Energy Standards Review - Scottish Passivhaus Equivalent Working Group minutes: February 2024

Attendees and apologies

• Michael Barton-Maynard, Building Standards Division
• Vikki Bell, Building Standards Division
• Ingrid Berkeley, Chartered Institution of Building Services Engineers
• Julio Bross-Williamson, The University of Edinburgh
• Patrick Brown, The Scottish Heads of Property Federation
• Colin Campbell, Scottish Futures Trust
• Ryan Cossar, Scottish Futures Trust
• Steven Earlie, Offsite Solutions Scotland
• Steven Fawcett, Homes for Scotland
• Jocyelyn Fleming, Chartered Institute of Building
• Daniel Foulds, Building Standards Division
• Jamie Goth, Scottish Futures Trust
• Eli Harji, Scottish Federation of Housing Associations
• Jack Haynes, Scottish Power Energy Networks
• Stuart Henderson, Homes for Scotland
• Jonathan Hines, The Passivhaus Trust
• Caitriona Jordan, Built Environment - Smarter Transformation (chair)
• Bryan Leask, Rural and Islands Housing Association Forum
• Sarah Lewis, The Passivhaus Trust
• Alan McAulay, Local Authority Building Standards Scotland
• Michael McGurk, Scottish Property Federation
• Steven Scott, Building Standards Division
• Colin Sinclair, Building Research Establishment
• John Smith, Structural Timber Association
• Robert Toomey, Royal Institution of Chartered Surveyors
• Paul Tuohy, The University of Strathclyde
• Mark Wilkinson, Construction Products Association

Apologies

• Anastasia Charalampidou, Scottish and Southern Electricity Networks
• Chris Dobson, Wheatley Group
• Peter Drummon, Royal Incorporation of Architects in Scotland
• Stephen Garvin, Head of Building Standards Division
• Stephen Good, Built Environment - Smarter Transformation
• Mike Leonard, The Building Alliance
• Stuart MacPherson, Chartered Institution of Building Services Engineers
• Lori McElroy, The University of Strathclyde

Items and actions

Welcome and introductions

Brief introductions were provided by new members Ingrid Berkeley (CIBSE), Colin Campbell (SFT) and Stuart Henderson (HFS), and apologies were noted.

BSD update on programme

Reference was made to document WG 25 (24).

Officials presented the current review programme confirming the continuing intent to publish a consultation over the summer to inform the laying of regulations by mid-December 2024.

BSD will be engaging with the WG to agree and confirm the consultation options and questions to be put to stakeholders.

Officials advised that the commissioning of research was later than planned due to the additional stakeholder engagement that had taken place since the last WG meeting was held.

Officials noted that the number of tasks required to be completed to enable regulations to be laid in December made for a busy timetable for the remainder of the year, particularly between now and June in the build-up to the consultation.

Chair noted that BSD had invited WG members to submit any futrher views on the review by 23 February and, in this regard, Homes for Scotland (HFS), the Passivhaus Trust (PHT), the Structural Timber Association (STA) and Scottish Futures Trust (SFT) would be presenting their views later in the meeting.

Sub Working Group Technical Workshops

Officials confirmed that between July 2023 and January 2024 a series of seven technical workshops had been held, workshop one facilitated by BSD and workshops two to seven by Built Environment - Smarter Transformation (BE-ST):

• 25 July 2023 - Form and orientation
• 28 September 2023 - Space heating demand
• 12 October 2023 - Airightness
• 24 October 2023 - Total energy use / energy use intensity
• 13 November 2023 - Calculation methodologies
• 5 December 2023 - Ventilation and overheating
• 16 January 2024 - Quality assurance, compliance and certification

Officials noted that the workshops had been successful in generating useful discussion and confirmed that summary notes from most of the sessions had now been circulated to the WG. Presentations to follow from PHT, HFS, STA and SFT include consideration of the workshop discussions.

BE-ST provided a summary presentation on the workshops (slides to be shared with members after the meeting), including the following context:

• BE-ST were commissioned by BSD to undertake and host the series of workshops
• seven sessions in total were facilitated by BE-ST - the first being held online and the remainder having a hybrid format (i.e., online and in-person)
• six of the sessions focused on specific technical topics, as noted previously (above). Participants having relevant experience/expertise in relation to the topics being discussed
• an additional final session taking the form of a wider engagement workshop, which was open to anyone with an interest in the review to attend
• the format of the sessions including posing key questions and considering current practice, the change agenda and the capacity for change
• the aim was to offer a broad perspective on each topic to assist in understanding what can be achieved

Once a method for sharing the finalised notes from the workshop has been agreed, BSD will provide a link on the WG webpage.

