Change A Vented Attic To An Unvented One

I live in maryland and own a house that has the hvac system in the attic.

Change a vented attic to an unvented one. Currently the attic is vented and has zero insulation anywhere. Your stated goal is to turn your attic into a non vented conditioned space. A vented attic system refers specifically to having working vents in the attic. Install insulation along the underside of the roof deck of an unvented attic rather than on the ceiling deck of a vented attic for either of two reasons.

Let s dive a little deeper into what that means exactly. In colder climates the main purpose of a vented roof is to keep the roof cold and reduce the formation of ice dams. I m unsure of what to do and i m unsure of the most. And i mean completely intact.

All openings that exist to ventilate the attic including ridge vents gable vents and soffit vents shall be closed off and sealed and new roofing installed as needed. However you do not describe the potential uses for that space and that gives me pause as to how to properly evaluate the risks of your options. An unvented attic is one which is not ventilated and this is important one where the ceiling has complete air vapor and thermal controls in place. The attic space becomes indirectly conditioned as a result of the air leakage heat transfer and vapor diffusion through the ceiling.

A secondary goal is to vent moisture that infiltrates the attic from the conditioned home. When insulating your attic the contractor can either spray the attic floor to keep a vented attic or spray the roof deck for an unvented system. An unvented attics is one where the air vapor and thermal controls are installed at the roof deck. To provide an unvented conditioned space for locating hvac equipment in the attic and or to provide a continuous thermal barrier for designs that have complex coffered ceiling planes and or numerous penetrations for lights speakers vents soffits etc which make it difficult to achieve an airtight ceiling plane.

If you planned to leave the open cell foam exposed to the attic it would certainly dry to the inside much more easily. If there is a vapor retarder on the attic floor it shall be removed to allow any moisture that builds up in an unvented attic to diffuse into the house below. A fundamental requirement of an unvented attic assembly is the use of air impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic.