Developing an Energy Efficiency Standard for Social Housing: consultation

This consultation seeks views on the proposed Energy Efficiency Standard for Social Housing (EESSH) to further improve the energy efficiency of social housing in Scotland.

5. Developing the standard

This chapter looks at:

  • How the standard has been developed
  • The research, modelling work and methodology used
  • Dealing with hard/expensive to treat properties


5.1 A working group was set up to develop a draft energy efficiency standard for public consultation, including representatives from the Scottish Government, the Energy Saving Trust ( EST), the Scottish Federation of Housing Associations ( SFHA), the Glasgow and West of Scotland Forum of Housing Associations ( GWSF), the Convention of Scottish Local Authorities ( COSLA) and the Association of Local Authority Chief Housing Officers ( ALACHO).

5.2 To support the working group, two further sub-groups were established: one to consider the technical issues around a standard; the other to look at financial and asset management issues. The technical group considered the method for setting a standard and the possible measures that can be installed to reduce emissions and increase energy efficiency. The financial and asset management group focussed on what funding is available to landlords as well as how to measure and monitor progress against the standard. Both sub-groups reported to the main working group.

5.3 The remits, agendas and notes of meetings of the different stakeholder groups are available on the Scottish Government website 30 . The groups have been working on the development of the standard for over a year, considering all the relevant issues and assessing the implications of different options.

5.4 Scottish Government officials gave presentations on the energy efficiency standard at workshops and conferences to raise awareness of this work, including:

  • SFHA Rural & Islands conference, Dunblane, October 2011
  • Energy Action Scotland conference, Clydebank, November 2011
  • SFHA Property Maintenance conference, Crieff, November 2011

Research - dwelling types and modelled case studies

5.5 Through examination of the Scottish House Condition Survey ( SHCS), the most common house types in Scottish social housing were identified, listed below . This allowed case studies to be developed based on these house types by modelling the impact of different energy efficiency improvements, as well as the likely cost of installation. A draft case study is attached below; further versions are available on the Scottish Government website at:

1. Pre 1919 solid wall flat - ground floor
2. Pre 1919 solid wall flat - mid-floor
3. Pre 1919 solid wall flat - top floor
4. Interwar cavity flat - mid-floor
5. Interwar cavity house - mid-terrace
6. Interwar cavity house - semi-detached
7. Four in a block - lower
8. Four in a block - upper
9. Post war 1950-64 - mid-floor
10. Post war 1950-64 - mid-terrace
11. Post war 1950-64 - semi-detached
12. 1976-83 - mid-floor
13. 1976-83 - mid-terrace
14. 1976-83 - semi-detached
15. 1984-91 - mid-floor
16. 1984-91 - mid-terrace
17. 1984-91 - semi-detached
18. 1992-98 - mid-floor
19. 1992-98 - mid-terrace
20. 1992-98 - semi-detached
21. 2003-07 - mid-floor
22. 2003-07 - mid-terrace
23. 2003-07 - semi-detached

5.6 Whilst it was considered informative to repeat such modelling on a wide variety of house types, there was also the risk that too many case studies would lead to confusion and make it harder for landlords to identify which case studies were relevant to their stock. The list above is thought to provide an indicative range of the most common dwelling types so that social landlords can gauge their stock as they work towards achieving the standard.

Hard/Expensive to treat properties

5.7 The draft case studies profile the most common constructional types (based on type of dwelling and when it was built). The age bands for the date of construction represent typical levels of thermal performance for that period, where revisions to building regulations have increasingly improved these levels. The mix of bands also reflects the Scottish House Condition Survey ( SHCS) categories of housing stock. It was recognised that the type of house or flat also has a bearing. For a house, this is likely to be a semi-detached, end-terraced or mid-terraced. Detached houses were not modelled as they represent less than 1% of the stock. For flats, modelling was done on top, middle and ground floors. Modelling for the draft case studies was done for both gas central heating and electric storage heating.

