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

1. Introduction

1.1 Project aims

9. The overall aim of this project was to assess and identify the potential for further improvement in energy and emissions performance for new domestic and non-domestic buildings constructed in Scotland set via Standard 6.1 (carbon dioxide emissions) and supporting guidance within The Scottish Government's Building Standards Technical Handbooks. 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 domestic buildings.

10. Standard 6.1 of the Scottish Building Regulations (Scottish Government, 2004) specifies that for new domestic and non-domestic buildings:

"Every building must be designed and constructed in such a way that:

a. the energy performance is estimated in accordance with a methodology of calculation approved under regulation 7(a) of the Energy Performance of Buildings (Scotland) Regulations 2008, and

b. the energy performance of the building is capable of reducing carbon dioxide emissions."

The accompanying technical handbooks (Scottish Government, 2019a) provide guidance on achieving this standard.

11. The two key outputs required from the project were:

• Revised notional building(s) for application within the 2021 standards. The Scottish Government has indicated that this should be based on a single fuel type, and that in the next (2024) revision the intention is to move to low carbon heating systems, so the 2021 specification should be in this context. It was recognised that there may need to be a variation of a core notional building specification for different building types to reflect the practicality of a particular level of improvement for different building types (e.g. high-rise flats).
• Illustration of the costs and benefits of the options assessed for the revised notional building. This should inform a subsequent business and regulatory impact assessment to be undertaken by the client. It should include assessing the national cost impact taking into account the capital and life cycle costs (e.g. maintenance and asset replacement), and the national benefit impact taking into account any change in energy demand and carbon emissions, and pricing this according to UK Government. The impact assessment should be undertaken in accordance with The Green Book and accompanying supplementary guidance 'valuation of energy use and greenhouse gas emissions for appraisal' (HM Treasury, 2018).

1.2 Policy context

1.2.1 National climate change targets

12. The recent UK Climate Change Act amendment committed Scotland to a target of net zero emissions of all greenhouse gases by 2045 (HM Government, 2019). This reflects the Committee on Climate Change's report on achieving net zero, which stated that Scotland has proportionately greater potential for emissions removal than the UK overall and can credibly adopt a more ambitious target of net zero greenhouse gas emissions by 2045 (compared to 2050 for England) (Committee on Climate Change, 2019a). The Scottish Government has also adopted a new target to reduce emissions by 75% by 2030 compared to 1990 levels (Scottish Government, 2019b).

1.2.2 Programme for Government 2019-20

13. To achieve net zero emissions, it will be necessary to significantly reduce (or eliminate) carbon emissions from the operation of buildings. Currently, the majority of emissions in buildings, particularly for residential buildings, are from the use of higher carbon fossil fuels to heat buildings. Hence, it is a priority to install low carbon heating sources. Photovoltaics are not a substitute for low-carbon heat; carbon savings associated with this generation will decline as the grid decarbonises. In the Programme for Government 2019-20, Scottish Ministers have committed to the decarbonisation of heat in new homes from 2024 and consideration of similar actions for new non-domestic buildings from that date (Scottish Government, 2019c):

"Our consultation… on new building regulations will include measures to improve energy efficiency… and we will work with stakeholders to develop regulations to ensure that new homes from 2024 must use renewable or low carbon heat. Similarly, our ambition is to phase in renewable and low carbon heating systems for new non-domestic buildings consented from 2024. We will work with the construction, property and commercial development sectors to identify and support good practice to inform the development of standards on how we can achieve this".

14. There are several points of note relating to this:

• Energy efficiency: It is important to minimise the energy demand from new buildings. High efficiency standards complement low carbon heating through lower demand for low carbon energy, and lower running costs. Reduced peak energy demands also reduce the impact on energy supply and distribution infrastructure. There are potentially significant capital cost savings in terms of distribution pipework and heat emitter costs in buildings, arising from reduced space heating demand.
• Potential adverse impacts: Care needs to be taken to ensure that higher fabric standards and ventilation specifications do not lead to poor indoor air quality through under-ventilation or summer overheating, and avoid higher energy demand through installation of active cooling.
• Renewable and low carbon heating: The 2021 revision of the standards should provide a trajectory to low carbon heat in all new buildings. Recent work for the UK and Welsh Governments on their energy standards (MHCLG, 2019f; Welsh Government, 2019b) suggests that it is possible to set reasonable but stringent notional buildings based on fossil fuels (e.g. gas) which encourage the installation of low carbon heating now (e.g. heat pumps) as with grid decarbonisation, it results in lower capital costs for compliance. Minimum fabric and services efficiency standards will need to be carefully considered, particularly in this case.
• Consideration of future-proofing: The asset life of the building fabric means that it is likely to still be in place come 2045 and it is relatively expensive to retrofit. This suggests standards for building fabric should be set at a level that they do not require costly energy-efficiency retrofit to meet these future targets. Similar consideration should also be given the building services as although they have a shorter asset-life, systems may well still be in-use come 2045, albeit the expectation is that there will need to be a transformation across the building stock to move to low carbon heating. There may be measures which would provide benefits now, and make it easier to install heat pumps or district heating in future, such as low flow temperature heating systems being installed in new homes.

1.2.3 Scottish energy strategy

15. It is noted that these changes should be viewed within the context of the Scotland's energy strategy (Scottish Government, 2017b). This set out the vision for the future energy system in Scotland including prioritising energy efficiency and renewable and low carbon solutions. It also set a particular aim of stimulating the deployment of district and communal heating as means of supplying low carbon heat. This was made clear at the start of the decade in the 2020 Routemap for Renewable Energy in Scotland (Scottish Government, 2011) which included a target for 1.5TWh of heat demand to be delivered by district or community heating by 2020. More recently, this ambition to increase deployment of district heating was made clear in the Scottish Government's second consultation on district heating regulation and local heat and energy efficiency strategies (Scottish Government, 2017a). As a result, an aspect of the current project was to assess the implications of new standards on the feasibility and viability of connecting to heat networks.

