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

3. Proposed components of the standard - Design

Section 3 of the consultation paper set out and discussed proposed actions to improve the setting of energy performance and ventilation standards for new buildings, including consideration of the approach taken by the Passivhaus standard.

Standard 6.1 and approved calculation methodology

Q3. On the basis that HEM and SBEM are reviewed and shown to report representative outcomes, do you support the continued use of calculation tools which implement the UK methodologies?

Please provide information on why you agree or disagree or if you consider other actions need to be considered, including your experience of PHPP as a calculation tool.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	32	57	11
All answering	311	36	64	-
Individuals	163	21	79	-
Organisations:	148	52	48	-
- Designer / Consultant	58	26	74	-
- Contractor / Developer	17	88	12	-
- Industry Association	16	69	31	-
- Local Authority	17	88	12	-
- Manufacturer	14	50	50	-
- Housing Provider / RSL	7	86	14	-
- Professional Body	5	80	20	-
- Other	14	29	71	-

Of those answering Q3 (89% of all respondents), two thirds (64%) did not support the continued use of calculation tools which implement the UK methodologies, with one third (36%) in favour. Individuals were more likely to be opposed than organisations at 79% and 48% respectively. Relatively high levels of support were recorded by several organisation types, with the highest among contractor/developers (88%). However, only half (50%) of manufacturers and 26% of designer/consultants were in favour.

Almost nine tenths of all respondents commented at Q3. The most prevalent themes were positive views of PHPP as a calculation tool, concerns over continued use of current calculation tools, that HEM was untested or that more work was needed on tools.

Positive opinions about PHPP

Many respondents left positive comments about using PHPP. These views frequently described PHPP as robust, accurate and well proven and that it could support both design and compliance. Several respondents suggested that PHPP could be adopted as the approved methodology until HEM is ready, and a few felt PHPP could be used for compliance generally, depending on the size of the domestic project. This theme was more prevalent among designer/consultants than other organisations.

A common response was that PHPP was a robust tool that supported compliance and should be an approved methodology, that SAP did not accurately reflect real-world performance, and that the HEM was an 'unknown entity'; these points were all raised by the Passivhaus Trust in their response. Some other respondents used this precise phrasing, suggesting they had drawn upon the Passivhaus Trust's response when making their points.

Concerns about calculation tools

Concerns were raised by many respondents about current or potential methodologies, such as SAP, HEM and SBEM. These included not giving accurate results or reflecting real life performance, that it could increase the performance gap, and that they did not support the design process. For instance, one highlighted different tools handled heat loss measurements in very different ways.

One national voluntary organisation therefore highlighted different Energy Performance Certificate (EPC) ratings could be achieved depending on the assessment tool used – HEM, SAP or Passivhaus. Some cited the results of the review of the English Wrapper for the Future Homes Standard, mostly perceiving these as 'disappointing'. For instance, one industry association noted the results were similar to those given by SAP, leading to 'significant discrepancies between predicted and actual energy use'. They felt this was a risk as the error percentage outcomes derived from these tools increases substantially in lower-energy buildings.

HEM / SBEM are untested

As part of a critique of the calculation tools, many took the opportunity to highlight that the development of HEM and changes to SBEM are still in progress. Where reasons for answers were given, concerns were raised over a lack of awareness of the tools and their accuracy. For example, one national voluntary organisation highlighted the need for HEM to capture as much detail as possible about buildings to increase accuracy of ratings and outputs. Specific comments included the potential for increased complexity in the design process, training implications or qualified support subject to continued testing and enhancement. More support was given for using HEM assuming it had been fully tested and operationalised. A few indicated it was difficult to comment on this question because of their lack of knowledge of HEM.

Agreement with the proposal

Several agreed with the proposal, with comments including that existing tools aligned with the UK, were recognised by industry, that a Scottish wrapper could allow for deviations such as climate differences and buildings, and that these tools could produce similar results to PHPP. Some added caveats or highlighted areas for improvement, such as the need for tools to be simple, accurate and subject to review. One highlighted standard reports produced as part of the EPC process could not be interrogated whereas they felt PHPP produced user friendly metrics and reports that could be analysed. Some recommended retaining the existing tools to align with UK methodologies. Reasons included for consistency, familiarity, simplicity and supply chain continuity.

Comments on tools

Some highlighted specific methodological aspects they felt should be addressed, such as calculation tools needing to be robust and accurate, or emphasising the need for such tools. A few gave views on other aspects to include in tools, such as dynamic simulation modelling, embodied carbon, thermal conductivity, an ability to vary exposure/wind speeds and take account of form factors, or for the 'wrapper' to easily be removed to see underlying calculations. An industry association recommended a hybrid approach, where PHPP can be used alongside SBEM for non-domestic buildings to allow the strengths of both methodologies to be leveraged.

A few respondents left wide-ranging comments on EPCs, notably that tools should align with, and be used for producing, EPCs. One organisation highlighted existing tools could do this.

Caution around the use of PHPP

The need for more development, a lack of experience of using PHPP or a preference not to adopt PHPP were issues highlighted by some. Perceived drawbacks included that PHPP is time consuming and complex to use, there is insufficient experience in the sector of using it, and that there was limited independent analysis of the results from a PHPP calculation. Concerns were also raised about PHPP being an Excel spreadsheet and respondents felt it should be further developed. For instance one designer/consultant felt PHPP should be subject to the same alignment that iSBEM and Dynamic Simulation Modelling have gone through to ensure similar results at the compliance stage.

Other comments

A few called for more clarity or guidance, such as to take account of different build types or clarify how heat networks would be assessed. A few commented on the need for upskilling, for instance, to ensure modelling and assessments were carried out by trained or accredited modellers. One Passivhaus consultant respondent felt PHPP had been 'quite easy to use' following good training and support.

Approach to defining overall building energy targets

Q4. Do you support retention of the current approach and the setting of relative performance targets for new buildings through an approved calculation methodology?

