2.1 – Roof stratigraphy – 6. Controlled diffusion roof 85 VAPOR BRAKING MEMBRANE BELOW THE INSULATION A breathable membrane positioned above a breathable insulating membrane (for example in natural or mineral fibers) and a vapor braking membrane (Sd 2 meters DVA 15 g/m²/24h) positioned underneath guarantee correct passage of vapor in winter, without saturating the insulation with humidity that could condensate in low temperatures. In summer, humidity arriving from outdoors passes through the insulating membrane, drying. WITHOUT VAPOR BRAKING MEMBRANE BELOW THE INSULATING MEMBRANE Not using a vapor braking membrane or replacing it with a breathable membrane would result in better performance in summer, with greater internal “back-drying” of the humidity, but would expose the package to the serious risk of the formation of condensation in winter in the upper part (colder) of the insulation, caused by the humidity arriving from indoors. WINTER WINTER SUMMER SUMMER OK OK OK X -10 / +20 °C -10 / +20 °C +40 / +50 °C +40 / +50 °C -10 / +10 °C -10 / +10 °C +25 / +35 °C +25 / +35 °C +20 / +25 °C +20 / +25 °C +20 / +25 °C +20 / +25 °C ~ 60% U.R. ~ 80% U.R. ~ 80% U.R. ~ 60% U.R. EXCERPT
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