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I have a house whose outer walls are insulated in 40 + 10 polystyrene plasterboard. I will change my window in 2015, should I take the opportunity to redo my insulation from the inside 100 + 10. Is there a significant gain? (I live in Essonne).

It all depends on the percentage of glazed surfaces. If the house is equipped with large windows, replacing these openings with new ones will bring significant energy savings, but taking back the insulation of the walls will not bring a significant gain of insulation. If, on the contrary, the wall surfaces are the most important, increasing the thickness of insulation will be beneficial, but at the cost of heavy work, including the total renovation of the decoration. You must be aware!

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