Please provide information on why you agree or disagree or if you consider other actions need to be considered.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	23	64	13
All answering	304	27	73	-
Individuals	162	13	87	-
Organisations:	142	42	58	-
- Designer / Consultant	57	12	88	-
- Contractor / Developer	17	82	18	-
- Industry Association	12	58	42	-
- Local Authority	17	82	18	-
- Manufacturer	15	47	53	-
- Housing Provider / RSL	6	83	17	-
- Professional Body	4	75	25	-
- Other	14	21	79	-

Of those answering Q4 (87% of all respondents), almost three quarters (73%) did not support this proposal, with 27% in favour. While many individuals who answered were opposed (87%), opinion was more mixed among organisations with 42% supporting and 58% opposed to the proposed approach. Support varied considerably among organisations who answered, ranging from 12% among designer/consultants to 83% of housing providers/RSLs.

Over four fifths of all respondents left an open comment explaining their answer. By far, the most prevalent theme was a call for the use of absolute or defined targets, with issues with relative or 'notional' targets as the second most prevalent theme.

Use absolute targets

More than half of respondents left comments advocating the use of absolute, defined targets, with many highlighting this would align to the Passivhaus approach. Perceived benefits of adopting absolute targets included:

• Clarity over targets, making them easier to adhere to and evaluate.
• Endorsement by industry bodies such as Low Energy Transformation Initiative, Royal Institute of British Architects, Building Research Establishment and the UK Net Zero Carbon Building Standard.
• Leading the way in sustainable building practices and helping drive public awareness.

Evidence of successfully using absolute measures in practice was given. Several highlighted the use of an absolute target in recent Scottish school builds as part of Scotland's Learning Estate Investment Programme (LEIP). One industry association set out a detailed case for using absolute measures; to illustrate, one perceived benefit was that they remained relevant over time as they are not influenced by the performance of existing buildings or changing benchmarks. One individual who identified as a senior employee in a design firm felt in their experience, absolute targets can easily be understood within the construction industry.

As with Q3, there was evidence of the Passivhaus Trust's response being used to shape other responses. For instance, some used the exact phrase 'Only absolute targets can deliver a Scottish Passivhaus equivalent'.

Issues with relative targets

Perceived drawbacks with relative or 'notional' targets were raised by many, often in tandem with making a case to use absolute targets. Comments included that comparisons, as used in relative targets, were less precise than absolute targets and could lead to design problems and performance gaps. A few felt relative targets could compound a 'minimum compliance' mindset or distort design decisions by penalising efficient design. One highlighted using relative performance targets created difficulties setting performance requirements consistent with the national carbon budget, making it hard to track progress against budget.

Agree, relative targets are needed

Conversely, some were in favour of retaining relative targets, as used currently. The most common reason given was their perceived flexibility. In addition, it was highlighted this approach was already embedded throughout industry and offered better value for money. One respondent felt absolute targets would have detrimental consequences for the visual impact of new developments and would constrain new developments due to limitations of form and orientation.

Issues with absolute targets

A few highlighted concerns with using absolute targets. Respondents noted more challenging sites or aspects may have difficulty meeting defined targets, that certain design options and solutions could be constrained, or perceived costs would increase.

Other themes

A few raised other themes including calls to ensure flexibility, calls for an effective methodology and comments on the use of both relative and absolute targets. One professional body felt caution was needed, noting that absolute targets could 'relatively easily' be calculated from SAP or PHPP inputs but felt these would need to be sufficiently trialled. It highlighted the current approach was attractive in its simplicity, flexibility and predictability.

Q5. Do you agree with the proposal to retain delivered energy, covering only regulated energy use, as the main compliance metric for targets set under standard 6.1 (energy demand)?

Please provide information on why you agree or disagree or if you consider other actions need to be considered.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	23	63	14
All answering	301	27	73	-
Individuals	159	11	89	-
Organisations:	142	44	56	-
- Designer / Consultant	57	19	81	-
- Contractor / Developer	16	88	13	-
- Industry Association	14	50	50	-
- Local Authority	17	71	29	-
- Manufacturer	14	50	50	-
- Housing Provider / RSL	6	67	33	-
- Professional Body	5	80	20	-
- Other	13	23	77	-

Among those answering Q5 (86% of all respondents), 73% disagreed with the proposals to retain delivered energy as the main compliance metric for targets set under standard 6.1, and 27% agreed. Most individuals (89%) were opposed, but among organisations who answered 44% were in favour and 56% opposed. Views varied by organisation type – while 88% of contractor/developers and 80% of professional bodies agreed, 81% of designer/consultants disagreed.

Almost four fifths of all respondents left an open comment to explain their view, mostly explaining their opposition to the proposal to cover only regulated energy. Several suggested including an EUI metric.

Disagree, include unregulated energy use

Around half of respondents called for unregulated energy to be included in the compliance metric. A range of benefits of this approach were set out. For instance, greater awareness of, and taking action to reduce, energy consumption could help reduce a significant proportion of a building's energy use and could become increasingly important in future as technology creates new uses for energy in homes and buildings.

As for the previous question, there was evidence of the Passivhaus Trust's response being mirrored by others, for instance, to call for unregulated energy use to be included and use an EUI metric, and that doing so would align with industry standards and best practice.

Disagree, include an EUI metric

Several respondents, the majority of whom disagreed with the proposal, endorsed using an EUI metric that would account for total energy use. This was felt to be important for accurate monitoring, to drive reductions in energy use, and to improve in-use performance.

Disagree, needs to align to other policies

Several disagreed with the proposal, suggesting including unregulated energy is necessary to help meet other policy targets. In order of prevalence policies addressing climate change, fuel poverty and public health. Including unregulated energy was seen to align to industry bodies such as those noted in Q4. One highlighted the need for alignment with local heat and energy efficiency strategies.

Agreement with including only regulated energy

A few agreed with the proposal to only include regulated energy and a few agreed on the basis that it was not possible to control unregulated energy, as its use was determined by building occupants. Retaining a delivered energy metric was perceived to offer industry continuity, for instance by avoiding confusion and complexity, or that it was inappropriate to include non-fixed appliances like cooking facilities and white goods.

