I want to re-insulate the sub-slopes of the attic of my house frame 1976. The thickness available between rafters is very small (10 cm) and currently has old glass wool surely original that seems "stunted" and stuck to the cover (mechanical tiles). The only possible solution proposed by a craftsman is to renew this glass wool with a rock wool roll 70mm (air gap 30mm) thick for a R 1.65 m2 K / W, laying by decoiling. Indeed, for now I do not want to do anything inside and the sarking is beyond my means. The other craftsmen that I met tell me that it is useless given the little heat gain. But maybe it's time to change the old glass wool all the same? What do you think?
For converted attics, the minimum regulatory R to be implemented is R = 4m².K / W. To be eligible for the tax credit the value climbs to a minimum R = 6 m².K / W for converted attics you see that with the solution of your artisan, you are far from the account! I think you should seriously consider efficient insulation from the inside, with metal framing fixed to the rafters and plasterboard lining. It would be much cheaper than removing tiles. I invite you to consult our sheet on the reinforced insulation under framework.
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