Air sealing and insulation get sold as one thing, and they are not. Insulation slows heat moving through solid material. Air sealing closes the paths that let air move between your house and the spaces around it. Neither does the other's job, and a house can easily have plenty of the first and almost none of the second, and there is no way to tell which from a chair in the living room.
Order matters more here than anywhere else in this trade. Once new insulation is spread across an attic floor, getting back to the openings underneath means moving material you just paid for. That is why a contractor who knows the work wants sealing done before insulation goes down, and why it should show up on your bid as its own line rather than as an assumption.
Air sealing is priced on how many openings there are and how hard they are to reach, not on square footage the way insulation is. A house with an open, walkable attic and a handful of penetrations is a completely different job from one with low clearance, finished bonus rooms, dropped soffits, and thirty can lights. Whether old insulation has to be pulled back or removed to reach the ceiling plane matters too, as does how much of the work sits in a crawl space. Ask for sealing quoted as its own line so you can see what you are buying and compare bids honestly.
You can, and the result is usually partial. Air moving through unsealed openings carries heat past insulation rather than through it, so the new material never performs the way it was supposed to. You also make the sealing harder to do later, because reaching those openings then means moving everything you just installed.
Drafts near baseboards and outlets, dust streaks around ceiling fixtures, rooms that lose temperature quickly once the system stops, and an attic that smells like the house are all hints. None of them are proof on their own, which is why somebody should look at the attic and basement rather than guess from inside the rooms.
Related, but much smaller in scale. Weatherstripping addresses the openings you use every day. Air sealing in this trade is mostly about the ceiling plane and the band at the foundation, where air moves vertically through the house. Those paths are larger, which is why attic and crawl space work comes first.
Tight houses need attention to ventilation, and that is a real consideration and a reason to work with a contractor who thinks about the house as a whole. It is not a reason to leave large attic openings unsealed. Ask how ventilation is being handled rather than treating leakage as a substitute for it.
The attic is where most of your heat goes, which is why it is usually the first place a contractor looks. Older Utah homes often have coverage that has settled, thinned near the edges, or been pushed aside by past work.
Learn more →The band where your floor framing meets the foundation gets skipped more often than any other part of the house. If your floors never feel warm and the furnace seems fine, this is worth having somebody crawl under and look at.
Learn more →Walls are closed assemblies, so the question is how a contractor gets material into them and whether the cavity can take it. Blown-in, batt, and foam each suit different framing, and foam is not automatically the better one.
Learn more →Sometimes the old material has to come out first. Rodent damage, water staining from a roof leak, and smoke contamination are all reasons adding new insulation on top would bury a problem instead of solving it.
Learn more →Cold rooms, drafts, ice at the eaves, or an attic you have never been in. Any of it is a place to start.