Home Insulation Guide: Types, Costs & Savings

Why insulation matters

Heating and cooling account for 50 to 70 percent of the average home's energy use. When your building envelope leaks heat, your HVAC system has to run longer and harder to compensate, driving up your bill and wearing out equipment faster. Insulation raises the thermal resistance of your walls, attic, and floors so that conditioned air stays where you want it.

Before upgrading insulation, it helps to know exactly how much energy your home currently uses. The Home Energy Calculator gives you a baseline across all your systems so you can measure the impact of any improvements you make.

Insulation types compared

Each insulation material has a different R-value per inch, installation method, and cost profile. Here is how the most common options compare:

• Fiberglass batts — R-3.2 per inch. The most affordable and widely available option. Easy DIY installation in open wall cavities and attic floors, but leaves gaps around framing if not cut carefully.
• Closed-cell spray foam — R-6.5 per inch. The highest R-value per inch and the best air seal of any material. Ideal for tight spaces, rim joists, and attic hatch edges. Professional installation required; premium cost.
• Cellulose — R-3.5 per inch. Made from recycled paper and blown in with a machine. Eco-friendly, excellent for attic top-ups, and conforms around obstacles better than batts. Settles slightly over time.
• Mineral wool (rock wool) — R-3.3 per inch. Naturally fire resistant, moisture resistant, and sound dampening. A premium alternative to fiberglass batts with fewer irritant fibers. Good choice for party walls and mechanical rooms.

Understanding R-values

R-value measures thermal resistance: the higher the number, the more the material resists heat flow. Doubling the R-value does not double the energy savings because heat loss follows a curve of diminishing returns. Going from R-11 to R-22 saves much more than going from R-38 to R-60, which is why targeting the right zones first matters.

The U.S. Department of Energy recommends these ranges depending on your climate zone:

• Attic — R-38 to R-60. Because heat rises, the attic is where most homes lose the most energy and where insulation pays off fastest.
• Exterior walls — R-13 to R-21. Standard 2x4 framing limits you to around R-15 with batts; 2x6 framing allows R-21. Adding rigid foam outside the sheathing can supplement further.
• Floors over unconditioned spaces — R-25 to R-30. Floors above garages, crawlspaces, and cantilevered sections can be major cold spots in winter.

Use the Insulation Savings Calculator to model the annual savings of reaching your target R-value based on your local energy prices and climate zone.

Where to insulate first

Not every area of your home delivers equal return. Prioritizing by ROI helps you get the most savings for each dollar spent:

• Attic — Highest ROI of any location. Most homes with inadequate attic insulation save 15 to 25 percent on heating and cooling after upgrading. Air sealing the attic floor before adding insulation amplifies the benefit.
• Exterior walls — More disruptive and expensive to retrofit, but can cut heating loads by 10 to 20 percent in older homes with little or no wall insulation.
• Basement and crawlspace — Insulating basement walls or the crawlspace ceiling stops cold floors and pipe freeze risk. Expect 5 to 15 percent savings depending on climate.
• Floors over garages — Often overlooked, cantilevered floors and rooms above attached garages are among the coldest spots in the house. Addressing them can noticeably improve comfort with modest cost.

Costs and ROI timeline

Insulation costs vary by region, material, and how accessible the area is. These ranges reflect typical professional installation in the U.S.:

• Attic insulation — $1,500 to $3,000 for a typical home. Most attic projects pay back in 2 to 4 years through energy savings, making this the most cost-effective home upgrade available.
• Exterior wall insulation — $3,000 to $8,000 for blown-in or injection foam retrofits, depending on square footage. Payback periods range from 5 to 12 years.
• Spray foam premium — Closed-cell spray foam can cost two to three times more than fiberglass or cellulose per square foot, but its superior air sealing often delivers better real-world performance than R-value alone suggests.

Run the numbers for your specific situation with the Insulation Savings Calculator before requesting quotes, so you can evaluate contractor proposals with confidence.

Pairing insulation with heat pumps

A heat pump is most efficient when your home is well sealed and insulated. Because heat pumps move heat rather than generate it, they are sized to the actual load of the building. If your home leaks heat, you need a larger, more expensive unit that runs less efficiently. Completing insulation work first lets you right-size the heat pump, which lowers both the upfront equipment cost and the ongoing operating cost.

If you are planning both upgrades, insulation should come first. Once your envelope is tight, use the Heat Pump Cost Calculator to estimate the right system size and expected savings based on your improved load profile.