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

4. Proposed components of the standard - Compliance

This chapter explores proposed actions to improve assurance that the design intent for energy performance and ventilation standards for new buildings is achieved in practice. Consideration is also given to how this can be reported on. Detailed processes to demonstrate compliance will be set out in the stage 2 consultation.

Principles of an evidence-led approach to compliance

Q15. Do you currently apply an in-house or third-party compliance management process to your projects which specifically addresses energy and environmental project elements?

If you answered 'Yes', please provide information summarising your approach and the key benefits you derive from its application in practice.

Of those answering Q15 (61% of all respondents), over half (55%) indicated that they currently apply the approach outlined in this question, with 45% indicating they do not. Just under half (47%) of individuals stated they did, compared to over three fifths (63%) of organisations. Levels of application were highest among designer/consultants (78%) and manufacturers (73%), and lowest among housing providers/RSLs (40%) and local authorities (38%).

Nearly two fifths of all respondents left an open comment at Q15. The most prevalent approach applied by respondents was using Passivhaus tools, supported by an assessor, though in-house or other certification routes were reportedly used.

Passivhaus tools

The most prevalent theme, mentioned by several, was the use of Passivhaus tools, such as PHPP and Certification processes and assessors. It was highlighted that Passivhaus guidance such as the Passivhaus Building Certification Guide produced by the Passive House Institute was used, often alongside PHPP, to support this approach in practice. One called for the use of Passivhaus Plus and Premium standard to be used to tackle the scale of climate change.

Benefits of this approach were commonly provided. These included that it could ensure compliance with UK building regulations, a strong focus on achieving the required outcomes and a safe, tidy site, as well as deliver improved quality, value for money and healthy and comfortable homes. One housing provider/RSL for instance, highlighted it employed a Passivhaus Assessor to check the design against the PHPP tool, obtain regular reports showing evidence of compliance and carry out on-site inspections.

Develop in-house tools and approaches

Next most prevalent was the use of quality assurance mechanisms developed in-house. Some respondents described a range of methods that are used together to produce quality assurance over the lifetime of projects, and a few highlighted the use of calculation tools or photographic evidence.

Examples included:

• Developing in-house tools such as carbon calculations and thermal bridging software.
• Provision of a full heating system design service, heat pump sizing service and a SAP consultancy service.
• Requiring thermographic surveys of completed buildings and considering investing in indoor quality monitoring.
• Commissioning quality assurance services, beyond the typical requirement and akin to the Passivhaus certification process.

Use of other certification tools

A wide range of certifications were mentioned by some. These included:

• ISO standards with ISO 14001 on environmental management being most mentioned.
• Association for Environment Conscious Building (AECB) CarbonLite New Build standards.
• EnerPHit for retrofitting with Passivhaus components.
• Part L of the English building regulations.
• Buildoffsite Property Assurance Scheme and Building Services Research.
• British Board of Agrement: Construction Product Certification.
• Scottish Health Technical Memorandum.
• Royal Institute of British Architects Plan of Work (including Passivhaus overlay) and Architects Registration Board Code of Practice.
• Building Services Research and Information Association (BSRIA) Soft Landings framework^[6].

One professional body highlighted its publications were well integrated into Scotland's building regulations. It felt "many more technical memoranda, guides, codes and certification schemes" could be considered for reference in the revised technical guide and provided a suggested list in its response.

A few mentioned the use of carbon tools such as FCBS Carbon, Carbo Life Calculator and the UK Net Zero Carbon Building Standard.

Use third parties

Some mentioned the use of third-party verification, again, often deployed across the full life of the project. Sometimes this was used in the context of Passivhaus approach, which requires third party verification, though others cited Section 6 certifiers. Two noted third parties were used due to a lack of in-house expertise, one of whom highlighted regulatory compliance was a complex area.

Employ specialist staff or consultants

Employing or commissioning an expert to assist with quality assurance was a strategy highlighted by a few. Most highlighted were Clerk of Works and mechanical, electrical and plumbing (MEP) specialists, though designers were also mentioned. One described how carbon energy assessors undertook a range of compliance management processes from outline to building handover stages, such as advising on specific performance metrics needed, reviewing architectural specifications against requirements and reviewing as-built information and photographic evidence. Another noted the use of third-party consultants for air filtration testing.

Preparation and design stage to issue of building warrant

Q16. From your experience of delivering very low energy buildings, what are the most common risks identified at an early design stage and how are they managed most effectively?

Over half of all respondents answered Q16. Following the request in the question, many respondents answered by outlining risks followed by how they might be managed. To retain the meaning of responses, this section follows the same approach, presenting risks in order of prevalence alongside their potential solutions. The main risks at an early design stage were felt to be overly complex designs, cost factors, overheating risks and supply chain issues.

Risks and mitigating actions associated with design

Risks associated with the ability to build specified designs were raised by several respondents including individuals and most types of organisation. Design complexity in particular was highlighted as a risk, as this could make it more difficult to achieve intended outcomes. It was felt that increasing complexity could require contractors to find solutions to overcome poor or insufficient design, which in turn could increase costs and delays. Challenging design aspects could include poor form factor, overly complicated build-ups and junction details, changes to the design, insufficient initial design, integrating systems into smaller domestic properties, or too much glass. A few raised challenges with modelling, such as accurate modelling being necessary, the model not including all energy sources, or the complexity of integrating the modelling into design processes post-design.

Suggested solutions to design complexity included keeping designs simple, using an energy modelling tool that supports design, using bioclimatic design such as orientation, location, shading, and having continuous communication between the design and construction teams. Suggestions were also made to improve the knowledge of designers such as increasing awareness of how to manipulate design to achieve high levels of building performance and how to consider form factor.

Three main areas were highlighted by some as requiring particular attention at an early design stage - achieving airtightness and avoiding thermal bridging and overheating. It was noted that these are critical to producing energy efficient homes. Taking mitigating actions at an early design stage was felt able to help avoid subsequent issues and included:

• For thermal bridging: Detailed thermal modelling, keeping the number of penetrations and fixing points to a minimum with all penetrations in place before starting work, agreeing sealing methods at design stage, choosing an optimum site for the MVHR system to reduce the need for cold services ducting, and performing detailed thermal bridging analyses.
• For air tightness: Developing a robust specification for airtightness, introducing an airtightness strategy to help coordinate ventilation and heating systems with design, identifying a ventilation system early, early design reviews and using multiple air pressure tests at different stages.
• For overheating or excessive solar gain: balance glazing ratios to optimise useful gain, consider building orientation and window size and shading and entering important variables into the modelling strategy.

A few highlighted the risk of 'value engineering', or the systematic method of reducing the cost of a product, service or system while preserving its essential function. Linking the building quality to certification and compliance requirements was seen to mitigate this risk.

Risks and mitigating actions associated with costs

Some highlighted risks associated with costs such as: missed opportunities for long-term savings due to the focus on finance being at the project outset; increasing costs as a project progresses; procurement restrictions; and a lack of client understanding of the costs involved in building a very low energy building, often leading to revised plans once costs are determined. Suggested mitigating actions for addressing costs included conducting detailed cost-benefit analyses or lifecycle costings to demonstrate long-term savings, prioritising cost-effective measures with the greatest impact, or to use straightforward commissioning systems and seasonal commissioning^[7]. For instance, one housing provider/RSL highlighted that work is being undertaken to develop a compromise standard intended to be "realistic, achievable and more affordable" compared to the use of the Passivhaus standard.

