Whilst the principle of using thermal imaging to identify houses (or parts thereof) that are leaking increasingly precious energy out into the world at large is to be praised, its use to sell plastic windows is perhaps questionable. Looking at the images of my own house, and indeed those of my neighbours, the shock of glowing thermal radiation seemingly pouring out is almost enough to make one send for the salesmen.

However, interleaved amongst these horrors, there are images of the even numbered houses on the other side of the street. These present an almost uniformly dark picture of good buildings letting little out. On realising that the street runs east-west, that my house faces south and that these' cool' buildings face north, the true picture emerges. It would appear that the company responsible took the thermal images on a bright sunny day, which is far from ideal. In such conditions north facing buildings will appear thermally cool in their perpetual shade, whilst those like mine are in fact showing the effects of thermal warming. The brickwork is bathing in the sunshine and solar gain through the windows is creating warm rooms in behind, all leading to the glowing report given in the pictures.

After such a day of sunshine, simply closing the thick curtains to retain heat is probably far more effective and certainly cheaper than installing double glazing. In fact if the truth is known, approximately 20% of an average house's energy is lost through single glazing and upgrading it to double provides a potential 1 0% saving in your energy bills. But considering the cost of double glazing this makes for a very long payback period.

A cheaper and much more efficient energy saving measure, applicable to many but not all houses, is a gable warmer, which can save 20% off your bills. All being well, I will present one such as a pioneering example in the next issue.

PATRICK TAYLOR, Conservation Architect