November 2011: Fixing and Repairing Return Ductwork
Fixing and Repairing Return Ductwork
Return ducts in garage ceilings can often be the most problematic. Determining which floor cavities are being used and which direction the return air pathway is taking is critical. The easiest way to determine this is to go to the conditioned space, remove the register in the floor or wall and drill down along the joists. Then inserting a wire or hanger will define the cavity below. Now, one can install a bulkhead to the backside when the main trunk is located (a 2”-3” slot allows for dense pack cellulose and insertion of blocking should access be limited from above.
In some situations, wall cavities can be planned for returns or are being used as existing return pathways. One needs to insure that these runs are not packed with cellulose. Identifying and marking them on the exterior beforehand is necessary to NOT having to vacuum them out later. Any adjoining floor cavities that feed into the vertical runs should be checked and blocked also. Additionally, wall cavities that extend over a planned return chase should be sealed on top whether it is a one or two story structure.
Big gaps sometimes can often be found over the top of panned areas where transitions occur usually in basements. Sometimes the panned area can drop down 1”- 2” in the center. If hard to access, one can cut a piece of one inch RFI a little longer than the panned area, load up the two critical sides with Mastic and slide it into place after most of the surfaces have first been cleaned of dust. Where large expanses of returns need to be insulated (returns that terminate on an exterior wall in the rim joist) they should always be finished with an inert material like reflect a foil and sealed into place with mastic.