Insulation Types and How They Compare for Cost, Performance, and Installation

What R-value means and why air sealing matters too

R-value measures how well a material resists heat flow. The higher the number, the more slowly heat moves through it. The U.S. Department of Energy publishes recommended R-values by climate zone, ranging roughly from R-13 in mild southern climates to R-60 for attics in cold northern regions.

However, R-value is measured under laboratory conditions with no air movement. A wall insulated to R-19 with fiberglass batts but full of gaps and bypasses can perform closer to R-10 in practice. That gap happens because air carries heat faster than conduction through solid material. Combining good insulation with proper air sealing closes that performance gap. For a hands-on approach to finding and fixing air leaks alongside insulation work, see this guide to sealing a drafty house.

Fiberglass batts

Fiberglass batts are pre-cut panels of spun glass fiber, sold to fit standard 16-inch and 24-inch stud spacing. They are the most widely available insulation product and the least expensive per square foot. A homeowner with basic skills can install them in open wall or floor cavities without renting equipment.

The trade-offs are real. Batts must fit tightly against every surface to perform as rated. Any compression, gap, or void around wires and pipes reduces effective R-value. They provide no meaningful air sealing on their own. In humid climates, improperly installed batts can trap moisture and develop mold if vapor management is not addressed during installation.

Typical installed cost for fiberglass batts runs lower than other options, making them the default choice when walls are already open during renovation or new construction.

Blown-in cellulose

Cellulose is made from recycled paper treated with borate for fire and pest resistance. Installers blow it into place using a hose and blowing machine, which allows the material to settle around obstructions like wiring, plumbing, and irregular framing.

For attics, blown-in cellulose is a practical retrofit option because installers can add depth without tearing out drywall. It achieves roughly R-3.5 per inch. Dense-pack cellulose, blown into closed wall cavities through small holes, can also reduce air infiltration better than loose-fill fiberglass under the same conditions.

Machine rental is available at many home improvement stores for DIY attic projects, though dense-pack wall installation generally requires professional equipment and technique to achieve adequate density. Material cost is modest; labor drives the total price for professional installation.

Spray foam

Spray polyurethane foam comes in two main types. Open-cell foam is softer and less dense, achieving about R-3.7 per inch, and allows some vapor transmission. Closed-cell foam is rigid, denser, and reaches R-6 to R-7 per inch while acting as a vapor barrier.

Both types expand to fill gaps and bond to surfaces, which provides significant air sealing alongside thermal resistance. This makes spray foam particularly useful in rim joists (the framing at the top of a foundation wall), crawl spaces, and cathedral ceiling cavities where air movement is difficult to stop otherwise.

The cost is substantially higher than other insulation types, often three to five times the installed price of fiberglass batts for the same area. Professional installation is required because the chemicals involved are hazardous during application and the mixing ratios must be precise. DIY spray foam kits exist for small areas like rim joists, but whole-house spray foam is not a realistic DIY project.

Rigid foam board

Rigid foam panels are manufactured in three main formulations: expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate (polyiso). R-values range from about R-3.8 per inch for EPS to R-6 or more per inch for polyiso, depending on temperature and age of the board.

Rigid foam works where flexible materials cannot: below a concrete slab before pouring, against a basement wall on the interior, or as a continuous layer on the exterior sheathing of a home to eliminate thermal bridging through studs. Thermal bridging occurs when framing members conduct heat around the insulation between them, reducing whole-wall performance.

Cutting and installing rigid foam is a manageable DIY task using a utility knife or circular saw. Many foam board products require a fire-rated covering (typically drywall) on the interior due to building codes. Verify local requirements before leaving foam exposed.

Choosing based on your actual situation

The right insulation depends on where you are installing it, what access you have, and what your budget allows. Open stud bays during a remodel point toward batts for cost reasons. An accessible attic with no existing insulation is a strong candidate for blown-in cellulose. Rim joists and crawl spaces, where air leakage is substantial, often justify the higher cost of spray foam because the performance gain is concentrated in a small area. Basement walls and exterior continuous insulation layers call for rigid foam board.

Before purchasing materials, check whether your local utility or state energy office offers rebates for insulation upgrades. Many programs exist that can reduce out-of-pocket costs, though availability and terms vary by location.