Response to the Scottish Government Consultation on a Passivhaus Equivalent

The Scottish Government’s consultation on developing a Passivhaus-equivalent standard is a crucial step towards improving building energy and environmental performance. This is our CEOs, Dan Gates, response, outlining our views on the proposed principles, methodologies, and targets, drawing from our experience in delivering sustainable building solutions. 

Find the link here: Building Regulations: Determining the principles for a Scottish equivalent Passivhaus Standard: Stage 1 Consultation

Do you broadly agree with the statements on what ‘equivalent’ should not mean, in delivery of amended building standards to address energy and environmental performance?

Yes
The Passivhaus (PH) approach to target setting is well-proven. However:

• We believe the Passivhaus Equivalent should be mandated for all new developments. To make it universally applicable, it could be slightly relaxed from the original PH standards.
• Standards must consistently achieve outcomes at least as good as Passivhaus. This requires quality control during construction, with independent experts assessing product quality and workmanship. Compliance methods are key to Passivhaus success.
• The Scottish PH standard could relax certain energy-relevant building specifications.

Specifically:

• Existing methods like SAP and SBEM, especially when used with dynamic modelling tools such as IES-VE, are as effective as PHPP. However, standard EPC reports are unsuitable, whereas PHPP generates user-friendly, analysable metrics.
• PHPP targets, such as an airtightness of 0.6 air changes per hour (ACH), can be overly restrictive. A target of 1.0 ACH is more practical. Similarly, triple glazing is often unnecessary. For example, in one project, switching from triple to double glazing reduced embodied carbon and costs, with only a 1% increase in energy demand.

Do you broadly agree with the statements on what ‘equivalent’ should require consideration of, in delivery of amended building standards to address energy and environmental performance?

Yes
The most critical factor is ensuring improved assurance that standards and design intent are achieved in practice. This can be accomplished with independent assessors and robust quality control measures.

On the basis that the Home Energy Model (HEM) and Simplified Building Energy Model (SBEM) are reviewed and shown to report representative outcomes, do you support the continued use of calculation tools which implement the UK methodologies?

Yes
Existing methods like HEM/SAP and SBEM, especially when combined with dynamic modelling tools like IES-VE, are effective. However, EPC-standard reports lack usability, whereas PHPP produces more analysable and user-friendly metrics.

The long delays in updating SAP and SBEM are concerning. Meanwhile, PHPP should be considered as a compliance tool since it is ready to implement.

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

Relative targets have demonstrated energy reduction success. However, absolute targets are simpler to understand, compare, enforce, and measure.

We recommend relaxing strict Passivhaus targets to align with LETI standards.

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)?

Yes
While unregulated energy should be considered to capture total energy consumption, adding this complexity is unnecessary to assess building performance. Unregulated energy, mainly electrical, is set to decarbonise by 2030 in Scotland.

Best practices, such as mandating lighting controls, can nudge homeowners towards genuine energy reductions.

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

A prescriptive space heating demand limit is essential for driving higher energy efficiency standards.

Such limits reduce energy consumption, lower utility bills, cut emissions, and lessen grid impacts. Targets like AECB’s or slightly higher values (20–25 kWh/m²/year) would be effective and could tighten over time.

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

Incorporating local climate data is crucial for accurate building performance assessments. Dynamic tools like IES-VE, with superior datasets, should remain available as an option.

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?

We deliver energy assessments and designs for both new and existing builds. Our qualifications include PHPP, IES-VE, SAP, and SBEM.

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

PHPP airtightness targets (0.6 ACH at 50Pa) are challenging, but 1.0 ACH at 50Pa is a practical alternative. This would still necessitate MVHR, encouraging innovation and better air quality.

Currently, the 3.1 m³/m²/hr target at 50Pa permits less effective solutions like DMEV, which fail to deliver sufficient energy savings or air quality. Studies confirm this inadequacy.

A realistic target of 1.0 ACH would mandate MVHR and eliminate substandard alternatives like trickle vents or DMEV. Additionally, social housing could include temperature and humidity monitoring, ensuring occupant health and system efficiency.

Specifically for new homes, should further guidance be given on Mechanical Ventilation with Heat Recovery (MVHR), generally, and through the Technical Handbooks?

The current guidance and domestic ventilation guide are adequate. However, practical training at institutions like BE-ST and colleges should be expanded.

Monitoring temperature and humidity in social housing could further ensure MVHR systems remain operational.

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

Passivhaus Certification is a feasible and effective alternative for compliance with Standard 6.1. However, some criteria, such as airtightness, could be relaxed for practicality.

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

Insulation and systems like solar PV are well-understood by most stakeholders. However, airtightness and thermal bridging are often neglected or misunderstood.

These risks are best managed by experienced practitioners during the PHPP process, where design is closely aligned with performance outcomes.

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

Risk management should continue throughout construction.

As Certifiers of Design for Section 6, we find it effective to extend oversight to onsite verification. Independent inspections of thermal bridging, insulation, and airtightness layers are crucial. Expanding the Certifiers of Design scheme to include construction oversight would ensure better outcomes.

Do you have experience implementing methods to effectively de-risk very low energy building aspects of design and construction, and ensure compliant solutions are delivered as intended?

Yes
We are independent, qualified design engineers. Builders often prioritise cost savings, which can compromise design intent.

For example, narrower ducts save costs but increase noise, causing occupants to disable MVHR systems. Independent design ensures these trade-offs are balanced for optimal performance and occupant comfort.