Converting Vented Attic To Unvented

Asked by gary lichtenstein.

Converting vented attic to unvented.

Converting an attic from vented to unvented can reduce utility costs while improving comfort indoor air quality and durability. If installing insulation above the decking remove existing roof tiles or shingles and replace weather resistant barrier if needed. 5 dumb ways to build in the south. Currently the attic is vented and has zero insulation anywhere.

I m considering converting my vented attic into a non vented conditioned space. This allows you to install your bulkheads above the ceiling plane without the need for spray foam insulation. I ve been warned that closed cell foam can lead to sheathing rot from either roof leak or vapors from the house. I live in maryland and own a house that has the hvac system in the attic.

If the insulation is only placed on the bottom of the roof deck between the rafters it must be air impermeable. An unvented attic system relies on an air seal and no vents to make the attic a conditioned space. I m unsure of what to do and i m unsure of the most. Unvented attics are not allowed by the building code yet in canada but are allowed in the international residential code in the us in section r806 which describes three different insulation strategies for unvented roofs.

An alternate to spray foam insulation in an unvented attic is plenum trusses which allow you create a reverse bulkhead above the ceiling plane that is insulated. If you convert your vented unconditioned attic to an unvented conditioned attic by installing open cell spray foam on the underside of your roof sheathing you may be surprised to discover that your attic is now the most humid room in your house. I ve been researching several methods to insulate my attic. From my research it looks like the best option is to make the attic a conditioned nonvented space.

By using an air impermeable insulation like spray foam on the roof deck will stop any air movement. Close and seal all attic vents including roof deck and soffit vents. Convert a vented attic to an unvented attic and insulate using one of the methods described in the description tab or similar.