Condensation occurs when water vapour that has been rising through a home or building comes in contact with the cold air outside. Metal roofs, unlike conventional roofs, generally do not have to be replaced every 10 to 12 years, but they are still susceptible to condensation. Fortunately, there are a few things you can do to prevent metal roof condensation.
Install a vapour retarder on the attic side of the ceiling board. The ideal vapour retarder is a thin, flexible membrane that has a perm rating of .5 or less. Common vapour retarders that meet this requirement include polythene film that's 4 to 6mm thick, asphalt-coated papers, laminated papers and kraft-backed aluminium foil.
Install eave, gable, turbine, roof or continuous ridge vents in your attic. For proper ventilation, attics require 1 square foot of unobstructed ventilation area for each 150 square feet of attic area.
Circulate the air. Air circulation in your home and attic is essential to preventing condensation on your roof. One of the most effective ways to improve circulation is to run an attic fan. Fans are distinguished by the cubic feet of air, or cfm, they move per minute. To determine the minimum cfm necessary for your attic, multiply the total cubic feet of the attic by 7 and divide that number by 60.
Run a dehumidifier. Dehumidifiers are designed to remove moisture from the air. By running a dehumidifier, you can help prevent moisture from rising in your home and condensing on your roof. Many dehumidifiers come with a relative humidity gauge. The Environmental Protection Agency recommends keeping the relative humidity in your home between 30 and 50 per cent.