What R-value do I need for my attic?

The DOE recommends R-30 to R-60 for attics in most climate zones. Homes in colder regions (Zones 5-7) should have R-49 to R-60. Southern homes (Zones 1-2) can use R-30. Check your local building code for exact requirements.

How many bags of blown-in insulation do I need?

For 1,000 sq ft of attic space at R-38 using cellulose blown-in insulation, you need approximately 38 bags (each covering about 27 sq ft at R-38). Use our calculator above with your exact measurements and desired R-value.

Insulation Calculator — Batts & R-Value Guide

Calculate batt or blown-in insulation for walls, attics, and floors. Free, accurate estimates.

How to Use This Insulation Calculator

Choose batt/roll or blown-in insulation. Enter your area in square feet. For batts, select the R-value for your application — R-13 for 2×4 walls, R-19 for 2×6 walls, R-30 for attics, R-38 for cold-climate attics. For blown-in, pick your target R-value and material type. The calculator shows units needed and recommended depth.

Insulation Guide: Choosing the Right R-Value and Type

Proper insulation is the single best investment you can make in home energy efficiency. The Department of Energy estimates that 90% of homes in the US are under-insulated. Here's what you need to know to get it right.

R-Value by Location

Attic: R-30 to R-60. The attic is where most heat escapes — it's the most important place to insulate well.
2×4 Walls: R-13 to R-15 (the cavity only fits 3.5 inches). Consider rigid foam sheathing on the exterior for additional R-value.
2×6 Walls: R-19 to R-21.
Floors over unheated space: R-19 to R-30.
Basement/crawlspace walls: R-10 to R-19 (use rigid foam board — fiberglass batts can trap moisture here).

Batts vs Blown-In

Batts are ideal for open walls during new construction and accessible attics with standard joist spacing. They're DIY-friendly and cost $0.30-0.50 per sq ft. Blown-in is better for existing attics with irregular joist spacing, around obstructions, and for topping up existing insulation. It fills gaps more completely than batts but requires a blowing machine (free rental with purchase at most home centers). Cost is similar: $0.40-0.70 per sq ft.

Insulation Calculator