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Tuesday29 July 2014

White Design’s Dartington Primary School

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With its individual timber-clad classrooms, Dartington Primary School in Devon by White Design blends into the rural landscape while creating one of the greenest schools in the UK.

Dartington Primary School, near Totnes in Devon, displays its sustainable credentials proudly. Solar panels glisten on the steeply pitched roofs of each timber classroom. Portholes above each toilet reveal the level of collected rainwater used for flushing. An acoustic buffer of reclaimed tyres is attractively planted with flowers. But the £6.5 million school designed by White Design, is about far more than nice little eco-touches. From its concrete-light foundations to its highly insulated timber frame, this is a design driven by sustainable principles while at the same time providing an enviably attractive environment for learning.

Many start off with the aspiration of creating as sustainable a building as possible only to find these intentions watered down during the course of the project. With the new school building in only its first term of operation, it is still early days. But first indications are that Dartington Primary School may be one of the rare public-sector projects that has actually managed to hold on to its sustainable ideals through the design and construction process. Credit should go to the school client, which declared its intention to commission a truly sustainable building at the onset, and to Devon County Council which financed it.

’It was very brave of the local authority to go with it and not have a more conventional building,” says project architect Andrew Docherty. “It was very far-sighted.

“In terms of materials and construction it must be one of the greenest schools in the UK. It’s all made from timber products. The building fabric is as green as you could make it.”

White Design, a Bristol-based practice with sustainable credentials, was asked to create a new primary school on a literally green-field site with a southern boundary of mature trees. The picturesque location is close to Dartington’s previous school, where teachers had taught in temporary accommodation for years.

While these cabins were cold in winter and too hot in summer, they influenced the new design – teachers liked the way individual classrooms encouraged children to spend more time outside, but wanted a more efficient, and comfortable version.

The result was a village-style arrangement with three clusters of individual classrooms for reception, Key Stage 1 and Key Stage 2 ages grouped around open spaces in the same way that cottages might overlook a village green or market square. The similarity was such that during construction, some locals mistook the chalet-style appearance for a housing scheme.

The brief specifically requested no corridors. Instead pupils circulate outside with the help of covered porches and a large canopy – even in cool weather the school is keen on outdoor learning. Classrooms are linked by small rooms for more individual teaching space. Other facilities are housed in a fourth cluster containing central facilities such as dining room, staff room and reception. Aesthetically, the clusters of individual buildings create a friendly ambience for the children who obviously enjoy the variety of play opportunities provided in the courtyards and around the perimeter. The developments, with the chestnut cladding already bleaching, blend comfortably into the rural landscape.

The site’s natural topography informed the plan. The nature area was suited to the southern edge alongside the mature trees, while the classroom clusters spread out away from the noise of the road towards the fields. A playing field is positioned close to the entrance while the main pitches are to the north, where the site is higher.

For Docherty, the classrooms are the key spaces in the school. Each one is 8m x 8m – slightly larger than average – and characterised by a lofty, 5.8m height, which maximises ambient north light, and the ability to open up to the outside through the large sliding door at the entrance and also a door at the rear. The form of the classrooms is dictated by a combination of two angles: the steep pitch which lets in as much light as possible while minimising direct sunlight; and the shallow pitch more suited to solar panels on the other side. In the rural setting, the form seems appropriate and redolent of barns and other farm buildings.

PROJECT TEAM

Designer/landscape architect White Design
M&E engineer Arup
Structural engineer Rambol
Timber frame engineer Eurban
Main contractor Interserve
Project manager NPS
Quantity surveyor Ridge

White Design decided early on in the design process that a timber-framed construction was the most sustainable way forward, specifying an insulated solid timber panel system which gives a U value of 0.19w/m2 compared with the 0.35 required by regulations. Engineered by Eurban from Swiss-grown larch, the panels are then insulated with Pavatherm natural wood insulation and clad in sweet chestnut. This was chosen over the more common western red cedar because it could be sourced locally from chestnuts coppiced to allow the trees to grow back more quickly. With the structural frame made almost entirely from wood products, there is no need for a breather membrane.

“The main concern with timber buildings is that they don’t have the thermal mass,” says Docherty. “But because these are single storey, lighting and heating is very simple and overheating isn’t problematic as they can just open doors and windows… It’s a modern, vernacular construction.”

The structure sits on lightweight foundations specially developed with structural engineer Rambol to use less concrete. Instead of the usual solid foundations, nine drainage rings of concrete per classroom were poured and back-filled with earth. These are spanned by concrete beams with the timber slab on top. At plinth level Onduline, a roof product made from recycled materials is used as skirting. The structural timber panels go up to 8m x 3m in size and are pre-cut in the factory and bonded with organic glue. Off-cuts are used as furniture and planters in the landscape.

There’s a huge amount of timber – 700cu m – in each structural frame. At the end of its life, says Docherty, this can be wood-chipped and provide enough heat for 130 homes for a year.

“Deconstructing buildings isn’t talked about much,” he says, “but it’s something we’ll have to think of [in the future].”

Internally, the wood panels are exposed at high level but plaster-boarded lower down to accommodate service voids and also to avoid too much timber.

