Attic Air Sealing & Insulation in Duluth, MN

Attic air sealing and insulation is the most common job we do in Duluth, because the attic is where an old house loses the most heat. Warm air rises and slips through every opening in the top-floor ceiling: around plumbing stacks, chimneys, light fixtures, wiring holes, the attic hatch and the top plates of interior walls. In the attic it warms the underside of the roof, melts snow, and the water refreezes at the cold eaves. That is an ice dam. The same moist air also condenses and freezes on roofing nails and sheathing, and drips when it thaws.

Sealing comes before insulation

Piling more insulation on an unsealed ceiling helps less than people expect, because air moves right through loose fill and batts. We seal the openings first with foam, caulk and rigid board, weatherstrip and insulate the hatch, and make sure bath fans vent outdoors. Then we add insulation to depth.

How much is enough

St. Louis County is in Climate Zone 7. The 2012 IECC prescriptive table lists R-49 for ceilings in that zone, and the U.S. Department of Energy suggests R-60 for an uninsulated attic in Zone 7. With blown fiberglass at roughly R-2.2 to R-2.9 per inch and cellulose at R-3.1 to R-3.8 (HomeGuide), that means well over a foot of loose fill. Foam on the attic floor is an option for tight spots, but on an open attic, blown-in is usually the better value.

Ventilation stays open

An attic in Duluth should stay cold and dry. Before we blow insulation toward the eaves, we install baffles so the soffit vents keep feeding air into the attic. Covering the soffits is a common mistake that leads to frost and mold.

Things we look for first

Water stains on the sheathing, frost or rust on nails, mold, rodent nests, knob-and-tube wiring and vermiculite. Some of these need to be fixed or tested before new insulation goes in, and we will tell you which.