My house is isolated in the attic by rockwool projected between the joists of an American frame. It is about 10 cm thick. I find that too little. So I want to go up to 20 cm. 1- Is it possible to re-project over another 10 cm, but how is it going to stand? 2- Is it possible to unroll on glass wool or rock without fire?
It is true that 10 cm is little, 30 cm would be ideal. It is possible to re-project over rockwool but with the risk of creating areas of different density. The intervention of a professional is then desirable. Woolen roll is to be avoided because thermal bridges can be created because of the difference of density of the materials and the voids which can occur between the two insulators. The ideal would be to completely remove the old insulation to start on a good basis and to choose your new insulation.
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