BBM Sustainable Design, a specialist in green architecture, assisted a private client in Cuilfail, Lewes, East Sussex, in fulfilling his ambition of designing an eco-friendly house, Baldy's Garden. As Sutherland Lyall discovers from project architect Duncan Baker-Brown, the design maximises the use of local, recycled and organic materials to create a brilliant sustainable home GRAND DESIGNS It is difficult enough having a client who decides to be his own Grand Designs-style builder, but it's something else when the client also wants to design an authentic green house. Architect Duncan Baker-Brown is philosophical about the extra, unpaid time that is involved in sorting out construction and procurement - rather than architectural problems - as he has built his own home, so knows both the ropes and the potential psychological damage involved in self-building. The green bit hardly fazes him because his practice with Ian McKay, BBM Sustainable Design, is a specialist in green architecture. It is currently busy with sustainable buildings, including community centres, schools and houses in the South East, so this house is not an experiment but part of a considerable body of work. Baker-Brown says: 'The client is passionate about sustainability. From an environmental point of view, he has gone just about as green as he can go.'
SHAPING THE PLAN Several years ago the client, who, like a lot of private house clients, does not want to be identified, bought a white-walled, at-roofed house at Cuilfail with great views of the East Sussex town of Lewes to the South Downs beyond. Built in the post-war years, the house had not worn well. Its L-shaped plan was based upon an en-lade circulation pattern with rooms opening into each other rather than on to a corridor. Baker-Brown is not entirely happy with the plan that he finally agreed with the client. His suspicion is that because the client had lived in the old house for a year, he and his family became used to its idiosyncratic plan, and recent memories of it have, not entirely happily, been incorporated into the design of the new house. One clear example of this is the fact that the utility room and the back door can only be accessed through the small guest bedroom.
The new timber-framed house has an angled L footprint of living and play spaces on the ground oor, with the guest bedroom and the utility room at one end, at whose door is a hot tub and a staircase leading up to the first floor. On the - rst oor are bedrooms, bathrooms, a meditation room, a nice big clerestory-lit space under a sloping roof across the back and a deck outside the main bedroom. The south-facing bedrooms on this oor overhang, shading the groundfloor living room from the summer sun. Baker-Brown is a bit concerned that the south-facing bedroom windows will be unsheltered in the summer, following the abandonment of an array of shading photovoltaic cells. There is a at-roofed double garage by the north-west entrance with a sedum roof, which Baker-Brown had earlier hoped, if it were affordable, might form the covering for other roofs.
Although BBM's relationship with the client is enshrined in a conventional appointment contract with periodic inspections of the work, there is no building contract. The client runs the job himself.
Baker-Brown says that the client had first appointed a project manager who had been a BBM client and knew the ropes. But, after about four months he realised he could manage it himself.
'We had to tell him he was responsible for the site and health and safety so he got the appropriate public-liability insurance. He has an advantage in that he can work on it full-time, he likes doing it and he has been lined up by his predecessor with really good people. There has been, for example, an amazing carpenter who did all the framing. And now there are three other good chippies.'
On balance, Baker-Brown prefers to have a conventional contractor: 'You would think from the television programmes that most self-build projects are [self project managed] like this one.
I prefer the conventional design team and contractor. But it is difficult to convince people. I'm not sure that he's getting it any cheaper than with a contractor and this way of operating is not so good for us. They phone you all the time with basic questions.
If you have someone running the project, the meetings you have with the client are about creative issues - like the design of the stairs, rather than why the screed looks funny.
'But this guy is very tenacious. This was very clear, for example, when we had forgotten about the timber treatment.'
Baker-Brown had discovered that the wood treatment that the practice normally uses was not quite so benign after all: 'The chippie turned out to be allergic to preservatives and at one stage we thought we might have to do the frame in Douglas fir - which does not need treatment. But the client found a non-toxic treatment all by himself.' This was ProBor timber preservative by Safeguard Europe, which was, Baker-Brown says, the only genuinely non-toxic treatment available.
Baker-Brown adds: 'The quantity surveyor did a cost plan at the beginning, which was useful for knowing how much things would cost. And it is coming in on budget.'
SPECIFICATION Baker-Brown used Barbour's Specification Writer but has moved on to the NBS (National Building Specification) because there are more sections in it than in the Barbour program. The practice uses Vector Works and has been Mac-based since it started.
Baker-Brown says, 'We are using local materials - especially sweet chestnut. It is a beautiful material and we have used it as glulam and laminated and finger jointed. The glues are water-based. And the glulam maker is only seven miles north of the office. We recently used circular glulam columns on a community centre in Hastings with sweet chestnut from coppices all within 10 miles. It is incredibly durable and we just oil it with Danish tun oil, which stops it leaching and allows the tannin to be absorbed.
It has a guaranteed life of 30 years and because it is simply pinned to the frame it is easy to pull off when it needs to be renewed.
There are tens of thousands of hectares of sweet chestnut so you have lots of coppiced timber in straight poles. But, they have a 15year cycle and need to be worked, so by using the sweet chestnut we are rejuvenating coppices: within three months of harvesting they can be in use.' (See April's AJ Specification, pages 32-34. ) It needs to be said that sourcing green materials is not always straightforward. A school the practice has just completed in Sussex has sweet chestnut cladding, much of which it had to go to France to get, although it found some of it in the Duchy of Cornwall, and it may not be available from there next year.
