|naturalspace magazine : Sustainable architecture and the natural world: Natural Space Ltd|
House For The Future Text
The House For The Future Images section shows the general character of the house against a backdrop of natural light. The rich palette of natural materials gives the house a special lustre that is heightened by the high level of daylight. The photographs were taken with a slightly overcast sky and just a hint of winter sunlight. They demonstrate how the house has carefully exploited this winter light, one of our greatest resources.
The house exploits solar radiation by facing the main living spaces to the south. The large slate roof, areas of glazing and oak structure all dominate the facade. The solar and photovoltaic panels are positioned on top of the roof, presumably to avoid shading from the mature tree in the foreground.
From the north the house is organised as a thermal buffer with smaller openings from the utility spaces on the ground floor and the bedrooms and bathrooms on the upper floor. The walls are lined in Welsh oak boarding and rendered in lime render. A large rain water collection tank is positioned along the length of the roof at gutter level and collects the filtered water running from the sedum planted rear curved roof.
Three double sets of sliding glazed doors open up the south-facing wall towards the garden. The large sloping oak structure is continues through the facade down to the ground. Sunlight coming through the sloping glazed section of the roof is filtered through the blinds to give a more diffuse less intense light. This light brings life to the rich colour of the walls that are clad internally in clay boarding and the superb colour of the oak frame. These natural colours together with the slate floor are what give the internal spaces their strong character. The only applied colour is on the very pale blue doors on some of the kitchen cupboards
The space above the living areas continues up to the balcony that links the upper bedrooms. The large sloping roof surface channels hot summer air up into the void above the balcony to be ventilated out at high level.
View from the kitchen overlooking the living spaces and garden.
This section looks at the Ecological strategy and highlights how the house uses energy, selected materials and deals with waste.
The house was conceived as one that would make no net contributions to carbon dioxide emissions. It would also create a healthy and ecologically friendly indoor climate by utilising only natural materials free from chemical treatments. They would have a low embodied energy rating and as much as possible would be sourced locally. The house would be flexible and adaptable in order to address the needs of family life for the future, both from changing working and living trends and also suitable for lifetime use remaining accessible as mobility decreases. The house would make use of a passive solar strategy by facing the living accommodation to the south. By super insulating the envelope and controlling thermal mass the heat input required would be kept to a minimum. It would use an oak frame to enable the house to remain flexible.
The house draws on solar gain to contribute to the daytime heating requirements. The remaining heat comes from a 2.3kW heat pump boosted by a 3.4kW electric boiler. It produces three units of heat for every unit of energy used. SWALEC whose source is hydro and wind-power supplies the energy input. The heat pump required a 30m vertical hole to be bored through the bedrock towards the front of the house where the soil is warmer. The result is water at about 50 deg C that is fed into a conventional central heating system. A wood pellet heater has been installed to complement the pump during peak demands. The pellets are manufactured from sawdust. An array of photovoltaic panels produce 800 Watts of electricity. This is equivalent to the lighting demand, which has a central radio and voice activated control system. Remaining electricity is supplied by SWALEC.
The material selection process used the Environmental Preference Method by David Anik, Chiel Boonstra and John Mak in combination with guidance by the Building Research Establishment. The resultant embodied energy ratings have been shown to be 18 percent lower than a typical house. The structural timbers were green oak for the frame, Douglas Fir for the secondary joists and rafters. External cladding is oak. External walls use a lime render, roof finish is reclaimed Welsh slates to the south which has to endure greater exposure. Recycled aluminium was used for several components including the rear sedum planted roof. Clay board and clay plaster were used instead of plasterboard and plaster. Earth blocks were formed from clay extracted from the site for use on ground floor partitions. In addition to the solid slate covered floor the earth blocks provide additional thermal mass.
The rear eaves are specially formed to conceal polyethylene water storage tanks (680 litres) to collect rainwater for use in toilet cisterns and an outside tap for garden use. The rainwater is mechanically filtered before being fed into the tanks. Bathroom appliances are chosen to reduce water demand by having a dual flush operation. Construction and demolition waste was used for the hardcore below the ground floor slab.
The 3D Study section takes a look at the structure of the house and highlights the materials used in the construction.
The oak frame uses a renewable source of locally produced untreated solid green oak and is prefabricated into four separate frames set 3600mm apart forming three structural bays. The posts are 150 x 175mm and the beams are 250mm deep. The curved roof beams that were formed on a 15m radius from naturally curving oak trees, are 300mm deep. External walls are built around the oak frame by using Douglas fir stud framing and 200mm sheep's wool insulation using a 'breathing wall' construction. This has a ventilated cavity to the outside and support for cladding in untreated Welsh oak and lime render. The external walls are clad internally using clay board in place of traditional plasterboard.
The plan is organised with all the living space to the south and all the utility spaces to the north. A bedroom is located on this level together with a handicapped toilet. This ensures that the house could serve as a lifelong home. Although the living spaces are open plan they could easily be altered to provide a separation between them. Indeed the house, which occupies three structural bays, could easily have been built in two or four bays. The flexibility provided by the oak frame, means that it would be very simple to extend or alter the house in the future. This is an important consideration as a life long home which can be extended or divided could greatly extend the life of the house. The environmental implications are obvious.
An open stair leads up from the living spaces on the ground floor to the bedroom areas of this floor. Three bedrooms are located here with an access balcony overlooking the floor below. Bathroom appliances are chosen to reduce water demand by having a dual flush toilet with set buttons for full flush or partial flush This gives four or two litre flushes and is located in the main bedroom. The bathrooms have a super efficient ventilating system which ventilates directly from under the toilet seat, triggered by passive infra red detection.
The sedum planted curved roof to the north of the house contains 200mm of cellulose insulation. The sedum is planted directly onto a standing seam roof of recycled aluminium. This lightweight approach does not require the heavy construction required for traditional grass roofs and therefor a lot of process energy is saved.
The lightweight external wall construction meant that thermal mass would need to be provided by the floor and internal partition walls. The ground floor does this by being of solid construction. It has an insulated concrete slab that uses recycled aggregate and is covered in Welsh slate. Clay from excavations below the house were manufactured into bricks on site thus reducing energy costs by avoiding the usual double transport of soil out and bricks in. These bricks were used to form the ground floor partition walls and also give some thermal mass.
The Solar Study section allows us to see the extent of sun penetration at different times of day and in different seasons. The lengths of shadows can be observed and demonstrate why this is often a major problem for solar houses during winter months.
The design strategy of south facing housing to benefit from passive solar gain has to be looked at very carefully. In many more denser conventional developments the spacing between the houses would have to be considerable to benefit from winter sun. The period of greater solar need is also the period with greatly lengthened shadows which would block out the sun. The studies show the extent of winter shading which would have to be taken into consideration in determining the heights and densities of a development. It should be rememberd that this is a fairly low lying house so shadows in a typical housing project would increase greatly with scale but also with latitude. The decision to locate the solar panels on the roof and the manner with which it is done greatly extends the shading. 9am December 21st shows this to good effect. Consideration should also be given to large areas of sloping glazing. Due to the low winter solar altitudes sloping glazing would allow in much less sunlight than vertical would therefore minimising the solar effects of the glazing. The opposite is true in summer when the higher altitudes would let in more sunlight than vertical glazing therefore increasing the overheating factor.
|naturalspace magazine : Sustainable architecture and the natural world : copyright Natural Space Ltd 2004|