Best Vapor Barrier For Metal Roof

We ll add a vapor barrier so the moist air does not flow up through the insulation and condense on the roof.

Best vapor barrier for metal roof.

The problem with using. Fiberglass batts or glass mineral wool metal roof insulation the most common material used for an insulating metal roof is fiberglass batts or glass mineral wool. Most roofing membranes as well as a single layer self adhered bituminous sheets are class i vapor retarders. Will kraft faced 4 fiberglass insulation installed from the inside between the 5 1 2 wide trusses 12 on center be sufficient to inhibit condensation on the back of the metal roofing.

You ll also need to make sure there s good ventilation to allow for proper airflow. A roof vapor barrier needs to have different properties to a barrier in a wall or one used to prevent radon permeating through a floor. To prevent too much condensation from forming under your metal roof it s best. However if a class i vapor retarder is used there is concern that any moisture e g construction moisture due to installation methods bulk water from weather etc that enters a roof system won t be able to dry out.

Traditionally we ve insulated the roof panel to try and keep the temperature on the panel from reaching the dew point. Architectural metal roofs with felt underlayment are best suited for buildings with proper slope and low moisture loads in dry or arid climates. The batts are located side to side on the rafter of the roof. Both materials make a great physical barrier between the interior building and the metal roof.

Felt underlayment provides little resistance to air and moisture vapor migration and does not serve as an effective air barrier. Do you need a vapor barrier under a metal roof. If a vapor barrier is installed correctly over the purlins no holes or seams can be present which covers all possibilities of climbing the roof via the purlin footholds. But a preinstalled membrane may be even more effective at removing condensation.