The firm's recent community centre in Hastings was originally going to be insulated with recycled ax, but at the time it could not source it. Looking at the specification it is clear that Natural Building Technologies has been a major source of legitimate green materials, from non-toxic paints to specialist insulation boards.
On other occasions, price is the problem. The original idea was to have sweet chestnut shingles on the sloping roof, but the budget required that this roof along the back of the house should be in cedar shingles from Rawnsley Woodland Products.
Where once all the at roofs were in sedum, cost dictated that they are Prelasti from AAC Waterproofing. Prelasti is a single-ply rubber (rather than polymer) membrane with a high proportion of recycled rubber which goes on quickly - the green alternative to, say, Trocal or Sarnafil. It is the material Simon Conder used at his house on the shingle of Dungeness. It is laid on a 22mm-thick Isolaire fibreboard insulation/sarking, fixed on battens and counter battens with a quilt of Isonat measuring 300mm to 400mm between the rafters underneath. The at roofs are laid to falls, followed by a vapour-control layer on top of the plasterboard.
Baker-Brown describes the Isolaire as 'waste timber mushed up into a pulp and stuck together with resins from the wood and then dried. Isonat, from Natural Building Technologies, is a mix of hemp and recycled cotton fibres - a slightly cheaper alternative to recycled ax or the lambswool that the practice has used elsewhere - which is straight off the sheep with a little borax to discourage insects. None of these involves installers with the nasty particles you get with some insulation. Baker-Brown has also used this insulation between the firstfloor joists, partly for thermal reasons and partly to minimise sound transmission.
The external cladding is either white render or sweet chestnut horizontal boarding. The render, from Natural Building Technologies again, is a Bayosan lime-silicate render on a Diffutherm wood-fibre insulation board, fixed to the timber frame.
Baker-Brown says: 'Here, we are talking about materials which are easier to work and which are safer.'
The sweet chestnut boarding from Inwood Developments is a rainscreen, with each board chamfered top and bottom to throw off most of the water, and a 10mm gap between boards that facilitates air movement in this breathable wall. The boards are cut from strips of sweet chestnut, -nger-jointed together. Once they are fixed, they are treated with Danish tun oil which inhibits leaching and allows the natural tannins to be absorbed back into the timber.
Behind the sweet chestnut rainscreen is the 37mm air gap around the counter battens and then Pavatherm wood-fibre insulation with a latex additive by Natural Building Technologies, nailed to the 150mm-deep studs. They are stuffed with hemp and recycled-cotton Isonat insulation. As these are breathing walls, there is no vapour barrier. External walls have U-values of 0.14.
The windows, which have composite aluminium and timber frames, are from Velfac Direct and include big sliding windows to the upstairs bedroom. Baker-Brown says: 'They are the skinniest frames you can get and there is no difference between opening and closing lights. They are very refined and have good U-values.' The downstairs folding and sliding doors to the dining and living rooms have integral blinds by I-D-Systems in place of the original proposal for timber brises soleil.
Although the external Bayosan lime-silicate render is a specialist product, there is a wide range of colours. Not so for the non-toxic, organic paint for the internal walls which are clay plaster. Baker-Brown says: 'You prime the plasterboard and then apply 3mm of clay plaster as a rough coat and let it almost go off.
Then you smooth it with a soft plastic trowel or sponge. We use it because it absorbs airborne toxins, the manufacturing processes are less damaging and it looks good.'
The client was either prescient of current water shortages or was following conventional green practice when he asked for a rainwater-harvesting capacity. This is not a matter of installing green plastic butts at strategic positions but of building it into the site. Rainwater will drain away to a 600 litre underground collection tank by Gusto Products, from where it is pumped back for non-potable activities such as washing and running the hot tub.
For the first two years, the run-off from the cedar shingle roof will have tannin in it and this water will drain away directly into the public sewer until it is clear. Then the rainwater from this roof will be diverted back into the main system. Baker-Brown emphasises the point: 'This is not grey-water harvesting. That requires human intervention; occupants have to remember to change filters. Our green water-management system is idiot proof.'
The boiler is a condensing gas boiler by ATAG Heating and the solar heating is an evacuated solar-tube system by Viessmann, located on the flat roof above the main bedroom.
Baker-Brown has solar tubes on his own house and they are so efficient that it was only during a very cold spell in the winter, after they were installed, that he realised that his boiler had never worked and the solar tubes had been supplying all his heating.
He explains, 'They last for ever. They are copper filaments inside evacuated glass tubes that heat water at each end, which indirectly heats the water in the main tank. You use that in combination with the thermal mass of concrete floors to radiate heat back during the night.'
Baker-Brown is looking at further developments in sustainability. He adds, 'At the moment we are quite interested in domestic wind turbines, which cost about ú1,500 installed and have a 25-year life expectancy.'
Credits Architect BBM Sustainable Design: Duncan BakerBrown, Megali Marcoire, Daniel Harding, Abraham Mohsin, Ian McKay Main contractor The client is the contractor; this is a self-build project Quantity surveyor Cotton Thompson Cole Structural engineer Gyoury-Self Partnership Form of contract None Gross external floor area 275m 2Total cost ú380,000 Start on site August 2005 Expected completion August 2006 CAD Packages used VectorWorks 11.0