IN Brief:
- Scotland is consulting on revised energy and environmental standards for new buildings.
- Passivhaus certification and modified PHPP calculations could become recognised routes to compliance.
- The Passivhaus Trust supports the direction but wants tighter airtightness and ventilation requirements.
The Passivhaus Trust has backed several central elements of Scotland’s proposed energy and environmental building standards while pressing for tighter airtightness requirements and changes to the treatment of ventilation losses.
Its response relates to the Scottish Government’s Stage 2 consultation on a Scottish equivalent to the Passivhaus standard, which opened on 24 July and runs until 16 October. The proposals set out performance targets, calculation methods, and construction-assurance measures intended to reshape energy compliance for new buildings.
One of the most significant changes would allow certified Passivhaus buildings to use an alternative route for demonstrating compliance with standard 6.1 on energy demand. The government is also proposing delivered energy as the principal compliance metric, supported by a space-heating demand figure intended to place greater emphasis on building-fabric performance.
The Passivhaus Trust supports both directions and has welcomed the proposed recognition of a modified Passivhaus Planning Package, or PHPP, as an approved calculation method. Separate approaches are envisaged for domestic and non-domestic buildings alongside government assessment tools.
The consultation goes considerably further than formal recognition of Passivhaus certification. It proposes changes to target setting, airtightness, insulation, ventilation, overheating, energy use, and the evidence needed to demonstrate that what was designed has actually been delivered through construction.
For homes, the government is consulting on three levels of uplift producing aggregate emissions reductions ranging from zero to 37% against the February 2023 standards. Options for new non-domestic buildings range from zero to 11.5% against the same baseline.
A declared design air-infiltration upper limit of 5m³/(h.m²) is included in the proposals. The Passivhaus Trust regards that as an improvement but considers the threshold too loose for a regime intended to drive high fabric performance, particularly where uncontrolled air leakage adds to heating demand.
The Trust has also challenged how ventilation is treated within the proposed space-heating metric. It wants ventilation losses included so that the calculation reflects the interaction between fabric performance and the ventilation system rather than assessing heat loss through the envelope in isolation.
That distinction becomes important once design targets reach levels where workmanship and services installation can materially alter actual performance. High insulation values on drawings do little to compensate for poorly detailed junctions, uncontrolled leakage, badly commissioned ventilation, or penetrations that compromise the intended air barrier.
The Scottish proposals attempt to address that gap through a stronger assurance process. A proposed Building Standards Energy and Environmental Compliance Handbook is structured around airtight construction, high-performance insulation, thermal-bridge-free design, ventilation, and optimised energy use.
Design and construction statements would form part of that regime, leaving a clearer evidence trail from the original energy strategy through site delivery. Contractors, designers, certifiers, and verifiers would therefore have to demonstrate more than a compliant calculation at design stage; details and installation quality would need to remain traceable through construction.
The implications are particularly direct for trade interfaces. Membranes, insulation, windows, service penetrations, ducts, pipework, electrical containment, fire stopping, and structural junctions can all cross the thermal or airtight envelope, so performance depends on sequencing and supervision across several subcontract packages rather than one specialist carrying sole responsibility.
Implementation has already moved back from the timetable set when the underlying regulations were laid in 2024. The original coming-into-force date was 31 March 2028, but the government now intends to publish guidance and approved methodologies in autumn 2027 and introduce mandatory requirements in autumn 2029.
The consultation is also considering whether implementation should take place in full, be phased, or operate voluntarily before becoming compulsory. That gives the sector more preparation time for training, approved calculations, standard details, procurement changes, testing capacity, and the quality-assurance procedures required on site.
The Passivhaus Trust supports the overall technical direction but does not regard the current proposals as fully equivalent to Passivhaus. Alongside tighter airtightness and different treatment of ventilation, it has raised concerns about photovoltaic generation within the methodology and suggested that an optional peak heat-load metric in the region of 10–15W/m² could assist compliance and heat-pump sizing.
Those remaining points will be argued through the consultation, but the direction of travel is already clearer. Scotland is moving towards a system in which measured fabric demand, approved calculation tools, airtightness, ventilation, and construction evidence carry more weight in proving compliance.
The harder part will be carrying those requirements through the building site. Higher standards depend on designers providing buildable details, contractors protecting the intended envelope, specialists coordinating penetrations and services, and verification catching defects before finishes make them expensive to reach.
The consultation remains open until 16 October, with revised guidance planned for 2027 and mandatory implementation currently targeted for autumn 2029. That gives the industry time to prepare, but it also makes the next three years a practical test of whether tighter energy standards can be converted into repeatable construction methods rather than another layer of calculations attached to the design file.
