Put it our loft and keeps the temperature down throughout.
It killed a few installers during our insulation blitz under Kevin07
We have not had any problems. 
No dead tradesmen in your attic? 
When we had the house completely refurbished, foil backed plasterboard was used for the upper floor ceilings and I can definitely agree it not only helps heat heat in, it also reflects roof void heat back into the roof space, thus keeping the rooms below cooler during hot weather.