Framing Roof Vapor Barrier

16 gauge purlins to secure the metal roof panels.

Framing roof vapor barrier.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. 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. The purpose of vapour barriers a vapour barrier is an important component in building construction. 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.

Understand these are climate specific recommendations. In the morning when the sun comes up the steel on your roof is cool and the humidity is high. A vapor barrier against the concrete surface is generally recommended before wood framing or flooring materials are installed. The two main types of substrates used with metal roofing systems are open framing and solid substrates composite or plywood.

To know if you need a vapor retarder ask yourself a few basic questions. We ll add a vapor barrier so the moist air does not flow up through the insulation and condense on the roof. A vapor barrier under your concrete slab is essential for moisture prevention. When and where do you need them how to install them and the importanc.

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. The open frame substrate uses wood or metal framing members such as bar joists or min. Very hot and humid climates may benefit from an exterior vapor barrier that keeps outside humidity from penetrating into walls. In this episode of the build show sponsored by siga we are discussing vapor barriers.

Add a preinstalled membrane to absorb and release the condensation as it forms with the natural weather cycle traditionally we ve insulated the roof panel to try and keep the temperature on the panel from reaching the dew point. Single bubble vapor barrier has a white underside and foil on the top side that goes against the roof metal. That reduction of air and moisture infiltration can then help improve roof longevity. 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.

A vapor barrier under your slab will also protect you from harmful ground pollutants like radon gas.