5.8 The housing typologies in the list above account for a substantial majority of the social rented housing stock. The remaining dwellings mainly consists of non-traditional dwelling types, which can often be harder (or at least more expensive) to treat. The modelling work is being peer reviewed by external technical experts at the same time as this consultation process and final versions of the case studies will be published at the same time as the energy efficiency standard. As part of the peer review process, we have also asked the reviewers to model further case studies for some of the non-traditional/harder to treat types as well as for other fuel sources, such as oil and coal. These additional case studies will be published towards the end of the year alongside the final version of the standard.

Question 8: Do you think that example case studies will be helpful or unhelpful in taking forward the Standard? If you think they are helpful:

Question 8 (a): Are these the right range of dwelling types to be represented as case studies?

Question 8 (b): Are there any other types (including hard to treat) that you would like to be included as a case study? Yes/No

Question 8 (c): If yes please state type and say why you think they should be included?

Energy Performance of Buildings Directive - methodology used to model case studies

5.9 The most common assessment of the energy efficiency of dwellings is the Energy Performance Certificate ( EPC). The Energy Performance of Buildings Directive 2002/91/EC ( EPBD) 31 was introduced to promote the improvement of the energy performance of buildings. A key aspect of this Directive has been the introduction of EPCs, which are produced using the UK Government's Standard Assessment Procedure for the Energy Rating of Dwellings ( SAP), which is compliant with the Energy Performance of Buildings Directive. Reduced data SAP ( RdSAP) follows the same methodology as SAP but has been developed to handle situations where less data is known about an existing dwelling. With reduced data input the RdSAP methodology uses standard assumptions to model energy efficiency.

5.10 RdSAP has been developed by the UK Government for use in the energy assessment of existing dwellings. The methodology meets the requirements of the Energy Performance of Buildings Directive and the calculation itself is carried out using computer software, approved for use in Scotland. The software tool produces both the Energy Efficiency and Environmental Impact Ratings (see below).

5.11 RdSAP is reviewed from time to time to take account of regulatory and technical developments that have arisen. The current published edition of RdSAP is RdSAP 2009 (v9.90). However, RdSAP 2009 (v9.91) will be implemented in Scotland in October 2012; this is to take account of the Green Deal and the Energy Company Obligation ( ECO). The final standard will be drafted in relation to RdSAP V9.91. Scottish Government will monitor any subsequent changes in the SAP or RdSAP methodology to ensure that it remains relevant to the standard.

5.12 EPCs are also subject to periodical reviews and, following a recent consultation, a revised format for the EPC will be available from October 2012. The Sustainable Housing Strategy is also seeking people's views on how EPCs can drive behaviour change 32 .

5.13 EPCs have two ratings: the Energy Efficiency ( EE) rating and the Environmental Impact ( EI) Rating. The proposed energy efficiency standard will be based on one or both of these ratings (see paragraphs 6.2-6.3 below). The EE rating (which is also known as the SAP rating) is based on the energy costs associated with the energy delivered to the dwelling to provide heating, ventilation and lighting. The EE rating assumes standard conditions of occupancy and use, calculated using UK average weather data. The rating is expressed on a scale of 1 to 100, the higher the number the lower the running costs.

5.14 The Environmental Impact Rating relates to the annual CO 2 emissions. To assess the rating the amount of kilograms of CO 2 emissions per square metre of a dwelling's floor area per year is calculated. Again the rating is based on standard conditions of occupancy and use, calculated using UK average weather data. The result is then converted into a scale ranging from 1 to 100, where an EI rating of 100 represents zero net emissions. An EI rating of 1 means that a dwelling has a very poor rating and will produce a large amount of CO 2 per square metre.

5.15 The Environmental Impact rating is calculated from an assessment of the carbon emissions resulting from the energy delivered to a dwelling based on the set assumptions. The assessment takes account of the carbon emissions generated by different fuel types.

