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.
Attic air barrier.
A radiant barrier can lower heat transfer from attics to the building below keep the attic space cooler and lower cooling costs by up to 17 in warmer climates.
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.
The reduced heat gain may even allow for a smaller air conditioning system.
Some regions don t require a vapor barrier.
Some studies show that radiant barriers can reduce cooling costs 5 to 10 when used in a warm sunny climate.
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.