Insulation cost per square foot

Three pages here price the same job at different grains. The attic insulation cost hub gives the installed total for a whole attic. The blown-in page prices that one job three ways: per square foot, per bag, and as a flat quote. This page is about the unit itself. What the number counts, what it hides, and how far it moves between materials. Walls are priced in the same unit, and wall insulation cost covers that job.

Start with the layer you were quoted. Most numbers you will find are the first row, and most are printed without saying so.

Every figure below is one named product's price, divided by the area that product covers at that R-value. Nothing is averaged. Nothing is filled in where a maker publishes no coverage. The blanks are the point, and there are two kinds. A batt sold at R-30 has no published coverage at R-49, so that cell reads "no coverage published". A radiant barrier has no R per inch at all, so it cannot be priced this way in any cell.

Figures: material only, no labor. 6 of the 7 prices were read off live product pages at The Home Depot on 2026-08-11, each confirmed by a second read of the same page. The blown fiberglass row comes from the same product the site's cost model uses, read 2026-08-07. One retailer, and one day. Prices move by store and by ZIP.

At R-30, the only target every priced material publishes coverage for, the spread is about 17 to one. The floor is blown cellulose at $0.58 a square foot. The ceiling is a do-it-yourself closed-cell foam kit at $10.06. That gap is material only. It shrinks once a crew is added, because labor lands on the cheap material and the dear one alike.

Two of the rows need reading with care. The cellulose figure is a range because the maker publishes two coverage columns, one with no allowance for framing and one adjusted for 2x6 joists at 16 inch centers. The foam kit figure is a range because closed-cell foam is rated over a band of R per inch, not a single value.

The foam row answers a common question on its own. A do-it-yourself closed-cell kit costs 8.7 to 10.2 times what blown fiberglass costs at the same R-value, in material alone. The maker also calls the kit's yield "theoretical" board feet, which is its own way of saying real yield comes in lower.

Material is only half the question. Here is the same product priced installed, so you can see what the crew adds. This is blown fiberglass into an open, walkable, empty attic. It is the one material this site models installed, because it has a measured wage and a published coverage chart behind it.

Figures: Insulation Report Cost Model, August 2026. Labor is 9 to 12 crew-hours per 1,000 square feet, at the BLS May 2025 mean wage for insulation workers of $26.32 an hour, times 2.0 to 3.0 for what a worker costs beyond pay. Those last two inputs are estimates, not measurements, so every installed figure here is an estimate.

Read the last column across and you get the finding. Labor is 18 to 49 percent of an installed price, and its share falls as the target rises. In this model the crew's hours follow floor area, not depth. So a deeper attic buys more bags against the same labor line.

That tells you which half of a quote to argue about. On a deep retrofit you are mostly buying bags, and bags cost the same in every state. On a shallow one you are mostly buying hours. The state cost index ranks all 51 jurisdictions on the wage behind those hours.

This is the error that costs the most money, and it never shows up in the price itself. A price per square foot is only right if it is multiplied by the right area. The area is the attic floor, which is the ceiling of the rooms below it.

On a single-story house the attic floor is close to the house floor area. On a two-story house it is not. Take a 2,400 square foot home with two equal floors. Its attic sits over 1,200 square feet, not 2,400. Priced at the model's $2.18 to $2.66 a square foot for R-49, the real job models $2,600 to $3,200. The same rate on the house figure models $5,250 to $6,400. That is $2,650 to $3,200 of air, about as much again as the job itself.

The per square foot rate is identical in both. Only the area moved. This is why a quote with no floor area written on it cannot be judged at all, and why the first question to ask is not the price. Once the area is measured, the attic insulation calculator turns it into a whole-attic figure for a blown-in job.

Roof area is a third number again, and larger than both. A roof plane is a slope, so it covers more surface than the floor beneath it. 1,200 square feet of attic floor under a 6 in 12 roof carries about 1,342 square feet of roof surface, roughly 12 percent more. That is geometry, not a survey of houses. It matters when a quote prices work at the roof deck, such as a radiant barrier stapled to the rafters, rather than on the floor.

