Where does air leak in the home? Well, BPI certified professionals look to these 19 areas when spray foam insulating a home. You can save yourself loads of cash by air-sealing a house properly and actually get a much higher return on investment by foam insulating these certain leaks as opposed to just blowing a bunch of insulation on top of your ceilings and calling it a day. So where do you start?
1. Attic air sealing – Having your insulation act as a heat retainer and not as an air-stopper is the biggest key to stopping drafts and sealing a house from leaks. Sealing where the dry wall meets the top plate of the wall is the best way to do this. Any wall that meets an attic should be sealed all along the “partition”, or top, plate. Before any insulation is put on top this is an absolute must. 2. Duct Shaft/Piping Shafts and Chimney Penetrations – Any kind of duct, shaft, or cavity containing piping or wiring can leak air into insulated and uninsulated (unconditioned) spaces. Have your contractor inspect where your chimney is, as well as any electrical outlets such as recessed lights to find where to seal. 3. Attic Kneewalls – Kneewalls are the walls that square rooms off so there is a boundary between the storage space and the corners of the house. Just like partition plates, kneewalls let a ton of air through the living space and into the attic. To seal a knee wall, you must air seal the joist cavities (where the floor of the attic meets the bottom of the wall) as well as where the outside wall meets the roof line. 4. Where Stairs Meet the Wall – Caulk the board that runs up the steps on the staircase. Use caulk if the area is already painted, use tape and joint compound if the area will be painted. This area is often forgotten as a place where air moves when the stairs are being/were built. 
5. Attic Access/Pull-Down Stairs – If there isn’t a cap above your pull down stairs then you are losing lots of energy. Air leaks right through your attic cap and all the heated air you pay money for goes right into your attic. If you do get an attic cap, make sure you get one with a corresponding gasket system that keeps it tight in place. Air can still get through a cap just standing by itself. 6. Exterior Walls – Your exterior walls have a great burden in keeping your home airtight, and a large variety of things can go wrong when it comes to letting conditioned air out. All plumbing penetrations should be caulked, along with bathtubs lining exterior walls. Any exhaust fans should have caulking on the outside as well. Other than that, walls can get much more complicated with larger amounts of damage. 7. Recessed Lights – One of the biggest drawers of energy in newer homes is recessed lights. Although they look great, recessed lights have a reputation of being one of the least efficient things to put on your home. Hot air created by the light bulb creates a vacuum that sucks air right into the attic. Below is a picture of us sealing up a recessed light with a can we constructed. We seal around the can with foam insulation to give it the air-stopping power required. 
8. Fireplace Walls – Just like around staircases, using firecaulking to seal fireplace walls where they meet the interior walls is a great way to seal up your home. Especially when the fireplace is in use, the amount of air moving through those spaces is evn more so than normal, and so firecaulk is an effective method in sealing that lost air. Also make sure that your fireplace flue is closed when the fireplace is not in use. 9. Basement Rim Joists, Sill Plates, Foundation – All along the edge of where your home meets its foundation is leaking air. Sealing the rim joists (the space in between the studs on the foundation line) is one of the best ways you can avoid overall draftiness in the home. Below is a graphic detailing which part of the joist is being insulated, as circled below.
10. Windows and Doors – When windows/doors are installed in a home, the opening between the window frame and the window itself is about 1.5 inches. Lots of air moves through that space and it is important that your windows be caulked and weather stripped. If that isn’t enough, replacement windows are a great option, just make sure you have an experienced installer who insulates around that 1.5 inch space; which nowadays is filled with low expansion foam insulation.
