The tech tip today is a video put out by my friend Brad Hicks from the HVAC in SC YouTube Channel. Thanks Brad!
Ok, so this has nothing to do with raccoons but I like that photo.
Whenever you are installing duct boxes (also called boots or cans) in an aftermarket application, make sure to place a bead of sealant like mastic or silicone on the flange so that as it presses against the substrate it will seal against leaks to and from the unconditioned space. When installing in a new construction environment where the boxes / boots / cans go in before the substrate you will either want to use boots that already have gaskets or you will want to add a gasket to the flange such as foam tape. In these cases, it is still a good idea to seal the edge further from the inside once the drywall (or similar) is in place and before the grilles and registers are installed.