Landmark airtightness result achieved at Caledonia High School

The school has achieved an airtightness result that places it among the most energy-efficient education buildings in Scotland, challenging long-standing assumptions about what’s achievable in sustainable construction. 

For pupils, staff and families, that translates into a building that delivers thermal comfort, excellent indoor environmental quality and long-term operational performance.

Performance in practice

The building has achieved an airtightness result of 0.337 ACH @ 50Pa, significantly outperforming the Passivhaus requirement of 0.6 ACH. For a building at 16,412 sqm GIFA, this is a strong result and reflects a consistent focus on build quality and detailing throughout.

This level of airtightness works in tandem with a high-efficiency MVHR system, ensuring a continuous supply of fresh, filtered air while minimising heat loss. The result is reduced space heating demand and consistently high indoor air quality across the school.

We’ve used PHPP (Passive House Planning Package) throughout the design process to test and validate performance. Careful control of the heat form factor, combined with minimised thermal bridging and disciplined junction detailing, has been critical to achieving these outcomes at this scale.

From the outset, the focus has been on wellbeing. Replacing Inverkeithing High School, the building is designed to support health, comfort and learning outcomes, with strong daylighting, high indoor air quality, stable internal conditions and clear, intuitive spatial planning.

A fabric-first approach prioritises the performance of the building envelope - insulation, airtightness and thermal bridge mitigation - before layering in building services. The school is targeting Passivhaus Classic certification, and performance to date shows it is firmly on track.

Steel frame construction

A key aspect of the project is how it addresses the perceived limitations of steel frame construction in Passivhaus design. Managing thermal bridging and maintaining airtightness continuity in steel structures has traditionally been seen as a barrier.

Through this project, and building on earlier work at Woodmill and St Columba’s RC High School, the world’s largest Passivhaus certified education building, we’ve shown these challenges can be overcome. Caledonia High School goes further, demonstrating that steel-framed buildings can not only meet Passivhaus standards, but exceed them.

Whole-life sustainability

Our sustainability strategy extends beyond operational energy, targeting alignment with the RIBA 2030 Climate Challenge for embodied carbon and the Scottish Futures Trust Net Zero Public Sector Building Standard.

Taking a whole-life carbon approach, we’ve considered both embodied and operational impacts — supporting Fife Council’s Net Zero ambitions and Scotland’s 2045 net zero target while ensuring long term value for the council and wider community

Inclusivity has been central to the design, with integrated supported learner provision (SLP) that supports accessibility, privacy and dignity. External learning and sports spaces are designed to be flexible and accessible, making the most of the site’s orientation and wider landscape.

Due for completion later this year, Caledonia High School represents what can be achieved through a clear brief, close collaboration and a rigorous approach to building performance, and we’re proud to see it setting a new benchmark for Passivhaus education buildings in the UK.