Passivhaus school stays active in heat wave: design and performance notes for engineers
Reviewed by Tom Sullivan
First reported on The Construction Index
30 Second Briefing
Buntingford First School in Hertfordshire, delivered by Morgan Sindall Construction in 2023, has become England’s first Passivhaus Trust-certified school, staying open during the recent heat wave while many others closed, with internal temperatures held below about 26°C using PV-powered cooling coils in the ventilation plant. The ten-classroom, cross laminated timber frame building cut embodied carbon to 50% below LETI’s 600 kgCO2/m² target, saved 1,160 tonnes of carbon via CLT and 200 tonnes via reduced concrete with 50% GGBS, and cut construction traffic by 90%. Operational energy use in year one was 39.44 kWh/m²/yr, over 20 kWh/m²/yr below LETI guidance, supported by 184 PV panels, air source heat pumps, U-values below 0.1 W/m²K, airtightness under 0.6 ACH, and elimination of façade thermal bridges.
Technical Brief
- Cooling strategy uses PV-powered coils in the ventilation plant to provide peak lopping during heatwaves.
- CarboniCa digital monitoring was used live in design to quantify impacts of material and layout choices.
- Operational performance between Sept 2024–Dec 2025 was net negative, saving 11.7 kg CO₂ overall.
- CLT frame saved 2 tCO₂ per m³, totalling 1,160 tCO₂ and cutting construction traffic by 90%.
- Foundations used recycled pipework for piles and concrete with 70% recycled aggregate plus 50% GGBS.
- HVO replaced diesel for site plant, with monitored logistics showing an additional 82 tCO₂ saving.
- Hot water sinks were omitted from non-essential classrooms to reduce pipe runs, hot water load and overheating.
- All teaching spaces face north, with south-facing social spaces used to capture solar gains where beneficial.
- Indoor environment design addressed VOC/formaldehyde mitigation, natural materials, daylight, views and controlled natural ventilation.
Our Take
Morgan Sindall Construction’s use of the CarboniCa tool at Buntingford First School mirrors its deployment on the St Margaret’s Hospital diagnostic centre and the MY Central office scheme, signalling that quantified whole-life carbon tracking is becoming standard practice on its UK social infrastructure projects.
The combination of high GGBS content in foundations and extensive CLT at this Hertfordshire site gives local authorities such as Huntingdon County Council a worked example of how to align 2030 carbon-neutral aspirations with mainstream procurement routes, something only a small subset of the 880 Infrastructure stories in our coverage currently demonstrate in detail.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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