Here we used spray foam and foam board to air seal an attic. Sealing the gaps that leak conditioned air into the attic, which is essentially outdoors, can drastically reduce a house’s overall air leakage.
Sealing is the necessary first step before re-insulating, because insulation does nothing to stop air leakage, and it works far worse when air moves through it. Once the sealing is done, we blow a thick layer of cellulose over the attic floor to meet the most stringent energy targets.
In deep energy upgrades we often cut air leakage by 50% and triple the insulation value.