Comments on energy use metrics

A few highlighted that to align with Passivhaus, the metric should include unregulated energy, or that the Passivhaus approach, which included unregulated energy, should be used. Benefits of doing so were perceived to be that Passivhaus was a proven, rigorous approach, that it could help educate people about energy use, and that it was central to the successful performance of Passivhaus buildings.

Wide ranging comments were left by some on issues relating to the introduction of an energy metric. These included in order of prevalence:

• A few highlighted the need to consider how occupier or site generated energy would be addressed in the metric, with suggestions this could be used towards meeting targets. One conversely felt energy use limits should include energy generated on-site to avoid a loophole of not having to work to meet the target.
• The potential for a delivered energy metric to be used to reduce quality housebuilding or increase emissions, for instance, by meeting the target through installing inefficient renewable solutions but not making fabric improvements.
• The need to consider how a metric applies to electric vehicles or heat networks.
• Owner occupiers easily being able to monitor energy use to help lower demand.
• To include unregulated energy as an optional metric for domestic but retain a calculated metric for non-domestic builds.

Q6. Do you support further consideration of the introduction of a prescriptive space heating demand limit for new buildings through building regulations?

If you answered 'Yes', please provide information on what form of prescription you would support and the potential benefits and/or risks this may create.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	75	13	12
All answering	307	86	14	-
Individuals	160	93	7	-
Organisations:	147	78	22	-
- Designer / Consultant	57	98	2	-
- Contractor / Developer	17	24	76	-
- Industry Association	14	64	36	-
- Local Authority	17	65	35	-
- Manufacturer	15	73	27	-
- Housing Provider / RSL	7	100	0	-
- Professional Body	5	80	20	-
- Other	15	80	20	-

Of those answering Q6 (88% of all respondents), over four fifths (86%) supported this proposal, with 14% opposed. A majority of both individuals and organisations were in favour, at 93% and 78% respectively. Over three fifths of each type of organisation supported the proposal, apart from contractor/developers who answered, of whom 24% were in favour and 76% opposed. Support was highest among housing providers/RSLs (100%) and designers/consultants (98%).

Over four fifths of all respondents left an open comment at Q6, most of whom described benefits of introducing a prescriptive space heating demand limit, with risks less frequently mentioned. Some also suggested the metric to use or other factors to consider.

Acts as a driver for improvement

Prescriptive limits were viewed by many as a way of improving building performance, driving higher standards of energy efficiency, for instance by constructing buildings with the best possible building fabric, and encouraging innovation and competition in the market. However, comments were generally brief and did not give further detail. Again, respondents' views at times mirrored those of the Passivhaus Trust. For instance, very similar wording was used by several to comment that a prescriptive space demand standard was 'crucial' for driving 'higher standards of energy efficiency' in new buildings.

Can improve occupant wellbeing

Occupant wellbeing was seen by many as a benefit of setting limits. For example, it was suggested that limits could help reduce energy use, leading to lower bills for occupants. This was widely viewed as a possible way to address fuel poverty. Comfortable indoor temperature was also a perceived benefit, and a few noted resultant positive health gains could reduce pressure on health services. A few felt it would be useful for addressing summer comfort levels, or overheating, in buildings.

It can be used flexibly

Several felt design flexibility could be maintained when measured as heating demand (kWh/m²a) or a peak heat load (W/m²). Perceived benefits included good design optimisation and choice of a wider range of solutions, tailored to different building types. One designer/consultant for instance, felt including both heating demand and peak heat load allowed flexibility without compromising on energy performance, while accommodating practical needs across different building types.

Aligns with other policies

Several felt introducing a limit would align with other policies or best practice. In order of prevalence, and reflecting the theme above, the policies it was felt to align to were: Net Zero Carbon, fuel poverty and public health outcomes. One noted the proposal aligned with international best practices including those of Passivhaus, European energy performance directives, international building performance standards and global carbon reduction commitments.

Several recommended using the Passivhaus approach, noting the ability of PHPP to incorporate space heating demand limits. Views were expressed on its success in improving energy efficiency and the need not to dilute the Passivhaus approach.

General support

Some expressed broad support for the proposal, notably as it would reduce energy demand; a few highlighted this could reduce pressure on the grid. An individual working for a designer/consultant reported low overall demand helped maximise heat pump efficiency, again, reducing overall demand.

Clear targets are beneficial

Setting clear targets in building regulations offered various benefits according to some. These included improving standards and changing attitudes towards energy monitoring.

Comments on the metric to adopt

Diverse views were expressed by some on which metric to adopt. There was no consensus as to whether it should be higher or lower than 15 kWh/m2/yr, with calls made for both. A few commented on the proposal to whether compliance with Standard 6.2 (building insulation envelope) should be demonstrated by not exceeding a set of maximum U-values. Views ranged from a preference not to use these, as they could be complex or restrict flexibility, to an understanding of the need for these, albeit alongside calls for greater clarity, and refinement, of the metrics to be used.

A few highlighted the current levels of sustainability set out in Section 7 of the Scottish Building Standards Technical Handbooks. One professional body highlighted that a space heating demand target has been used for many years when building affordable housing, as achieving Silver Aspect 2 level is a requirement for funding, and perceived a large proportion of the residential industry is already familiar with such metrics. Two respondents felt using these levels would promote improvements and choice. One highlighted PHPP calculated energy demand in-use and instead called for a Whole Life Carbon (WLC) target that included carbon used during construction.

Perceived risks

Three main potential risks were raised by respondents, each raised by a few. These were that any changes could be overly complex to achieve, that aspects such as building size or form was an issue, or a perception of increased costs or diminishing returns.

A few felt there was a need for support for industry to adapt, such as to address workforce upskilling, and for checks on the quality of work. Areas of training suggested included detailed risk assessments of airtightness, adopting new technology and maintenance.

Risks associated with building size or form were highlighted by a few. These included that the larger the building, the more easily it would hit the absolute target. Other suggested building types or forms that might need amended targets were swimming pools or ice rinks, flat roofs, bungalows, lighter build materials, and integral garages. A limit was perceived by a few to have an increased risk of costs, with comments highlighting the potential for diminishing returns or costs outweighing benefits.

Q7. Do you support the move to application of regional climate data within the approved calculation methodologies and their application within compliance targets?

