Architype Architect’s RIBA Award-winning St Luke’s School in Wolverhampton is the very embodiment of success breeding success.

When Shropshire Council, an organisation with a strong sustainability agenda, set out to provide new, modern primary and nursery school facilities for Ashford Carbonell, near Ludlow, it took a tour of St Luke’s as part of its evaluation process.

The councillors obviously liked what they saw as they awarded the £3m contract for Bishop Hooper Church of England primary school to Hereford and London-based Architype and joint bidder and main contractor Thomas Vale Construction.
The single-storey Bishop Hooper is based on the St Luke’s model, but in a much smaller package, according to project architect George Mikurcik. Its footprint is a compact 925m² and it will accommodate just four classrooms, along with nursery and break-out facilities.

Open spaces
It is rectilinear in form, with varying height elevations and monopitch roofs and, internally, just as in St Luke’s, the design minimises corridors and corners – recognised for their bully ambush potential – with a “cluster” of classrooms arranged around internal open spaces or “hubs”.

These hubs are multi-purpose for foundation stage (ages three to five) and key stage one and two (ages seven to eleven) pupils and the school will also incorporate an element of community-use facilities. The main hall will be available for local community events, as will one or two rooms which will have their own secure entrance.

The configuration of the building has largely been informed by the environmental requirements of natural daylight and ventilation: “We modelled the daylighting and optimised it to get good levels of natural daylight and minimise the need for lighting loads,” said Mikurcik. “The building is also designed to be naturally ventilated, with only the main hall being automatic ventilation, linked to the building management system.”

The south-facing classrooms benefit from rooflights, but also feature extensive glazing. “This is beneficial for solar gain and we will control that with a free-standing 2.5m-wide continuous canopy. This will provide shading and extend the useable space for the classroom – they can open the sliding doors and move outside in all but the harshest weather.”

This south-side canopy, which comprises softwood rafters and 18mm T&G OSB, supported on glulam beams is repeated on the east side of the building and over the entrance to the building on the north side, providing a covered waiting area for parents – but here the canopies are a continuation of the main sedum roof.

The canopies and the timber frame structure of the building itself are made and erected by Presteigne-based Frame Wise Ltd, a timber frame manufacturer which has worked with Architype before and which has long experience in the schools sector – 40% of its volume is new schools and school extensions and, said managing director Simon Orrells, that volume is growing year on year.

Frame Wise’s twin frame system, which the company developed as “an extension” of open panel timber frame in order to improve U-values and airtightness performance, was chosen for the Bishop Hooper project.

“The key benefits are having two separate studs, so you’ve got stud, cavity, stud, fully filled with insulation,” said Orrells. “There’s minimal connection between the studs so you’ve got reduced cold bridging and vastly improved acoustic performance. If you simply had one deeper stud you would lose that thermal and acoustic performance.

“We can achieve a U-value of less than 0.09W/m²K with twin frame and improved airtightness of 1m3/h/m² with some of our latest detailing,” added Orrells.

Bishop Hooper’s timber frame sits on a block upstand on a beam and block floor. The gaps between the separated studs are fully filled with 270mm-thick Superglass semi-rigid glass fibre insulation, with a 9mm Panelvent board on the outside, followed by external timber or stone cladding. A Pro Clima Intello vapour check membrane on the inside is followed by a 38mm service zone and internal plasterboard linings.

“Normally we would put the sole plate right above the ground level, but Frame Wise suggested going down to finished floor level, so at the damp-proof course level we are installing an insulated render system up to 200mm above the ground level to protect the timber frame,” said Mikurcik.

Irregular heights
The elevations are irregular in height, with the lowest walls at the classroom side at 2.6m, rising to 3.3m in other areas. The hall, however, towers above at 6.5m, but the walls here still comprise single panels. “Frame Wise has used double or triple studs and staggered them so it can achieve the height in one panel, rather than jointing two together,” said Mikurcik.

Frame Wise’s twin frame system was chosen for the development

Glulam “stiffeners” were also incorporated into these high wall panels and were used to support the roof structure above the high level windows, added Orrells.

Glulam beams, which will be left exposed to view, provide structural support in the large-span spaces – the main hall and the open hubs.

“One of the common problems is, if the glulam structure penetrates the thermal envelope it causes problems with airtightness,” said Mikurcik. “So there was quite a bit of communication between us and Frame Wise during the detailed design stage and it was decided to move the glulam beams from the thermal envelope to the interior to completely avoid thermal bridging and ensure that the airtightness layer is intact.”

The three monopitch roofs feature glulam purlins and 300mm-deep Boise I-joists, the gaps between which are filled with Superglass insulation. Panelvent and breather membrane sit on top of the roof cassette and in turn are topped with a 100mm ventilation zone, then an 18mm OSB deck, which supports a sedum roof.

Breathable structure
This ventilation zone – and, indeed, the breathability of the whole structure – is critical for Architype and one of the reasons it specified Panelvent which has vapour permeable properties, allowing moisture to escape.

“We persuaded the client that breathable construction was the way to go, minimising build-up of moisture and the risk of structure failure,” said Mikurcik. “It cost the client more money, but it’s money well spent as it will ensure the longevity of the building.”

While apart from the glulam beams, much of the timber will be hidden behind plasterboard inside the building, as at St Luke’s, the classroom ceilings are formed of “hit and miss” timber slats, which improve the acoustics.

As for the exterior, the school will blend into its rural setting via a combination of local stone cladding on the hall and untreated Douglas fir square-edge cladding elsewhere. The different spaces and functions of the spaces within will be highlighted by using the timber cladding horizontally or vertically.

Along with the sliding glazed doors at classroom level, a continuous high level clerestory window runs through the heart of the building and the rooflights bring both natural daylight and cross-ventilation into the classrooms. Aluminium louvres on the outside of the classroom windows provide secure vents. “It allows night-time purging of the spaces in the summer and encourages the users to moderate the temperature of the building themselves,” said Mikurcik.

The school will feature underfloor heating linked to a biomass boiler – Shropshire Council’s preferred option as it has ready access to a local woodchip supply.

With both Architype and Frame Wise being advocates of the “fabric first” philosophy, that’s the extent of the renewable energy technology for Bishop Hooper. The U-value target through the walls and roof is 0.12W/m²K, all of which will be achieved by attention to airtightness and insulation. “I would hope the predicted heating and hot water energy use would be below 50kW/hr/m²/yr,” said Mikurcik.

Frame Wise completed the erection of the timber frame in mid-April and Bishop Hooper will be ready for the new school year in September. The result, said George Mikurcik, will be “a really compact, efficient rural school that hopefully can be replicated as a model around the country”.

And, who knows, it may just pick up an award in the process.

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