• Ask for the attic floor area in square feet, written on the quote.
• Check it against the footprint of the heated rooms below, not the total living area of the house.
• Subtract what is not getting insulated. An open stairwell, a cathedral section or a floored storage deck the crew works around all shrink the real area.

The second trap is quieter. A price per square foot with no R-value next to it is not a price. It is half of one. The same attic, the same crew and the same material give two very different numbers depending on how deep the layer goes.

Work it from the coverage charts rather than from opinion. In blown fiberglass, material at R-60 costs $2.13 a square foot against $0.99 at R-30. That is about 2.2 times. In cellulose, the same move is about 2.2 to 2.3 times.

Notice that both are more than two, not less. Loose fill packs down under its own weight, so a deeper layer is a denser layer, and each bag covers less floor than a simple depth calculation predicts. The U.S. Department of Energy describes the same effect. Settled density rises with installed thickness, so R-value does not scale strictly with depth.

So two quotes are only comparable when both name a target. ENERGY STAR recommends R-30 for a bare attic in climate zone 1, R-49 in zones 2 and 3, and R-60 in zones 4 through 8, which cover most of the country. Those levels are based on the 2021 IECC model code table. Energy codes cover new building and work done under a permit. They do not usually cover adding insulation to an attic you already have. Which edition applies where you live depends on your state, and often on your city. Your local building department is the only authority on it. The zone-by-zone page gives the target for your own zone, and the ZIP lookup finds the zone.

Do this before you accept or reject anything. It takes a calculator and two questions to the contractor. It ends in a verdict.

1. Get the attic floor area in writing. Square feet of attic floor, not living area, and not roof area. If nobody measured it, that is the first problem.
2. Get the target R-value and the material in writing. A bid at R-38 and a bid at R-60 are different jobs. So are cellulose and stone wool.
3. Divide the price by the area. A $2,600 quote on 1,200 square feet is $2.17 a square foot. Write the R-value beside it.
4. Compare it with the band for that target in the installed table above: $1.46 to $1.93 at R-30, $2.18 to $2.66 at R-49, and $2.60 to $3.07 at R-60. Those bands are blown fiberglass only. For batts or foam, the material table gives you the floor the price cannot go below, and nothing here prices their labor.

Then read the answer off these three bands.

• Below the band. Verdict: check the scope before you celebrate. It can be honest, because the model buys material at shelf price and a contractor buys under it. It can also mean a thinner job. Confirm the R-value, the bag count and the eaves detail in writing, then accept.
• Inside the band, scope written down. Verdict: accept it. That is a normal price for the job as described. Get a second bid only if the first will not put the scope on paper.
• Above the band. Verdict: fair only if the extra is named. Hard access, air sealing, baffles, removal and disposal all belong above the band, and each should appear as a line. Above the band with nothing named and nothing itemized: decline it, and get another quote.

The bands lean low on purpose, because material is priced at the retail shelf and a contractor pays less. So a quote this test flags as high is worth a conversation, not an accusation. The cost hub runs the wider version of this test across the whole scope.

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A cheap unit price usually means a smaller job, not a better deal. Three lines are missing from most low bids, and all three cost real money later.

