2020 -11 % -14 % -18 %
2030 -17 % -25 % -37 %
2050 -26 % -40 % -60 %

It is clear that the 20 per cent energy demand reduction targets for 2020 for the pilot action stock (taking account of space and water heating and lighting) will not be met by the current trend scenario, scenario B or scenario C (which falls just 1 per cent of the target). However, it is acknowledged that other measures in the residential sector outside of space heating, water heating and lighting (as detailed in the Unlocking the Energy Efficiency Opportunity Report [SEAI 2015] will contribute to reaching the 2020 energy reduction target.

The CO2 emissions trend scenario results are summarised in Table 5.

Table 5:       CO2 Emissions Reductions Target Predictions

CO2 Reduction (base 1990) Trend Scenario Scenario B Scenario C Targets
2015 -17 % -17 % -17 %
2020 -23 % -26 % -31 % -20 %
2030 -33 % -41 % -52 % -40 %
2050 -48 % -60 % -80 % -80 %

The current trend scenario will meet the 2020 CO2 emissions reduction target but falls well short of the 2030 and 2050 targets. The 80 per cent CO2 emissions reduction target from 1990 levels by 2050 (taking account of space and water heating and lighting) will only be met by Scenario C.


When coming to conclusions, it is important to refer to the current situation in Ireland regarding energy and CO2 emissions targets. The latest National Energy Efficiency Action Plan [DCENR 2014] states a 20 per cent energy saving target by 2020 spread across all sectors. It reports on savings made to date and outlines a basket of measures and actions across all sectors that will collectively enable the 2020 target to be reached. Thus, it does not explicitly lay out specific targets for the residential sector. Also, NEEAP 2014 does not focus on CO2 emissions targets for 2020 or beyond. At this time, national energy savings targets are not yet agreed for 2030 (and 2050 is not under immediate consideration).

The recent Unlocking the Energy Efficiency Opportunity Report (June 2015) published by SEAI also outlines the energy saving potential across all sectors up to 2020 and 2030 [SEAI 2015]. This report includes very comprehensive analysis but it stops short of specific energy demand and CO2 emissions targets for the residential building stock.

From the pilot action analysis, it is clear that targets will be missed if business as usual continues. In order to give a greater focus on the residential building stock, it is recommended that specific targets for the residential sector be set out in future revisions to the National Energy Efficiency Action Plan.

Approaches for continuous monitoring of energy performance of the national housing stock

Arising from the EPISCOPE Pilot Action, it is recommended that:

  • A national housing energy efficiency/house condition survey, similar to the English and Scottish House Condition Surveys, should be established to comprehensively track the energy efficiency of the residential housing stock and enable more accurate o forecasting to 2020, 2030 and 2050;
  • A detailed study should be conducted to record measured energy use in residential buildings on an ongoing basis. The study needs to take account of the wide variation in building types and BER ratings for both new and existing dwellings. This will enable calibration rates of predicted energy use (via BER) to actual energy use to be established. This study should take account of gas, oil, electricity use and should separate out BER energy use (space and water heating, lighting and pumps AND fans) from other energy use such as appliances. The survey should also consider the use of temperature monitors to compare achieved and assumed room temperatures;
  • Where possible, in future revisions of NEEAP [DCENR 2014], specific targets for reduction in energy demand and CO2 should be set for the residential sector for 2020, 2030 and 2050. The setting of these sector-specific targets will provide a greater focus on the achievement of energy saving measures in the sector;
  • The analysis conducted on the EPC database for the EPISCOPE Pilot Action should also be continued, further developed and cross-referenced to the recommended field survey and measured energy consumption data processes. The EPC database will continue to grow and will form a crucial element of future energy and CO2 trend modelling;
  • It will also be important to establish a clear reporting system for the residential building sector to establish progress over time.

EPISCOPE Mapping Tool:

The current situation is starkly shown in the BER mapping tool developed by Energy Action with the assistance and co-operation of  SEAI as part of the Irish EPISCOPE pilot action. The tool is available here. The BER data supplied by SEAI was geo-coded and then aggregated to Small Areas (50-200 dwellings)and Electroral Division clusters (1,500 dwellings approx.) to provide the data for the maps contained in the tool. More than 20 mapping views are available showing key BER-related building energy characteristics.

Energy Action was the only EPISCOPE partner to develop a BER mapping application. The BER mapping tool has been highly commended by the EU Commission and was demonstrated at the EU Sustainable Energy Week networking village in Brussels in June 2015.


Sources / References:



Concrete reference (in respective language) Short description (in English)
[CSO n.d.] Central Statistics Office (CSO) (n.d.): 2011 Census Results. Available at:
National Census 2011
[DCENR 2014] Department of Communications, Energy and Natural Resources (DCENR) (2014): National Energy Efficiency Action Plan 2014. Available at  [2015-07-17] National Energy Efficiency Action Plan 2014
[DECLG 2012] Department of the Environment, Community an Local Government (DECLG) (2012): Towards Nearly Zero Energy Buildings in Ireland – Planning for 2020 and Beyond Towards NZEB in Ireland  – Planning for 2020 and beyond
[Energy Action 2015] Energy Action (2015): EPC Mapping tool showing Energy Efficiency of Housing on the Northside of Dublin City. Available at [2015-09-03] EPISCOPE EPC mapping  tool
[EPA 2015] Environmental Protection Agency (2015): Greenhouse Gas Emissions by Sector. Available at [2015-09-08]
Irish Greenhouse Gas Emissions by Sector
[© OpenStreetMap contributors] Map Data available under the Open Database License:

Copyright and Licence available at: [2015-08-05]

Open Data Commons Open Database License (ODbL) available at:

[SEAI 2015] Sustainable Energy Authority of Ireland (SEAI) (2015): Unlocking the Energy Efficiency Opportunity, June 2015. Available at [2015-07-17] Unlocking the Energy Efficiency Opportunity O'RiordanElecenergy,housing,SEAI
Author: Michael Hanratty, BE, MEI, energy consultant The Intelligent Energy Europe EPISCOPE (2013-2016) project is seeking to develop mechanisms to track the rate of energy refurbishment of housing stocks against the background of energy saving and climate protection needs. In addition, projections to 2020, 2030 and 2050 are made within...