Risks and mitigating actions associated with lack of understanding

A small number of risks associated with poor understanding of energy efficient homes were raised by some. These included a 'design for compliance' culture and a perceived lack of ambition, or a lack of occupant understanding of how the building operated, which could result in unintended consequences.

Suggested mitigations included training and information for occupants and end users, specifying aftercare responsibilities in contracts, using easy to use smart energy controls and more awareness and buy-in among designers and clients.

Risks and mitigating actions associated with the supply chain

Supply chain issues were highlighted by some, with a few also highlighting challenges sourcing appropriate materials. Supply chain concerns centred around having a sufficiently skilled and experienced workforce and singular comments included risks of having sufficient surrounding available power to support electrical requirements or there being only a limited supply of tested new technologies. The need for good communication, coordination, and early engagement between designers and contractors, training and robust quality assurance were recommended ways to mitigate workforce related risks.

Finding appropriate products was also highlighted as a risk by some, such as sourcing products that meet very low U-value requirements, good quality door components such as door sills, or insulation material that is not overly thick. The noise generated by air source heat pumps was also raised as an issue. Suggested mitigations included focusing specifications on performance targets within a tolerance range rather than specific products, involving contractors in discussions about materials, and limiting options at the design stage.

Risks and mitigating actions associated with targets

Risks associated with targets were raised by some. Unclear targets, complex or competing requirements or obtaining consents and warrants in a timely manner were seen as potential early stage risks. Consequences of this were felt to lead to uncertainty and poor decision-making and expensive later upgrades, a lack of clear direction and difficulties getting information from planning departments. While the Passivhaus approach was advocated as an existing process that provides clarity, one cautioned on potential conflict between different approaches, highlighting NHS England's Health Technical Memorandum 03-01 which required significantly higher air flow rates than the Passivhaus standard.

Recommended mitigating actions at an early stage were to adopt clear, straightforward targets, use a certification process, undertake inspections and monitor compliance, and produce guidance e.g. around thermal bridging or testing. Where a preference was expressed, respondents called for clear absolute targets. An individual cited experience of working on the EUI metric in Scottish LEIP schools, which was felt effective in transforming practice.

Q17. Do you consider there are practical limits to effective risk management at design stage alone and can you give examples of where management of risk is more effective at a later (construction) stage?

Two fifths of all respondents answered Q17. Situations considered to be more challenging to manage risk included where changes occurred at the construction stage or due to issues with the workforce, such as poor quality installations. Some felt that risk management should occur at both design and construction phase, and some noted that many risks could be mitigated with regular testing and compliance checks or good early design.

As the focus of responses varied, with some concerning practical limits and others addressing solutions, the analysis below presents limits first in order of prevalence, followed by ways that risks can be better managed.

Limit: Changes between design and construction

The most commonly raised issue was the impact of deviations from the design occurring during the construction phase, which was raised across several themes. Some highlighted that materials could be substituted from the original design, which could compromise the building's performance. This situation could occur where contractors considered it more practical to do so, for instance, depending on what stock was available.

A few highlighted that certain issues could only be identified during construction, for instance challenges ensuring air tightness during installation, resulting in the need for on-site adjustments. A few also highlighted financial risks, such as accurate costs only becoming known during construction, or changes incurring additional costs. The risk of cost considerations taking priority over quality building was highlighted, such as substituting cheaper materials.

Risks arising from such changes included poor building performance, where outcomes deviated considerably from predicted calculation, or toxins and emissions released from cheaper materials.

Limit: Quality of workmanship

A risk raised by a few that could be better managed at construction phase is the quality of workmanship. Respondents expressed a view that highly skilled tradesmen were required to build to Passivhaus standards, and that a lack of understanding or training could lead to installation problems or difficulties achieving airtightness targets. One individual also highlighted that Section 6 Certifiers may be unfamiliar with non-traditional building approaches which could lead to areas where performance gaps could emerge.

Limit: Lack of information or clear specification

Certain information only being available at a later stage or the lack of clear specification or design, for instance due to being considered overly complex or being made only during the construction phase, were also highlighted as risks – each by a few. Information not considered available early enough included subcontractor designs or test results. Associated risks were that not having sufficient information could impact on warrant approval processes, that insufficient data was available for accurate modelling or that performance issues would not be identified early enough.

Solution: Regular testing and quality control

The most prevalent theme mentioned by some to manage many of the risks noted above was to use quality control during construction, involving regular testing and verification. The need to focus on achieving air tightness, quality workmanship, system commissioning such as for mechanical ventilation systems, and to avoid performance failure was emphasised. One highlighted that checks should also be carried out to ensure the site is protected, so no latent moisture enters the building due to the elements.

Suggested actions included: on-site installation checks of insulation products, membranes and thermal bridging; monitoring ventilation air flow rates; using an independent Clerk of Works role; using infrared-photography; and appointing air tightness and quality assurance experts. Another called for the role of Certifiers of Design for Section 6 to be extended, so that it tracked the project onsite, as well as at design stage. An individual noted new English regulations on evidence provision may assist, such as producing regular photographic evidence of construction details or thermographic surveys and felt something similar could be adopted in Scotland.

Solution: Good design and modelling

Some highlighted that good design helped to minimise risks, and that builds that followed their design were more likely to have good performance levels. Determining the energy model from the outset and good early design decisions were seen as ways to reduce risks such as increasing costs or delays. However, it was recognised that not all risks could be mitigated pre-construction. When part of the early stage design, the importance of using modelling was emphasised, followed by a review of any changes needed to meet the revised model.

Solution: Skilled and coordinated workforce

The next two themes, both raised by some, related to the quality of the workforce and the need for effective collaboration between those involved to mitigate risks arising from changes at the construction stage or poor workmanship.

In addition to quality control noted above, on-site management and training were seen as important ways to address workforce issues. Suggested ways to promote good design included through engaging contractors earlier, increasing training for designers on how to develop sympathetic airtightness junctions and ensuring designers have relevant delivery experience. A thorough understanding of the design, of the implications of poor workmanship or quality control, and of different ways to achieve the same results were highlighted as being as needed by those involved in building very low energy buildings. One highlighted the need for tradesmen to put aside their traditional ways of working and consider more energy efficient alternatives.

The importance of on-site coordination between trades was noted by some. Regular communication and feedback could mitigate risks associated with design, product and model revisions, for instance. The need for designers, clients and contractors to be involved in discussions around design parameters was also highlighted, with one suggesting time should be set aside "for review and design iterations to achieve an optimum design and site implementation".

Other themes

Some emphasised the need for effective risk management strategies, usually across different project stages. A few highlighted that Passivhaus processes were an effective way to manage risks, with respondents highlighting aspects such as its quality assurance process of documenting as-built conditions and remodelling, if necessary, the PHPP tool and the Certifier role. Passivhaus Toolbox talks and training were also highlighted as good ways to upskill staff.

