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.
Air barrier attic.
Whether using loose fill or batts put the vapor barrier closest to the warm side of your installation where hot moist air would get in facing the house s interior in cold climates beneath floor insulation and the attic s interior in hot climates on top of floor insulation.
Attic access except unvented attic knee wall door or drop down stair is sealed.
Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case.
Ideally no services such as hvac distribution ducts air handlers plumbing or fire sprinkler systems should be located external to the air barrier.
Recessed light fixtures penetrating the thermal envelope are air tight ic rated and sealed to drywall.
This acts as a barrier to keep heated moist air from rising up into the attic during cold weather.
In addition ideally all water vapor would be managed with mechanical systems.
I put this in the air gap between my roof decking and new metal roof.
Therefore an air barrier at the ceiling line such as sealed gypsum board should be present to isolate the attic space from the conditioned space.
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.
A proper air barrier reduces heat loss in winter overheating in summer and prevents moisture build up in walls which can lead to mould.
The key to this discussion is understanding the movement of air and water vapor.
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My ac run time is significantly lower now dennis in tx.
Some regions don t require a vapor barrier.
I never dreamed that it would make such a difference in the attic temperature.
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Air barrier in any dropped ceiling soffit is substantially aligned with insulation and any gaps are sealed.
Air water vapor movement.