Please provide information on why you agree or disagree or if you consider other actions need to be considered.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	80	7	13
All answering	306	92	8	-
Individuals	161	94	6	-
Organisations:	145	88	12	-
- Designer / Consultant	57	100	0	-
- Contractor / Developer	16	44	56	-
- Industry Association	13	92	8	-
- Local Authority	16	88	13	-
- Manufacturer	15	80	20	-
- Housing Provider / RSL	7	100	0	-
- Professional Body	5	100	0	-
- Other	16	88	13	-

For those answering Q7 (87% of all respondents), a very high level of support for this proposal was recorded, with 92% of all answering, 94% of individuals and 88% of organisations in favour of the application of regional climate data. Over four fifths of each type of organisation supported the proposal, except for contractor/developers who answered, of whom 44% were in favour and 56% opposed. All designers/consultants, housing providers/RSLs and professional bodies who answered were in favour.

Over four fifths of all respondents left an open comment at Q7. In line with the closed question data, most comments were in favour of the proposal, with reasons given including that it is more accurate, enhances building resilience and can enhance comfort.

Take regional variation into account

The most prevalent theme in comments was support for using regional climate data in approved calculation methodologies. Many comments in this theme frequently reflected one or more of the following points, in order of prevalence:

• Scotland is diverse, and its different climates should be recognised.
• Using regional climate data leads to accurate outcomes.
• Using regional climate data allows better sizing of heat equipment such as pumps.

Suggested factors to include were prevailing weather patterns, exposure, humidity, wind speeds, temperatures, solar radiation, sunshine hours, and long-term climatic predictions. One Contractor/Developer reported non-domestic compliance calculations currently only allowed selection between Glasgow and Edinburgh, which they considered 'extremely limiting'.

Can improve building performance or resilience

According to several respondents, possible benefits of taking regional data into account include improved design decisions along with improved performance, such as reducing performance gaps. An ability to incorporate and test future climate scenarios in the methodology to increase future climate resilience was also highlighted by a few.

Can optimise comfort

Several felt using regional data in calculation tools, and regional cooling strategies, could help optimise summer comfort by addressing overheating. For instance, one housing provider/RSL highlighted cooling was becoming more of a consideration for them than it had been 10-15 years ago. Some also highlighted a positive impact on winter comfort.

Could disadvantage parts of Scotland

A few disagreed with the proposal and felt it could place a disproportionate burden on those in remote or rural areas, where it was perceived that additional work would be required to meet the target, despite being areas with greater economic challenges.

Other comments

Some suggested a range of factors they felt should be considered when using space heating limits, including the need for variations based on building types to correctly size heat equipment and to wait until it is seen how HEM will contribute to calculations.

More general comments on targets were left by some. These included the need for these to reflect local climate data, for instance, because this was the only way to meet an absolute target. Some also commented that the use of regional climate data aligned with Passivhaus and PHPP or called for its adoption. Less commonly mentioned themes given as reasons not to support the proposal, mentioned by a few, included perceived increased complexity, disproportionate costs, or a lack of belief it was needed.

Building fabric standards

Q8. Do you 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?

If you answered 'Yes', please provide information on the solutions you apply, any challenges experience and your views on wider application of such solutions.

Of those answering Q8 (68% of all respondents), 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. This included 61% of individuals and 73% of organisations who answered. Most organisation types had at least some experience of this type of delivery, with the lowest levels among professional bodies (25%) and other organisations (17%).

Just under half of all respondents provided commented at Q8. A range of solutions, challenges and other considerations were detailed by respondents. This included designing to Passivhaus standards, considering specific design features, cost challenges and design complexity.

Already design to Passivhaus or higher standards

The most prevalent theme, raised by several respondents, was that they exceed backstop values for fabric performance ('backstop values') set under standards 6.2 or 6.1, either by following the Passivhaus standard or by certifying buildings as Passivhaus, or more generally by following higher standards. Reasons for following higher standards and exceeding backstop values included clients wanting higher standards and a desire to follow local standards which require higher backstop values, though these were not specified. Respondents also noted other benefits of following Passivhaus standards, such as high indoor air quality, thermal comfort and taking a whole building view. A very few noted that SAP compliance often requires going further than minimum backstop values.

Some respondents detailed why they choose to exceed backstop values more generally. This included clients setting new levels to reach, the individual or organisation choosing to aim for higher values for various reasons, as well as general statements that they do exceed backstop values. A few respondents provided suggested U-value specifications.

Solutions

Some respondents suggested specific design features to exceed backstop values. This included triple glazing, limiting thermal bridging, increasing airtightness, increasing insulation, and focusing on areas such as floors, roofs, windows and doors. A few respondents made suggestions on fabrics used, with a very few specifying taking a fabric first approach or improving insulation as a solution.

Providing industry training and upskilling to support quality workmanship was mentioned as a solution by a few respondents. There were also notes that there is existing capability within the industry.

Challenges

Some respondents noted cost factors can pose a challenge to exceeding backstop values. They noted an increased cost to exceed backstop values, particularly overall cost increases when following Passivhaus standards, even if there are reduced running costs as a result. Respondents also commented that cost pressures could lead to an aim of meeting rather than exceeding minimum standards.

A few respondents raised challenges with design complexity when seeking to exceed backstop values. This included increased timeframes, complexity resulting from increased insulation, and the need for detailed designs and planning. A few noted similar practical challenges with exceeding backstop values. Challenges around ensuring staff skills and knowledge are sufficient to allow steps to be taken to exceed backstop values were also noted, with additional training being presented as a solution.

Comments were made by a small number about embodied carbon, increased carbon emissions and other environmental-related concerns; for example, challenges with embodied carbon in polyisocyanurate^[5] and polyurethane materials were noted. A very few respondents noted challenges in using Passivhaus standards for non-domestic or larger buildings or depending on building locations. For instance, one individual felt larger Passivhaus projects might not always meet SAP backstops.

Wider application

Following Passivhaus (PHPP) standards and to consider other targets were suggested by a few respondents for wider application of solutions to exceed backstop values. For example, having thermal bridging targets in the regulation rather than only fabric U-value targets was suggested. The need to incentivise better performance and to provide additional roles and responsibilities guidance was also noted by a few.

