Bar the sedum roofs and the brises soleil jutting out over the south-west-facing windows, a new 30-unit housing unit about to get under way in Wolverhampton’s Blakenhall district does not especially declaim the shape of environmentally-sound domesticity to come. But, while it may not exactly wear the fact on its sleeve, the Bromford Housing Group project is undoubtedly an advance for “green” architecture in Britain.
The development, which, pending final ‘i’ dotting, should start construction in May, has been designed by Cole Thompson Anders Architects (CTA) with added technical input from INTEGER, the ‘action network’ dedicated to the use of sustainable, intelligent construction systems, in which CTA is a lead partner (see panel).
The complex’s three houses and 27 flats are set out in three blocks, forming an L-shaped site plan enclosing a car park and “eco-park” garden.
Among the key environmental design aspects of the development are the scale and siting.
“The terraced nature and height of the blocks ensures minimal external wall surface, minimising heat loss,” said CTA partner and INTEGER design director Craig Anders. “Most major spaces are also located behind the south facades to ensure passive solar gain in the winter.”
The basic benefits of this combination of building form and orientation will be amplified by heavily insulated, high-speed timber frame panel construction. At the time of writing the architects and INTEGER had yet to find the supplier and system that met all their requirements and had rejected a number. Broadly what they’re looking for is 180mm or 200mm prefabricated timber frame panels, delivered as ready-to-use cassettes with pre-cut window and door openings. One well-known system ‘brand’, comprising two OSB3 boards bonded to a rigid urethane insulation core, was still in the running for the project. But the team behind the building clearly wanted to explore other options and the final choice of approach, based on a mixture of practicalities, price and performance criteria, was unlikely to be made until after the appointment of the contractor in March.
Despite the fact that the right system hasn’t just dropped from the tree, there doesn’t seem to have been any danger of CTA going non-timber. Timber frame is now a staple of its construction approach, following on from its original á Ü use in the experimental INTEGER Millennium House at the Building Research Establishment.
“We rarely use brick and block because of the embodied energy levels,” said Anders. “We have used modular steel frame in a school building and would consider it again, but we’re not so familiar with it and there seems to be less choice of systems.
“We’ve used timber frame exclusively for almost 10 years and as far as we’re concerned it is the system that’s most sustainable and easiest to work with.”
Timber frame’s added environmental attractions, he maintained, were minimal wastage in construction, the ready ability to accommodate 200mm of insulation and speed of erection.
“With previous projects, rather than concrete strip, we’ve used short bore mini pile or screw pile foundations, which take about a week to complete, with ground beams and a steel plate set on top and the timber frame built on this,” said Anders. “The actual timber frame shell in this size of building is generally up in two to three weeks and we’re expecting the whole project to be finished in 10 months.”
A recently expressed concern about the UK’s increasing conversion to timber frame building is that lack of thermal mass may leave us all sweltering in globally warmed-up summers. INTEGER clearly takes the issue seriously too and last year ran a seminar on it. But the outcome of this and wider research indicates that there are ready solutions. “It’s about achieving the optimal level of thermal mass,” said Anders, “so you could use a double layer of plasterboard, or a little solid flooring in a solar space conservatory. You can also shade the south side of a building and use shutters on the west to protect against the low evening sun, as they do in France and other parts of the Mediterranean. Combine this with good through-ventilation and there shouldn’t be a problem. Millions of people in the tropics living in timber buildings without air conditioning testify to that.”
While many architects and developers still lean towards the conservative approach of wrapping a second skin around a timber frame, generally brick, CTA and INTEGER are advocates of the single skin approach.
“There’s still a tendency among town planners to prefer bricky buildings in bricky areas and a taste among developers for the neo-Victorian parsonage style, even if the houses have PVCu windows that open inwards!” said Anders. “As far as we’re concerned these outer skins provide no benefit and bring in the wet trades, which we want to avoid. Our approach is generally to use timber cladding, or render on blueboard, or a mixture of the two, using each where it’s most appropriate.”
Another reason for the undisguised single-skin approach is because CTA clearly likes its buildings, while not perhaps to proclaim their eco-credentials conspicuously, to look like the contemporary structures they are. This will certainly be the case at Bromford which will feature different coloured acrylic renders on the street side, and cedar cladding elsewhere – a combination which has already featured successfully on a number of other CTA/INTEGER developments.
The uninitiated might expect the houses to be rounded off with some of the more headline-grabbing eco-architectural technologies, such as solar panels and wind turbines. But director Peter Colebrook said that INTEGER eschews these in favour of the things that not only work, but can be designed in without significant cost or buildability implications. These may be less exciting, including grey water processes, water-saving taps and shower-heads, ultra low-flush loos, passive stack ventilation and so-called sun-pipes – Le Corbusier referred to them as light-cannons – that direct light into stairwells. But these ostensibly unremarkable items perform. In the new building they’ll be used in conjunction with a wood chip boiler which will serviceá Ü all the houses and flats, with each householder metered and charged for the heat and hot water they use. The system from KWB of Austria being evaluated emits 25 grams of C02 per kw hour, compared with 192 grams for gas and 400 grams for electricity and is also claimed to be 10 times more energy efficient than the gas-fired equivalent.
“We’re getting to the point,” said Colebrook, “where the building’s energy demand is so low that conventional technologies and solutions won’t work. Developers who put in an electric radiator lose their environmental credentials.”
The development will also have ultra energy-efficient windows, with double-glazed, argon-filled designs from Danish producer Rationel among the options being considered.
The ultimate aim of the INTEGER/CTA approach is buildings that work and that the residents like – and they do seem to be achieving it. Another of their developments, on the Lyng estate in West Bromwich, combined contemporary aesthetics with a programme to educate residents about the design and building processes involved. The result, according to INTEGER programme manager, Alison Nicholl, is minimal vandalism and increased estate identity.
As the new development goes into construction, INTEGER and CTA are turning to other projects. They’ve won a competition to design affordable housing for the Joseph Rowntree Trust in the New Earswick Garden City near York, which is now at planning stage, and have been commissioned to design a flagship housing scheme in Letchworth Garden City. In London they’ve devised an environmentally-efficient renovation scheme for a Pimlico council tower block which is due for completion in April.
These projects too are in the INTEGER tradition of no fuss, environmentally-sound construction. “The idea at INTEGER,” said Nicholl, “is to ask what you can achieve. What’s simple? What’s effective?”