In summary, discussion points from the workshops included:

• space heating demand - general comments made around the methodologies and their usefulness, including the pros and cons of alternative approaches such as the Passivhaus Planning Package (PHPP). The identification of specific gaps in the process and consideration of how to potentially address these was also mentioned
• airtightness - the need for attention to detail was highlighted, noting the clsoe linkage with thermal bridging details. The need for consistency of approach and consideration at an early design stage, along with detailed information to facilitate appropriate action on site. Engagement is required across design and construction teams to confirm the viability of construction details, noting having a designated 'airtightness champion' on site would also be beneficial
• energy use intensity - concerns were raised over costs, with a call for evidence on comparative costs. With reference to the accuracy of SAP verses PHPP, the need for an understaning of how to report outcomes robustly
• calculation methodologies - the need to understand and consider the key differences around the assertions applied by each tool and the impact this has on the reported outcomes. The need to understand the proposed timetable for the development and implementation of SAP 11/Home Energy Model (HEM)
• ventilation and overheating - discussion focused on mechanical ventilation with heat recovery (MVHR) in relation to understanding design and installation quality and collective experience of the challenges of MVHR
• QA and compliance - discussion focused on how to adopt a robist assurance compliance regime within the current building standards system
• general feedback - key question - what is equivalence? Potential for modern methods of construction to play a role. A need to avoid overcomplication. Risk of certification 'bottleneck'. Potential role for Section 6 Certifiers of Design. Significant upskilling required - large scale and small contractors, certifiers and verifiers

Appreciation expressed for everyone's collaborative particaption across the series of workshops.

Reviewing the WG terms of reference, WG member representing HFS reiterated that the group's purpose is to offer advice and expertise to SG to inform what a Scottish Passivhaus equivalent could look like. Noting Mr Rowley's bill proposal focused mainly on fuel poverty and energy efficiency/thermal performance, HFS are keen for a plan to be put in place and applied even if delivered in stages, including recognition of the levels of performance already being delivered under current standards.

HFS position is that the Passivhaus equivalent (PHE) standard has to represent a level of ambition deliverable at a national level without unintended consequences and without impeding the delivery of new homes. HFS consider at present the requried infrastructure is not in place to enable the delivery of fully certified Passivhaus homes at a national scale.

Homes for Scotland presentation

Noting the above context, work has been undertaken by HFS looking at current outcomes and what a PHE standard might look like.

Report produced which sets out HFS's suggestion on how to join up feedback into an illustration of a PHE specification, based on a typical two-bed terraced home.

Presentation focused on the executive sumamry - full report to be shared after the meeting.

Main points presented:

• our journey to net zero requires step changes deliverable at scale whist maintaining affordability
• HFS SAP modelling indicates space heating represents 14% of the total energy demand in an example home compliant to 2024 energy standards, whereas unregulated energy represents 62% of the total energy demand
• benefit identified in using onsite generation to offset total energy demand
• for homes with a heat pump specification, photovoltaic (PV) provision is not necessary to achieve compliance with the 2024 energy standards
• HFS proposition for a PHE standard is a '2024 NBHS home' (e.g., ASHP solution) with the addition of PV generation to increase effective offsetting
• illustration of annual costs for new build, including energy, mortgage and maintenance costs - maintenance costs not significantly differnet annually, though greater complexity increases costs
• 2024 NBHS increases energy costs - bring in PV addresses this
• change comes at a capital on ongoing cost - focus should be on solutions that optimise cost/benefit
• assertion that in comparison to the PH standard, HFS PHE proposal achieves lower operational energy use (kWh/sqm/yr) and delivery cost
• HFS proposal places less demand on the electricity grid, supporting broader ongoing efforts to decarbonise the grid
• proposal also reduces whole life carbon impacts
• in terms of next steps, HFS suggest initial deliverability is delayed until 2027, with route map to be set out, including introduction of requirement to undertake whole life carbon assessments. HFS specification to also be validated using PHPP and HEM methodologies
• acknowledgement that this initial proposal focuses on energy targets, HFS will develop a separate proposal on the compliance/QA element

Follow-up comments/discussion points included:

• PHPP is a tougher test for fuel poverty due to SAP including higher gains etc
• concern in relation to ensuring the effective use of PV, e.g., a heat pump solution with PV also requries a PV diverter to achieve benefit
• in practice, use of PV does not translate into reducing grid reinforcement requirements
• potential role of micro grids and local battery storage - recognition of peak sharing ability
• regulating PV in a binary way is not necessarily helpful - demand response considered to be a better way to moderate demand
• the PHT have investigated treating a building as a flexible asset to respond to the electricity grid. Good building fabric reduces the power injection needed and power can be provided at any time to maintain a comfortable indoor temperature, which is less peak demand dependent. PHT would welcome the opportunity to collaborate with HFS' to model their proposed PHE specification in PHPP and HEM, similar to the work undertaken by PHT in relation to the Future Homes Hub (FHH) contender specifications for the Future Homes Standard in England. Noting, due to PHPP modelling a higher space heating demand, this resulted in some of the specifications being 'flipped'
• if people don't use heating how is minimum temperature maintained?
• PHT noted research undertaken related to a safety hours' metric. Key finding - home built to building regulations took four hours for temperature to drop below threshold - PH home took four days
• PHT noted instances of occupants choosing not to use heating, potentially resulting in heat pumps being run intermittently which can be sub-optimal

Passivhaus Trust presentation

PHT have also considered current outcomes and what a PHE standard should be, taking the workshop discussions into account.

Main points presented:

• use of the PH standard as an established approach is growing worldwide
• the standard is applicable to all building types and sizes
• the standard has been consistently demonstrated to elimiate the 'performance gap'
• the SAP 10 methodology is inaccurate, as demonstrated by the modelling undertaken for FHH contender specifications, reinforcing the need to compare HFS work against PHPP and HEM
• need to consider and manage building energy losses and gains effectively
• need to avoid unintended consequences of a partial solution
• reducing energy demand reduces the need to offset that demand
• peak demand exacerbares the challenge of any offsetting solution. On-siet generation alone is not the solution, the focus needs to be on demand reduction
• PH is a comfort/health standard, relevant to the route to net zero, energy standard and quality standard. There is a risk in picking and choosing certain elements rather than considering holistically
• key PH principles, including form and orientation, are fundamental
• key benefits include quality assurance, accurate modelling in PHPP, validated low infiltration, etc.
• alignment of PH processes against building warrant stages and RIBA work stages
• issues to address - upskilling of contractors and supply chain, MVHR regime, professional capacity to verify and certify. This needs to be addressed to achieve effective delivery
• the PHE should meet all of the key criteria of the PH standard
• energy use intensity (EUI) metric considered essential
• delivery via existing building standards verification system
• PHPP to be accepted as an approved methodology, noting early testing of HEM indicates concerns around assumptions within FHS wrapper being similar to SAP 10
• propose a transition period to enable effective development of skills and capacity allowing industry to adapt to the revised approach
• PH certification to be accepted as 'deemed to satisfy' as soon as it is practically to validate such an option
• suggested implementation leading to change in 2027

Follow-up comments/discussion points included

• concern that home occupants will switch off or fail to effectively maintain MVHR systems
• would be useful to consider the role of MVHR in relation to achieving low space heating demand as part of SAP/PHPP comparison exercise
• inevitable reliance on people using the building correctly regardless of the ventilation systemm specified. There is a lot of data on the health and wellbeing benefits of MVHR due to its ability to achieve good indoor air quality. Benefits of using MVHR correctly outweigh the risks assocaited with misuse
• Shetland example supports this position - due to the extreme environment, for the past 15 years homes have been built with high levels of airtightness and MVHR as standard. Tenants have adopted this easily
• concerns around deliverability of PH homes at scale. Home building industry is customer led. Form and orientation element of PH is impractical at scale. Adoption of PH standard as a minimum standard would result in less homes being built on the same site. 'Equivalent' is not 'the same'. Includes deliverabilty and overall cost considerations, including whole life carbon implications
• PH solutions can be achieved on any site but the cost and challenge wil vary. The level of consistency of specification associated with the PH standard gives better assurance of delivered outcome
• supportive of a PH equivalent standard which continues to allow specification fo double glazing
• challenges in sourcing heat pumps that are appropriately sized to meet low space heating demand. Oversizing reduces effective co-efficiency of performance

Structural Timber Association presentation

STA thoughts on the review so far, taking the workshop discussions into account.