Post-warrant action and construction phase

Q18. Do you currently 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? If you answered 'Yes', please provide information summarising your approach and the key benefits you derive from its application in practice.

While three fifths (62%) of those answering Q18 indicated that they do 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, there was a difference between the proportion of organisations (72%) and individuals (49%) who do so. Over four fifths of manufacturers (89%), contractor/developers (88%) and designer/consultants (81%) apply a particular approach, compared to around half of other types of organisation.

Over two fifths of all respondents left an open comment outlining their approach to the recording of information during construction to demonstrate compliance, with a wide variety of approaches evident. Most commonly, the use of the Passivhaus approach was referred to, followed by photographic evidence, documentation on the build and its progress, and modelling.

Use Passivhaus processes

The most common approach highlighted was using Passivhaus to record and monitor data. Positive aspects of this approach which were highlighted included regular remodelling, third party verification, specific testing such as for airtightness and system commissioning, submission of photographic evidence and providing evidence of the correct equipment being installed. Documenting a clear auditable trail of how energy related aspects have been handled was felt to help compliance, transparency and accountability according to one advisory body/committee.

Visual evidence

Aside from those mentioning photographic evidence as part of Passivhaus methods, some highlighted using photographic or other visual evidence. Photos were commonly used to evidence how the build was progressing over time and confirm correct completion. Other visual evidence included construction drawings, thermographic imaging, 360 photographic surveys and AI tools such as Open Space, which uses headcam recordings to help project teams resolve issues quickly. While this theme was mentioned by several types of organisation, it was slightly more likely to be raised by manufacturers than other groups.

Documentation related to the build

Evidence of recording across the build was given by some. This included recording details such as construction records, performance data, emails, 'snagging' records and evolution of works. Ways of doing this varied and ranged from software or cloud-based solutions, devising checklists, trackers and schedules of critical details before construction and using technical submittal forms for reviewing MEP system proposals during construction stage.

Test records and use of modelling

Records of tests undertaken were kept by some. The need for ongoing monitoring and continual updating of calculations to achieve expected outcomes was emphasised, with records kept on air tightness tests and U-value calculations.

Internal quality assurance processes

A few referred to Clerk of Works being appointed to oversee record keeping and conduct site inspections. It was noted that this could highlight concerns or issues to the design team and contractor and allow remedial action to be taken.

Other procedures or methods followed

A wide range of other ways of recording information were given by a few respondents. These included through the AECB certification process, evidence compiled to process Energy Performance Certificates or Part L of the Building Standards in England, post occupancy evaluation or National House Building Council (NHBC) insurance cover. A few also highlighted storing installation records and commissioning records, such as receipts or invoices from suppliers to prove the materials used onsite.

A few highlighted the involvement of third parties to verify information or mentioned keeping evidence to support regulatory compliance, such as periodic reporting and assessments against key targets. Such recording was considered helpful by one individual to verify projects are still on track with energy and carbon targets and ensure issues can be identified and addressed promptly. A few noted they followed a commissioning approach, for instance, one had adopted the BSRIA and CIBSE Commissioning guidance that requires a commissioning plan, detailed 'tracker' document, and a commissioning manager who can support upskilling.

Completion of project

Q19. Do you 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?

If you answered 'Yes', please provide information summarising your approach and the key benefits you derive from its application in practice.

Over half (55%) of those answering Q19 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, with 45% not. Just under half (46%) of individuals stated they did, compared to almost two thirds (64%) of organisations. This varied considerably by type of organisation, from 80% of contractor/developers to half (50%) of local authorities, housing providers/RSLs and professional bodies, and 33% of industry associations.

One third of all respondents left an open comment on information provided as part of the handover stage. Practice varied widely, and it was noted that the approach used could be project dependent. Comments demonstrated a range of approaches, from not providing information above that required by building regulations to much more detailed accounts of how respondents supported the handover of information.

The most common themes were that detailed documentation would be provided for the customer, providing user manuals for occupants or post occupancy evaluation, and the use of a Passivhaus approach.

Detailed documentation

Some respondents explained that once the building was completed, they used detailed documentation about the building as part of a handover. This tended to be targeted at the client or building owner and were more technical in nature than information described for occupants. Contents varied, though typically used one or more of: evidence gathered during construction; user guidance, such as operation and maintenance manuals; certifications; test results; photographic evidence and proof of materials used. While this theme was raised by most types of organisation, it was more prevalent in comments made by housing providers/RSLs.

A few highlighted they had adopted the New Homes Quality code produced by the New Homes Quality Board, which mandates the provision of details on energy efficiency and the estimated ongoing costs of running the home.

Four respondents advocated the use of the 'soft landings' approach to enabling a smooth transition from construction to operation. One organisation described what their input to this looked like, such as chairing quarterly aftercare meetings, benchmarking the building's energy use compared to similar buildings and conducting post occupancy evaluations.

Information for occupants

Instructions for occupants on how to use the building effectively were given by some, including leaflets, handbooks and 'quick start' guides. Three mentioned the use of post-occupancy evaluation (POE), with one highlighting a requirement within CIBSE Building Performance Awards is to provide evidence that a POE had been undertaken.

For Passivhaus projects

It was noted by some that Passivhaus certification required information on the completed building beyond that required by building standards. A few noted they had only gone beyond the minimum when working on Passivhaus projects. The key elements of Passivhaus requirements includes an updated PHPP model, detailed construction documentation and photographic records, airtightness test results, ventilation commissioning, an operation and maintenance manual, certification documentation and signed contractor declaration.

Other themes

Themes were raised, each by a few, that covered specific aspects of information gathered for the handover stage, such as relevant test results, modelling, visual methods and sign offs. Data collected focused on providing an updated energy model and results of airtightness tests. Two also referred to data included in building information management systems, and one also included "evidence of material thermal conductivities, window specification and detailed performance data". Drawings, photos or other visual methods were highlighted. Three mentioned the use of 3D-scans.

A few also noted they went beyond the minimum requirements when gathering evidence to assist the production of EPCs, though two felt there was "no guarantee" this informed the operations and maintenance manual. A few noted they worked to compliance with the building regulations, such as producing health and safety files, tenant handbooks and certificates. One highlighted ISO9001 sets out a process for delivering information on completion of a project.

Risk management

Q20. Do you have experience of implementing methods to effectively de-risk the very low energy building aspects of design and construction and provide assurance that the compliant solutions are properly considered and delivered as intended?

If you answered 'Yes', please provide information summarising your experience.

Among those answering Q20, almost three fifths (58%) have experience of the situation outlined in the question. This included half (49%) of individuals and two thirds (65%) of organisations who answered. Experience varied by type of organisation, from 80% of consultant/developers to 31% of local authorities who answered.

Almost two fifths of all respondents 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 main methods were the same as those discussed in Q16 and are therefore not repeated here. The most prevalent themes were to ensure a qualified and competent workforce, undertaking compliance or QA processes, ensuring good design, using Passivhaus certification processes or using modelling calculations.

Less commonly mentioned themes raised by a few respondents included airtightness strategies and testing, collaboration and inter-disciplinary meetings, and third-party certification. A few also highlighted their overall construction approach such as using tried and tested methods, described specific materials used such as closed timber panels, used handover approaches such as 'soft landings', or emphasised the need to understand appliances, such as commissioning and testing of MVHR systems to ensure they operate as intended and meet performance criteria.

