If you are unclear about the building requirements, you may need to consult with other contractors in your region, or calculate your building's needs according to criteria laid out by established professional organizations. This circumstance may prevent water vapour from drying, which in turn can cause rot and mold. And, if installed in the wrong climate or on the wrong side of building materials, a vapour barrier can cause more harm than good. You may find that vapour barriers are often not required in warmer climates. In many colder North American climates, vapour barriers are a required part of building construction. Some may ask, is a vapour barrier necessary? As a builder, your first step is to consult your local and provincial/state building codes. The same is true for commercial buildings, even though the activities taking place inside may be different. This air then naturally seeks to find a way out of walls, ceilings, etc., through diffusion. The difference in vapour pressure between two sides of a building envelope assembly is the driving force behind vapour transmission.Īs the Canadian Mortgage and Housing Corporation (CMHC) points out, many everyday human activities such as laundry, cooking and bathing release water vapour into a building and increase its humidity. (Sources: Ecohome.)Īccording to sustainability expert and architect Daniel Overbey, water vapour transmission is an important but rather confusing issue. As water vapour passes through a wall, ceiling or other barrier and meets a surface that has a temperature below the dew point (when water vapour condenses), then it becomes condensation – and a threat to the integrity of your building materials. Water vapour constantly diffuses through building materials from the warm, humid interior of a house toward the cold, dry exterior. Water vapour is water in its gaseous state (instead of as a liquid or solid) and is totally invisible.
VAPOR BARRIER INSTALL
You can save yourself this costly headache by learning when, how, why and where to install a vapour barrier in your next project. 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.ĭamage from water condensation due to water vapour movement (called "water vapour drive") can wreak havoc on even the sturdiest of built structures, and threaten the effectiveness of insulation. Department of Energy.)Ī vapour barrier is an important component in building construction. In a typical commercial building or home, vapour barriers or vapour diffusion retarders can improve energy efficiency and comfort, while also preventing problems from moisture and dampness. An Introduction to Vapour Barriers and Vapour RetardersĪ vapour barrier (sometimes referred to as vapour retarder) is typically a plastic or foil sheet used for damp proofing to prevent interstitial condensation from forming in various building assemblies such as walls, roofs, foundations and floors.
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