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Oak Meadow School

One of many interesting talks at last week’s UK Passivhaus Conference focused on Architype’s two Passivhaus schools in Wolverhampton, and the challenges of delivering Passivhaus standards at no extra cost.

Jonathan Hines of Architype explained that the Wolverhampton Passivhaus schools built on the practice’s past experience  at St Luke’s Church of England Primary School (the first UK primary school to achieve BREEAM Excellent) and relied on fundamental principles of sustainable design: extensive use of daylight and natural materials.

St Luke's Church of England Primary School

Jonathan said in their new schools they had managed to ‘keep hold of their passion for design and materials whilst achieving Passivhaus’.

Oak Meadow School

Oak Meadow School has recently completed. Work began on site in September 2010, after Architype were appointed to carry out the design by Wolverhampton City Council, in December 2009. Architype promoted the use of Passivhaus to the client as a better alternative to BREEAM.

Jonathan described how they managed to achieve Passivhaus at no extra cost using his personal approach to cost estimating: ‘if you think it costs more, then it will’. In order to keep costs down, the architects focused on simplicity, constantly asking themselves  what could be taken out to make the building work better.

Oak Meadow school is designed on a north - south axis and organised around shared hub spaces. This rational plan layout creates a simple extruded section.

Bushbury Hills Primary School

Similar to Oak Meadow, Bushbury Hills Primary School is also on a north - south axis with central shared spaces. The building has a simple section; making the most of daylighting by borrowing light from the central hub space for rooms on the north side of the building.

Jonathan’s presentation was complimented by Nick Grant of Elemental Solutions, the Passivhaus consultant for both schools. Nick spoke of the need for simple solutions, likening the structure of the building to that of a human body.

Using Passivhaus standards for school buildings differs to domestic; different, more complex issues arise due to greater amounts of people using the buildings at varying times. The ventilation strategies were developed to supply the classrooms and group rooms and to extract from the toilets and hub spaces. Classroom spaces were used to regulate CO2 levels when children were no longer using the spaces.  Ventilation issues included:

• timed control
• problems with the filters in the MVHR units drying out
• CO2 modulation
• kitchen comfort ventilation
• summer toilet ventilation
• secure night ventilation

The team opted for a ventilation strategy that relies turning the MVHR unit off in the summer when natural ventilation can be used. Windows are opened by a mix of automatic and manual controls.

Schools need heating systems which respond quickly to changing circumstances. Heating mainly relies mainly on internal gains, but controllability and user understanding is critically important. Gas boilers are easy to understand and can be controlled thermostatically on a room by room basis. This raises the question of whether too much thermal mass in a school actually works against its thermal performance. Lightweight structures allow the building to both heat up and cool down quicker, in response to building use (such as after school holidays or on a Monday morning).

Nick finished his short presentation with this statement, ‘What you put in a building may make it good, but it’s what you leave out that can make it great’. This poignant sentence highlights Architype’s focus on simple, sustainable design.

Matt Wisdom of Thomas Vale, the contractors on both Passivhaus schools,  gave his take on the projects.  He spoke of the need for partnerships and good relationships throughout the process. Passivhaus was a learning curve for the whole team; noone had done a Passivhaus building before and taking on two schools simultaneously was quite a challenge.

Thermal imaging was used to discover any air leakage, and the buildings were smoke tested. This allowed discrepancies to be picked up and rectified early. Matt highlighted the importance of the supply chain. As Passivhaus is relatively new, it can be difficult to source materials in the UK which can mean increased costs.  In terms of cost, there is no question that Architype’s Passivhaus schools offer value for money. Capita Symonds’ recent cost model for a typical sustainable school suggested prices of £2,151/m3. Oak Meadow and Bushbury Schools came in at £2,069/m3, just exceeding Architype’s BREEAM Excellent St Luke’s, which cost £2,030/m3.

The team agreed that Passivhaus was achieved by the standard being integrated into the design approach from the outset, by the appointment of a contractor committed to achieving Passivhaus, through teamwork, and through continuous and rigorous site inspection.

by Laura Mark, past AJ sustainability intern

Jonathan has kindly invited me to visit in the next few weeks so watch this space.   Hattie

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