The energy strategy, developed with M&E consultant Arup, makes maximum use of natural daylight provided by the pitched roof form – lights are rarely used – as well as stack-effect natural ventilation and a heat recovery system in the winter. Staff are encouraged to moderate temperatures by opening and closing doors and roof lights, with instructions placed on each classroom wall. When lights are used, they are self-dimming and use-responsive.

From a materials and construction point of view, it’s hard to fault the sustainability credentials. Heating has proved more complex. The council could not support a biomass boiler but White and Arup were keen to incorporate renewable energy sources. Wind and water turbines were unfeasible, while the hard ground made ground-source heat pumps difficult. Instead air-source heat pumps supply underfloor heating, assisted by high-conductivity Knauf floorboarding. Each of the four clusters has a mini plant room – more efficient than a centralised one – and these provide about a third of the school’s heating energy.

THE ENGINEER’S REPORT

The construction industry’s response to rainwater harvesting has been mainly driven by the supply industry, which has re-marketed underground tanks for rainwater harvesting.
At Dartington, we developed an idea from another project where we removed the need for pumping water up from the tanks by having the water go directly into the cistern.

We put the water through a filter on the roof itself to clean and attenuate the flow, using the roof membrane as a store instead of digging a hole in the ground. Clean water then goes straight down and through into an enlarged flushing cistern in the toilets. This is a good way of using the void behind the cubicles and it also allows the pupils to see the water level. We did consider putting plastic ducks in there to add to the new experience of seeing the workings of a flushing mechanism.

Pipex made the prototype for us and is marketing it as Flowstow. It could be especially suitable for retrofitting in areas where it isn’t possible to put in underground tanks.

David George, associate environmental service engineer, Arup

Dartington’s rainwater collection system, designed by Arup, feeds directly into the greywater cisterns in the toilets, with an overflow system to channel any excess in times of sudden downpour. To prevent water washing straight off the surface,White specified porous paving and created attenuation tanks under the pitch nearest to the school entrance and the first cluster of classrooms. A swale has been created in the south-west corner as well as a reed bed into which the water is gradually released.

Unusually, a sizeable proportion of the budget – £750,000 – was allocated for landscaping. This was a major priority because being on a greenfield site, it had to be seen to demonstrate exemplar sustainable design and landscaping as a benchmark for other projects built in land not previously designated for development.

White and Arup have left prominent instructions and information in the classrooms. But in the long term it’s up to the school to maintain the vision it showed in commissioning such a green building. “People have to understand the building to be able to use the building properly,” says Docherty. “How a building is used can halve or double its energy use.”

This has already become clear – the first energy bill was disappointingly high; then the school realised the external lighting had been accidentally programmed to come on all night.
A post-occupancy assessment next year will reveal the full sustainability story. But for now it’s off to a good start with both teachers and children alike. And never has flushing the loo been so much fun.

ANDREW DOCHERTY’S TOP FIVE REFERENCES

English villages

English villages

Initial design discussions for the school considered the project as a modern vernacular village embodying the school’s role as a community within the community.This is reflected in the domestic scale and layout of the buildings and landscaping. These features include terraced decks, grassy lawns, planted beds, ponds and courtyards. Farm gates, timber fencing and village signposts have been used for zoning and way-finding. The village clusters, shared facilities and play spaces encourage interaction within year groups and familiarity across them.

 

Kingsmead School White Design

Kingsmead School, Northwich, Cheshire, White Design, 2004

Kingsmead, the first primary school we designed, tested many of the ideas that we have developed through all of our recent architecturalwork. The connection between classrooms and external space wasn’t discussed that much when White Design planned the school in 2004 but became an important and popular element of the design. The classrooms have conservatories to the rear that can be used as group rooms, cloak rooms, or opened out into the playground. This has become very important in modern learning and is explored in detail with Dartington.

 

Re-thinking school building White Design

Re-thinking school building, BRE Innovation Park, Watford, White Design, 2006

Four years ago we did a small test school for the Building Research Establishment using a solid timber system. The idea was to explore modern methods of construction. This was a two-storey demonstration model which contained lots of the ideas that we’ve developed in subsequent projects such as the solid timber construction method and the integration of toilets into the classroom area. The timber product was engineered by Eurban, the same company we used on Dartington.

 

Devon landscape and weather

The rural site is a fantastic asset for Dartington Primary School. The buildings’ open layouts promote direct contact and engagement with the landscape. The children and staff can take their learning outside in all weathers. The swales and ponds that form part of the sustainable drainage strategy will be full and fast flowing in winter and damp and boggy in summer, while the extensive planting and wildlife will change with the seasons. The landscape will provide a rich learning resource for children and a varied habitat for local plants and animals.

 

Fuji Montessori Kindergarden

Fuji Montessori Kindergarden Tokyo, Japan, Tezuka Architects, 2007

Dartington embodies similar values to this building, which is shaped like a circle. The roof deck is a playground – it’s like a racetrack with the children charging round and round it in circles at playtime. The value placed on physical, external play and learning is something which is very important to education at Dartington.

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