No way I'd use fibre glass in the roof space, Suzanne. There are a lot of better and more ecological solutions. We opted for "ouate de cellulose" http://fr.wikipedia.org/wiki/Ouate_de_cellulose (sorry, don't know the correct English term). It's basically recycled newsprint mixed with a fire-proofing and an anti-mould additives. Ours was blown in as a loose product which gets into every nook and cranny but I gather it also exists in sheet form which might suit you better if you plan to convert part of the attic. It has the added advantage of being disagreeable to four-legged furry creatures that used to nest in the fibre glass! It made a huge difference to the warmth of our house and the heating bill!