Air Barrier In The Attic

Ideally no services such as hvac distribution ducts air handlers plumbing or fire sprinkler systems should be located external to the air barrier figure 3.

Air barrier in the attic.

The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below. Hey i ve bashed fiberglass here in this blog. It is important to choose an air barrier and insulation material that will reduce the air leakage and heat loss as much as possible. Exterior air barriers control infiltration of exterior air into the wall cavity and through the attic limit the ability of moist outdoor air to enter the wall cavity during the cooling season and prevent wind washing of wall insulation i e even though a house tests tight on the interior it could have a leaky exterior wall and top plate that cause big energy losses.

This acts as a barrier to keep heated moist air from rising up into the attic during cold weather. Just because a failure in the air control layer air barrier shows up in the heat control layer insulation doesn t mean it s the fault of the insulation. Properly sealing and insulating attic knee walls can significantly reduce air leakage and heat loss between the conditioned space and the unfinished attic. Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers.

A good building will have control layers that control the flows of heat air and moisture. Radiant barriers are more effective in hot climates than in cool climates especially when cooling air ducts are located in the attic. Some studies show that radiant barriers can reduce cooling costs 5 to 10 when used in a warm sunny climate. Attics heat up when the sun s radiant energy heats the shingles and the heat is transferred to the interior attic space through the roofing materials via conduction.

Gaps in the attic or between the lower floors and the attic will let heated or cooled air escape to the great unconditioned outdoors making any insulation you add essentially useless. Radiant barriers are utilized to reduce summer heat gain in attics. Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case. The best approach for a vented attic in a cold climate is installing a layer of drywall with a good coat of latex paint the paint creates a semi permeable vapor barrier.