Attic Insulation Cost and Guide 2021

This attic insulation cost guide addresses both popular types of attic insulation costs: fiberglass/rockwool/cellulose on one hand and spray foam insulation on the other. In other words, non-foam and foam insulation. Let’s start with the first category.

Attic Insulation Cost

Attic insulation cost ranges from $1.25 to $2.75 per square foot when blown in insulation, aka loose fill, or roll insulation is used. Materials are fiberglass, cellulose or rockwool (mineral wool).

The depth of the insulation is the key factor. Adding 4-6 inches of extra insulation costs on the low end; when insulating new construction with 12-20+ inches of insulation, cost is on the high end of the spectrum.

  • 1,000 square foot attic insulation costs $1,250 to $2,750
  • 1,250 square foot attic insulation cost is $1,565 to $3,440
  • 1,500 square foot attic insulation costs $1,875 to $4,125

The cost of spray foam insulation in the attic ranges from $4.15 to about $6.50 per square foot when just the floor is done, which isn’t common. When the attic ceiling and walls are insulated, cost is $3.80 to $6.75 per square foot.

Material

Full Depth/Sq. Ft.

Additional Depth/Sq. Ft. (1)

Fiberglass

$1.60 - $2.40

$1.25 - $1.75

Rockwool

$1.75 - $2.65

$1.40 - $2.00

Cellulose

$1.90 - $2.75

$1.55 - $2.25

(1) Added Depth - When the attic already has minimal insultion.

Material

Cost to Insulate Envelope

Open Cell Foam

$3.80 - $4.95/Sq. Ft.

Closed Celll Foam

$5.35 - $6.75/Sq. Ft.

In the above chart, we include encasing and sealing the entire envelope of the attic with spray foam insulation – a tactic becoming much more popular as energy efficiency becomes a top priority for builders and homeowners. Plus, if you’re converting the attic to a cozy extra bedroom or kid’s play area or your private retreat, then creating an envelope around it is essential. Details on this practice are found below.

Note: Attic insulation removal cost is an extra expense. The cost and why this would be done is discussed below too.

How Much Attic Insulation Do I Need?

How much attic insulation is right for your home depends on two factors:

1 – How much insulation is there/New construction vs existing construction. Adding insulation to an attic is necessary in most homes according to the Department of Energy, which says most attics are under-insulated by 25% or more.

2 – Your climate is a factor, but to a lesser degree.

Did you know? Hot climate homes should have just as much insulation in the attic as homes in cold climates. Unless you live in a really temperate zone, the US DOE recommends a whopping R-60 in attics. Check out this map and chart.

insulation R value section
insulation R value section

Why is this the case? Because, as you likely know, insulation stops heat from leaving a home in winter and it prevents heat transfer into your house in summer. The right amount of insulation is crucial in both cases.

Attic Insulation Options: Cost, Pros & Cons

This section covers your choices with a reminder of their costs plus the pros and cons of attic insulation choices.

The list starts with non-foam options and concludes with the two spray foam insulation choices. Spray foam, or SPF (spray polyurethane foam), is best used to encapsulate an attic. It is rarely used on attic floors.

What is attic encapsulation? It is the process of creating an insulation envelope around the walls and ceiling of the attic. By “ceiling,” we mean the underside of the roof deck. All ventilation – soffit, gable, ridge, etc., are covered and then sealed with foam insulation to produce an airtight (or nearly so) space. The attic can then be heated and cooled, if desired.

Attic encapsulation is a newer concept, but it is gaining popularity among green building enthusiasts because it stops air leaks. And…

Did you know? Stopping air leaks is considered just as important as having sufficient attic insulation. Why? Because air leaks allow warm air to leave in winter and penetrate your home in summer. You can have a huge pile of insulation in the attic, but if air is going in and out of your living space, the insulation is ineffective.

You can learn more about encapsulation in our Ultimate Spray Foam Insulation Cost Guide and in this short video.

OK, let’s get on to your best attic insulation material options.

Fiberglass Insulation

This material remains the most popular attic insulation. Your options and their pros & cons are:

Rolls: These are long rolls of insulation, and they are also called blankets. They come in the various widths to fit between roof joists and R-values. Common fiberglass roll options for the attic are R-19, R-30, R-38 and R-49. Popular brands are Owens Corning, Johns Manville and Knauf. They’re easy to roll out between joists, and then they are cut to fit the right length.

Rolls are easy to work with, but you have to cut around vents and other protrusions. And don’t let the insulation get too close to hot can lights protruding into the ceiling. In fact, if you have can lights in your ceiling, we’d recommend replacing them with cool LED lighting.

The one concern about rolls is that they might leave small gaps at the sides, against the joists, where heat from inside the house can escape in winter – or penetrate the house from a hot attic in summer.

Pro Tip: You can add a second layer of rolls to existing insulation. Let’s say your attic is under-insulated, as many are. Maybe it has a blanket of R-19 or R-30 insulation. Add a layer of R-30 to achieve a much more efficient R-49 or R-60.

