Attic Air-Sealing & Insulation in Missoula, MT

Adding more blown-in on top of an under-insulated attic is the usual reflex, but if nobody ever sealed the ceiling plane underneath it, heated indoor air just keeps escaping upward — through top plates, wiring and plumbing penetrations, the attic hatch, and dropped-soffit chases — no matter how deep the pile gets. That lost heat warms the roof deck unevenly, melts the snowpack, and refreezes it at the cold eaves — the ice dams that show up on older Missoula bungalows and Rattlesnake-area homes after a wet snow.

We close up that ceiling plane before anything else, then build the attic to Montana's Zone 6 code target — an assembly landing in the R-49-to-R-60 band under the 2021 IECC the state builds to, with R-49 accepted over a raised-heel truss that keeps full depth out over the wall plates. Sealing the plane is also what lets a house actually hit the 4-air-changes-per-hour blower-door threshold the code calls for in this zone, and it's the single biggest lever on a January heating bill in an inversion valley where the furnace runs close to five months.