• Air sealing. Sealing the top plates, the wiring holes, the plumbing stacks and the hatch is slow hand work. Its hours follow how many holes are in your ceiling, not how many square feet. So it cannot be priced per square foot at all, and it is the line most often left out. DOE guidance treats sealing the ceiling plane as the partner job, and on a leaky ceiling it is the better first spend. Air sealing covers the order of work.
• Disposal. If old material comes out, that is a separate job with its own price, and bagging and hauling it is part of that price. Insulation removal cost prices it, and remove or add over decides whether it needs to happen at all.
• What happens at the eaves. This is the line a homeowner never thinks to ask about and the one that separates two bids most often. Loose fill blown to the edge plugs the soffit vents, which stops the attic breathing. Rigid baffles go in first, one per rafter bay, so the count follows your eave length rather than your floor area. The insulation also gets thin where the roof meets the wall, which is the hardest strip of the ceiling to cover to full depth. Where the 2021 IECC asks for R-60 in the ceiling, R-49 is enough on one condition. The insulation has to run all the way out over the top of the outside wall at its full depth, with nothing squashing it. That normally takes a raised-heel truss, which lifts the roof to make room. Energy codes cover new building and work done under a permit. They do not usually cover adding insulation to an attic you already have. Which edition applies where you live depends on your state, and often on your city. Your local building department is the only authority on it. Baffles shows what a correct eave looks like.

So when two bids differ by half, compare the scopes before the prices. Ask each contractor for one sheet: attic floor area, target R-value, material, bag count or coverage, and a yes or no on air sealing, baffles, removal and disposal. Most of the gap closes right there.

We do not sell insulation and we do not install it, which is why this section exists. Three cases where the per square foot question is the wrong one.

• Your attic is already close to target. Heat flow falls as one over R, so the last increment returns a small fraction of the first. If you are within about R-10 of the ENERGY STAR level for your zone, which for zones 4 through 8 means roughly R-50 already down, air sealing usually beats more depth. That R-10 threshold is this site's editorial judgment, labeled an estimate rather than a measurement. The depth checker turns your measured inches into an R-value range first.
• You are topping up, not starting bare. Every figure on this page prices a full depth onto a bare ceiling. If your attic already holds R-30 and you are going to R-60, you buy the difference, not the whole thing. A per square foot rate from any table will overstate that job. Adding over existing insulation works the smaller number.
• You are pricing a radiant barrier. A radiant barrier reflects radiant heat rather than resisting conduction, so it has no useful R-value per inch and cannot be counted toward an R-value target. It is measured differently from bulk insulation and the two do not add together. Anyone selling you one at a price per square foot "at R-whatever" is selling a number that does not exist. Radiant barrier gives the two narrow cases where it earns its money.

Each price is one product on one day, quoted rather than averaged. That is a deliberate trade: a single named listing you can go and check beats an average of numbers nobody can trace. It also means no row here is the market. A second glass fiber batt and a second stone wool batt, both at the same R-value, priced differently on the same day. The caveat column records both.

Coverage is the harder half. A bag price alone says nothing, because a bag of cellulose and a bag of batts do not cover the same floor, and neither covers its label figure unless your target matches the label's R-value. Retail listings publish one coverage number per bag, and for loose fill it is the R-19 figure. So the cellulose coverage here comes from the maker's attic data card instead, which publishes a column per R-value.

The two columns are not the same claim. The framed column covers more floor per bag because joists take up part of the space. Which one applies depends on your framing, so the table above carries both ends as a range rather than picking one.

One more thing worth knowing before you price a rental machine into the job. Both major retailers give the blower away with a bag order rather than renting it by the day. The Home Depot states the first day free with 10 bags of cellulose, and free 24 hour rental with 10 bags of the fiberglass system. Lowe's states free 24 hour rental with 10 bags or more. Neither publishes a paid daily rate on the rental listing, so for a whole attic the machine costs nothing. A deposit or card hold at the counter is normal and is not published. Blower rental covers the terms, and do it yourself or hire covers whether it is worth it.

Coverage charts and labeled R-values are governed by the FTC R-value Rule (16 CFR Part 460), using test methods such as ASTM C518. Cellulose is made to ASTM C739. So both numbers this page needs, price and coverage, are printed on the bag or on the maker's sheet for whatever product you are actually quoted. Use those over any table.

• Attic insulation cost: the installed total, by size and target
• Blown-in cost: per square foot, per bag, installed
• Batt insulation cost
• What a 2,000 square foot attic costs
• Cellulose against fiberglass
• How much R-value do I need