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Insulating and Air-Sealing Around Exhaust Vent Pipe in Conditioned Attic

justinlacy | Posted in General Questions on

New build, zone 2A. Conditioned/unvented attic…

Roof design is a standard gable-end roof that extends (on one of the “non-gable side”) over a covered porch. The porch will have a built-in grill with a vent hood above it. The vent hood won’t have a cabinet around it, i.e., it will be the kind that everything shows between the bottom of the hood and where it penetrates the ceiling. That means the outdoor vent hood’s exhaust pipe will run thru the conditioned attic to exit out the roof. There will probably be about six feet of vent pipe in the conditioned attic (between porch ceiling and roof above).

Should I do anything for the vent pipe in the attic? For example, should I put a plywood box around it in the attic, then seal and insulate the box so that the vent pipe is isolated from the conditioned attic? Or should I seal and insulate around the pipe in the attic where it enters and exits? Any other ideas?


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  1. charlie_sullivan | | #1

    My first thought is to put an insulated wall in the attic between the part of the attic that is above conditioned space and the part that's over the porch, and don't condition the part that's above the porch. That will require less insulation and have less heat load because of the reduced area you are insulating. Is there are reason not to do that?

  2. justinlacy | | #2

    A large part of the HVAC ductwork is in that area of the conditioned attic.

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