Determining the principles for a Scottish equivalent to the Passivhaus standard - Analysis of Consultation Responses

Executive Summary

Introduction

In December 2022 the Scottish Government committed to make subordinate legislation by 14 December 2024 to deliver a Scottish equivalent to the Passivhaus standard.

To inform this process, the Building Regulations: Determining the principles for a Scottish equivalent to the Passivhaus standard: Stage 1 consultation ran from 31 July to 23 October 2024. The consultation invited stakeholders' views and information on the form and approach that a Scottish equivalent to the Passivhaus standard could adopt. It also sought information on the implementation of the 2023 energy standards.

This report presents the analysis of responses to this first of two planned consultations, considering the technical, commercial and wider policy implications of improvements to standards. In total, 350 consultation responses were received from 164 individuals and 186 organisations. The most common types of organisations responding were designers/consultants, contractors/developers and industry associations.

Defining a Scottish equivalent to the Passivhaus standard

Two thirds (65%) disagreed with the statements on what a Scottish 'equivalent' to the Passivhaus standard should not mean, while 35% agreed. Many respondents disagreed that 'equivalent' should not necessarily mean a standard is set that requires a similar level of prescription on key energy-related elements of building specification. Several called for the full Passivhaus approach to be adopted, while some raised concerns with using Passivhaus, though it was unclear whether concerns related to the full or equivalent version.

However, the suggestion that 'equivalent' should not necessarily mean Passivhaus is adopted for all new developments was supported by many, and several endorsed the proposal that outcomes did not necessarily mean that standards must consistently achieve built outcomes at least as good as Passivhaus.

A similar proportion (63%) disagreed with statements provided in the consultation paper on what 'equivalent' should require consideration of, while 37% agreed. Many agreed with some, most or all of the twelve considerations proposed. The most prevalent view was agreement with all points except points four and five, and to a lesser extent, point 10. In response to concerns about these points, respondents respectively emphasised that methodologies should aim to match in-use performance, many queried how comparable outcomes to those of Passivhaus certified projects could be achieved, and several called for the health and comfort metric of Passivhaus to be included. Varied suggestions on how the standard should be developed and introduced were given.

Proposed components of the standard - Design

Two thirds (64%) disagreed with the continued use of calculation tools which implement the UK methodologies, with one third (36%) in favour. Individuals opposed continued use more than organisations (79% and 48% respectively). Most prevalent in open comments was positive views about using the Passive House Planning Package (PHPP) followed by concerns on current or potential methodologies, such as SAP (Standard Assessment Procedure), HEM (Home Energy Model) and SBEM (Simplified Building Energy Model), with respondents often stating they felt these tools are still under development. Conversely, 36% agreed with the proposal because, for instance, existing tools aligned with the UK and were recognised by industry. Some highlighted specific methodological aspects they felt should be addressed, such as the need for robust and accurate calculation tools.

Approach to defining overall building energy targets

Almost three quarters (73%) did not support the proposal to retain the current approach and the setting of relative performance targets for new buildings through an approved calculation methodology. Open comments tended to support the use of absolute, defined targets, with many believing this aligned to the Passivhaus approach. Many outlined potential drawbacks of using relative or 'notional' targets, often while making a case to use absolute targets. Conversely, some favoured retaining relative targets, as used currently.

The same proportion (73%) disagreed with proposals to retain delivered energy as the main compliance metric for targets set under standard 6.1, and 27% agreed. Around half of those commenting felt unregulated energy should be included in the compliance metric, often alongside calls to include an Energy Use Intensity (EUI) metric. Several felt including unregulated energy was needed to help meet other policy targets. Other aspects to consider included how site generated energy would be addressed in the metric and the potential for a delivered energy metric to have unintended consequences.

Over four fifths (86%) supported further consideration of the introduction of a prescriptive space heating demand limit for new buildings. Benefits of introducing a prescriptive space heating demand limit were commonly described in open comments, with risks less frequently mentioned. Prescriptive limits were viewed by many as a way of improving building performance, driving higher standards of energy efficiency, improving occupant wellbeing, design flexibility, alignment with other policies or best practices, and reducing energy demand. Some also suggested the metric to use or other factors to consider. Potential risks, each identified by a few, were that any changes could be overly complex to achieve, that aspects such as building size or form could be issues, or a perception of increased costs or diminishing returns.

