Building regulations - new domestic buildings: identification and assessment of energy standard improvements

2. Introduction

AECOM and Currie and Brown have undertaken a technical, capital expenditure (CAPEX) and a cost impact assessment (CIA) on a range of options for new build dwelling notional performance standards to inform Scottish Government (SG) updates to Section 6 of the Building Standards Domestic Technical Handbook.

SG have recently consulted on a Passivhaus equivalent standard for new build dwellings. Whilst the work in this report more specifically focuses on the techno-economic impacts performance standard uplifts, it also references how the options considered might align with/support a Passivhaus equivalent standard.

This report presents the assessments and their findings in the following key sections:

• Archetype information - defining a set of key dwelling types which represent the composition of new build domestic development in Scotland,
• Definition of specifications - developing a range of specification levels which are compatible with the heating technology types expected to be installed in new build dwellings,
• Methodology - considering the appropriateness of the use of available modelling methodologies to represent the energy performance of new build dwellings,
• Technical and CAPEX modelling results - presenting key metrics from technical modelling to identify feasible and cost-effective delivery strategies for energy efficient dwellings, and
• Cost impact assessment – presents the costs and benefits associated with the alternative specification options for the notional which are presented throughout the report.

Three options have been considered for each of the heating technology options permitted by the Scottish New Build Heat Standard. These include a BAU, which represents the current industry approach to meeting Section 6.1 standards, and two improvement scenarios based on series of cost-effective improvement measures and measures required to deliver a Passivhaus equivalent standard for new build dwellings in Scotland. To better inform the sensitivity of modelling approach, the following three software packages have been used:

• Standard Assessment Procedure (SAP) version 10.2;
• Passivhaus Planning Package (PHPP) version 10.6; and
• Home Energy Model (HEM) version 0.33 with the Future Homes Standard Wrapper (FHS) version 0.24.

The conclusions presented in this report draw on technical performance and CAPEX results associated with the delivery of the new domestic building stock in Scotland. The CIA projects the long-term impact of each option. Evidence-based recommendations have been made to Scottish Government for consideration within the updates to the Section 6 of the Building Regulations Domestic Technical Handbook.