Delivering diagnostic and completion-stage air tightness testing against the Passivhaus standard for a bespoke steel-frame new build featured on Grand Designs.
Project Overview
- Client: Duncan Eastland (Self-Builder; North Cotswolds Passivhaus Premium project featured on Grand Designs)
- Sector: Private Residential – New Build
- Location: North Cotswolds, Gloucestershire
- Services Provided: Passivhaus Air Tightness Testing (pre-completion diagnostic test, final ATTMA-certified test)
- Scale: Single detached, steel-frame dwelling designed by Atelier73 Architects – 1,135 m² envelope area, 1,642 m³ volume, two storeys
- Target: Passivhaus air permeability target of ≤0.60 m³/(h·m²)@50Pa, in pursuit of Passivhaus Premium certification
The Challenge
Duncan Eastland’s new home in the North Cotswolds – designed by Atelier73 Architects and built to be the UK’s first residential Passivhaus Premium – set out to generate significantly more energy than it consumes, but that ambition depended on the building envelope performing to an exceptionally tight airtightness standard first. The design’s complexity, including three separately pitched roof sections and a mix of steel frame, timber panel and concrete construction, made consistent sealing across the whole envelope a genuine technical challenge rather than a formality. With the project also featured on Channel 4’s Grand Designs, there was no room for an unverified result – independent, certified testing was the only way to confirm the building had achieved Passivhaus-level airtightness.
The Solution
Two-Stage Passivhaus Air Tightness Testing
We carried out an initial diagnostic test ahead of completion, testing in both pressurisation and depressurisation, to identify any remaining leakage paths ahead of final certification. Once the build was complete, we returned to carry out the final whole-building test to the ATTMA standard, confirming the completed performance against the Passivhaus 0.60 target – a result that mattered beyond the certificate itself, since the home’s continuous mechanical ventilation with heat recovery system depends on a genuinely airtight envelope to work as designed.
The Outcome
The pre-completion test showed strong performance, with an air permeability of 0.53 m³/(h·m²)@50Pa and an air change rate of 0.37 – comfortably inside the 0.60 target in both measures. The final test at completion landed right at the threshold: an overall air permeability of 0.60, with the depressurisation direction passing at 0.60 and the pressurisation direction at 0.61. The testing gave independent, certified evidence of the building’s airtightness performance to support the project’s Passivhaus Premium ambition.
Key Contacts
Ryan Jones — Head of Testing
Project Location
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