Insulation Types and R-Values Explained

Understanding R-value

R-value measures how well insulation resists heat flow. A higher R-value means better insulation performance. Your climate zone determines the minimum R-value required by energy code.

In warm climates, walls typically require R-13 and attics R-30 to R-38. In cold climates, walls may require R-20 to R-21 and attics R-49 to R-60. When insulation is replaced during an insurance repair, it must meet the current code requirement for your zone.

Fiberglass batt insulation

Fiberglass batts are the most common and least expensive type. They come in pre-cut widths to fit standard wall cavities (R-13 for 2x4 walls, R-19 for 2x6 walls). Material costs are $0.

50-$1. 00 per square foot, with installation adding $1. 00-$2.

00. Batts are easy to install but leave gaps around pipes, wires, and outlets that reduce their effective R-value. They are a solid budget option for standard wall cavities.

Blown-in insulation

Blown-in insulation (cellulose or fiberglass) is pumped into cavities through a hose. It fills irregular spaces better than batts, conforming around wires and pipes. Cellulose is made from recycled paper treated with fire retardant and costs $1.

00-$1. 50 per square foot installed. Blown-in fiberglass costs slightly more.

This type is excellent for attics and for retrofilling existing walls without removing drywall, though it settles over time and may lose some R-value.

Spray foam insulation

Spray foam provides the highest R-value per inch and also acts as an air barrier. Open-cell spray foam costs $1. 50-$2.

50 per square foot and provides about R-3. 7 per inch. Closed-cell spray foam costs $2.

50-$4. 00 per square foot and provides R-6 to R-7 per inch, plus it adds structural rigidity and moisture resistance. Spray foam is the premium option and is especially valuable in areas where air sealing is important.

What to do

When your repair opens wall or attic cavities, check what type of insulation was there and what the current code requires. If the existing insulation was damaged by water, it must be replaced because wet insulation loses its effectiveness and can promote mold growth. Make sure your estimate specifies the correct type and R-value for the location.

If the estimate just says 'insulation' without specifying type and R-value, ask for clarification.