Building regulations - new non-domestic buildings - modelling of proposed energy improvements: research report

Executive Summary

1. The aim of this project was to assess and identify potential improvements in energy and emissions performance for new domestic and non-domestic buildings constructed in Scotland set via Standard 6.1 (carbon dioxide emissions). This was to inform the setting of targets within the next set of energy standards, programmed for implementation in 2021. This report focuses on the project findings for new non-domestic buildings.

2. Improvements to the current notional (reference) building were identified based on a review of current practice in Scotland and other relevant literature. The relative cost-effectiveness and feasibility of these improved measures were assessed. Based on this, three new alternative standards (“Low”, “Medium” and “High”) were proposed. Their benefits and costs were assessed at an individual building and national level.

3. The fabric standard of the “Low” option is aligned to the better of the two fabric standards used under the current Section 6 2015 standard. Further fabric improvements are included in the “Medium” and “High” options. All three options include improvements in the efficiency of most elements of building services over the 2015 standards.

4. For all three options, it is proposed that the notional building is based on gas heating plus PV with an increase in the array size compared to the current notional building. An exception is proposed if a heat pump is used in the actual building, where an air source heat pump (ASHP) is included and the PV removed in the notional building. This would simplify the current approach where the fuel in the notional building depends on that included in the actual building. This is to help avoid heat pumps being able to meet the gas heating targets whilst relaxing other elements of specification such as fabric.

5. The “Low”, “Medium” and “High” options are estimated to reduce carbon emissions by 8%, 16% and 25% respectively across the build mix. This was evaluated using SBEM v5.6a and the proposed new carbon emission factors, across 12 building archetypes. This compares to a recommendation in the 2007 Sullivan Report to achieve aggregate emission reductions of at least 37% on 2015 standards. Hence none of these options would meet this recommendation without a move away from the use of mains gas.

6. It is estimated that the capital cost of compliant solutions comprising gas heating + PV are typically 1 – 3% higher than the current standard across the different building types and the three alternative standards. ASHP solutions are estimated to always be more expensive; in some cases this difference is very small.

7. The national cost benefit analysis shows that the “Low”, “Medium” and “High” options result in a net cost of £6m, £23m and £107m respectively.

8. The Scottish Government proposes that primary energy becomes the main target metric. This analysis demonstrated the benefit in retaining the carbon dioxide equivalent emissions target as an additional metric to encourage a move to lower carbon fuels.