Intent to develop guidance/application in practice

The consultation paper (section 4.3) sets out a case for why strengthened compliance processes - with associated guidance – are needed to deliver very low energy buildings. This section is framed in terms of 'why' (Q21), 'what' (Q22), 'when' (Q23), 'how' (Q24) and 'who' (Q25).

Q21. Do you consider the proposals set out present a reasonable summary of why there is a need for improvement in compliance processes to deliver very low energy buildings?

Please provide information on why you agree or disagree and on any drivers for improvement you consider particularly important.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	46	10	44
All answering	195	82	18	-
Individuals	88	74	26	-
Organisations:	107	89	11	-
- Designer / Consultant	36	92	8	-
- Contractor / Developer	15	87	13	-
- Industry Association	12	100	0	-
- Local Authority	17	88	12	-
- Manufacturer	10	50	50	-
- Housing Provider / RSL	7	100	0	-
- Professional Body	4	100	0	-
- Other	6	100	0	-

Of those answering Q21 (56% of all respondents), over four fifths 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. Three quarters (74%) of individuals and 89% of organisations who answered agreed. Very high levels of at least 87% agreement were recorded by almost all types of organisation, except for manufacturers of whom 50% agreed.

Over one third of all respondents left an open comment, mainly expressing agreement with the proposals or suggesting revisions to the guidance or compliance approach.

Agreement with the proposals

Some expressed their support of the proposals, with the main theme being that these were necessary. Some specifically noted they felt the proposals were necessary to improve compliance processes. In particular, respondents emphasised the importance of reducing performance gaps, or noted aspects of compliance they felt are required, notably absolute targets, adequate calculation methodologies and quality control. Some also left positive general comments on the proposals with calls to use Passivhaus as a mechanism for compliance, and a few agreed the proposals were sensible.

Suggested revisions

Less commonly mentioned themes, each mentioned by a few respondents, included in order of prevalence: specific suggestions for compliance; suggested revisions for the guidance; calls for flexibility; and requests for greater clarity. Specific suggestions for compliance, in order of prevalence, included:

• Using evidence throughout the construction process to ensure consistent application of standards. For instance, a few recommended including post occupancy evaluation and one suggested the compliance plan should be signed off at the warrant application stage as plans cannot be altered post-construction.
• The need to recognise a comprehensive approach that includes an integrated understanding of design, construction and operational performance, rather than being focused on compliance only.
• Using specific proposed targets such as those aligned to climate change targets, a minimum Pre-Manufactured Value or similar measure, and improved occupant comfort measures.
• The need for third party verification or developing an Approved Certifier of Construction Scheme for energy.

Suggested revisions for guidance included setting out best practice guidance on how to achieve standards and assurance processes. This could set out roles and responsibilities, focus on how to reduce the performance gap, refer to the need to develop an airtightness and thermal line strategy early on, or consider how to tackle unregulated energy or existing buildings. For instance, one industry association felt it would be helpful to developers for the guide to clearly outline actions required at each stage, particularly at the pre-building warrant stage.

Calls were made for guidance to be developed with stakeholders and to learn from existing low energy building projects, as well as to be kept under regular review. A few also felt more clarity or detail was needed in guidance.

A few emphasised the need for flexibility, mainly to enable a smooth transition phase and allow for workforce upskilling, but also to recognise the longer time required to build to Passivhaus standards or in the methods used to meet the standards.

Concerns about the proposal

Very few commented expressing concerns with the proposed approach. These were that change was unnecessary or would make arrangements more complex or less robust, for instance due to greater scope in methodology and design delivery. This led one to suggest setting minimum requirements to prevent "significant differences in the performance of buildings". Another called for fully developed agnostic standards, recommending an independent Government product approval scheme, to avoid reliance on the commercially produced Passivhaus assessment and certification scheme.

Q22. Do you consider the proposed scope of application and recommended actions are appropriate to address the effective delivery of very low energy buildings?

Please provide information on why you agree or disagree and on what other actions may be useful in driving compliance.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	41	11	48
All answering	183	78	22	-
Individuals	84	70	30	-
Organisations:	99	85	15	-
- Designer / Consultant	36	83	17	-
- Contractor / Developer	15	93	7	-
- Industry Association	8	88	13	-
- Local Authority	17	82	18	-
- Manufacturer	8	50	50	-
- Housing Provider / RSL	5	100	0	-
- Professional Body	3	100	0	-
- Other	7	100	0	-

Of those answering Q22 (52% of all respondents), 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. High levels of agreement were recorded among both organisations (85%) and individuals (70%). Very high levels of at least 82% agreement were recorded by almost all types of organisation except for manufacturers (50% agreed).

Around one third of all respondents commented at Q22, with the most prevalent theme being support for the proposed scope, though a few disagreed or sought further clarity. Others highlighted a range of other aspects to consider.

General agreement

Aligned to the results of the closed question, some respondents left comments indicating their support of the proposals, though often also provided other aspects to consider. Reasons for agreeing with the proposals included its comprehensive, balanced approach with a focus on quality assurance and verification, and that it acknowledged where improvements were needed.

Unsure or disagree

A few were unsure or requested further clarity and a few disagreed, due to fears of the system becoming overly complex, concerns that it could exacerbate the housing crisis, or because they felt the current arrangements are sufficient. A few felt unable to comment without more information, such as knowledge of HEM or what actions would be adopted.

Other factors to consider

Several left wide-ranging suggestions for other aspects that they felt should be considered to support the delivery of very low energy buildings. Almost all these points are already covered elsewhere in this report and so are only listed briefly below for completeness.

In order of prevalence, themes by a few respondents included: training, using the Passivhaus methodology, specific aspects to include in the guide, reviews, targets, resources, calculation tools, roles and responsibilities, and quality assurance. A few commented regarding aspects they would like to see strengthened in the guidance, including a requirement for an operations and maintenance manual or thorough building documentation to pass on to others. Other suggested areas to consider were a broader consideration of how to promote sustainability, a review of fire regulations, the need for post-completion monitoring, the quality of workmanship and how to demonstrate competence, and the standard on condensation. Two felt the compliance plan should set out what party is responsible for providing evidence at what stage. Regular views of compliance requirements were suggested to ensure they remained effective.

A few felt the focus on new builds specifically was unnecessary, highlighting that most properties are already built and that a focus on new builds increased costs for relatively little gain. These respondents called for the need to consider how existing buildings could be retrofitted to improve energy efficiency or questioned whether this would be done in future. One professional body highlighted the quality of UK homes was considered to be the 'leakiest' in Europe, with an industry association noting up to 26% of heat loss can be attributed to uncontrolled air infiltration.

