The primary concerns here are energies associated with maintaining a thermally comfortable environment within our homes. Significant energies are also used in construction but not included here. A dwelling may be considered the final product. Energy will have been used to produce that dwelling and will be required to maintain it as a comfortable home (which in turn will include the capital energy costs of repair and adaption as well as direct fuel bills for space heating/cooling and water heating. Even improvements intended to reduce direct fuel costs (eg insulation, solar collectors) will incur a capital energy cost which may take a number of months or years to pay off in terms of energy savings.
Capital energy costs can be reduced by building in a way that repairs and maintenance can be carried out without wholescale replacement of existing materials and that dismantling can occur such that materials can be reused. Capital energy costs must consider the lifecycle of manufactured and finished products.
Whilst improvements have been made to building regulations to reduce energy consumption for space heating it must be remembered that the energy use in dwellings is the sum total of energy used in each dwelling and that whilst the energy consumed in running newer homes may be much less than older buildings, domestic buildings generally have a high life expectancy. The energy efficiency of older dwellings will thus also need improving if this category of energy use is to be reduced significantly. In the demolition and replacement of older buildings, the capital energy costs involved with demolition, rebuilding as well as other social, environmental and economic consequences should be considered.
* base: 1996
Table 8: Population and household size trends 
Another factor which must be considered is the number of dwellings our society demands. Any single building will use less energy with two persons living in it, than two similar buildings with one occupant each. The predicted growth in housing demand ([4.4 million: , now estimated at 5.5 million: )) will therefore have an adverse effect on energy use if it is met. The predicted rise in number of households of 17% (from 1996) will require a reduction of 17% in energy consumed by each household just to stay even. Remedies to tackle the social factors which have brought about such a demand or the design of dwellings better suited to the demands of smaller households whilst fulfilling their aspirations in an energy efficient manner may be appropriate.
The type of dwellings and their size will also be a factor concerning the energy required for space heating. New dwellings built in the UK must adhere to the Approved document L, Conservation of fuel and power . This defines a number of ways in which approval may be given for different buildings regarding thermal performance. One of these methods, uses U-values for walls (0.45), floors (0.35), roofs (0.2) and windows (3.0, maximum 22.5% of area). Using this method, different performances are to be expected for different house designs, in particular, detached, semi-detached, terraces and flats. Table 9 illustrates the results of energy modelling a simple house specification using the BRE Domestic Energy Model .
*Assumes floor area 100m2, Building Regulation U-values for external surfaces, frontage 5m wide, depth 10m. Glazing of 5m2 to both front and rear (North and South).
Table 9: Annual Fuel Use (GJ/annum) for new houses according to type 
Thus a detached house built to the same specification as a terraced house may consume approximately 70% more energy. The pattern in house building appears to be towards an increasing proportion of detached dwellings. This is shown in Table 10.
Table 10: Number of different dwelling forms within the entire building stock (England) for years 1993/4 and 1995/6 
The size of dwellings will also have an impact on energy use and despite decreasing household size (table 8), their appears to be a trend towards larger dwellings as indicated by the numbers of bedrooms in newly built houses (Table 11)
Table 11: Proportion of dwellings completed in the years 1986 and 1996 according to number of bedrooms