Framing Roof Vapor Barrier

Class i vapor retarders i e.

Framing roof vapor barrier. Whether or not you need a vapor retarder hinges on three main factors your climate your home and the location of the wall you re insulating. We ll add a vapor barrier so the moist air does not flow up through the insulation and condense on the roof. Wind snow rain and dead ex. A vapor barrier under your slab will also protect you from harmful ground pollutants like radon gas.

It is frightening indeed that construction practices can be so dramatically. Vapor barriers are a recommendation but not a requirement by a number of roofing panel system manufacturers. To know if you need a vapor retarder ask yourself a few basic questions. A vapor barrier against the concrete surface is generally recommended before wood framing or flooring materials are installed.

Rose 1997 regales readers of this history. A roof design that includes an adhered roof membrane with multiple layers of insulation with board joints offset and staggered over a vapor retarder air barrier helps lower the risk that air and the moisture it carries will infiltrate the roof system. The history of cold climate vapor barriers itself is a story based more on personalities than physics. Crawl spaces benefit from a polyethylene moisture barrier placed directly over the exposed earth.

Hvac units roof materials etc loads to the supporting joists or purlins. Some moisture load in conditioned post frame buildings can be relieved via diffusion hence a vapor retarder in a ceiling rather than a vapor barrier through a roof assembly able to handle it example a vented attic in a moderately cold climate or mixed climate. That reduction of air and moisture infiltration can then help improve roof longevity. A vapor barrier under your concrete slab is essential for moisture prevention.

It serves as a structural member transferring the weight of both live ex. In theory if a building houses a moisture producing activity such as a kitchen or locker rooms then a vapor barrier is essential to slow moisture from escaping into the roofing system. Vapor barriers are also a cold climate artifact that have diffused into other climates more from ignorance than need. That air condenses on the cooler concrete floor.

The two main types of substrates used with metal roofing systems are open framing and solid substrates composite or plywood. Post frame buildings with metal roofs and especially buildings with minimal insulation hold warm moist air. Understand these are climate specific recommendations.