A good way to start air sealing your home is to do a Blower Door Test, which determines the air infiltration rate of a building and the areas that leak energy can be found by holding a smoke / incense stick close to potential leak sites while the blower door test is running. In general, door frames and window frames leak energy like sieves so starting there can give most bang for the buck, so to speak. Most building contractors like to use fiberglass for air-sealing, DO NOT do this, fiberglass doesn’t do anything in terms of air-sealing. Instead use a mix of spray foam and caulking.
Next seal your rim joists (where your concrete foundation meets the wood frame of the house) by spray foaming these gaps. Modern construction technique place a thin compressable membrane there, which is enough to keep the joints sealed, but if your house has an older construction, you may need to find these gaps and fill them yourself.
Here are some examples of where we have air-sealed – that can still be seen! Most stuff is hidden behind trims.