Q9. Do you have any particular views on limiting fabric infiltration through the building standards?

If you answered 'Yes', please provide your views and any supporting information on the benefits and risks arising from greater prescription on this topic.

The Scottish Government proposes to continue to set a relative energy performance target, specifying a value for building infiltration to be used in the calculation of targets. Views were sought on whether these targets should be more prescriptive in future.

Over three quarters (77%) of those answering the closed element of Q9 indicated they had views on limiting fabric infiltration through the building standards. This included 67% of individuals and 87% of organisations who answered this question, and the vast majority of each type of organisation.

Almost two thirds of all respondents provided comments to Q9. The most prevalent theme was respondents outlining the benefits of limiting fabric infiltration through building standards. This was followed by support for mandatory limits, comments on ventilation, comments on staff expertise/training/capability, and issues with MVHR, methodologies and being prescriptive.

Supports better build quality and comfort levels

Several respondents described the benefits of limiting fabric infiltration through the building standards. Three strands of comments evident in this theme, in order of prevalence, were: improved build quality and performance, better comfort levels and benefits of using MVHR.

Regarding improved build quality and performance, respondents noted how limits can improve airtightness, prevent uncontrolled air movement, prevent moisture and fabric damage, avoid heat loss, increase building durability, and improve energy efficiency which in turn reduces running costs.

Several noted this would provide better comfort levels for occupants with improvements in health, air quality, thermal comfort, and sound pollution. Some reported that this could result in the need for MVHR, described its benefits and encouraged its use. This is discussed further in Q10.

Support for mandatory limits

There was support for targets, standards or regulation from several respondents, with some arguing for those to be mandatory. It was suggested to follow existing Passivhaus criteria, specifications for targets were noted, and to ensure compliance. While respondents from all types of organisation raised this theme, it was more prevalent in comments from local authorities compared with those made by other types of organisation.

Comments on ventilation

Some respondents commented on ventilation, excluding MVHR, including the need for good ventilation in tandem with limits on fabric infiltration, issues with current ventilation systems, and the need for ventilation systems to be fit-for-purpose by property. Refer to Q10 for more on ventilation.

Availability of expertise and capacity in the industry

Some commented on the need for training, upskilling or education to support industry capability to make these changes, though it was acknowledged that this may take time. It was also noted that there is some existing expertise in the industry, however a lack of capacity was also noted as an additional challenge. For instance, one highlighted forecasts from the Construction Industry Training Board that an additional 3,910 people will be required annually to meet demand for sustainable and energy-efficient construction.

Issues with the need for MVHR, methodologies and being prescriptive

Potential issues with low infiltration rates were noted by some respondents. Themes raised in order of prevalence, were: issues from requiring the use of MVHR, general challenges, issues with testing methodologies, overly prescriptive limits and a need for flexibility, cost factors, and issues with occupant behaviour and compliance.

Some raised concerns about limiting fabric infiltration likely requiring the use of MVHR and expressed concerns about using this ventilation system. These concerns are also reflected in Q10 so are not duplicated here. However, this was more likely to be a concern among housing providers/RSLs than other types of organisation. Potential challenges and complexities arising from limiting fabric infiltration were noted by some, including longer timeframes and extra design considerations. Issues with testing methodologies were described by some – such as a need for improvements to air tightness testing methodologies and a need for compliance testing.

A few stated that limits could be overly prescriptive and flexibility for designer and client choice is needed. The potential increased costs for both the construction and client were also raised by a few respondents. Issues with occupant behaviour and compliance were noted by a few, these are also addressed in Q12.

Other themes

A range of other factors for consideration regarding this question were each raised by a small number of respondents. These included: health risks for occupants, current specifications are sufficient (i.e. no need to change), suggestions to take a whole building view for the standards, and one respondent suggested conducting research prior to setting the standard and another noted concerns around sound transmission. A few also raised environmental-related comments on meeting net zero goals, reducing carbon emissions and embodied carbon concerns.

Ventilation and occupant comfort

Views were sought on how effective ventilation can best be achieved, with a view to informing proposals to be developed for the stage 2 consultation.

Q10. Do you have any particular views on the means by which effective ventilation of new buildings is best achieved?

If you answered 'Yes', please provide your views and any supporting information on the benefits and risks identified in the delivery of your projects.

Over half of all respondents elaborated on their views at Q10. The most prevalent theme was that MVHR is the best way to achieve effective ventilation of new buildings. 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 systems.

MVHR is most effective

Many respondents including individuals and most types of organisation supported MVHR as the best way to effectively ventilate new buildings. They felt MVHR results in better indoor air quality, increased energy efficiency, heat retention, lower running costs, and better thermal comfort and health than other options. It was also frequently suggested that MVHR should become mandatory. However, respondents noted that for MVHR to be used effectively, it should be accompanied by occupant guidelines and education, maintenance information and good installation. Some suggested its use along with natural ventilation.

Conversely, some respondents highlighted possible risks of using MVHR or consequences of poorly installed MVHR systems. These included potential challenges with maintenance, occupant error, noise in use, a negative impact on occupant health and system costs.

Need for natural ventilation

Several respondents suggested the use of natural ventilation or to use a mix of ventilation methods to effectively ventilate new buildings. It was suggested by some that this could occur alongside using MVHR or by following passive ventilation methods. This included suggestions of purge ventilation such as occupants being able to open windows, background ventilation, combined ventilation approaches, and trickle vents.

Some countered this view, stating that natural ventilation strategies are not effective. Specifically, they felt that natural ventilation leads to heat loss, condensation, mould, poor indoor air quality, is inconsistent, and relies too heavily on occupant behaviour.

Need for occupant consideration

Consideration of the occupant when designing new builds and installing ventilation systems was requested by some and was a more prevalent theme in comments made by housing providers/RSLs compared to other organisations. Specifically, the need to consider education and guidance to enable to correct use of installed ventilation systems (see Q11), occupant comfort, usability and accessibility of systems, costs, occupant preferences, and health.

