Those in glass houses . . .

FOR READERS who wrote asking whether the new Channel 4 building designed by the Richard Rogers Partnership was energy efficient - so much glass, presumably so much wasted energy - here is the answer.

The architects found that C 4's old building used twice as much energy as a normal office: heat generated by electrical equipment caused C 4 to spend more on cooling than heating. The extensive glass walls of its new building allow it to cool with minimal use of energy. A solar mesh protects the walls from heat and glare, allaying the solar gain associated with thoughtlessly designed glass buildings.

C 4's air conditioning system can recover all the heat it generates, while the amount of fresh air pumped through is regulated automatically by the number of people in the building at any one time, outside temperature and humidity. The result is that C 4 will save up to 50 per cent on energy bills.

It is no longer possible to judge the energy efficiency of a building solely on the way it looks.