Passivhaus primary schools: Bushbury Hills by Architype Architects
Architype was determined to prove that Passivhaus certification need not cost more, nor limit architectural expression
Bushbury Hill Primary School is a new-build school for 240 children. It replaces an existing school on the same site, and is one of five schools completed to date by Architype for Wolverhampton City Council.
The existing relationship with the client was a key factor in the decision to proceed with Passivhaus, with the proviso that it would not impact the programme or budget. Architype set out to confound the accepted wisdom that Passivhaus costs more.
A lightweight, well-insulated timber frame is wrapped in a ‘duvet’ of insulation to create an airtightness layer with minimal penetrations and to reduce thermal bridging. Rigorous site inspection and workshops with site staff and suppliers were essential in achieving the level of workmanship required.
AJ Buildings Library
Q + A Jonathan Hines, director, Architype
Why did you decide to go for Passivhaus on these schools?
Architype’s approach has always been to design buildings to do all the hard work: to save energy rather than rely on renewables. We’d already done three projects for Wolverhampton City Council, including St Luke’s which was the first primary school in Great Britain to achieve BREEAM Excellent. When Wolverhampton commissioned us to do two more schools, we recommended Passivhaus over BREEAM because we could reduce running costs and provide better internal comfort.
Why go for Passivhaus certification rather than simply work using Passivhaus principles?
There is an absolutely fundamental difference between the two. A lot of people say they are designing to Passivhaus principles and they are generally following the U-values and airtightness guidelines. What we understood early on is that it is the most amazing quality assurance system. Passive House Planning Package (PHPP) is a design tool which proves the performance of the design. This is different from SAP and SBEM, which are just compliance tools.
What is also critical and what people don’t realise until they have done it, is that the certification process is incredibly rigorous because you have to provide not only your PHPP calculations and air pressure tests, but also evidence that the windows specified were actually supplied, and that the insulation specified was actually installed, with photographs and delivery receipts. You have to provide air system commissioning reports and thermal bridging calculations. You have to provide so much evidence that it forces the entire project team to do everything you said you were going to do. This guarantees the quality of the result. The danger is that at the moment a lot of people are saying they are using Passivhaus principles, but this is as meaningless as saying ‘I’m doing an eco-building’.
What constraints on design are imposed by Passivhaus?
The main constraint that we found was optimising the building’s volume to surface area ratio. The more spread out and complicated the plan form, the more heat loss you get. We did some early analysis using parametric front-end PHPP to look at different massing and orientations. That led us to a two-storey design approach.
Apart from driving the initial form, we didn’t find that Passivhaus limited our expression. It actually does the opposite, because you can rely on it to produce buildings that will perform. It frees you up to think about the quality of spaces. It gives you a solid technical base which then allows you the freedom to be creative.
What was key to the success of these projects?
We had the same design team as on the other schools, so we already had a good collaborative understanding, and we were lucky that the contractor who had done the previous schools with us won the tender. You can’t deliver Passivhaus without collaboration.
Images and drawings of another Passivhaus school by Architype, Oak Meadow Primary in Wolverhampton, are also in the AJ Buildings Library