Energy standards review - Scottish Passivhaus Equivalent Working Group consensus report: November 2024

Background

The following report presents the recommendations and discussion points that have been identified at the Energy Standards Review Working Group - Consensus Workshops: hosted on 24 September and 8 October 2024 at Homes for Scotland (HfS) Offices in Edinburgh and online, by those members of the Working Group that could attend one, or both, of the workshops.

Not all members of the Working Group could attend both sessions so not all perspectives have been able to be captured completely, but these recommendations have been shared with all members of the Working Group and intend to reflect the general, agreed consensus view of the Working Group. It was agreed that Scottish Government officials would not attend these sessions.

A summary of the consensus reached on key issues, and recommendations are noted below and broken down into topical areas.

Timeline

The Working Group agree and support the requirement for a clear timeline and route map to accompany the proposed timeline by Scottish Government in implementing the Scottish Equivalent to Passivhaus Standard.

• priority areas are the provision of adequate time and resources for training. This will allow industry to upskill and reskill where required, supporting the proposed step change in the regulations to a proposed Passivhaus Scottish Equivalent Standard.
• training is required across industries including and not limited to designers, quantity surveyors, structural engineers, mechanical, electrical engineers, public health engineers, contractors, clients, building control officers, tradespersons and supply chain. This must adhere to a just transition, whilst maintaining delivery of new build projects and managing sustainable costs for owners and occupiers.
• the working group supports the ambitious changes and would recommend the development of a three-stage timeline to achieving the required upskilling and reskilling in line with the implementation plan

Tools

The Working Group agree that modelling tools that produce sufficiently accurate results are essential. By sufficiently accurate we mean with similar outcomes to the Passivhaus Planning Package (PHPP) which neither the Standard Assessment Procedure (SAP) or the Simplified Building Energy Model (SBEM) currently achieve.

The Working Group therefore supports: 

• the development of the Home Energy Model (HEM) with a bespoke Scottish wrapper, and its adoption into domestic building standards with a similar accuracy as PHPP
• the development of SBEM with a Scottish wrapper, for use in non-domestic building standards with a similar accuracy as PHPP
• the acceptance of PHPP as an accepted alternative modelling and compliance tool for both domestic and non-domestic building standards

We also recommend that:

• the option to apply either methodology (HEM/PHPP and SBEM/PHPP) should be referred to in the developed handbook to streamline acceptance
• this working group (or identified members) would like to be involved in identifying the requirements for the Scottish wrappers, including defining the specific metrics to be outputted
• once ready for testing and trialling, HEM and SBEM (Scottish version) should be evidenced as being accurate tools. This will require an agreed testing process and appropriate timeline for industry modelling.

Please note that:

• Passivhaus Trust and Homes for Scotland carried out a study in which the HfS house types used in HfS’s proposals were tested in PHPP. Both parties are satisfied in the accuracy demonstrated by PHPP, and expect HEM with Scottish Wrapper to achieve the equivalent accuracy in results provided.

Energy use intensity and unregulated energy

The Working Group unanimously agreed that:

• that Energy Use Intensity (EUI) should be one of the metrics included in the regulations
• unregulated energy should therefore be included (if technically allowed within building standards)
• for domestic, unregulated energy could be included through standard allowance (to be determined)
• for non-domestic, unregulated energy should be required to be calculated

Absolute targets

The consideration of the Working Group is to support the setting of absolute targets, rather than use notional building method which was the Scottish Governments intention. There is an argument that the notional building method undermines the intention to design more efficient buildings. However, we recognise and acknowledge that the home building sectors are not ready to adopt this for numerous reasons, particularly the requirement to maintain flexibility with designs to satisfy compliance with building standards.

The Working Group therefore recommends that:

• for non-domestic buildings, the notional building method is dropped from day one and replaced by a requirement to achieve absolute targets (with no offsetting)
• for domestic buildings because we recognise that greater flexibility is required, we propose that the notional building method is maintained for private development and affordable/social housing.
• a dual system is proposed for all tenure home builders with two alternative compliance routes being available:

1. compliance with a new absolute target (which would include an allowance for renewables offsetting to allow sufficient flexibility)
2. continued use of the notional building method.

• one-off bespoke residential and mixed used developments which include non-residential/residential should be required to comply with the absolute target route (i.e. not use notional building method)

We note that:

• this dual system route would enable all tenure home builders to gain the comfort required that absolute targets with offsetting gives them sufficient flexibility to satisfy the requirements of Scottish building standards (and for the Scottish Building Standards Division to see how this develops and assess the impact / effectiveness of both absolute and notional)
• the Passivhaus Trust also modelled the Homes for Scotland (HfS) house types in every orientation in order to demonstrate that the PHPP using peak heat load showed very little variation between orientations, that designs were well optimised and would therefore give developers the flexibility they require to develop standard house types, and/or different approaches to construction that work in every orientation. Whilst HfS acknowledge the results as demonstrated, it is acknowledged that the industry is not yet familiar enough with this approach to adopt it from day one, and therefore feel that the notional method should be maintained at this stage to retain flexibility. The Working Group therefore achieved consensus on the proposed dual approach.
• the setting of absolute targets requires an accurate tool as argued above

Quality assurance

It was noted that the current Compliance Plan working group for high-risk buildings is focused on fire risk and escape. However, we also recognise that research is taking place in respect of strengthening compliance with building standards for low rise volume housing sites.

The working group recognise the importance for rigorous levels of quality assurance checks at design and construction stage.

The group agree on the rigour in quality assurance and compliance process at both design and construction stages should be strengthened to ensure that any potential performance gap is negated over time.

Deemed to satisfy

The Working Group unanimously supports the proposal for fully certified Passivhaus to be ‘deemed to satisfy’ key elements of Part 6.1 and Part 3.14.

We recognise that this would avoid the need for the unnecessary cost of duplication of modelling, for those clients wishing to adopt full Passivhaus and therefore encourage its uptake within Scotland.

Embodied carbon

The working group agree that embodied carbon should and needs to be considered.

As Scotland moves towards meeting the 2045 targets, it can be significantly more complex to incorporate into the standards than operational energy, which can be more readily measured.

The group recommends that whole life carbon should be included at the next update to building regulations and a route map to adoption should be developed.

The consensus of the working group is that we want Scotland to avoid retrofitting post 2028 buildings due to embodied carbon issues.

Modern Methods of Construction

The group recommends the need to address and encourage wide scale adoption of Modern Methods of Construction (MMC) as the regulations move to the Passivhaus Scottish equivalent standard.

Incentivisation of the market may need to be considered if Scotland’s industries are to meet the requirements of MMC.

Collaboration and wider sector consideration:

Throughout the process of supporting the Scottish Government with this 2024 energy review it has become apparent as evidenced by the work carried out by the Energy review group, that for the successful delivery of policy change within the built environment, particularly the all-tenure home building sector, Government should seriously consider supporting the formation of a “Scottish Future Homes Steering Group” much like has been established in England with the Future Homes Hub.

By utilising the significant experience, skill set and knowledge base of the wider industry experts, we can deliver meaningful change that can be delivered in a practical and timely fashion.