Spray Foam Insulation in Duluth, MN

Spray foam insulation in Duluth has a hard job. The city's 1991-2020 climate normals list a January daily mean of 11.2F, an average January low of 2.4F and about 90 inches of snow a year, and Minnesota's residential energy rule sizes heating systems here for a winter design temperature of -20F. A house that leaks air through the attic, the rim joist and old wall cavities pays for it every month from October to April. We seal those leaks and insulate them with closed-cell or open-cell foam, blown-in cellulose or fiberglass, or a mix, depending on what each part of the house needs.

Old houses, new problems

Duluth grew fast in the late 1800s and early 1900s, and much of what was built then is still standing. The city's housing market analysis reports roughly 44 percent of its homes were built before 1940. Many have stone or block foundations, rim joists with nothing on them and attics insulated decades ago, if at all. Those houses leak heat in ways a new house does not, and the fixes are specific: foam on the rim, air sealing in the attic, and dense-packed walls where there is nothing in the cavities.

Closed cell vs open cell

Closed-cell foam is dense, rated about R-5 to R-7 per inch in HomeGuide's figures, and slows water vapor at typical thickness. It is the usual choice on rim joists, basement walls, crawl space walls and steel buildings. Open-cell foam is softer, about R-3.5 to R-3.7 per inch, and costs less per square foot. It seals air well and fits interior walls and some roof decks, but in a Climate Zone 7 roof assembly it needs the right vapor control. We tell you which one we would use where, and why.

Spray foam insulation cost

HomeGuide's 2026 guide puts installed spray foam at $1.50 to $5.00 per square foot, with open cell at $1.50 to $3.50 and closed cell at $3.00 to $5.00. Fixr lists $3.15 to $7.50 per square foot for existing walls. Small jobs often run into a minimum of $1,000 to $2,000 or more. Those are national numbers; ours comes after we have measured, and the written quote is what you pay.

Choosing among insulation contractors

When you compare spray foam insulation contractors or insulation companies in the Twin Ports, ask each one the same questions. Which foam will you use on each surface, and how thick? What R-value will each area reach? Will you seal the attic before adding insulation? How will you handle the rim joist? Is removal of old material included? A quote that answers those in writing is easier to compare than a single number.

If you searched for spray foam insulation near me and landed here, we work across Duluth, Superior, Hermantown, Proctor, Cloquet and up the shore to Two Harbors. Get a free estimate

We cover Duluth and Superior plus the towns around the head of the lake: Hermantown, Proctor and Rice Lake on the hill above the city; Cloquet, Scanlon, Esko, Carlton and Wrenshall along the St. Louis River in Carlton County; and Knife River and Two Harbors up the North Shore. Duluth's hillside neighborhoods have the oldest housing. Hermantown and Rice Lake have more ranch homes and split-levels from recent decades on bigger lots, often with a shop out back. Cloquet was largely rebuilt after the 1918 fire. The shore towns sit right on Lake Superior. Each place has its own mix of houses, and we plan the work around it.