Main points presented:

• a fabric first approach is essential to reduce the impact on the electricity grid and to mitigate the ongoing risk of future retrofit needs
• industry has solutions deliverable at scale right now
• around 90% of homes in Scotland are timber frame - naturally low in embodied energy
• two types of new build - site specific/bespoke (including apartment blocks) and standard building types (usually houses)
• feasible to consider from and orientation for bespoke projects but challenging for volume build. Around 75% of development uses standard house types
• there is a benefit of standardising design to deliver at scale - Edinburgh Homes Demonstrator (EHD) project as an example
• investment in facilities and automation is also easier with standardisation fo created elements, enabling delivery at volume
• also need to consider embodied/whol;e life carbon
• timber frame represents the lowest embodied carbon option for low-rise construction
• installed services over their whole lifecylce have a significant carbon load
• increased use of offsite construction potentially offers opportuinity to improve QA and therefore reduce the performance gap from construction quality issues. Opportunity to set minimum levels of prefabrication
• need for minimum quality standards both on-site and offsite

No follow-up comments/discussion points.

Scottish Futures Trust presentation

SFT throughts on the review so far, thaking the workshop discussions into accound and also SFT involvement in activity to date related to modern methods of construction, the EHD project, Net Zero and the Construction Quality Improvement Collaborative.

Main points presented:

• discussion so far has predominantly focused on housing, however non-domestic development also required consideration, including good practice examples such as the net Zero Public Sector Buildings Standard (NZPSBS)
• capacity and capability of industry is key - need to gather an evidence base o where this currently sits. Research on this needs to be wider than the proposed work
• need to understand how any new standard would interact with other new standards e.g., NZPSBS
• would promote gather evidence from specific Scottish examples to establish what Scotland is capable of
• EHD programme is looking at the cost of delivering higher performing homes - would hope to be able to share findings with the WG
• a capital cost uplift is unavoidable but this needs to be considered in a whole life costs context
• SFT would encourage engagement with the Contruction Leadership Forum for non-domestic/public buildings perspective
• need to avoid ambiguity in what we finally describe as a stand-alone process and maintain flexibility where it is viable to do so

No follow-up comments/discussion points.

Overview and next steps

Officials thanked presenters, noting others also welcome to provide/present their views. Further call made for any updates to the 'one-pagers' previously sought from WG members.

Noting the direction of travel and the broader regulatory context, including wider BSD programme of work and EPC changes (as set out in WG 23 (24) paper), we have a busy programme of work over the next few months to develop proposals for consultation this summer. The work will also continue post-consultation through the laying of amendment regulations and post-December to progress all the actions needed to give effect to the laid amendments.

In the immediate term we will seek to procure the development of consultation tools i.e., a Scottish HEM consultation wrapper and a Scottish spec within SBEM v7, noting the non-domestic methodology is not changing significantly compared to SAP/HEM. Our intent is also to consider the potential to use other compliance methodologies or alternative means of compliance.

Research specifications are currently in the process of being finalised, with a focus on comparative work, applying different tools to a set of agreed improvement options, with the recognition that metrics need to be robust and clearly defined.

We will consult on retaining the delivered energy metric. On the topic of absolute versus relative targets, we will also seek views on the potential introduction of a specific space heating demand metric.

In terms of performance requirements, we will consult on the retention of backstop values seeking views on where prescription on elemental performance is useful.

WG members were reminded that BSD are still looking to gather evidence on building specifications compliant with the 2023/2024 energy standards. BSD would ask for any available examples to be submitted to BSD as soon as possible, noting that feedback to date has been very limited. WG organisations encouraged to contribute if they can.

In terms of ventilation and overheating, intent is to consult on retaining the full range of solutions (again flexibility versus absolute limits). Ventilation rates will not be addressed, however, parallel work is planned to be undertaken on the ventilation standards.

We will also be seeking views on the current implementation of Standard 3.28 overheating which was introduced alongside the 2023 energy standards.

In relation to quality assurance, we will consult on proposals to improve assurance on compliance setting out a framework of actions expected by all parties involved in the design and construction process. This framework will align with (potentially plug-in to) our wider Compliance Plan approach.

BSD to share further detail on the research specifications with the WG when in a position to do so.

Any other business and meeting close

No other business riased

Next meeting scheduled for 3 April 2024.

Meeting closed.