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

Introduction and methodology

In June 2013, the Scottish Government published the Sustainable Housing Strategy, which set out its 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. This research was commissioned to inform that commitment.

The aim of the research was to establish the most effective ways to increase the energy efficiency of the Scottish private sector dwelling stock in EPC bands E, F and G, and to assess the impacts of improving these dwellings.

The project analysed and modelled existing data from the Scottish House Condition Survey (SHCS). It comprised three phases. The phase 1 objectives were to:

• develop a typology of the private sector housing stock in EPC bands EFG using data from the SHCS;
• identify archetypes - 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 costs of measures.

Developing the typology involved segmenting the data into similar dwellings in relation to the technical feasibility of improvement measures and likely gains in energy efficiency. Overall, 355 typology groupings were created with each representing around 1,100 dwellings on average (0.3% of the target stock).

In the second phase, the suitability and impact of various potential improvements were assessed for each archetype. Measures of impact modelled included energy efficiency (impact on SAP rating); CO2e emissions; primary and delivered energy; and cost effectiveness.

During the final phase, a number of policy scenarios were assessed using the modelled archetype data. As well as assessing the impact of individual measures, least costly packages of measures to take dwellings into the successive bandings - from Band G to Band F, from Band F to Band E, and from Band E to Band D - were identified and assessed.