Energy Efficiency Standard for Social Housing: peer review

2 Introduction

The Scottish Government appointed Changeworks to lead a Peer Review of the energy performance information provided in the Energy Efficiency Standard for Social Housing consultation document (issued June 2012). Changeworks led this process with support from David Adamson Chartered Surveyors and the Urban Energy Research Group at Heriot-Watt University.

The Peer Review had six objectives, as follows:

1. Check and provide commentary on the assumptions used for the 1990 baseline, the Scottish Housing Quality Standard and the further and advanced measures;
2. Reproduce the retrofit examples referred to in the consultation document using the most up-to-date version of RdSAP 2009 (v9.90) available;
3. Produce (a maximum of 12) similar retrofit examples for a range of representative expensive/harder-to-treat dwelling types modelled using RdSAP 2009 (v9.91);
4. Provide commentary on how communal improvements can be adequately accounted for in the approach;
5. Provide an indicative upgrade cost for meeting the standard for each retrofit example along with indicative energy savings for the tenant and carbon abatement, as well as aggregating these across the Scottish social housing stock to give aggregate upgrade costs, energy savings and carbon abatement for the standard as a whole;
6. Provide commentary on the technical, financial and organisational reasonableness and risks to landlords of meeting the proposed standards as set out in the consultation document.

Each of these objectives is addressed in the relevant chapter of this document, followed by conclusions for consideration and a set of recommendations to validate and refine the standard.

This Peer Review is intended for publication as a supporting document alongside the finalised Energy Efficiency Standard for Social Housing ( EESSH). The report has been written for the Scottish Government; however, social housing providers may also find the content helpful in understanding their requirements and how the standard has been developed. The EESSH consultation document attracted a large number of responses. These are available online and may also be of interest to social landlords.

2.1 RdSAP methodology

The basis of the EESSH is RdSAP, the same assessment methodology that underpins Energy Performance Certificates ( EPCs). RdSAP stands for Reduced data Standard Assessment Procedure. As the name suggests, therefore, it is a pared-down version of the full SAP. RdSAP is used to calculate energy efficiency and environmental performance ratings, and uses a combination of manually entered data sets and assumptions to estimate a property's performance. RdSAP is updated periodically to take account of new evidence and developments in both the software and its assumptions ( e.g. default U-values, building specifications, costs and CO ₂ factors etc.) For simplicity, both RdSAP 2009 v9.90 and RdSAP 2009 v9.91 use a series of defaults (best fits) for many factors such as walls. However, the latest version also provides scope for a more skilled energy assessor to specify values based on documented specifications, where they are available. This will be relevant to social landlords with non-standard properties that do not equate well with RdSAP defaults. This enhanced functionality is discussed in section 5.2.

General information on this tool is widely available ^[1] . However a more detailed awareness of its functions and assumptions is helpful in understanding how it predicts the energy efficiency, environmental impacts and energy costs of housing. This Peer Review identifies and explains a number of aspects of RdSAP that affect its performance predictions. Previous and current versions are compared; assumptions pertaining to energy use and property dimensions are highlighted; and its default specifications and values are assessed. The function of this Peer Review is not to scrutinise these issues in exhaustive detail; more details can be found in other research reports and publications ^[2] . It is important, however, to recognise the effect these issues can have on social landlords' ability to meet the proposed ratings within the EESSH.

2.2 Environmental Impact and Energy Efficiency ratings

Throughout the document, reference is made to various standards, ratings and sets of improvement measures. For clarification, ' EE' and ' EI' ratings refer to 'energy efficiency' ( EE) and 'environmental impact' ( EI) provided by RdSAP (the assessment methodology), with minimum bands proposed for each by the EESSH. It is important for landlords to be aware that the two ratings are not always closely linked, and it will be easier for some properties to meet one rating than the other.

2.3 Further and advanced measures

Reference is made in this document to 'further' and 'advanced measures': this refers to groups of improvement measures used as examples in the consultation document. 'Further' measures are those used to illustrate improvements that may be applied to take a property from the 2015 SHQS to the 2020 EESSH; 'advanced' measures are those used to illustrate improvements that may be applied to improve a property beyond the 2020 EESSH.

2.4 The Scottish Housing Quality Standard

The Scottish Housing Quality Standard ( SHQS) is based on a minimum NHER/ SAP score and the presence of prescribed elements. These are outlined in Appendix B.

2.5 The Energy Efficiency Standard for Social Housing

The new standard is based on the minimum energy efficiency rating specific to different types of property which takes account of the fuel used for space heating. The standards outlined in the consultation document are in Appendix C.