Q23. Do you support the application of provisions from an early (pre-warrant) design stage through to completion and handover of the building? Please provide information on points in the process you consider there may be a need for particular emphasis on action to manage the risk of failures in compliance.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	49	6	45
All answering	193	89	11	-
Individuals	89	85	15	-
Organisations:	104	91	9	-
- Designer / Consultant	34	91	9	-
- Contractor / Developer	16	100	0	-
- Industry Association	8	100	0	-
- Local Authority	17	82	18	-
- Manufacturer	10	80	20	-
- Housing Provider / RSL	7	86	14	-
- Professional Body	4	100	0	-
- Other	8	100	0	-

A very high level of support was recorded for the application of provisions from an early (pre-warrant) design stage through to completion and handover of the building. Nine in ten (89%) of those answering, including 85% of individuals and 91% of organisations agreed. At least four fifths of each type of organisation supported the proposal, including all consultant/developers, industry associations and professional bodies who answered.

One third of all respondents commented at Q23. In line with the closed question results, the most prevalent theme was agreement with the proposal, with several outlining the specific stages they felt were particularly important to consider. Conversely, however, some respondents expressed disagreement with, or concerns about, the proposal.

Agreement with provisions throughout the process

The most common theme in comments was broad agreement with the proposal to apply provisions from an early design stage through to completion and handover, with a few respondents emphasising the importance of continuous quality control at all stages to promote best practice and mitigate compliance failure risks. Other reasons for agreement with the proposals 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.

Suggestions for emphasis

The point in the process most frequently emphasised as being an important focus for action on compliance was the early, pre-construction stages of a project, including initial engagement, design, building warrant and application phases. Respondents noted that conducting thorough design reviews at the pre-warrant stage helps identify potential compliance issues early on. While a small number advocated for staged gateway checks and sign off procedures during the early stages, one local authority expressed a preference for early engagement to happen alongside development processes; they felt a gateway style arrangement may cause delays in the development of new projects.

A few noted the value of action and a focus on quality assurance at the construction phase including regular site inspections and checks on products, material quality and workmanship. Various suggestions were made about how this could be achieved, ranging from regularly providing evidence during construction, using a third party, such as a Clerk of Works, rather than a verifier, or ensuring that the responsibility lay with the contractor to prove the quality of their workmanship and installations. For instance, one housing provider/RSL suggested compliance checks should occur at four key risk stages: on erection of the kit and roof; wind and watertight (including insulation); installation of the services; and on completion. One individual suggested using advanced modelling tools throughout the construction phase to identify and address any deviations from predicted performance.

A few emphasised actions at the completion and handover stage. These included: provision of evidence of compliance, final inspections to confirm compliance, training and handover procedures and documentation for building occupants and facilities managers to support building energy efficiency performance over time, and increased scrutiny of handover. This was seen as important to promote good aftercare, verify that real world energy use meets predicted targets and improve understanding of the impact of regulations.

There were calls for post occupancy evaluation and monitoring to be recommended or strongly encouraged, if not mandated, or for the guide to clearly distinguish between mandatory and voluntary requirements. It was felt that this could facilitate feedback loops and ensure buildings are performing as intended.

A small number saw a role for certification, or Section 6 Certifiers, to demonstrate compliance at different project phases, or at the completion stage. One industry association and others recommended the use of Passivhaus Certification to demonstrate compliance with any new quality assurance requirements. A few supported the use of Construction Compliance Notification Plans (CCNP) and the Compliance Plan Approach. A few others supported aligning actions to recognised industry workplans such as the Royal Institute of British Architects (RIBA) Plan of Works Passivhaus Overlay or commented on their current use of such workplans.

Disagreement with, or concerns about, the proposed approach

Some disagreed with proposals to apply provisions from an early design stage through to completion and handover of the building or expressed concern about aspects of these. Most commonly, respondents highlighted the increased workload and resource demand this approach could generate, particularly for verifiers and local authorities. There were calls for increased resourcing to deliver the proposals and an intuitive software system which could make administrative processes easier.

Other specific concerns included that the proposals are unnecessary as the current process works well, are very bureaucratic, or that they may slow the design process and building programmes, increase costs, lead to confusion in roles and responsibilities, and represent a challenge for small scale, rural, or large temporary installation projects.

Other themes

Other considerations each mentioned by a few, included: The need for clear guidance, and aligning proposed quality assurance practices with evolving building standards to streamline compliance; a suggestion to include a section on building material types and VOC emissions in technical handbooks; and comments on the scalability of response.

Q24. Do you have any views on the key areas where the verification process should focus, to be effective in responding to an enhanced compliance reporting regime?

If you answered 'Yes', please provide your views.

Approximately a third of all respondents provided their views on the key areas where the verification process should focus, often reiterating the stages and themes outlined in Q23. From most to least prevalent, respondents highlighted the importance of continuous verification and quality assurance during construction and called for the verification process to review design proposals and to consider post occupancy evaluations.

Continuous quality assurance

Quality assurance - including testing and systems commissioning of onsite construction, correct installation, and the quality of workmanship and materials - was most frequently mentioned as a key area of focus for the verification process. While raised by a range of organisations, this area was marginally more likely to be mentioned by industry associations and local authorities.

Technical aspects and products identified as requiring verification included: airtightness, ventilation, thermal bridging, insulation levels and products, heating and hot water including pipework and appliances such as heat pumps and hot water storage, building junctions, glazing and window specifications including u and g values, renewable systems, consumer controls and material specification including toxicity. A few felt that consideration should be given to reviewing the competencies of specialist subcontractors to ensure that they are able to install and commission ventilation systems, for instance. As well as onsite inspections, review of onsite evidence such as photographs, CCNPs and compliance management documents were suggested to facilitate verification. A few also mentioned the importance or considering offsite construction methods and the use of Remote Verification Inspections (RVIs), given these practices are becoming more prevalent.

Design review

Some called for the verification process to review design proposals, energy models and documentation of performance assumptions. It was felt that doing so could create a clear baseline for verification, ensure transparency and accountability throughout the process, identify issues early, and facilitate better communication among stakeholders

Verification post-construction

Echoing views expressed at Q23, POEs, post construction performance checks, and review of handover procedures and compliance post handover were also identified as important areas of focus by some. Others also called for seasonal commissioning during the first year of building operation.

Additional guidance required

A small number mentioned specific standards they felt the verification process should focus on. There were calls for guidance on how Section 6 certification will be combined with a reasonable level of enquiry from local authority verifiers and clear guidelines on how certification and verification processes interact. A small number also requested more guidance around what good verification looks like during the building warrant approval and construction phases and feedback and continuous improvement to refine the verification process over time. One designer/consultant felt the verification process should incorporate standards 3.14 Ventilation and 3.28 Overheating risk for certain building types such as dwellings & residential accommodation, health and care establishments (care homes, mental health units etc.) as well as educational buildings.

Disagreement with enhanced verification

Conversely, a few respondents disagreed with the need for enhanced verification or felt that certain projects, such as temporary modular buildings, would need an alternative method of delivery. Others highlighted resource, capacity and cost impacts linked to enhanced verification processes or queried how these would be met. There were calls for the verification processes not to be too onerous or add additional work for project and local authority building teams or lead to delays in progressing projects. Additional funding, resourcing and training to deliver the proposals was also advocated.

Responsibility for verification

A range of views were expressed about who should be responsible for verification or involved in this process. As this is the focus of Q25, these comments have been included in the analysis of Q25 below. In addition, the importance of independent verification, to avoid conflicts of interest, was emphasised by a few.

