Insulation Estimating Guide
Insulation estimating for spray foam, blown-in, batt, and rigid foam applications.
Overview
Insulation estimating is based on the area to be insulated (square feet), the desired R-value, and the insulation type best suited for the application. Spray foam offers the highest R-value per inch but costs significantly more than fiberglass batts or blown-in cellulose. Proper insulation estimates also account for air sealing, vapor barriers, and any fire-stopping or code-required thermal barriers.
Common Projects
- →Attic insulation (blown-in or batts)
- →Wall cavity insulation for new construction
- →Spray foam insulation (open-cell and closed-cell)
- →Crawlspace insulation and encapsulation
- →Rim joist and band board insulation
- →Garage and bonus room insulation
Pricing Factors
- ✓Total area to insulate in square feet
- ✓Desired R-value and local code requirements
- ✓Insulation type (spray foam, blown-in, batts, rigid)
- ✓Accessibility of installation areas
- ✓Air sealing and vapor barrier requirements
- ✓Removal of existing insulation (if contaminated or insufficient)
Materials List
- •Fiberglass batts (R-13, R-19, R-30, R-38)
- •Blown-in cellulose or fiberglass
- •Open-cell spray foam
- •Closed-cell spray foam
- •Rigid foam board (XPS, EPS, polyiso)
- •Vapor barrier and poly sheeting
- •Insulation supports and netting
Estimating Tips
- ★Always check local energy code requirements for minimum R-values in walls, ceilings, and floors before bidding.
- ★Price spray foam per board foot (one square foot at one inch thick), not per square foot, to accurately account for varying thickness requirements.
- ★Include air sealing as a separate line item — it is often required by code and adds significant energy performance value.
- ★Factor in protective equipment costs (respirators, suits) for spray foam and removal of old insulation.
- ★Account for coverage rates: fiberglass batts are straightforward, but blown-in coverage depends on settled density.
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Common questions about insulation estimating
Costs vary dramatically by type: fiberglass batts run $0.50-$1.50 per square foot installed, blown-in cellulose or fiberglass costs $1.00-$2.50 per square foot, open-cell spray foam runs $0.50-$1.00 per board foot, and closed-cell spray foam costs $1.25-$2.50 per board foot. Remember that spray foam is priced per board foot, not per square foot.
Spray foam is ideal for air sealing and moisture-prone areas like crawlspaces and rim joists, and for maximizing R-value in limited spaces. Traditional batts and blown-in insulation are more cost-effective for standard wall cavities and open attic spaces. Offer both options in your estimate and let the customer decide based on budget and performance goals.
A board foot is one square foot of coverage at one inch of thickness. To calculate board feet, multiply the area in square feet by the desired thickness in inches. For example, 1,000 square feet at 3 inches thick equals 3,000 board feet of spray foam.