House Insulation Cost Calculator

Insulating a house runs about $1.50 to $4.50+ per square foot, so most whole-home projects land between $2,000 and $9,000, with the typical homeowner paying $3,000 to $6,000. Insulating just the attic is cheaper ($1,500–$3,000), while a large home in premium spray foam can top $10,000–$15,000. The price is driven by the area's square footage, the material, which part of the house you're insulating, and how hard the access is. Use the calculator above to price your specific project by area, material, and access.

It depends on the area and your budget. Fiberglass batts (~$1.50/sq ft) are the cheapest and DIY-friendly, best for open framing in new construction. Blown-in cellulose or fiberglass (~$2.00) is the popular, cost-effective pick for attics and for retrofitting finished walls without opening them. Mineral wool (~$2.70) costs more but adds fire and sound resistance and won't settle. Spray foam (~$4.50) is the premium option — the highest R-value per inch and it air-seals as it expands — ideal for crawl spaces, rim joists, and high-performance builds. Many homes use a mix: blown-in in the attic, foam in the crawl space, batts in open walls.

R-value measures insulation's resistance to heat flow — higher is better. How much you need depends on your climate zone and which area you're insulating. The U.S. Department of Energy recommends roughly R-30 to R-60 in attics (more in cold climates), R-13 to R-21 in walls, and R-13 to R-30 in floors over unconditioned spaces. Materials hit those targets at different thicknesses: closed-cell spray foam is about R-6–7 per inch, while fiberglass and cellulose are about R-3–4 per inch, so foam reaches a target R-value in less space. Check the DOE map for your zone, and in older homes an energy audit reveals where you're short.

Start with the attic — it's usually the highest-impact and most cost-effective area, since heat rises and most homes (especially older ones) are under-insulated up top. Next come the exterior walls (blown-in can fill finished wall cavities through small holes), then floors over unconditioned spaces like crawl spaces and garages, and finally the crawl space or basement walls and rim joists, which are common air-leak spots. Air-sealing gaps and leaks alongside insulating dramatically boosts the payoff. An energy audit with a blower-door test pinpoints exactly where your home is losing the most energy.

Properly insulating and air-sealing an under-insulated home typically cuts heating and cooling energy use by about 10–20%. ENERGY STAR estimates homeowners save an average of roughly 15% on heating and cooling costs (about 11% of total energy costs) by sealing and adding insulation in key areas. Savings are largest for leaky, poorly insulated homes and in climates with harsh winters or hot summers; well-insulated homes see less. Because insulation is relatively affordable and the savings are ongoing, it's consistently one of the best-returning home energy upgrades — and it may qualify for rebates or tax credits that improve the payback.

Not always. If the existing insulation is dry, clean, and intact, you can usually add new insulation right over it — common and economical in attics (just don't compress it). Remove the old insulation first if it's wet, water-damaged, moldy, pest-infested, contaminated with droppings, badly deteriorated, or if you're switching to spray foam (which needs a clean substrate). One important caution: very old vermiculite insulation can contain asbestos and requires professional testing and abatement — never disturb it yourself. Adding new insulation over a moisture, mold, or pest problem just traps it and undermines performance. Removal is a selectable add-on when it's warranted.

Often, yes — in the right places. Spray foam costs roughly 2–3× more than blown-in or batts, but it delivers the highest R-value per inch and, crucially, air-seals as it expands, which stops the drafts and leaks that insulation alone can't. That makes it excellent for crawl spaces, rim joists, cathedral ceilings, and irregular or hard-to-insulate cavities. Closed-cell foam also resists moisture and adds rigidity. Where it's less justified is a straightforward, accessible attic, where cost-effective blown-in reaches a high R-value for far less. Many homeowners get the best value using foam strategically for sealing and problem areas, and cheaper materials elsewhere.

Yes. New construction with open walls is the cheapest and easiest scenario (about 10% less in our model), because crews have full access before drywall goes up. A standard retrofit on an accessible attic is the baseline. Difficult access — finished walls that must be drilled and filled, tight crawl spaces, or awkward angles — adds about 20% for the extra labor and care. Insulating which area also matters: the attic is the easiest and runs about 10% less, whole-home is the baseline scope, and walls or harder-to-reach areas run about 15% more. The calculator lets you set both access and area.

Absolutely — air-sealing and insulation work as a team, and sealing first makes the insulation far more effective. Insulation slows conductive heat transfer, but it doesn't stop air leaking through gaps around wiring, plumbing, recessed lights, attic hatches, and rim joists. Those leaks let conditioned air escape and drafts in, undercutting even a thick layer of insulation. Sealing the gaps (caulk, foam, weatherstripping) before or alongside insulating is inexpensive relative to the payoff and is a key reason the DOE and ENERGY STAR always pair 'seal and insulate.' Air sealing is a low-cost add-on in the calculator and one of the highest-value choices you can make.

Some parts, yes. Laying fiberglass batts in an open, accessible attic or unfinished framing is a common DIY job, and rolling out attic blankets is manageable. Rented blowers make DIY blown-in attic insulation possible too. But spray foam, dense-packing finished walls, crawl-space encapsulation, and anything requiring an asbestos check or careful air-sealing are best left to pros — improper spray foam or trapped moisture can create expensive problems. DIY saves on labor for simple attic work, but a professional install gets you correct R-values, proper air-sealing, and access to rebates that often require certified installation. Weigh the savings against the complexity of your specific area.