I completed a job yesterday which I had been putting off for some time due to the unpleasantness of working in the loft during this current heat wave. The job was a partial re-wire of the lighting circuit which was a strange one to me as it involved the mains feed looped through each wall switch usi ng a red and green striped cable carrying a single red live and an earth. T he neutral was a single strand wire which did not always follow the same ro ute as the live all this buried under 270mm of insulation. So I went for a more common wiring system looping through junction boxes teeing off to the switches and light fittings as required and all this wiring was routed over the top of the insulation. What I did note after doing the first fix routi ng all the cables was just how warm these cables became after a day of the sun beating down on the roof. Myself I found I could not work for more than 20 mins. at a time, no idea what the temp. was up there but I felt I lost a few kilos of sweat. It occurred to me taking de-rating into consideration that the cables now above the insulation were subject to more heating than laid below, therefore should I have used heavier gauge than the 1.5mm sq., the house is a bungalow with the main lighting circuit feed being no more than about 20m when it is all replaced.
Richard