Most respondents (92%) supported a proposal to apply regional climate data within approved calculation methodologies and within compliance targets. It was felt Scotland's diverse climate should be acknowledged and that using regional climate provided more accurate outcomes and allowed better sizing of heat equipment. Several felt using regional data in calculation tools, and regional cooling strategies, could help optimise summer comfort by addressing overheating. A few disagreed with the proposal and felt it could place a disproportionate burden on those in remote or rural areas.

Building fabric standards

Two thirds (67%) indicated that they currently deliver new buildings that exceed 'backstop' values for fabric performance set under standard 6.2 or those used to define the notional building in guidance to standard 6.1. The most prevalent theme among those who elaborated was that they do this either by following the Passivhaus standard or achieving certification, or by following higher standards. Other issues included specific design feature suggestions to exceed backstop values or cost factors posing a challenge to exceeding backstop values.

Almost two thirds of respondents commented on limiting fabric infiltration through the building standards. The most prevalent theme was the benefits of taking this approach, notably improved build quality and performance, better comfort levels and benefits of using MVHR (Mechanical Ventilation with Heat Recovery). Comments about support for mandatory limits, on ventilation, staff expertise, training and capability, issues with MVHR, testing methodologies and being overly prescriptive were also raised.

Ventilation and occupant comfort

The most prevalent view on how effective ventilation of new buildings is best achieved was that MVHR is most effective. This was followed by the suggested use of natural ventilation, the need to consider occupants, risks of using MVHR, having flexibility to decide on the best ventilation system by property, risks of using natural ventilation and the risks and benefits of using MEV/dMEV (Mechanical Extract Ventilation / Decentralised Mechanical Extract Ventilation) systems.

Almost nine in ten (88%) agreed that further guidance should be given on MVHR. Reasons for providing further guidance included to support occupant compliance, address design and maintenance requirements, minimise the impact of poor workmanship and address the need for industry training.

Half of respondents commented on potential risks to occupant comfort that should be better addressed through the building standards. The most mentioned were summer comfort and winter comfort, poor air quality, occupant compliance and costs. Solutions, from most to least mentioned were using effective design tools, better targets, effective design features, thermal bridging, good ventilation and limiting fabric infiltration.

Alternative means of compliance

Nine in ten (89%) agreed that Passivhaus Certification offers a feasible alternative means of compliance with standard 6.1 (energy demand). A range of views were given in open comments, mostly supporting the proposal, for instance, noting it could help scale up the Passivhaus approach in Scotland.

Further views on the proposed components of the review centred around factors to consider when devising a Scottish equivalent to the Passivhaus standard, the need for quality assurance systems, ensuring workforce readiness and comments on building materials and embodied carbon. Factors to consider when devising the approach included the construction approach, variables that impact energy demand, and limits of site orientation. The need for occupant engagement was also highlighted.

Proposed components of the standard – Compliance

Over half (55%) indicated that they currently apply in-house or third party compliance management processes to their projects that address energy and environmental project elements. While Passivhaus tools, such as PHPP and Certification processes and assessors were most used, some had developed in-house approaches or used third party verification, and a wide range of certification tools were mentioned.

Preparation and design stage to issue of building warrant

The main risks at an early design stage were felt to be overly complex designs, cost factors, overheating risks and supply chain issues. Design complexity in particular was highlighted as a risk. Three main areas were highlighted by some as requiring particular attention at an early design stage - achieving airtightness and avoiding thermal bridging and overheating. Some raised cost related risks, with mitigating actions including detailed cost-benefit analyses or lifecycle costings to demonstrate long-term savings. Other risks included poor understanding of energy efficient homes among all parties and unclear targets or competing requirements.

Situations considered more challenging to manage risk at the design stage included where changes occurred at the construction stage or due to issues with the workforce, such as poor quality installations. It was felt risk management should occur at both design and construction phase, with many risks potentially mitigated through regular testing and compliance checks, on-site management, training, or good early design and collaboration.

Post-warrant action and construction phase

Three fifths (62%) indicated that they apply a particular approach to the recording of project information during construction that can demonstrate, to a third party, that work complies with energy-related aspects of building regulations. A wide variety of approaches were evident. Most commonly, the use of Passivhaus was referred to, followed by photographic evidence, documentation on the build and its progress, and modelling.

