Super-economical super-insulation with straw bales

This house in rural Herefordshire is an example of a thoroughly practical approach to designing and building to reduce environmental impacts. It is constructed with straw hales within a timber frame to provide insulation in the external walls. It is an interesting example of building within one’s means without the need for borrowing, with development taking place slowly as money becomes available. The builder and owner is an expert in water conservation and alternative sewerage treatment systems, which he has incorporated into his house.

super-insulation with straw bales

 

Incremental development

Ten years ago Nick and Sheila bought a bare field on top of a low hill deep in the countryside. They set up on-site in a small caravan acquired for £400. They were both working from the caravan, as well as living in it. Nick recounts how the fax machine was mounted at high level, and occasionally spewed out paper over the person sitting and eating below. They set about taming the landscape by planting a garden and trees, and making it more productive by growing fruit and veg and establishing a coppice of willow and hazel for basket-making.

The next stage of development was to construct an interim house, larger than the caravan, better insulated and more comfortable – but still very compact, with 30 square metres of floor space, half of which was devoted to badly needed workshop space. Income from the next job contributed to the very modest cost of £3,000. The house had two rooms and a compost toilet.

Autonomous living

Nick and Sheila were living off the grid, relying on second-hand photovoltaic panels and a small wind generator linked to a bank of second-hand batteries for the storage of power. In these circumstances you become acutely aware of how much power is consumed by every light and appliance you own. Nick can tell you the power consumption of a television on stand-by, or a printer which is apparently turned off. Although their new house is supplied with power from the grid, Nick and Sheila have a low-power-consumption lifestyle to this day.

The permanent house

After living on the site for five years, sufficient money had been accumulated to embark on the permanent house. The initial budget was £40,000 for a 100 square metre house – although that area does not include the porch and two mezzanine areas which make good use of the space under the lofty roof and bring the size of the house up to 130 square metres. The cost rose to around £50,000 over the four years it took to build, fitting the construction around the demands of work and the need to generate cash for building. The ground floor slab was constructed two years before the timber frame was erected on it, the roof followed a year later, and this sheltered the straw before the external walls were completed. It then took another year to complete the house to the point of moving in.

The permanent house is a straightforward, practical design, with every aspect of design and construction carefully thought out and beautifully built. The final result is a house with a very special sense of quality and very good performance.

The layout of the house

The layout developed over a number of months, during which time Nick and Sheila got to know the site and tried out different arrangements in model form. In early designs, the house was long and thin with the rooms facing south with extensive windows. The house they built is much more compact, with relatively few windows facing the view and the garden to the west; instead the house turns its back on the winter storms that come from that direction. It consists of a large main room with a kitchen at one end, a sitting area around a wood- burning stove at the other and an area for eating in between. There is a bedroom, bathroom and toilet off to one side, with a mezzanine above and a home office and visitor’s bedroom with a second study mezzanine above off to the other side of the main space. There is a large porch at the front which keeps the heat in and the winter weather out, and which has a sink and the freezer, and serves as a utility room. This is a brave and unusual idea to enter the house through the place usually reserved for keeping things out of sight around the back somewhere. A conservatory is planned, to lead out to the garden at the back.

A timeless interior

The interior draws inspiration from Christopher Alexander’s ‘Timeless Way’, and has a number of interesting corners and places to sit, with deep window seats and an alcove with a small settle. The ceiling is high, with a rooflight, and is supported on high posts with knee braces with traditional pegged joints. The stair to the mezzanine rises on one side and turns through a right angle avoiding the structure and forming the alcove below. This rather picturesque arrangement was the product of a fortunate mistake: as can happen, the stairs needed to occupy a larger space than originally envisaged, and so a change of design was required during the course of construction.

Although the house is timber-framed, it has a very solid feel to it which derives in part from the quality and type of finishes used: the walls and ceilings are wet-plastered, with a slightly rough finish with rounded corners, painted with slightly textured mineral paint in beautiful shades of grey and ochre and purple. The floor is concrete, and was given a fine finish when it was cast with a ‘power- float’ machine which smooths the wet material with a circular motion. This was then ground to a polish and waxed on completion to give a richly coloured and patterned floor. The stair and fireplace are unfinished natural concrete. The balustrade to the stair of galvanized steel cable and painted steel tube was adapted by Nick, using his welding skills, from a balustrade that was being thrown out of a museum that was being renovated. The bathroom is tiled with travertine on the floor and walls. The generally industrial light fittings were largely obtained second-hand from car-boot sales for around £2-£5 each, and were carefully chosen for their design. The beautiful doors and other joinery were made from Welsh oak by a local joiner. In spite of, or perhaps because of, the simplicity and economy of the materials, the whole effect is one of quality and solidity.

Straw is cheap, and it cost only a few hundred pounds for all the wall insulation for the house; it is a virtually zero-embodied-energy material, which will compost back into the earth at the end of the life of the building – but you are dependent on the seasons to obtain it, and could not plan it into a tight building programme. Straw bales are dense and do not support combustion, and are also too dense for rodents to become established. One of the effects of straw-bale construction is to create very thick walls, which create deep window sills, good for sitting in and for plants, but which do tend to isolate the inside from the outside of the building (and which incidentally make it very difficult to reach the kitchen window over the sink). It is important to design the window reveals at an angle so that not too much light is cut off and to prevent too abrupt a contrast between the brightness of the window and the inside wall.

There are other ways of building with straw bales, either within a post and beam timber frame, or which use the bales as the structure which supports the building and which are rendered with lime render inside and out. There can be difficulties with this approach, as the straw is susceptible to movement and will decay if moisture penetrates the render. This technique has been widely used in the south-west states of America, where there is a hot dry climate. Meanwhile, there is now a significant number of straw-bale houses in Britain, and one building firm that specializes in this form of construction.

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