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I would like to complete the insulation of my living room whose ceiling is under crawling roof with exposed beams 17 cm. I would like to keep the aspect at best. Currently the insulation is: under tile 7 cm of glass wool vapor barrier alu and plaster on Nergalto grid between the beams. I thought to fix 2cm battens for air vacuum then thin quality insulation, re-battens 2cm and plasterboard. Knowing that you are against this insulation, what would you propose to me?

I will certainly disappoint you by telling you that the "gas" plant that you are considering will not do much... With 7 cm of glass wool, your insulation is currently insufficient. Thin reflective products can provide additional insulation, but if placed before the fibrous insulation and not after... The creation of an air gap with a waterproof product will only create the ideal conditions for the formation of condensation. I have no other solution to offer you than to redo everything, replacing the glass wool with a composite panel of 100 mm (plasterboard and expanded or extruded polystyrene) which will leave you, air space included, 4 cm of exposed beams and will guarantee a R = 2.80 to 3 depending on the insulation.

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