Flexibility

It was suggested by some respondents that there should be a flexible approach to ventilation, allowing designers and clients to decide on the best ventilation system for each property. Again, this theme was more prevalent in comments from housing providers/RSLs compared to other organisations. This includes considering the client, building type, cost and location. Respondents suggested taking a whole-house approach to choosing a ventilation system and to consider a range of methods. There were also comments stating a want for MVHR use to not be prescribed.

MEV/dMEV risks and benefits

Some respondents described potential risks with using MEV/dMEV systems, which they felt can result in poor indoor air quality, mould, reliance on occupant behaviour, energy loss, occupant discomfort and poor health. However, a few respondents described potential benefits of using MEV/dMEV systems, such as easier installation and maintenance than other ventilation systems and good indoor air quality.

Other considerations

A range of other considerations to effectively ventilate new buildings were noted by respondents. These largely highlighted requirements for effective ventilation without specifying which ventilation systems would be most effective. This included suggestions for good commissioning, design, installation, workmanship and verification of ventilation systems. The importance of having constant ventilation, considering carbon reduction targets and following PHPP guidance was also noted.

Q11. Specifically for new homes should further guidance be given on MVHR, generally, and through the Technical Handbooks?

If you answered 'Yes', please describe what approach to this work you consider would be most appropriate in driving forward informed, good practice on both energy and ventilation performance.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	62	9	29
All answering	247	88	12	-
Individuals	122	84	16	-
Organisations:	125	91	9	-
- Designer / Consultant	48	100	0	-
- Contractor / Developer	17	82	18	-
- Industry Association	11	82	18	-
- Local Authority	17	82	18	-
- Manufacturer	12	92	8	-
- Housing Provider / RSL	6	100	0	-
- Professional Body	5	60	40	-
- Other	9	100	0	-

Almost nine in ten (88%) of those answering Q11 agreed that further guidance should be given on MVHR, including 84% of individuals and 91% of organisations. At least four fifths of most types of organisation agreed, including all designer/consultants and housing providers/RSL, with professional bodies being least likely to think this is required (60%).

Over half of all respondents provided an open response to this question. In line with the high levels of support expressed at the closed question, the main themes focused on reasons for providing further guidance, including to: support occupant compliance; address design and maintenance requirements; and minimise the impact of poor workmanship and the need for industry training. Other respondents provided suggestions for the guidance or requested flexibility in approaches.

Support occupant behaviour and compliance

Several respondents suggested improving occupant behaviour and compliance through education and guidance, to support good energy and ventilation performance of MVHR systems. Respondents suggested guidance could be provided via an occupant handbook, videos or classes and could provide an understanding of MVHR systems in an accessible and easy to understand way. It could include content on MVHR maintenance and the importance of not turning MVHR systems off. It was noted that this improved compliance could support good internal air quality, occupant comfort, and enable good ventilation performance and energy efficiency.

Address design and maintenance requirements

A recurring theme was for any guidance to address design and maintenance requirements of MVHR systems, to ensure good practice on both energy and ventilation performance. Respondents described a range of possible considerations including: the overall building performance with MVHR, limiting noise, correctly installing MVHR systems, suitably designing ducting, and considering fire regulations and embodied carbon.Maintenance and cleaning requirements for the MVHR system to function properly were also highlighted, such as replacing filters and the need to place systems in locations that are easily accessible for maintenance. It was noted that guidance on these points, including within the Technical Handbooks, would be beneficial.

Improved industry training and workmanship

Some highlighted challenges that could arise from poor workmanship and the resulting poor build quality, as well as solutions required to remedy this. For example, challenges included noisy MVHR systems due to poor installation which occupants then may turn off. Respondents highlighted the need for industry training, certification, guidance, upskilling and education, to achieve good design and installation of MVHR systems.

Guideline suggestions

Some respondents provided suggestions for the guidelines or agreed with having MVHR guidelines. Benefits of improved guidelines were mentioned, including improved occupant health, better design of MVHR systems, better installation and improved energy efficiency. Further specific suggestions included using existing Passivhaus guidance, and singular calls for keeping the guidelines simple and clear, including supplier lists such as a registered MVHR installer list, and indexing the guidelines.

Flexibility

As at Q10, some described the need to be less prescriptive about ventilation systems, although a few expressed support for regulating the use of MVHR in some form. This would mean that the guidance also covers alternative ventilation types and allows for consideration of appropriate solutions based on the type of building or the affordability of ventilation systems.

Other themes

Some respondents highlighted the importance of commissioning requirements and guidance for MVHR systems. A few respondents commented on addressing winter comfort, such as through taking a fabric first approach, insulating, considering heating demand, and achieving air tightness. Comments on having effective and accurate tools, performance metrics and compliance checks were made by a few respondents.

Q12. Are there areas of newbuild design and specification you would wish to highlight as potential risks to occupant comfort that should be better addressed through the building standards?

If you answered 'Yes', please provide examples of the issues encountered and, where available, the solutions employed to address the problem.

The consultation paper notes occupant comfort has not been a significant focus within review discussions to date and the Scottish Government sought views on this topic.

Half of all respondents provided comments to Q12. Because respondents often outlined a variety of potential risks, and then varied solutions to address these issues, the analysis below firstly presents risks in order of prevalence, followed by suggested solutions. The most mentioned risks were regarding summer comfort and winter comfort, poor air quality, occupant compliance and costs. The most frequently cited solutions, from most to least mentioned, were using effective design tools, better targets, effective design features, thermal bridging, good ventilation and limiting fabric infiltration.

Issue: Summer and winter comfort

The most prevalent potential risk raised in comments was the need to consider summer comfort for occupants, specifically the risk of overheating, the resulting discomfort and potential health risks. The rise in temperature because of climate change and the need for future-resilient buildings was highlighted. Respondents commented that the increase in insulation and solar gains can result in this overheating. Solutions used to prevent overheating largely focused on design factors like shading, windows and ventilation, which could be addressed through the building standards.