Q25. Do the recommendations presented adequately describe action to affect the key roles and responsibilities of those who contribute to building compliance?

Please provide information on anything else you consider to be relevant to the actions of such parties.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	37	11	52
All answering	167	78	22	-
Individuals	74	72	28	-
Organisations:	93	83	17	-
- Designer / Consultant	32	78	22	-
- Contractor / Developer	16	88	13	-
- Industry Association	6	100	0	-
- Local Authority	17	82	18	-
- Manufacturer	8	75	25	-
- Housing Provider / RSL	5	60	40	-
- Professional Body	3	100	0	-
- Other	6	100	0	-

Of those answering Q25 (48% of all respondents), 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. This included 72% of individuals and 83% of organisations who answered. A majority of all types of organisation agreed, ranging from 60% of housing providers/RSLs to all industry associations and professional bodies.

Almost one quarter of all respondents commented at Q25. Most commonly, respondents discussed who should hold key roles and responsibilities for compliance. This was followed by the importance of specialist training, upskilling, education, continuing professional development, feedback loops, and accreditation of those in key roles. Some also outlined the importance of the verifier role or called for monitoring and verification to be emphasised within a future guide.

Key roles and responsibilities

Most commonly in responses to Q25, respondents described who should hold key roles and responsibilities for compliance. While a few voiced general agreement with the roles outlined in the consultation paper, others identified specific key roles or made additional suggestions for roles with responsibility. These include an applicant / building owner / relevant person, designers including Passivhaus designers, contractors, subcontractors, Section 6 certifiers, verifiers, occupants, project financers and corporations. A small number noted that for cultural change to take place, all those within the design and build process should understand how their role contributes to, and take responsibility for, post occupancy performance and compliance.

Specifically in relation to verification, respondents suggested a range of people with responsibility, including the responsible person, contractor, Compliance Plan Managers, local authority verifiers, Certifiers of Design or Construction, a new Scottish Building Standards Hub, professional bodies, third party assurers of build systems, and Chartered RIBA / RIAS Practices. A very small number suggested creating champions or expert roles within local authority teams to verify specific aspects of a build, while one respondent called for a review of the roles of those who contribute to the verification process to ensure that key players already in place are utilised effectively. Concerns about the capacity of local authority verifiers were also reiterated.

A few emphasised the importance of clearly defining the responsibilities of all involved in the compliance process or suggested the guide provide detailed descriptions of each role, including specific tasks and expectations at each stage. This point was more likely to be raised by manufacturers than other types of organisation. For instance, one designer/consultant proposed the development of competency frameworks to support the task of role definition. A few felt the recommendations could be strengthened by emphasising Passivhaus principles, or competency in Passivhaus standards, within definitions of roles and responsibilities.

Training and upskilling

Some raised the importance of specialist training, upskilling, education, continuing professional development, feedback loops, and accreditation of those in key roles. This was felt to be needed to: ensure actors are qualified; keep pace with innovation and drive continuous improvement; promote a culture of valuing safety and compliance over project timelines; ensure behaviour change and cultural transformation; support appropriate use of PHPP; and deliver high energy efficient builds. One individual also called for a public information campaign for those outwith the industry. However, one designer/consultant queried who would drive training and certification in the absence of set criteria.

A small number stressed the importance of Section 6 compliance assessments, in particular, being carried out by competent or accredited assessors. One designer/consultant expressed concern that the Scottish equivalent to the Passivhaus standard may not contain similar levels of quality assurance as Passivhaus, due to skills shortages and uncertainty over who could carry out this role. They suggested expanding the qualifications deemed acceptable to increase the pool of those certified to undertake verification checks. A few respondents agreed with the suggestion that current scheme providers can assist in assessing the capacity, capability and competency of the existing Section 6 Certifiers.

Emphasise monitoring and verification

Some outlined the importance of the verifier role or wanted monitoring and verification to be emphasised within a future guide; this was slightly more likely to be raised by local authorities and housing providers/RSLs than other organisations. There were calls for:

• Section 6 certification to be used to verify compliance.
• Enhanced verification and certification systems.
• A robust quality assurance framework, including regular inspections and checkpoints, testing, and documentation reviews through both design and construction phases.
• Independent assessments by third parties such as Passivhaus assessors or Clerk of Works.
• Better integration with building control regarding monitoring, feedback and verification.
• Certification to verify construction quality and delivery of design and ensure performance gap is omitted.
• Strengthening Section 6 based verification processes by following best practices from the Passivhaus Institute's Building Certification Guide.
• Establishing post-occupancy monitoring to ensure buildings perform as intended.
• Increasing uniformity of practice amongst local authority verifiers.

Two local authorities highlighted the increased workload and costs associated with enhanced verification processes or suggested ways to mitigate these, such as stratified testing of some, but not all, measures. There were also requests for further information on Item 6 within the guide specifying, for instance, whether the verifier role is the Building Control Officer or another third party and their relationship with the verifier of design.

Other themes

A few respondents noted the value of, or calls for, collaboration, communication, and strengthened relationships between different stakeholders to ensure a non-siloed approach, the embedding of energy efficient principles, and more successful outcomes. Similarly, a few highlighted the value of a holistic approach to building design and compliance or wanted the guide to adopt a more integrated approach to this.

There were mixed views about the compliance plan approach. A few felt this, or a compliance plan manager, would be helpful to oversee projects and co-ordinate stakeholders. However, others noted potential costs of this, with one querying whether this would be viable for housing projects who are not operating at the same economies of scale as high-risk builds. Another felt the compliance plan manager role needed further definition with one organisation suggesting that Passivhaus Certification processes could be used as a best practice reference for adopting this approach.

Call for information on current standards

This section sought views on a small number of broader issues materially associated with the ongoing development of energy standards, including the context in which these changes would be developed and proposed.

Q26. Are you currently designing buildings to the February 2023 standards and have confirmed specifications which are at a stage that have been or will be used in a building warrant application, that you would be happy to share with us?

If you answered 'Yes', please send calculation output sheets which detail your building specification(s) to buildingstandards@gov.scot with the subject title 'Call for evidence – February 2023 design specification'.

Evidence on current new build specifications was welcomed, particularly on solutions that do not use direct emission heating systems, within the context of an earlier call for evidence by the energy standards review.

Just over one tenth of all respondents commented at Q26. However, almost half of those who commented noted that this question was not applicable to them or that they were unable to share any evidence. A similar proportion noted they will submit, had already submitted, would encourage others to submit, or would be willing to submit evidence in the future, or requested that the Scottish Government contact them separately to get information. A very small number explained they are building to Passivhaus, low energy, or current regulation standards or detailed specific specifications they are building to.

Q27. With regards to the current approach to target setting and overheating risk, do you have experience related to either of these two issues you consider useful to inform review of the current published guidance or this review of current energy and environmental standards?

If you answered 'Yes', please provide information summarising your experience.

Two fifths (39%) of those answering Q27 indicated they had experience of the current approach to target setting and overheating risk that they considered useful to inform the review. This included 29% of individuals and 49% of organisations. Levels of experience varied considerably by type of organisation, ranging from no experience among housing providers/RSLs and 25% of professional bodies answering, to 53% of local authorities and 62% of designer/consultants.

