Powys powers up first Passivhaus primary school
The Welshpool CIW (Church in Wales) Primary School claims a Passivhaus first in Powys. Designed for Powys Council to align with the Wales 21st Century School Programme, the project was jointly funded by the Welsh Government, through its Sustainable Communities for Learning Programme. Built using timber construction, the pioneering certified Passivhaus school provides an exceptional operational energy performance of 56 kWh/m2/year - more than 80% better than a typical new build primary school.
Dominating UK Passivhaus school design, PHT Patrons Architype were appointed as lead architects and Passivhaus Designers, along with PHT Patrons WARM as the Passivhaus Certiifer. The school's design and Passivhaus requirements are delivering comfort to the pupils and staff at the school.
Classrooms receive ample natural daylight and benefit from a constant supply of fresh air through mechanical ventilation heat recovery. The classrooms and corridors have a noticeable quiet, thanks to the triple glazing eliminating external noise, while careful acoustic design minimises the reverberation of voices between classrooms, so common areas remain peaceful and undisturbed. The school building acts as a sustainable educational resource in its own right, with teachers expressing that the building gives them an opportunity to demonstrate real life examples of sustainability to pupils.
Key stats
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Construction
Modern methods of construction were used to achieve quicker assembly on site. This included the timber frame walls and floor which were prefabricated at a local factory and brought to site as cassettes. This saved time and also meant less timber was wasted. The timber frame comprised 390mm Larsen truss, filled with recycled newspaper insulation. The Larsen truss system was chosen as it allows for a thicker wall space. The project used 390mm to achieve a wall and roof U value of 0.10 W/m2K. 18mm of OSB boarding was used internally with airtight tape to maximise airtightness. Recycled newspaper insulation was pumped into the timber frame through holes which were then sealed with airtightness tape.
Embodied carbon
The embodied carbon emissions from the building were minimised by specification of low carbon natural materials including timber construction and cellulose (recycled newspaper) insulation. As well as the timber frame, the school is clad in timber and has a timber roof.
Local firms and suppliers were chosen to help support the local economy. Lowfield Timber Frames, the timber frame subcontractor responsible for the wall and roof supply, is just eight miles from the site and insulation in the walls and roof was provided by the Welshpool-based PYC Group less than a mile from the school.
U-values |
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Floor: 0.16 W/m2K
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Wall & Roof: 0.10 W/m2K 390mm Larsen truss timber frame cassette filled with recycled newspaper insulation. |
Welshpool Church In Wales Primary demonstrates that a beautiful, healthy and inspiring school and one that is ultra low carbon and energy can be achieved. Powys County Council declared a climate emergency in 2020. This included an ambition to reduce our carbon emissions to net zero, in line with the Welsh public sector target of 2030. By investing in Passivhaus we have demonstrated that huge savings can be made.
Marianne Evans, Head of Transforming Education, Powys County Council
Building performance
Designed energy performance |
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Airtightness n50 (≤ 0.6ACH @ 50 Pa) |
0.21ACH @ 50 Pa |
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Space Heating Demand (≤ 15 kWh/m².a) |
8.8 kWh/m².a |
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Heating Load (≤ 10 W/m²) |
7.7 W/m² |
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Primary Energy Renewable (PER) Demand (≤ 60 kWh/m².a*) |
75 kWh/m².a |
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Primary Energy Renewable Generation |
16 kWh/m².a |
*+/-15 kWh/m².a allowance if offset by energy generation. See Passivhaus criteria.
Services
The summer comfort strategy for the school includes use of MVHR on summer bypass mode, with night ventilation through openable windows behind secured vents. The school's heating system is delivered via radiators, which are not needed during the summer months. Renewable energy is generated through rooftop solar photovoltaic panels. Solar shading on the south elevation is achieved with an overhanging roof structure that minimised thermal bridging.
Lessons learned
- The original contractor going into administration halfway through the project was a challenge. The replacement contractor carried out remedial work for the already-installed timber frame, alongside a period of drying out of the building structure.
- Building performance monitoring will be undertaken on the building to further enhance building use and efficiency.
Key team
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Kudos to Powys Council for getting its first Passivhaus certified school across the line - hopefully the first of many! We are seeing a great uplift in Passivhaus schools across the UK, and especially in the devolved administrations of Wales and Scotland.
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Further information
Welshpool Church in Wales Primary School
Lowfield Timber Frames case study
Passivhaus Benefits guide & costs research
Passivhaus for Educational Buildings
Previous PHT story: Scottish Schools lead largescale Passivhaus – 8 April 2022
Previous PHT Story: Exemplar local policies - 6 May 2022
Previous PHT Story: Passivhaus delivers well-being in Wales - 16 November 2018
Previous PHT Story: Award winning Burry Port Primary certified - 10 May 2016