Green Building How To Build A Conditioned Attic

An unvented attic assembly a k a.

Green building how to build a conditioned attic.

That decision he writes has added a whole new level of complexity to his building process. The thermal boundary can be at the ceiling plane leaving the attic space above uninsulated and vented or the thermal boundary can be located at the roof line creating a sealed insulated conditioned or semi conditioned attic space. Department of energy through the building america program to research conditioned attics in nevada and texas. In a roof attic assembly the builder has two choices.

After experimenting with cellulose insulated roof assemblies and fiberglass insulated roof assemblies lstiburek began promoting conditioned attics insulated with open cell spray foam especially in. Code requirements vary across the country. My original plan was to build a conditioned attic and place 1 5 of foam xps board r7 5 installation on top of the roof deck and fill the old true 2x4 rafters and rafter walls with closed cell insulation and if able attach 3 of foam xps board r15 to the rafters in the attic. You can reduce dust buildup using an unvented attic versus a vented attic.

In an unvented attic assembly air impermeable insulation is applied directly to the underside of the structural roof deck and is tied into the insulation located in the walls so that the roof system becomes part of the insulated building enclosure. The attic space becomes indirectly conditioned as a result of the air leakage heat transfer and. During the 1990s the building science corporation received funding from the u s. Compact assembly or hot roof ventilated roof assembly you can insulate the rafter space provided that you leave a ventilation space between the top of the insulation typically fiberglass batts or blown cellulose and the underside of the roof sheathing section r806 1 ventilation required.

This has several advantages including less air transfer and what air does transfer is conditioned. The acceptance of unvented conditioned attics continues to grow among builders and building officials. One of them is what to do about the attic. The irc has permitted unvented conditioned attics since 2006 with certain requirements.