What does a Vapour barrier do?

A vapor barrier (or vapour barrier) is any material used for damp proofing, typically a plastic or foil sheet, that resists diffusion of moisture through the wall, floor, ceiling, or roof assemblies of buildings to prevent interstitial condensation and of packaging.Click to see full answer. Also question is, what is the purpose of a vapor barrier? The purpose of vapour barriers A vapour barrier is an important component in building construction. Its purpose is to help prevent water vapour from reaching building walls, ceilings, attics, crawlspaces or roofs, where it can condense and cause building materials to rot or grow mould.Subsequently, question is, do I really need a vapor barrier? The short answer is: if your wall doesn’t have a vapor retarder, there is no need to worry. Builders worry way too much about vapor diffusion and vapor retarders. It’s actually very rare for a building to have a problem caused by vapor diffusion. Similarly one may ask, where should vapor barrier be placed? In order to prevent condensation from forming, a vapor barrier should be placed on the warm side of your insulation to stop warm, moist air from condensing on a cold surface inside your wall. In cold climates like Canada, for most of the year the vapor barrier should be on the inside of the insulation.How do you fix a vapor barrier? How to Patch a Torn Basement Vapor Barrier Step 1 – Replacing the Vapor Barrier. Take the piece of vapor barrier which has been damaged and trim it away the damaged edges using the razor knife. Step 2 – Add a Layer of Mastic. Place some mastic onto a trowel and smear it into the space you have just created in the vapor barrier. Step 3 – Make the Patch.