Batts: Batt insulation is made for walls – cut to 8’, 9’ and 10’ lengths. However, you’ll find batts used in attics. Maybe bats too, but that’s a different story. Sometimes people have leftover batts from insulating the walls, and it’s OK to put them in the attic. However, they tend to not be as thick – they don’t have as high an R-value – as rolls.

Batts are easy to handle and require less cutting than rolls. Plus, layering is easy too – see the Pro Tip below – and you know exactly the R-value of your insulation layer.

The “con” of batts are gaps in the insulation at the ends of the batts and on the sides against roof joists.  

Pro Tip – Very Important: If you have batts with paper on them – called faced batts – you must remove the Kraft facing or paper before attic insulation. The facing is a vapor barrier, and you don’t want a vapor barrier on the floor of your attic. It will trap moisture and cause.

Blown In aka Loose Fill Fiberglass: This option is becoming more popular. Bags of loose fiberglass are loaded into a pneumatic machine with an agitator that loosens the clumps and feeds them into a blower – firehose style – that you or a pro installer uses to blow the insulation into place.

The top advantage with loose fill insulation is that it doesn’t leave gaps, so provides a more consistent blanket. Also, it allows you to choose the exact amount/depth of insulation to give you the desired R-value. That is, you don’t have to work with rolls with their predetermined thickness/R-values. Installation is fairly easy too.

There are a couple potential cons. First, you must place rulers around the attic to show the depth of the blanket being installed. And you must place baffles in the eaves to prevent covering soffit vents with insulation – because if you did, it would create a moisture problem with mold and rot in the attic framing.

Did you know? The PickHVAC pros have completed a complete Guide to Blown In Insulation that covers in depth all loose fill types, their R-values, blown in insulation cost and the best type for each application.

Cost: The cost of fiberglass attic insulation is $1.25 to $2.40 per square foot based on the amount of insulation/R-value required for new construction or adding insulation to a poorly insulated attic.

Mineral Wool

Fiberglass is molten, spun silica (sand). Mineral wool, or rockwool as it is often called using the name of a leading brand, is, according to Wikipedia, “Any fibrous material formed by spinning or drawing molten mineral or rock materials such as slag and ceramics.”

In short, it is similar in makeup to fiberglass and in its ability to stop the transfer of heat (R-value).

Mineral wool is produced in rolls and loose fill.

Its advantage over fiberglass and cellulose is that it is more resistant to fire. It dampens sound better too. The downside is that it costs about 30% more. If all you want is cost-effective insulation, then fiberglass provides a better value.

Pro Tip: Mineral wool is a great option for homeowners with a metal roof. If you have a metal roof, then you know one of the objections is that they can be noisy in a rain/hail storm or when debris hits or ice slides off it. Mineral wool might reduce the “clang” of a metal roof to a soothing “ding” :  )

Cost: $1.40 to $2.65 per square foot depending on the amount needed and installation factors discussed below.

Cellulose

This is a blown in / loose fill insulation only.

Made from recycled paper, the wood pulp is treated to resist fire, mold and insects. In the attic, the cellulose is installed dry, unlike in vertical applications where it is wetted, so that it can stick in place.

Cellulose attic insulation costs a little more than fiberglass and mineral wool, but it offers very good insulation. Its R-value is higher than fiberglass and about the same as mineral wool.

There is little downside to cellulose blown in insulation. In our Blown In Insulation Cost and Buying Guide, cellulose was named the best option for most applications.

Cost: $1.55 to $2.75 per square foot.

Open Cell Spray Foam

Open cell foam insulation is also called ½-pound foam after its weight per board foot. A board foot is one square foot, one inch deep: 12”x12”x1”. Another name for any spray foam insulation is spray polyurethane foam, commonly called SPF.

With an R-value of 3.5, it is equivalent to cellulose insulation and a little better insulator than fiberglass and mineral wool. But it costs a little more too.

Do’s and Don’ts with open cell spray foam:

DO: While insulation pros differ on this, we think open cell spray foam is a good choice for the underside of the roof deck in the attic. Why?

1 – Roofs leak

2 – Closed cell spray foam is waterproof, but open cell is not. Why is that a good thing?

It’s easy to think waterproof insulation is a better material if the roof leaks. However, the insulation won’t stop the leak, since it is applied on the underside of the roof and doesn’t do any good for leaky shingles or shakes. Instead, waterproof insulation traps moisture at least for a while that leaks through the roofing, so the homeowner doesn’t know the roof is leaking. The result is widespread roof damage and rot.

The point is that open cell insulation shows a leak quickly, because it will be stained/discolored by the water and dirt that comes with it. Water will pass through it too. If your roof leaks, you’ll know it more quickly and be able to make a repair before the damage gets out of control.

That’s the “Do.” Use open cell spray foam on the attic roof, i.e., the underside of the roof deck.

DON’T: Open cell foam insulation is water-based. Because of that, do not spray it on the floor of your attic. The moisture will be absorbed into the drywall beneath it and cause staining and/or warping.

Cost: $3.80 to $4.95 per square foot for most applications in which several inches of insulation are required.

Closed Cell Spray Foam

This SPF insulation might be the best home insulation available – but it is also the costliest and doesn’t make financial sense for all areas.