Completion of project

Over half (55%) indicated that they currently compile and report summary information on the completed building as part of a handover record of project information that goes beyond what is currently required by building regulations, though 45% did not. Stated practices varied, with the approach used often project dependent. The most common themes in comments were providing detailed documentation for the occupants and building users, post-occupancy evaluation, and using a Passivhaus approach.

Almost four in ten left an open comment describing methods they used to de-risk very low energy building aspects of design and construction and ensure intended performance levels. The most prevalent themes were to ensure a qualified and competent workforce, undertaking compliance or quality assurance processes, ensuring good design, using Passivhaus certification processes or using modelling calculations.

Intent to develop guidance/application in practice

Over four fifths (82%) agreed that the proposals in the consultation paper present a reasonable summary of why there is a need for improvement in compliance processes to deliver very low energy buildings. Open comments mainly expressed agreement with the proposals or suggested revisions to the guidance or compliance approach.

Over three quarters (78%) agreed that the proposed scope of application and recommended actions are appropriate to address the effective delivery of very low energy buildings. The most prevalent theme in open comments was support for the proposed scope, though a few disagreed or sought further clarity.

A high level of support (89%) was recorded for the application of provisions from an early (pre-warrant) design stage through to completion and handover of the building. Reasons for agreement included that these would mirror current practice, align with the Passivhaus approach, ensure the delivery of high quality, low-energy buildings that perform as expected, represent a holistic approach, and help meet Scottish Government sustainability goals. However, some highlighted the increased workload and resource demand this approach could generate, particularly for verifiers and local authorities.

Approximately a third of respondents provided views on where the verification process should focus. Themes from most to least prevalent were the importance of continuous verification and quality assurance during construction, calls for the verification process to review design proposals and to consider post occupancy evaluations.

Over three quarters (78%) agreed that the recommendations presented adequately describe action to affect the key roles and responsibilities of those who contribute to building compliance. Most commonly respondents described who should hold key roles and responsibilities for compliance, while some raised the importance of specialist training, upskilling, education, continuing professional development, feedback loops, and accreditation of those in key roles.

Call for information on current standards

Of those giving a view on the current approach to target setting and overheating risks, the most prevalent theme in comments was descriptions of factors that could cause overheating and how these could be mitigated, the importance of robust assessment, energy modelling calculations and stress testing to mitigate against overheating risks, and the pros and cons of dynamic versus simple models of overheating risk.

Most (84%) did not have experience of projects under the post-2023 energy standards which considered connection to a new or existing heat network. Comments by those who did have experience indicated that financial considerations, regulations, calculation targets and methodologies were factors in deciding to connect to a heat network. Where heat networks were not considered, reasons for this included a lack of infrastructure, concerns about their sustainability, and other financial or practical considerations.

Organisations were more likely than individuals to indicate they had experience of issues affecting development that they considered have arisen from applying current energy standards (58% compared to 37% respectively). Most prevalent were concerns about the affordability of complying with current standards. Others highlighted concerns about the performance gaps or about the limitations of calculations and assessments.

Proposed delivery programme

Three quarters (74%) agreed with the proposal to adopt as a voluntary standard from 2026 and mandate the standard in 2028. Most agreed with the phased approach or gave agreement alongside caveats or comments about the conditions needed for success. Conversely, some felt the timescale was dependent on the final proposed changes, while mixed views were expressed by others about whether the proposed timescale was either too fast or too slow.

Overview of campaign responses

Twenty four respondents submitted a campaign response to the consultation. All were construction and development organisations. The campaign responses used the same wording highlighting work undertaken by Homes for Scotland related to the proposals. Most responses began with an introduction to the work of the organisation responding, before highlighting their concerns about the proposals. In summary, the responses outline the positive effect of existing regulation on improving the energy efficiency of new buildings in Scotland but suggests that further regulation may have limited further impact on energy efficiency, but a significant impact on the supply of new homes in Scotland.

Conclusion

Many individuals and organisations with detailed knowledge participated in the consultation, sharing their views on defining a Scottish equivalent to the Passivhaus standard. Overall, the key message is that while there is support for the proposals among many groups, respondents identified multiple issues which they felt need to be considered in advance of progressing the proposals. The responses provide valuable and informative evidence for the Scottish Government to draw on when preparing amendments to regulations, to continue stakeholder engagement and to inform the structure and content of next year's consultation.