Several respondents raised potential risks around winter comfort for occupants, such as the risk of coldness, draughts, moisture, mould, humidity and condensation – all of which can have negative health impacts on occupants. Respondents described how these can result from issues with airtightness, poor ventilation and thermal bridging issues, which could be better addressed through the building standards.

Issue: Poor indoor air quality

Issues with poor indoor air quality in new buildings posing a health risk to occupants were raised by several respondents as an area that could be better addressed through building standards. Specifically, concerns around the health risks posed by toxic building products, volatile organic compounds (VOCs) and other air pollutants. Respondents highlighted the need to reduce these air quality factors, such as through mandating their reduction. Challenges around current under-ventilation in buildings, the need to use appropriate building materials and calls for improved air quality monitoring were also highlighted. One local authority, for instance, suggested low-emission materials and effective ventilation systems were necessary to enhance indoor air quality.

Issue: Occupant compliance, costs and other issues

Challenges surrounding occupant compliance and awareness were highlighted by a few respondents. These reflected many of the same issues and solutions outlined in more detail in Q11 and, were more common among comments from housing providers/RSLs than other organisations. Cost-related concerns were noted by a few respondents, including costs for ventilation, additional design features, and ongoing running costs.

The need to consider the location, local climate and type of building was mentioned by a few respondents, such as larger buildings being at greater risk of overheating. Other potential risks or issues with ventilation systems, including MVHR, aligned with themes already presented in Q10 and Q11.

Solution: Using effective tools, targets and design

Several respondents highlighted effective and accurate design tools as a solution to improve occupant comfort. This included suggestions to use existing the Passivhaus approach. Others highlighted the need for modelling, measuring and monitoring air quality.

Improving targets and regulations was requested by several respondents. Considerations they felt could improve occupant comfort, included: compliance, overheating, ventilation, building quality, noise, energy efficiency, air quality, durability and insulation. General comments were made on the need for inclusion of occupant comfort within building standards and to address the risks outlined in the responses to this question.

Another theme was the need for effective design, as it was felt that without effective design there can be negative physical and mental health impacts on occupants. This was noted as a solution to a range of issues mentioned above, such as summer and winter occupant comfort. Factors highlighted for consideration include orientation, solar gain, shading, ventilation, window size, daylight glazing fractions and flooring warmth. To illustrate, one local authority noted health benefits and comfort could be improved by balancing daylight ratios against thermal performance.

Solution: Thermal bridging, good ventilation and limiting fabric infiltration

Some respondents suggested focusing on minimising thermal bridging to support occupant comfort, through reduced risk of heat loss, condensation, moisture, cold and mould. Some commented on limiting fabric infiltration through using quality building fabric and adequately insulating.

Comments were made by some around good ventilation to support occupant comfort, which could be better addressed in the building standards. Again, the points made about the benefits, challenges and occupant understanding of ventilation and MVHR reiterated the themes already covered in Q10 and Q11.

Other solutions

A few respondents suggested providing guidance to occupants through education to remedy occupant-behaviour related issues, as detailed in Q11. A few others suggested reducing heating demand and peak heat load, and a very small number suggested using vapour permeable construction as a solution.

Alternative means of compliance

Q13. Do you consider that Passivhaus Certification offers a feasible alternative means of compliance with standard 6.1 (energy demand)?

Please provide information on why you agree or disagree and on the extents to which this alternative might be usefully applied in practice.

Audience	Sample size (n=)	% Yes	% No	% No answer
All respondents	350	77	9	13
All answering	303	89	11	-
Individuals	158	93	7	-
Organisations:	145	85	15	-
- Designer / Consultant	58	91	9	-
- Contractor / Developer	16	69	31	-
- Industry Association	16	75	25	-
- Local Authority	16	100	0	-
- Manufacturer	14	100	0	-
- Housing Provider / RSL	7	57	43	-
- Professional Body	6	67	33	-
- Other	12	75	25	-

Of those answering Q13 (87% of all respondents), nine in ten (89%) agreed that Passivhaus Certification offers a feasible alternative means of compliance with standard 6.1. Among individuals and organisations who answered 93% and 85% respectively agreed. A majority of all types of organisation agreed, from 57% of housing providers/RSLs and 67% of professional bodies to 91% of designer/consultants and all local authorities and manufacturers.

Almost four fifths of all respondents left an open comment, with a range of views evident. To answer the question, the analysis of responses is structured by giving arguments for and against the proposal, followed by discussion on how it could be applied in practice. Themes are presented in order of prevalence under each header. In summary, comments mostly supported the proposal, for instance, noting it could help scale up the Passivhaus approach in Scotland.

Agree, Passivhaus Certification is a feasible alternative

Most comments explained why respondents agreed Passivhaus Certification should be a feasible alternative means of achieving compliance with standard 6.1. Themes raised by several respondents, in order of prevalence, were: general agreement, including that this would simplify compliance; that it is tried and tested; that it could help scale up the Passivhaus approach and that it is reliable and effective.

Of those giving general support, it was commonly noted that this approach could be a good way to achieve compliance with standard 6.1, but also Section 3.14 on ventilation. It was also suggested it could reduce the need for multiple calculations, such as SAP and SBEM. A few agreed, with provisos, such as only if the standards are as rigorous as current building regulations and that it can help meet Net Zero targets.

Next most prevalent was support due to Passivhaus being a tried and tested approach, proven over many years. Some similarly felt it is a comprehensive or holistic approach. Respondents highlighted its years of development and testing, and therefore felt it was a mature approach.

It was also perceived that Passivhaus Certification as a means of achieving compliance could help scale up sustainable building practices in Scotland, for instance, through generating a welcoming environment for the introduction of a future Scottish equivalent to the Passivhaus standard. Some perceived Passivhaus would drive higher standards, for instance, because its targets were seen as more exacting than those under existing building regulations or because the approach encouraged improved workforce practices.

Several agreed as they described the Passivhaus approach to be reliable, effective, robust and rigorous. One highlighted its 'four eyes' approach where four different parties are responsible for robust design and construction, and suggested its layered approach to compliance can help reduce the likelihood of errors, poor workmanship and oversights.

