Developing regulation of energy efficiency of private sector housing (REEPS): modelling improvements to the target stock - Main Research Report

This report describes how the least energy efficient dwellings in the private sector were identified and how their ratings could be improved by a range of improvement measures. Modelling was used to ascertain the least cost way of reaching different standards, with findings presented on capital costs, fuel cost savings, carbon and energy reductions.

1 Introduction

1.1 In this section, we briefly outline the context of this report and overall structure of the research.

Policy Background

1.2 The Climate Change (Scotland) Act 2009 formally established in legislation the Scottish Government's ambitious target to cut the basket of 6 Kyoto Protocol greenhouse gas emissions by 42% by 2020 (compared to 1990/1995[2] base lines), and by 80% by 2050. Even before adopting this legislation, the Scottish Government had established a target to eradicate fuel poverty as far as reasonably practicable by 2016.

1.3 Within the social housing stock, the Scottish Government established minimum energy efficiency standards to be achieved by 2015 under the wider Scottish Housing Quality Standard (SHQS). Its successor, the Energy Efficiency Standard for Social Housing (EESSH), which is due to run from 2015 to 2020, sets out the energy efficiency standards that should be achieved within the social housing stock by 2020.

1.4 In June 2013, the Scottish Government published the Sustainable Housing Strategy, which set out a commitment to consult on draft regulations that would set minimum energy efficiency standards for private sector houses, including both the owner-occupied and private rented sectors. The only energy standards that had previously been set for private sector stock were through the Section 6: Energy standards (and their predecessor, the Part J standards) of the Scottish Building Regulations and the requirement to have loft insulation (if applicable) in the Tolerable Standard[3]. These apply to the construction of new build housing, extensions, and heating system replacements in the existing stock.

1.5 In order to consider issues around regulation and to help develop draft regulations for consultation, the Regulation of Energy Efficiency in Private Sector homes (REEPS) working group was set up. The main REEPS working group has been supported by two subgroups. The technical subgroup has been charged with examining technical measures to improve energy efficiency and how such measures will fit with regulation. The wider context subgroup was set up to consider issues around attitudes and behaviour in relation to energy efficiency, the relationship between incentives and regulation, and the wider impact of regulations on the housing market.

Overview of the project

1.6 This research was commissioned to support the REEPS technical sub-group to aid the development of the draft regulations for consultation. The main objective of the research was to examine potential policy options for raising the energy efficiency among the least energy efficient dwellings in the private sector housing stock by analysing and modelling data from the Scottish House Condition Survey (SHCS).

1.7 The research can be summarised as providing evidence to answer the following question:

"What are the most effective ways to increase the energy efficiency of the Scottish private sector dwelling stock in EPC bands E, F and G?"

1.8 The work involved modelling of energy efficiency performance characteristics of a range of different types of property that were broadly representative of the target stock - private sector dwellings in EPC bands EFG. The study was designed to allow an appropriate set of improvement measures to be modelled and to assess them in terms of their impact on energy demand and carbon reduction potential, cost effectiveness and technical feasibility

1.9 The project comprised three broad phases. In phase 1 of the research, the objectives were to:

  • Develop a typology of the private sector housing stock in EPC bands EFG using data from the Scottish House Condition Survey (SHCS).
  • Identify associated archetypes in the data, e.g. dwellings that would represent each typology group.
  • Identify the appropriate potential energy efficiency improvement measures.
  • Outline principles for constructing a hierarchy of measures to create packages that would reach minimum thresholds of energy efficiency.
  • Outline methods for determining the costs of measures.

1.10 In the second phase, the suitability and impact of the improvement measures were assessed for each archetype and the impact in relation to energy efficiency and related outcomes were assessed. The outcomes modelled included: energy efficiency (SAP rating); impact on CO2e emissions; impact on primary and delivered energy; and cost effectiveness.

1.11 Finally, in the third phase, a number of policy scenarios were assessed using the modelled archetype data.

Structure of the report

1.12 Chapter 2 provides a summary of the target stock before improvement. Chapter 3 details how a typology of this stock was developed and how the associated archetypes were chosen. Chapter 4 discusses what energy efficiency improvement measures were considered appropriate, the principles underpinning the choice of a package of measures to reach the next EPC band, and the assumptions underpinning the costing of the measures. Chapter 5 provides the results, grossed to the target stock for different policy scenarios and details of the impact of the measures individually. Chapter 6 provides a commentary on a range of technical issues and related assumptions of relevance. This report also includes a number of technical appendices.

1.13 Accompanying this report are details of the 355 individual archetype dwellings that were modelled. These give information on the base position of each dwelling, the appropriateness and impact of individual improvement measures, the packages of measures modelled, and the impact of these packages across a variety of measures.


1.14 The authors take full responsibility for the content of this report, but gratefully acknowledge the contribution of a wide range of people who have provided support and guidance throughout.

1.15 The research was overseen by a Research Advisory Group (RAG) who played a major role in steering the work[4]. The authors would like to thank Adam Krawczyk, Jamie Robertson, Oscar Guinea and Valerie Sneddon at the Scottish Government for their continued input, advice and guidance throughout the study and to the other members of the REEPS groups that contributed to the research. We would also like to acknowledge the assistance and expert input from Dave Cormack, Scott Restrick, Marcus Sheldrick and Steven Hope.

1.16 Perhaps most of all however, we are grateful to the thousands of householders across Scotland who agree to take part in the Scottish House Condition Survey each year. Each gives up to an hour of their time to complete the social survey and also allow a surveyor to assess their property, externally and internally. Without their goodwill, this work would not have been possible.

Chris Martin

Bill Sheldrick


Email: Silvia Palombi

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