Insulation R-Value Guide Calculator

Look up the recommended insulation R-value for your climate zone and building element per IRC/IECC code, then compare the cost of fiberglass batt, blown cellulose, and closed-cell spray foam to close the gap.

Insulation R-Value Guide

Climate Zone (IRC/IECC)

Building Element

Area to Insulate (sq ft)

Current R-Value

Pricing (edit to match local rates)

Fiberglass ($/roll)

Cellulose ($/bag)

Spray Foam ($/board ft)

Recommended R-Value

R-49

Zone 4 / Attic/Ceiling

R-Value Gap

R-49

Current R-0 needs +49

Cheapest Option

Fiberglass Batt

$660.00

Insulation Type	Material Needed	Estimated Cost
Fiberglass BattBest value	12 rolls/packs (15.3" thick)	$660.00
Blown Cellulose	95 bags (14.0" thick)	$3,325.00
Spray Foam (Closed-Cell)	7539 board feet (7.5" thick)	$11,307.69

Best value: Fiberglass Batt at $660.00For Zone 4 attic/ceiling insulation, the IRC/IECC recommends R-49. Fiberglass Batt is the most cost-effective option to close the R-49 gap at approximately 15.3 inches thick.

High R-Value GapWith an R-49 gap, you may need multiple layers of fiberglass batts. Consider blown cellulose or spray foam for high R-value applications, as they fill irregular cavities more completely and reduce thermal bridging.

R-value recommendations are based on IRC/IECC residential code minimums. Actual requirements may vary by local jurisdiction. Material costs are estimates and do not include labor. Consult a local insulation contractor for precise pricing and installation requirements.