To convert a house to spray foam insulation, you can expect to pay $7,000-$14,000 per 1,000 sq ft of attic. If you’re to narrow down the different parts of the home, the average costs could differ significantly. As of late 2021 with massive manufacturer price increases, for closed-cell foam, you can between $1.90 to $2.70 and $0.54 to $0.75 per board form for open-cell foam.