Building regulations - proposed changes to energy and environmental standards: SG response part 2 - onward review

3 Consultation section 3 – Proposed components of the standard – Design

3.1 Standard 6.1 and approved calculation methodology

Consultation question 3 sought views on the continued use of calculation tools implementing the UK methodologies i.e. the Home Energy Model (HEM) and the Simplified Building Energy Model (SBEM), on the basis that these tools are reviewed and shown to report representative outcomes. Respondents were encouraged to provide information supporting their views, including any experiences related to the use of the Passive House Planning Package (PHPP) as a calculation tool.

There was disagreement on the continued use of tools implementing the UK methodologies, with response themes including positive views of PHPP as a calculation tool, concerns that HEM was untested or that more work was needed on tools.

The Scottish Government recognises the importance of citing the use of compliance tools that are demonstrated to be robust, giving correct and consistent representation of the services and systems that are being selected in a useful way to provide compliance with building regulations for all developments across Scotland.

Interim consultation versions of the Scottish Wrapper/HEM and an updated SBEM were released for testing in September 2025. These reflect the proposed options for the level of challenge for new dwellings and non-domestic buildings and implement some additional elements as discussed elsewhere in this response.

It should be noted that these tools do not reflect some of the more procedural proposals of the review, such as the method of target setting. Once these have been confirmed, the compliance tools will be updated, with additional research activity where needed, and presented in final tools in 2026. This will enable extensive testing, use and any required refinement of the tools to take place in advance of the 31 March 2028 implementation date.

The Stage 2 consultation will provide further details on the proposed tools, request views on the direction of travel of finalising these tools and present consultation versions of the HEM/Scottish ‘wrapper’ and SBEM.

Given the responses to the Stage 1 consultation alongside industry feedback throughout the review via the Working Group consensus and with PHPP being a fundamental aspect of the Passivhaus system, we will continue work to recognise a modified PHPP as an additional tool that implements the approved methodology to demonstrate compliance with standard 6.1 ‘Energy demand’.

We will work with the Passivhaus Trust and research partners to modify the existing PHPP tool to align it with the requirements of a Building Regulations compliance tool.

Questions related to the proposed introduction of PHPP as a compliance tool will be presented in the Stage 2 consultation with associated research and procurement activity being initiated in 2026. A modified PHPP regulatory compliance tool will be developed and released for testing during 2026.

3.2 Approach to defining overall building energy targets

Consultation question 4 asked respondents if they supported retention of the current approach and setting of relative performance targets for new buildings through an approved calculation methodology.

The majority of respondents did not support this proposal, calling for the use of absolute or defined targets instead. In response to this feedback and following additional stakeholder engagement through 2025, we have reviewed the options for setting targets under standard 6.1 ‘Energy demand’. These options will be presented in the Stage 2 consultation.

Consultation question 5 sought views on retaining delivered energy, covering only regulated energy use, as the main compliance metric for targets set under standard 6.1 ‘Energy demand’.

There was disagreement on the continued use of the delivered energy metric, covering only regulated energy use, with respondents suggesting an Energy Use Intensity (EUI) metric including unregulated energy use should instead be adopted. There was limited commentary provided on the use of delivered as opposed to primary energy. As delivered energy remains the most relevant metric for those that occupy and manage buildings, we will retain this metric.

It is proposed that unregulated energy use, as calculated by the compliance calculation methodology, will be reported but will not be assigned within the compliance calculation. Presentation of unregulated loads as information rather than as part of the compliance calculation is a sensible enhancement. Introduction of reporting within a transparent framework would be beneficial in establishing a clearer picture of overall energy demand in use, albeit still applying standard occupancy assertions.

Consultation question 6 asked respondents if they supported further consideration of the introduction of a prescriptive space heating demand limit for new buildings through building regulations. Given the strong positive response to this question, we will progress proposals to introduce a Target Space Heating Rate (TSHR), as calculated through the approved methodologies, as an additional compliance metric under standard 6.2 ‘Building insulation envelope’. We will seek views on whether this should only include elements of the specification related to the fabric, not taking the benefit of active services systems into account.

Consultation question 7 sought views on moving to application of regional climate data within the approved calculation methodologies and their application within compliance targets. The responses and wider review engagement showed agreement for the use of regional climate data on the basis that this will enable a more informed approach to building design and reporting on performance, which better reflects the impact of location on the building. Consultation versions of the domestic and non-domestic tools have been developed which implement a range of Scottish weather files.

3.3 Building fabric standards

Consultation questions 8 and 9 asked for feedback on exceeding ‘backstop’ values for fabric performance and limiting fabric infiltration through the building standards.

Respondents provided a broad range of comments on these topics. Given the extent of change implemented by the February 2023 standards and the effect of other measures within Section 6 of the Technical Handbooks, the case to improve on the ’backstop’ U-values is limited. This reflects the reporting on the cost/benefit of further improvements to fabric performance within the domestic research undertaken and also the need to retain a reasonable degree of flexibility.

Limiting fabric infiltration is one of the key elements needed to satisfy the requirements of achieving the Passivhaus standard. From the feedback received in response to the consultation and from wider stakeholder engagement as part of this review, it is apparent that setting a reasonable limit on fabric infiltration could focus action that contributes to achieving the desired outcomes of the Scottish equivalent to the Passivhaus standard. We are progressing with consultation proposals to set a provision in guidance for an ‘upper limit’ for fabric air infiltration.

3.4 Ventilation and occupant comfort

Consultation questions 10 and 11 sought views on the means by which effective ventilation of new buildings is best achieved and on whether further guidance should be given on the application of Mechanical Ventilation with Heat Recovery (MVHR) in new homes.

Given the strong support indicated for the use of MVHR, we will procure research outwith the Stage 2 consultation to understand where additional guidance would be beneficial. This will consider previous research procured on the 2015 standards. Engagement with stakeholders will commence at the appropriate time to be captured in confirmed guidance prior to March 2028.

However, the need for flexibility in solution to satisfy the requirements of the existing and proposed standards has been a theme throughout this review and was picked up in responses to question 10. As part of the potential additional guidance on MVHR we will continue to allow all the available solutions as a means of meeting the requirements of standard 3.14 Ventilation.

Consultation question 12 sought information from respondents on potential risks to occupant comfort that should be better addressed through the building standards.

Given the prevalence of responses related to summer comfort, we will review the guidance provided in support of standard 3.28 ‘Overheating risk’ to identify and develop additional information supporting improved compliance with the standard. We will also develop draft guidance on the use of PHPP as an additional method to assess and mitigate overheating in dwellings and some non-residential buildings.

To inform this updated guidance a research project will be procured in Winter 2025 with the revised guidance drafted for consultation in Summer/Autumn 2026.

3.5 Alternative means of compliance

Consultation question 13 asked respondents if they considered Passivhaus Certification to offer a feasible alternative means of compliance with standard 6.1 energy demand.

Responses indicated strong support for amending standard 6.1 energy demand to recognise Passivhaus certification as an alternative means of compliance. This is one further useful change that we can make to support the standards and will be progressed as a separate change outwith the Stage 2 consultation for potential implementation prior to March 2028.

3.6 Summary of proposals

Consultation question 14 requested any further comments or observations on the proposed components of the review which relate to building design.

A broad range of feedback was provided, which is covered in aspects that are dealt with in responses elsewhere in this document.