Wall Insulation Calculator

R-value and material from climate zone and wall assembly.

Total wall area

sq ft

IECC Climate zone

Insulation material

Cavity / insulation depth

Energy cost per therm

Tab to move between fields

Insulation R-value

10.99

Insulation material cost

$1,050.00

≈ 8 pairs of sneakers

Total wall R-value12.85

Wall U-factor0.08

Code-required R-value20

Annual wall heat loss cost$149.00

Savings vs uninsulated$522.00

Meets CodeNo

Additional Thickness2.87

How to Use This Calculator

Enter Total wall area, IECC Climate zone, and Zone 1 (very hot — Miami, Key West).
Set Zone 2 (hot — Houston, Phoenix), Zone 3 (warm — Atlanta, Dallas), and Zone 4 (mixed — Baltimore, St. Louis).
Adjust Zone 5 (cool — Chicago, Boston), Zone 6 (cold — Minneapolis, Burlington) as needed.
Review Insulation R-value and Insulation material cost ($).
Use Total wall R-value and Wall U-factor to inform your decision.

How the result changes with Cavity / insulation depth

Total wall area: Total exterior wall area (minus windows and doors).
IECC Climate zone: IECC climate zone determines code-required R-value.
Insulation material: Type of insulation to use in wall cavities or as continuous insulation.
Cavity / insulation depth: Depth of wall cavity or insulation thickness. 2×4=3.5", 2×6=5.5".
Energy cost per therm: Cost per therm of natural gas (or equivalent). US average ~$1.00-1.50.

Insulation R-value: R-value of insulation alone at specified depth.
Total wall R-value: Whole-wall R-value including air films, drywall, and sheathing.
Wall U-factor: Overall heat transfer coefficient (BTU/hr·ft²·°F). Lower = better.
Code-required R-value: IECC minimum insulation R-value for your climate zone.
Annual wall heat loss cost: Yearly heating cost attributable to heat loss through walls.
Insulation material cost: Estimated insulation material cost for the wall area.
Savings vs uninsulated: Annual heating savings compared to an uninsulated wall.

Identify Input Parameters
4 parameters
Total wall area = 1200, IECC Climate zone = 4, Insulation material = 0, Cavity / insulation depth = 3.5 = 5 input(s) provided
Calculate Insulation R-value
Insulation R-value = mat.rPerInch * cavityDepth
10.99 = 10.99
Calculate Insulation material cost
Insulation material cost = wallArea * cavityDepth * mat.costPerSqftInch
1050 = $1,050
Calculate Total wall R-value
Total wall R-value = interiorAirFilm + drywall + cavityR + sheathing + exteriorAirFilm
12.85 = 12.85
Calculate Wall U-factor
Wall U-factor = 1 / totalR
0.0778 = 0.0778