5.16 Either RdSAP or full SAP calculations will be allowable for the purpose of the energy efficiency standard.

Question 9: What are your views on using the SAP/ RdSAP methodology for regulating energy performance in the social rented sector?

Modelling dwelling types

5.17 Both ratings in the EPC (Environmental Impact rating and Energy Efficiency rating) were used in modelling the impact of different measures on different dwelling types. The modelling was done using RdSAP 2005 v9.83, but as part of the peer review process we have asked the external experts to redo the modelling using RdSAP 2009 v9.91 (if available, otherwise v9.90 will be used).

1930-49 mid floor flat (78m2)
Fuel type : Gas
Energy Efficiency Measure Baseline: 1990 SHQS 2015 Further Measures 2020 Advanced Measures 2050
Walls No insulation Cavity filled - -
Floor - - - -
Roof - - - -
Windows 100% single glazing - 100% double glazing (post 2003) -
Open chimneys None - - -
Heating system Full central heating, boiler efficiency 60% - Full central heating, boiler efficiency 90.9% (combi boiler) -
Heating system controls Programmer - Time and temperature zone control -
Hot water system Cylinder thermostat and 25mm factory applied foam - - -
Secondary space heating Gas room heater - - -
Ventilation natural - - -
Low energy lighting None 100% - -
Solar PVs None - - -
Solar water heating None - - -
SAP Rating D (66) C (73) B (86) -
Approximate energy use (kWh/m 2 /year) 273 223 106 -
Percentage Improvement - 18% 61% -
EI Rating D (61) C (68) B (85) -
Approximate CO 2 emissions kg/m 2 /year 46 37 18 -
Percentage Improvement - 20% 61% -

5.18 As shown in the table above, for each case study four scenarios were modelled:

  • Baseline: 1990 Measures
  • Measures likely to be installed to meet the SHQS in 2015
  • Further Measures 2020
  • Advanced Measures 2050

Further examples can be found on the consultation pages of the Scottish Government website at:

5.19 The 'Baseline' represents the typical condition of each dwelling type in 1990 (or at the date of construction if this is later than 1990). We would welcome views on whether this is an accurate reflection of the typical condition of the housing stock in the 1990s. It is important that this assessment is reasonably accurate as improvements are measured from this baseline, and so the ratings used in the energy efficiency standard will be affected by the accuracy of the baseline.

Question 10: Do the 'Baseline: 1990 Measures' accurately reflect the energy efficiency performance of dwellings at that time? Yes/No

If not, please provide details.

5.20 The ' SHQS' column is the type of improvements likely to be installed to meet the SHQS in 2015. Some of the measures may exceed SHQS requirements, but are likely to be measures that landlords would consider installing. The 'Further Measures' column models improvements beyond the SHQS which would help contribute towards energy efficiency. The 'Advanced Measures' takes this even further to represent some of the more expensive improvements which are currently technically feasible. It is worth bearing in mind that, over time, these improvements should reduce in cost and there are likely to be more advanced solutions to consider.

5.21 Ideally, social landlords should work towards the 'Advanced Measures' where technically feasible to help to take their properties towards the more challenging longer term milestones (see Chapter 9). This level of improvement will be required in the longer term and it may be more cost effective and pragmatic to work towards that now rather than carry out two (or more) retro-fit programmes.

5.22 The modelling work only highlights suggested measures; there are many other options available to landlords to improve the energy efficiency of their stock. In particular, district heating and combined heat and power schemes may well provide the double benefit of improved energy efficiency and generating an income stream.

Question 11: Are the suggested improvements in the 'Further Measures' and 'Advanced Measures' columns of the case studies realistic and feasible? Yes/No

Question 11 (a): Please provide further explanation of any measures that you think should not be included within the modelled case studies.

Question 11 (b): Please provide further explanation of any measures not currently included in the case study modelling that you would like to see included?


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