One quarter of all respondents provided comments. It should be noted that in some instances it was unclear which standard respondents were referring to, or whether respondents were describing their experience developing Passivhaus standard buildings or demonstrating compliance to current standards. Most prevalent in comments were descriptions of factors that could cause overheating and how these could be mitigated, 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

Factors related to overheating risk and mitigation

Most commonly, respondents identified factors or aspects of standards related to overheating risk, or described their experience of, or recommendations for, mitigating this. These included considerations related to: ventilation, solar gains, shading, glazing, insulation, thermal mass, temperature or climate, internal heat gains, and user behaviour. One industry association also raised that overheating of corridors in heat network projects is a significant risk, which they noted can be addressed via the Heat Network Quality Assurance scheme.

A few raised the importance of thoughtful design measures to mitigate overheating or expressed concern about a lack of consideration of this at the design stage, leading to a reactive approach to compliance and suboptimal outcomes. There were calls for adopting a holistic approach to design and for balancing sometimes conflicting approaches to addressing overheating risk. One individual explained that while they had not found Standard 3.28 a barrier to designs, they were unaware whether those designs have been prone to overheating and called for better monitoring of outcomes. One local authority similarly called for clearer guidance and ways to encourage submissions which clarified if 3.28 requirements are being met.

Stress testing, planning and assessment tools for overheating risk

A few highlighted the importance of robust assessment, energy modelling calculations and stress testing to mitigate against overheating risks. Some explained that they use PHPP as a planning or assessment tool in this regard or discussed the benefits of this approach.

However, a small number highlighted limitations with PHPP, including: it being less robust in relation to more complex buildings and single room overheating risks (as compared to overall building performance); its dependence on fixed assumptions; and insufficient targets within Passivhaus certification. One designer/consultant highlighted the importance of scrutinising assumptions used in achieving performance targets, using the example of models that might suggest leaving windows open during summer nights, but that this might be impractical due to noise pollution, security concerns or insects.

A few explained they used other tools instead of, or as well as, PHPP, or stressed the importance of being able to maintain flexibility to use other methods for assessing overheating risk, especially for more complex buildings, including the use of third-party checks. Other types of modelling or risk assessment tools or targets noted as being used, or recommended, to meet standards and mitigate overheating risk included: future scenarios of the Intergovernmental Panel on Climate Change; Climate Based Daylight Modelling (CDBM); CIBSE TM52; TM59; IES; Part O; BB 101; and HTM 03-10.

Pros and cons of dynamic versus simple models of overheating risk

While a few respondents described using, or highlighted the benefits of, dynamic modelling of overheating risk for more complex structures, a few others raised limitations to this, or suggested incidences where simple models, such as SBEM, are more appropriate. This includes for one off dwellings or smaller standalone units on industrial sites, where the use of dynamic simulation modelling was seen as excessive. Others, however, highlighted issues with the simple method such as it: being unsuitable for larger developments; failing to take account of all the factors contributing to overheating risk or certain mitigation measures; and being too complex with the measurements involved taking considerable time.

Comments on 'Part O'/ English and Welsh regulations

A small number described learning from their experience building to English or Welsh regulations or 'Part O' of these. These included perceptions of: a lack of consistency in current and draft versions of the Approved Documents; conflicts between different requirements; fixed assumptions that render targets difficult to meet and lead to unusual design choices; and methods of overheating assessment being far more burdensome than originally anticipated. One contractor/developer advocated learning from these experiences and another urged avoidance of adopting a similar compliance process in Scotland.

Targets

Broad support for regulatory requirements to address overheating risks or in relation to target setting generally was expressed by a few. The need for clear and simple targets, or targets presented in absolute terms, was also emphasised. For instance, one designer/consultant felt more specificity was required on solar gain and called for either a specific standard to be met or for existing benchmarks to be mandated.

The importance of engaging occupants in targets and understanding and managing overheating risks to maintain long-term building performance was raised by a few; documentation and certification was identified as being helpful with this.

A few explained how they used Passivhaus principles in their processes for compliance. For example, one housing provider/RSL noted that they use the current building standards as the baseline, compare these with other higher energy targets such as Gold level in Section 7 of the Technical Handbook and Passivhaus, balance that with what is affordable for tenants and then look at the thermal comfort of these options against each standard.

Other themes

Other less commonly mentioned themes, raised by a few respondents each included:

• Negative comments about current standards, including that the overheating standard has not been well received by designers and is seen as "overkill", and gaps in standard 3.28 such as it not applying to extensions and alterations. Suggested improvements included more technical guidance, and clearer regulations and a requirement that individuals performing overheating assessments be qualified or accredited.
• The need to signpost to relevant guidelines or sources to inform the development of standards such as industry bodies, Passivhaus case studies, Passive House Institute Summer Comfort Guidelines, or CIBSE guidance in relation to targets or overheating risk.
• Positive comments about current standards, including that standard 3.28 has positively influenced the design of dwellings and that current standards have provided enough guidance to be reviewed against proposed designs and offer flexibility in design approach.

Q28. Have you undertaken any projects under the post-2023 energy standards which considered connection to a new or existing heat network, both district heat networks and communal heating systems?

The Scottish Government invited respondents to share experiences of connecting to a district heat network or a communal heating system, as defined in the Heat Networks (Scotland) Act 2021, and the extent to which considerations of standard 6.1 were impacted by doing so.

Of those answering Q28 (54% of all respondents), most (84%) did not have experience of the type of projects in question. Organisations who responded were slightly more likely to have experience than individuals (20% compared to 11% respectively). A majority of all types of organisation did not have this experience, with industry associations and manufacturers indicating they had no experience of this at all. Contractor/developers who answered were most likely to have undertaken these projects (44%).

If you answered 'Yes', please share any information you consider influenced the outcome of those projects, with reference to the type of system (district or communal) and the impact of current energy targets in particular.

Around one seventh of all respondents left an open comment outlining their experience. The most prevalent theme in comments was the influence of funding and cost considerations, followed by regulations, calculation targets and methodologies. A range of other points were also raised.

Funding and costs

Most commonly, funding or costs were discussed by a few respondents as influencing factors in the decision to connect to a heat network or the outcome of a project. While some raised costs as a barrier to utilising heat networks, others highlighted these as cost-effective to connect to, or that their use was made possible by infrastructure or grant funding keeping costs minimal. A small number of organisations also referenced the benefits of district heat networks or communal heating systems in terms of affordable energy costs and low maintenance costs for building occupants.

Regulations and calculation targets

Next most frequently, a small number of respondents highlighted regulations or calculation targets and methodologies as a constraint or influencing factor in the outcome of projects. The 2023 regulations, the New Build Heat Standard prohibiting the use of direct emissions heating systems in new builds, the new delivered energy metric and the changing nature of regulations were all referenced. One organisation stated they found little difference between electric heating and district heating for compliance.

Other themes

Other factors, each raised by a small number of respondents as influencing the decision to connect to a heat network or the outcome of the project included:

• Connection to a new or existing heat network being a sensible approach for reasons including: sustainability and practicality, with the waste to heat plant being close to the site; pre-established infrastructure being an enabler, reducing cost and disruption; or because this was dictated as part of the master planned site.
• Workload factors. For instance, one local authority commented that the overall design of their project has been complicated by the additional impact on the mechanical design strategies of connecting to an existing biomass heat network. However, another individual explained that no SAP/SBEM was required to established district heating to an existing building being extended.

