Why energy use is increasing in buildings in the UK

There are many reasons for the increasing use of energy in buildings, some of the most significant of these being lifestyle changes such as more people living singly, more electrical appliances and more sedentary occupations leading to greater building occupancy. There is also the important factor of greater wealth and low energy costs.

It appears that the largest proportion of energy use is still in the space heating of buildings, and that this is not diminishing as projected by government, even in relatively new buildings. The most important reason for this is the almost complete disjunction between theory and practice, or building designed performance and actual performance in the UK.

This is partly because there is almost no proper research in this subject and no monitoring of actual building performance. The theoretical projections of energy use and savings through new measures are simply paper exercises, and each new exercise compounds the fantasies and mistakes of the previous one. However from the small amount of research and monitoring that has been undertaken we can fairly clearly identify the areas where the disjunction has the greatest effect:

U Value calculations

U Values are the way that the insulation value of a building element (wall, roof, floor) is calculated. From this it should be possible to project the actual energy use of a building in practice. Unfortunately the way that most U Value calculations have been made till recently bears almost no relation to the form of the building, even in design terms.

The most important difference is that most U Values are based on only one square metre of wall/ roof/ floor etc, in an idealised situation (ie without openings, corners, plinths, eaves, verges etc etc). As such the amount of cold bridging built into the design is far less than it would be on average for the walls of the whole house. According to work done by David Olivier this can mean that both timber and masonry constructions can be over 50% worse in reality in design terms than those which are being claimed:

A timber frame with a supposed designed wall U Value of 0.35W/m2K will have a real designed U value, when all the coldbridging from the studwork is taken into account, of around 0.55W/m2K, only just better than the first Building Regs standards of 1976.

I myself have seen calculations done by commercial insulation companies for timber frame structures which showed U values of 0.20W/m2K, and which had not taken any coldbridging of the timber frame into account at all. In fact if the thermal bridges had been realistically taken into account this “superinsulated” design would probably have failed to meet the minimum building regulations requirement of 0.35W/m2K.

This issue is now being addressed by new Part L (2006) Building Regulations. It still remains to be seen however whether or not realistic calculations are made.