![]() In both cases, the vapour barrier is tasked with preventing warm, humid air from shedding its moisture as it meets a cool surface, no matter which direction it is travelling. for example, it should be installed on the outside of the insulation. In cold climates like Canada, for most of the year the vapour barrier should be on the inside of the insulation. In order to prevent condensation from forming, a vapour 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. This can be a problem if it happens inside your walls, so vapour barriers are there to mitigate that. The vast majority of Americans & Canadians live in a temperate climate, so for most of us a vapour barrier (or more accurately semi-permeable vapor retarder) that allows a certain amount of water vapour to pass through a wall could actually serve us better over the course of the year.Īs warm, humid air cools, air molecules shrink and squeeze out the moisture. #CANARI BARRIER PANT INSTALL#Is the solution then to not install a vapour barrier? No, but since there isn't a perfect solution that meets the needs of both climatic extremes, we should find a solution that at least takes them both into account. During those 30+° Celsius days with relative humidity levels upwards of 80% and an indoor air-conditioned environment some 10 degrees cooler, that vapour barrier is on the wrong side. In areas like that, the vapour barrier that works great in February isn't doing you any favours in July. Many parts of the country can range from extreme cold to extreme heat and humidity, with temperatures that vary as much as 60 degrees Celsius or more. The automatic installation of a polyethylene vapour barrier in every home from the Hudson Bay to the vineyards of Southern Ontario to the deserts of Arizona meets the state & provincial building codes, but completely ignores the reality of how different those climates are. The USA & Canada has many climatic zones, so there is not one building envelope that can possibly serve them all. Joe Lstiburek, Principal of Building Science Corporation It's time that the cult deprogramming started." This cult is responsible for many more building failures than building successes. This cult views the answer to all moisture problems as the installation of a polyethylene vapor barrier on the inside of buildings. "One of the problems in the building industry is that we have a spreading 'cult-like' mentality that worships at the 'church of polyethylene'. Despite it being used extensively in residential construction, it can be overkill in most Canadian homes, and can cause problems of its own. This is an ideal building practice in the extreme northern communities of Canada, less so as you come further south. The traditional approach to preventing water vapor from penetrating walls in homes is a 6 mil polyethylene vapour barrier, or 'vapor barrier' for our southern neighbours. An understanding of how water vapor moves through walls is important, so a good place to start would be with our page explaining moisture movement in homes (see related articles below). It would probably surprise many home builders to hear what really causes moisture accumulation in walls, and what to do to prevent it. Vapor Barriers in walls, why polyethylene can be problematic ![]()
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