If you answered 'No', please confirm the reason for not considering a heat network solution.

One fifth of all respondents commented in response to this question. Some stated they had no experience of post-2023 projects considering connection to a new or existing heat network but did not elaborate further or stated that this was not relevant to their work. The remaining themes were each raised by a few respondents, noting a lack of heat network infrastructure, concerns about the sustainability of heat networks and other financial or practical barriers.

Lack of infrastructure

The most common theme among those who provided more detail was the perceived lack of infrastructure, capacity, or available heat networks as a reason for not considering a heat network solution. Heat networks were described as not as ready an opportunity, or inappropriate, for remote, rural and sparsely populated areas, with long distances leading to heat and cost inefficiencies. The lack of local energy strategies was also mentioned. One local authority called for a resource similar to the London Heat Map to check the local availability of heat networks to inform design stages.

Not the most sustainable option

A few expressed concern that heat networks are not a sustainable solution or pointed to the perceived energy inefficiencies and heat loss associated with them. A few respondents indicated they had opted instead for a renewable energy solution that had been available to them. One commented that improving the building stock through retrofit is a better use of resources than grid modifications. Another felt heat networks should only be used when a full development had been built to the highest thermal efficiency.

Others commented that the low energy consumption of Passivhaus certified buildings means heat networks are an inappropriate solution. One individual explained that the losses associated with generation, storage and distribution of heat are often far greater than the heat demand of Passivhaus buildings, meaning more localised heat generation is more favourable. Another commented that district heating systems are more useful for improving the energy efficiency of existing buildings, where there are limits to possible fabric improvements.

Financial and practical barriers

The high installation, running and management costs of heat networks were seen as prohibitive by a few. One contractor/developer also expressed concern that heat networks are currently unregulated and risk exposing building occupants to volatile markets and potentially higher energy costs. Other identified barriers included: difficulties managing and monitoring systems; metering and billing issues; a lack of space within buildings; and heat networks not being suitable for temporary buildings; and risk concerns such as over reliance on specialist providers of systems or products that could fail.

Q29. Do you have experience of issues affecting development which you consider have arisen from application of current energy and environmental standards set under building regulations?

If you answered 'Yes', please provide information summarising your experience.

Experiences were mixed among those answering Q29, with 49% having had experience of issues affecting development which they consider have arisen from application of current energy and environmental standards set under building regulations, and 52% not. Organisations were more likely than individuals to indicate they had experience of this (58% compared to 37% respectively). Once again levels of experience varied considerably by type of organisation, ranging from 25% among professional bodies and 38% among manufacturers who answered, compared to 60% of contractor/developers, 75% of industry associations and 94% of local authorities.

Almost one third of all respondents commented at Q29. Most prevalent were concerns about the cost and affordability of complying with current standards, while some respondents raised a variety of concerns about current standards. Others highlighted concerns about the performance gaps or about the limitations of calculations and assessments.

Costs and affordability

The most prevalent theme among those who commented at this question was concerns about the negative impact of energy and environmental standards on development costs, commercial viability and housing and energy affordability. For example, one designer/consultant called for any new standard to conduct a cost-benefit analysis to ensure that changes do not make building new homes unaffordable. Other financial constraints mentioned included: service costs and the maintenance of mechanical systems, underestimation of the costs of building to Passivhaus standards, and the costs associated with having to use multiple assessment tools to appraise performance.

Regulation conflicts and concerns

Some raised conflicts between, or limitations with, current standards, including:

• These being too weak, with minimum standards leading to builds that will not meet future standards and will need to be retrofitted.
• Conflicts between Passivhaus and building standards leading to design and compliance complications and negatively impacting project performance.
• Regulations and standards being too complex, unclear, and without enough worked examples.
• Concerns about specific standards and regulations such as: the 2023 and 2024 changes leading to developers rushing through non-sustainable developments using polluting heating systems, and overheating regulations described as complicated with agents struggling to demonstrate compliance and meet this standard.
• Too rigid an application of standards or the need for a more nuanced approach to regulations that considers the context of each project.
• Builds being designed and constructed to suit regulations or meet numerical targets rather than in best interests of the end user, available energy resources, energy efficiency, or the building.
• Discrepancies in standards related to house sizes, with disproportionate effort to meet targets in smaller homes, for instance, or where different fuel packages are set different targets.

Performance gaps

Some respondents highlighted performance gaps between the design and delivery or a build or between predicted and actual energy use. Respondents linked this to: poor quality design, installation, workmanship, insulation, and sealing and ventilation systems; a disconnect between the design process and the final construction; insufficient or ineffective quality assurance mechanisms, compliance software regulation and onsite verification of compliance; and cost saving measures.

The above issues were described as leading to performance deficiencies and discomfort and health risks for occupants, such as damp and mould, higher bills, poor air quality and overheating. To close the performance gap, there were calls for adherence to the Passivhaus standards and Certification process, development of HEM as both a compliance and design tool, more detailed on-site verification of performance, MVHR as a mandatory requirement for ventilating buildings, and appraisal of the embodied carbon impact of buildings.

Limitations with calculations and assessments

Limitations with energy efficiency and performance calculations and compliance assessments were noted by some. These included:

• Software being insufficient to model projects, and issues linked to the lack of or interpretation of data in EPC's, SAP and SBEM leading to: the generation of inaccurate advice, performance gaps, and the energy efficiency impact of technologies not being recognised and incentivised.
• Complexity, cost and duplication of work associated with using multiple tools to measure performance.
• Too rigid an application of energy performance metrics that don't account for the characteristics of the site and lack of consideration of differences between geographical areas when carrying out calculations.
• Lack of integration between Section 6 and compliance and design factors, insufficient attention to whole building approaches at the initial design stage, and differences between designer and energy assessor assessments leading to compliance issues and missed opportunities to optimise energy performance.

There were calls for: future assessments to be carried out by experts with sufficient training and software accreditation; to update standards to better account for the impact of advanced energy efficiency measures like MVHR and airtightness; and to streamline compliance processes by recognising advanced certification systems and compliance tools such as PHPP. One respondent expressed support for developing HEM to be used as both a compliance and design tool.

Other themes

Less common themes, each mentioned by a few respondents included:

• Technical and project specific difficulties and inefficiencies linked to ventilation and airtightness, glazing factors for overheating, emergency heating in new builds, solar PVs and heat network compliance.
• Skills, infrastructure, capacity, supply chain and technology gaps.
• Workload, timescale, maintenance and practical difficulties linked to the application of current energy and environmental standards.
• Lack of feedback loops and performance tracking, and insufficient focus on maintenance of technology and buildings post construction. This includes standards making it difficult for end users to compare actual versus designed performance, identify whether their behaviour contributes to performance gaps, and budget. One designer/consultant advocated for more consumer-friendly metrics, with absolute targets for heating demand detailed in kWh to enable consumers to more easily compare anticipated energy use with meter readings and energy bills.