Concerns about using Passivhaus Certification

Less commonly mentioned themes, each raised by a few, indicated disagreement with the proposal. These were that using Passivhaus would be too time consuming or complex, perceptions of increased costs, that its Certification was only awarded at building completion and that the approach did not cover all aspects of building standards. Increased cost and complexity were perceived around consultancy and assessment, increased build time, reduced clarity, and the need to comply with two calculation methodologies to produce EPCs. One designer noted that the Gold level in Section 7 of the Technical Handbook covered additional sustainability aspects, such as space design and water consumption, whereas Passivhaus Certification did not. A professional body felt 'many questions, needed to be answered' before using Passivhaus Certification or integrating it into building standards. These included being clear where liability lies if completed properties do not meet the Passivhaus Certification criteria when in use, ensuring it conformed to the requirements of the Building (Procedure)(Scotland) Regulations 2004, that it addressed the requirements of Standards 6.2 – 6.11 and the requirements of the Domestic Services Guidance, and that it applied equally to different buildings.

As Passivhaus Certification is administered by an independent institute, a few respondents called for caution. It was suggested this could increase risks, for instance, if the government wished to amend targets. One 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.

Application in practice

Some recommended allowing a range of certifications, where Passivhaus was just one possible way to achieve compliance. While a majority of those raising this point agreed with the proposal, both those for and against made the point that Passivhaus Certification could be one of a number of acceptable compliance mechanisms used. Other examples were: HEM, BREEAM and Home Quality Mark delivered by BRE, Mynergie, and AECB Carbonlite New Build Standard and EasyPH which both use PHPP calculations, but are felt less demanding than Passivhaus. A few highlighted that some buildings may struggle to meet the standards.

Comments on upskilling and upscaling were provided by some. Designers, tradesmen and verifiers were all suggested as groups who would benefit from additional training. Conversely, a few highlighted many within the industry were already knowledgeable and experienced in building low energy buildings, therefore scaling up was feasible.

Issues of costs were raised by a few who left a variety of views. These included perceptions it would encourage Passivhaus to be chosen by clients if they did not need to pay for other compliance measures, or of increased building costs especially in rural areas. One felt PHPP was affordable, while another felt the costs and availability of Passivhaus Certification was a barrier to achieving application in practice.

A few felt the approach should be supported through the development of Certification of Design and Certification of Construction schemes. For instance, an advisory body/committee highlighted verifiers had no role prior to the registration of a building warrant and therefore felt it made sense to mandate the Certification of Design within the regulatory framework. One individual provided detailed information suggesting amendments to Section 6 to help achieve this. Comments included that the approach should be outlined in any mandatory standard and to be fully detailed in the Technical Handbook supporting guidance.

Q14. Are there any other comments or observations you wish to make on the proposed components of the review which relate to building design?

If you answered 'Yes', please provide your further comments or observations. Additional supporting information may also be provided by attaching a separate document to your response.

Section 3.7 of the consultation paper sets out a summary of proposals relating to the design and specification of new buildings, with a view to developing relevant standards. Question 14 sought any other views from respondents on these proposals. Two fifths of all respondents provided further comments or observations, providing a spread of views. The most prevalent themes were 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

A range of issues were raised that respondents felt need consideration when developing the relevant standards. These included factors to consider such as the construction approach, any variables that impact energy demand, and limits of site orientation. The need for occupant engagement was noted, with a few suggesting this could be challenging when working with vulnerable people.

Constraints should be understood

Some felt constraints should be addressed, such as making sure any changes to the design or materials, were practical and viable. Difficulties building energy efficient buildings were highlighted by some, for instance, due to site plotting orientations, with calls for flexibility to accommodate specific challenges.

A few highlighted a perceived conflict between Passivhaus and other regulations. For instance, one local authority commented that a requirement to use named components would contradict procurement regulations.

Need for quality assurance mechanisms

Enhanced verification and quality assurance mechanisms were recommended by some. Suggestions included that ongoing quality assurance, from the design stage, should be at the heart of the approach to reduce performance gaps and ensure quality builds.

Comments often highlighted the Passivhaus approach, and the use of PHPP, as a suitable tool to embed into calculation tools. This view was also held by an industry association who claimed using PHPP from the design stage can "significantly enhance the accuracy of performance predictions and support the delivery of high quality buildings".

However, a few felt it important to ensure that Passivhaus standards were as rigorously tested as existing regulations. One, for example, felt the PHPP comfort / overheating assessment should be tested as rigorously as those in Approved Document O of England's building regulations, including the dynamic thermal modelling route to overheating compliance.

Ensuring workforce readiness

Some felt more work was needed to ensure there were sufficient skills in the workforce, or an adequate supply chain to meet any standards. Topics suggested included training or guidance – especially for assessors - on tools like PHPP and on the benefits of high-performance buildings and how to maximise their use. Information for occupants was suggested by a few. Suggestions were given on how to off-set training costs such as caps or grants or subsidies to cover additional certification costs.

Comments on building materials and embodied carbon

Comments were made by some on building materials and embodied carbon. Most commonly, respondents called for embodied carbon to be included in targets, for instance, to help meet climate change targets and ensure carbon efficiency. One called for Solar PV (Polyvoltaic) not to be mandatory due to finite global resources for PV components, and because it is not useful for Scotland due to its poor solar gains, though others recommended Solar PV, with battery storage, be installed in new buildings. An industry association felt current building regulations discriminated against district heat networks in favour of heat pumps due to notional building specifications. Two called for the use of natural materials to be considered.

Support for the transition

Suggestions were made by some about how the transition period could be supported. These included using phases, subsidies or financial support, being "easy to implement" and providing guidance and support.

Other themes

Themes raised by a few included the need for flexibility, for instance, to allow greater choice in how to address house building constraints, or to adopt a voluntary approach initially. This theme was more likely to be mentioned by housing providers/RSLs than other types of organisation. A few commented on thermal bridging and air tightness; these views are addressed under Q16. A few called for alignment with UK regulations, highlighted the potential for unintended consequences or made other suggestions such as to change the name from 'equivalent to the Passivhaus standard' as they did not feel it was an equivalent and suggested it focused on 'enhanced low energy design that is based on key aspects of Passivhaus'.