Spray Foam Insulation Under Metal Roof Without Air Space Good

The biggest benefit of spray foam insulation is its air sealing quality so if air is infiltrating into a spray foam attic then the installers missed some spots and need to go back and make it right.

Spray foam insulation under metal roof without air space good.

In the knee wall area the insulation is in the floor and on the. Even small gaps can allow the passage of warm air through the foam rendering the foam all but useless as an insulator. You just need to make sure that you put in enough insulation to keep the sheathing above dew point temperature in the cold months. An unvented attic air sealed with spray foam insulation limits outdoor air entry and as a result indoor combustion air should not be considered available for fuel fired combustion appliances located within the attic space.

To get the best performance out of spray foam insulation you must cover the roof rafters and surrounding areas as thoroughly as possible. Cut and insert 1 or thicker high r foam insulation sheets r 8 per inch against the furring giving a 1 or greater air path between the insulation and the roof deck under the cathedral ceiling. The building envelope should completely surround the conditioned space and the insulation needs to be in contact with the air barrier. They are not susceptible to moisture infiltration and will keep the roof dry even without a good ventilation system.

Moisture from the house picture this. A roof breathes without spray on foam insulation to some extent and it also allows you to see where any dampness is coming in and repair it in this area. You take a shower but forget to turn the bath fan on. Nail 1 furring along every rafter side against the roof deck.

For best protection professional contractors recommend at least 6 inches of foam insulation board.