One major consideration in our house is the level of insulation to the main roof. One superior product that is being installed in french houses is Airflex Insulation - an aluminium backed foam' geotextile insulation. However, it is not cheap and I am yet to be convinced, 100%, about is qualities and its price justification
. Leclerc have had an offer recently on a similar product, that is a lot cheaper, but because we have not used it I cannot compare.
Airflex is not cheap. 100 square metres cost 1,000 euros