Passivhaus Affiliate

Passivhaus school first for Bedfordshire

A new teaching block for Thornhill Primary School is the first in Central Bedfordshire built to the Passivhaus standard and is also the first certified Passivhaus school for the architect, MEP engineer & main contractor. 

Thornhill Primary School Passivhaus extension. Image credit ECD Architects

Central Bedfordshire Council commissioned the newbuild building to help accommodate the growing needs for school places in the area, with the school increasing its capacity from 210 pupils to 630, plus nursery places. The project is intended to set a precedent for robust low energy and sustainability standards to inform the local authority’s future projects.


ECD Architects introduced the concept of designing and building to the Passivhaus Standard at RIBA stage 1.   This was received positively by Central Bedfordshire who instructed us to target certification to benefit from the health and well-being benefits of improved thermal comfort and air quality, as well as to reduce financial running costs.

Gary Alston, Design and Technical Director, ECD Architects


Key stats

  • Occupancy: 450 (year groups 2-6)

  • Completion date: July 2022

  • Construction: Glulam & CLT

  • TFA:  2050m

  • Certified: July 2022

Thornhill Primary School Passivhaus extension. Image credit ECD Architects

Choosing Passivhaus 

Passivhaus was selected to ensure the new building’s quality of construction, while also providing significant benefits to the whole life cycle cost, a reduction in its financial running costs when compared with standard UK Building Regulations and improving thermal comfort and indoor air quality.  

In pre-application discussions between the project's architects, PHT member ECD Architects, and Central Bedfordshire Council's Sustainability Officer, the Passivhaus standard was agreed to replace BREEAM as the building's environmental goal - a recognition that Passivhaus, as a more focused and specific target, is much more stringent in terms of building energy performance. However, BREEAM targets concerning water usage and management were retained.

Cost analysis carried out during Stage 4 by the cost consultant illustrated that the cost for Passivhaus represented 5.4% of the total construction costs (including overhead profits and preliminaries).

Thornhill Primary School Passivhaus extension. Image credit ECD Architects


Embodied carbon

The building was constructed in Cross Laminated Timber & Glulam, using offsite manufacture, to keep embodied carbon emissions low. The project also aimed to follow the principles of the Circular Economy - striving to lock in and retain the value of materials used within a building, and using the built asset as a material bank during its operation, to be unlocked at the end of its usable life. 



As the scheme was developed from a pre-approved outline planning permission, orientation and outlook of the building were already fixed.  

The building design incorporates a  deck wrapping the entire two-storey section of the building, providing valuable breakout space for smaller group learning, connecting teaching with the outside. The building also includes a double-height entrance atrium and split-level library, adjacent to the new sports/ dining hall.

A comprehensive shading strategy was implemented, including: roof overhang to East & West elevations; a brise-soleil (serving first floor classrooms) and first floor walkway (serving ground floor classrooms) to South elevation; and an external fabric canopy serving the South elevation


Thornhill Primary School Passivhaus extension. Image credit ECD Architects

We cannot wait to open up this outstanding space for students at Thornhill in September. Its forward-thinking design will allow us immeasurable opportunities for furthering the children’s awareness around environmental innovations, enriching their educational aspirations and providing boundless benefits to our growing community for future generations.

Claire Bryan, Co-Chair of Thornhill Primary School Governors


Thornhill Primary School Passivhaus extension. Image credit ECD Architects


Brick finish: Brick, air cavity, low thermal conductivity brick ties, rigid insulation, airtightness membrane, CLT panel, timber battens, plasterboard

U value: 0.07 W/m2K

Zinc finish: Zinc, plywood, air cavity, thermally broken helping hand brackets, rock fibre insulation, airtightness membrane, CLT panel, timber battens, plasterboard

U value:0.13-0.14 W/m2K


Screed, reinforced concrete slab, DPM, closed cell insulation 

U value: 0.11 W/m2


Zinc finish: Zinc, plywood, rigid insulation, airtightness membrane, CLT panel

U value: 0.06-0.07 W/m2

Felt finish: Felt, plywood, rigid insulation, airtightness membrane, CLT panel

U value: 0.11 W/m2


Measured energy performance 

Airtightness (≤0.6ACH@50pascals)  

0.42 @50pascals

Thermal Energy Demand (≤15kWh/m².yr)

15 kWh/m².yr  

Thermal Energy Load (≤10W/m²)

12 W/m²

Primary Energy Demand (≤120kWh/m².yr)

126 kWh/m².yr

Primary Energy Renewable Demand 

 85 kWh/m².yr


Lessons learned

  • The material specification was key to the success of the project, for both the building construction and services, and ensured the Passivhaus principles were achieved.   Tried and tested products were used backed up with advice from manufacturers and product suppliers.
  • Working with a collaborative, pro-active contractor with high quality management monitoring standards and a willingness to learn and adopt the required skills, through on-site Toolbox Talks, ensured a compliant building was achieved.


We are delighted to have completed this ground-breaking project, delivering an outstanding educational facility that has achieved the very highest of sustainability credentials, and has been recognised by the Passivhaus Institute as a fully certified building.

Andrew Morris, Business Development Director, Ashe Construction



Key team

  • Client: Central Bedfordshire Council

  • Architect & Passivhaus DesignerECD Architects

  • Main contractor: Ashe Group

  • PHPP consultant: Georgia Laganakou (pre-RIBA Stage 5) Elementa Consulting (RIBA Stage 5/6)

  • Cost consultant / Contract administrator / Principal Designer: Keegans

  • Structural engineer: Engenuiti

  • M&E consultant: MHL Consulting

  • Energy consultant: IES

  • Passivhaus certifierEtude

Thornhill Primary School Passivhaus extension. Image credit ECD Architects


We are very excited that the pupils & staff of Thornhill Primary will gain the benefits of this new building when they return in September. Better air quality and thermal comfort, and improved well-being, with reduced running costs; it is no surprise that more councils and education bodies are choosing to build to the Passivhaus standard and with CLT to provide exemplar learning environments like Thornhill for future generations to benefit from.

John Heaney MCIAT, Senior Architectural Technologist, ECD Architects 


Further information

Thornhill Primary School Expansion

Work completes on new Thornhill Primary School building

Schools back for the summer

Previous PHT story: New Passivhaus primary in the pipeline - 16 December 2019

Passivhaus Educational Buildings Case Studies

Passivhaus for Educational Buildings Campaign

PHT guidance: Qualiity Assurance for large & complex buildings

14th September 2022

Never miss UK Passivhaus news by joining the Passivhaus Trust mailing list Follow us on twitter @PassivhausTrust

< Back To News