1.2.4 Scottish low carbon building standards strategy and review

16. In 2007, Scottish Ministers convened an expert panel to advise on the development of a low carbon building standards strategy to increase energy efficiency and reduce carbon emissions. This resulted in the Sullivan Report – a low carbon building standards strategy for Scotland (Scottish Building Standards Agency, 2007). Key recommendations included the following:

• Net zero carbon buildings (i.e. space and water heating, lighting and ventilation) by 2016/2017, if practical.
• Two intermediate stages on the way to net zero carbon buildings, one change in energy standards in 2010 (low carbon buildings) and another in 2013 (very low carbon buildings).
• The 2010 change in energy standards for non-domestic buildings should deliver carbon dioxide savings of 50% more than 2007 standards. The 2010 change in energy standards for domestic buildings should deliver carbon dioxide savings of 30% more than 2007 standards.
• The 2013 change in energy standards for non-domestic buildings should deliver carbon dioxide savings of 75% more than 2007 standards. The 2013 change in energy standards for domestic buildings should deliver carbon dioxide savings of 60% more than 2007 standards.

17. In May 2013 Scottish Ministers reconvened the Sullivan panel with a view to revisiting some of their original recommendations, including those above, taking account of the impact of the economic downturn on the construction sector. Whilst maintaining the level of ambition, the 2013 update report (Building Standards Division, 2013) recommended a more moderate pace of change. However, the improvement standards recommended in the original Sullivan Report act as a benchmark for this current review. The carbon dioxide emissions savings from the proposed improved notional buildings have been compared against the recommendations from the Sullivan Report.

18. The current review of the energy standards in the Scottish Building Regulations had already commenced prior to the start of this project. Scottish Ministers designated energy efficiency as a national infrastructure priority in 2015. They noted that whilst new buildings constructed to current building standards already achieve a good level of energy efficiency, they wish to explore options to build upon the progress made to date in providing energy efficient buildings with reduced carbon emissions. Hence, they called for a review of the building regulations and the energy standards that apply to both domestic and non-domestic buildings.

19. As a first step, a public consultation was undertaken to seek the views of stakeholders on the impact the 2015 energy standards had, or continue to have, on industry in designing and constructing buildings (Scottish Government, 2018). The consultation asked stakeholders about the challenges faced in meeting the 2015 standards and how they were overcome. It also consultation asked for feedback on practical opportunities to further improve the energy performance of buildings. These responses have informed the current project.

1.2.5 Energy Performance of Buildings Directive

20. The Energy Performance of Buildings Directive set a number of requirements for EU Member States that also needed to be considered in this project. The Directive places a requirement on Member States to review the minimum energy performance requirements set for buildings at intervals not exceeding 5 years. It also sets a requirement for minimum energy performance standards for new buildings to be 'nearly zero energy'. In particular, by 31 December 2020, all new buildings should be nearly zero-energy buildings; and after 31 December 2018, new buildings occupied and owned by public authorities should be nearly zero-energy buildings. The 2018 call for evidence to support this Building Standards review stated that "UK work in this area is on-going and proposals will be developed for Ministers to consider in the context of Scotland's position in Europe, post-exit" (Scottish Government, 2018).

21. The 2018 amended Energy Performance of Buildings Directive called for member states to express the energy performance of buildings by a numeric indicator of primary energy use for the purpose of reporting and as the principal metric for the setting of minimum energy performance requirements. This differs from the current metric for performance for the energy standards of carbon dioxide equivalent emissions. The Scottish Government indicated the intention to retain the carbon dioxide equivalent emissions target as an additional metric, in the context of its overall carbon emission targets, and this has been explored a part of the project.

22. It should be noted that there are other European requirements that impact on new build standards. For example, the recently amended Energy Performance of Buildings Directive introduces a requirement for self-regulated devices and the Energy Efficiency Directives sets minimum standards for building services. Whilst it is expected that such requirements are unlikely to impact on the notional buildings themselves, they are likely to impact more on other parts of Standard 6.

1.3 Policy and research implications

23. The research undertaken as part of the project, the proposals made for the notional building, and the findings from the cost benefit assessment may raise issues which have implications for policy or strategy beyond Building Standards Section 6, or which require further research or action. Key implications have been highlighted in the report.

24. In particular, wider work outside the scope of Building Standards Section 6 will be required to facilitate the transition to low carbon heating systems, and to support an increase in localised embedded renewable energy generation more generally. This is in the context of 2021 and future standards, and of current electricity grid constraints and a drive for future electrification across different sectors. Supportive measures are also likely to be needed to facilitate other future changes in construction practices associated with improvements to standards set by the notional building. Particularly relevant concerns and some suggestions for how to address these are discussed in sections 1.7.2, 1.9 and 1.10.6 of this report.

25. Changes to Section 6 may also require, or benefit from, a review of some of the guidance in other areas of the Technical Handbooks, for example parts of Section 7. Additionally, work is likely to be required outside of this review to help ensure that indoor air quality and overheating (discussed in section 1.8 of this report) – or other sustainability risks – do not impact negatively on new homes in Scotland. There are also various decisions on Section 6 amendments outside of the scope of the current project which the Scottish Government's Building Standards Division will need to consider, such as changes to minimum elemental performance standards.