Converting Vented Attic To Unvented

Should i use open cell or closed cell foam to insulate.

Converting vented attic to unvented.

I m unsure of what to do and i m unsure of the most. I ve been researching several methods to insulate my attic. Convert a vented attic to an unvented attic and insulate using one of the methods described in the description tab or similar. If installing insulation above the decking remove existing roof tiles or shingles and replace weather resistant barrier if needed.

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. Watch this if you ve not seen it. Currently the attic is vented and has zero insulation anywhere. If the insulation is only placed on the bottom of the roof deck between the rafters it must be air impermeable.

5 dumb ways to build in the south. I m converting my attic into a non vented conditioned space. Asked by gary lichtenstein. 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.

I ve been warned that closed cell foam can lead to sheathing rot from either roof leak or vapors from the house. I m considering converting my vented attic into a non vented conditioned space. An unvented attic system relies on an air seal and no vents to make the attic a conditioned space. Converting an attic from vented to unvented can reduce utility costs while improving comfort indoor air quality and durability.

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. Close and seal all attic vents including roof deck and soffit vents. I live in maryland and own a house that has the hvac system in the attic.