What is a Vapor Barrier?
Metal roofs are notorious for the annoying drips that occur inside the building. A single bubble vapor barrier is designed to prevent such “inside rain” by keeping the metal from sweating. Unlike felt paper, which attempts to trap condensation until it can evaporate, single bubble vapor barrier prevents the metal from sweating in the first place. In addition to keeping your post frame building dry on the inside, single bubble vapor barrier also reduces the noise of rain on your metal roof and adds a small insulating value.
How Does It Work?
Single bubble vapor barrier has a white underside and foil on the top side that goes against the roof metal. In the morning when the sun comes up, the steel on your roof is cool and the humidity is high. As the sun warms the steel on the roof, the outside of the roof naturally heats up faster than the inside of the roof, creating condensation and allowing moisture into your pole building. Single bubble vapor barrier acts as a reflector. As the sun’s ray heat the steel, the heat radiates through the metal but is reflected back out of the roof by the foil side of the vapor barrier. This reflection of the heat eliminates the temperature difference that causes the metal to sweat and drip.