In the attic, its best application is for the walls of the attic and over vent areas such as gable vents and soffit vents.

Closed cell SPF creates a vapor and moisture barrier. That means it seals the surface against air leaks and moisture penetration.

Cost: $5.35 to $6.75 per square foot based on application thickness. A minimum of two inches should be applied to insure a seal against airflow.

Attic Insulation Cost Factors

Briefly, these factors will determine your total attic insulation cost.

  • Who installs the insulation: DIY is pretty easy with loose fill attic insulation like cellulose and fiberglass. You can save around 25% with foam to 50% for loose fill by doing it yourself. We don’t recommend DIY if you choose to encapsulate your attic space with SPF spray foam insulation.
  • Insulation type: Spray foam insulation, especially closed cell material, is quite a bit more expensive than other types. See the Cost Chart above for details.
  • Size of the attic: Cost per square foot drops a bit the larger the space, though, of course, your total cost is higher the larger the attic.
  • Floor insulation vs encapsulation: Encapsulating an attic in foam insulation will always cost more than insulating just the floor of the attic regardless of the material used.
  • Removing old insulation: Material that is wet or has been greatly compressed won’t insulate well, so it should be removed. Attic insulation removal cost is discussed below.

How to Insulate an Attic Properly

We recommend having pros do the work if you’re encapsulating your attic in spray foam / SPF.

If you’re insulating the floor of the attic with rolls or loose fill/blown in insulation, then here are tips for optimizing the performance of the materials you use.

1 – Use spray foam to seal the area around pipes, vents or other protrusions in the floor of the attic. This prevents air transfer to and from the attic and your living space that can reduce your home’s climate comfort and raise energy costs. You can buy small cans of spray foam for this purpose.

2 – Prevent the insulation from covering the soffit vents by cutting rolls short of the vents or by installing baffles (aka stops or air chutes) for the purpose if using blowing in loose fill insulation. This image shows how properly installed baffles allow airflow in through the soffit vents. The air carries heat and moisture up and out the ridge vents (not pictured). This cools the attic and just as importantly removes moisture that might cause mold and rot.

attic eave loose fill insulation 2d

3 – For loose fill, use a series of “rulers” at key points of the attic to ensure the right depth of insulation. These can be made from rigid cardboard stapled to joists, but something a little tougher, like wood stakes nailed to the joists, won’t be blown over as easily. Most insulation manufacturers make rulers, like this one from Owens Corning.

attic Insulation rulers

4 – Also for loose fill, learn how to use the machine and get the right settings for the type of insulation you’re using. Too much air can make the insulation fluffy, and you’ll think you have enough depth only to have the insulation settle after you install it. Suddenly what you think is R-49 because it is too fluffy settles into R-35, its true R-value for the amount of insulation there is, and you don’t have your preferred insulation amount. While there are a few types of machines, this excellent video gives you the basics of the type of machine you can rent or borrow at Home Depot, Lowe’s, etc.

5. – Start at the furthest point from the attic hatch or opening. Like painting a floor, you don’t want to insulate yourself into a corner. Gradually work from the furthest point back towards the hatch. Cover each area to its full depth as you go.

Attic Insulation Removal Cost

The cost to remove attic insulation is about $1.00 to $2.00 per square foot. Yes, that’s a broad range, but it is based on several factors:

  • How much insulation there is
  • How easy it is to remove
  • Whether it is done with a machine (quick) or by hand (takes longer – higher cost)
  • Whether it is wet – such as from a roof leak
  • Where you live – the general cost of living in your area

Attic Insulation Removal FAQ

Here are the two most common questions we get on removing insulation.

Should I remove old attic insulation before installing new?

If it is less than 10 or 15 years old and in good condition, then it is okay to leave it. If you know it has gotten wet, has visible mold, has been infested with rodents, has a bad odor or is old and has visibly disintegrated (look for dust particles of insulation beneath the roll or at the bottom of the loose fill), then we recommend removing it.

Then, vacuum out the attic. Alleviate any mold issues. And install your new attic insulation.

What’s the best way to remove old attic insulation?

If it is rolls, roll them up and stuff them in large garbage bags or contractor bags (heavier-duty) before taking them out of the attic.

If it is blown in insulation, you can rake it into bags or rent a commercial vacuum with a really long hose and vacuum it out. Here’s a concise guide to attic insulation removal cost and how to do it.

Energy Rebates for Attic Insulation

Your energy company might give you money back when you install an appropriate amount of insulation and provide them with the receipt.

This issue is covered in our Blown In Insulation Cost Guide and Review and in our Spray Foam Insulation Cost Guide and Review

Here’s what we said in the latter guide:

“Many local energy companies offer rebates for the addition of insulation to your home. Consumers Energy is just one example.

At this writing, Consumers Energy is offering:

  1. $50 each location for upgrading attic or below-grade wall insulation
  2. $70 for upgrading wall insulation
  3. $20 for rim joist insulation
  4. $10 for crawl space insulation

The best place to find these rebates is on your utility’s website. Search its name and “rebates” to see what’s available. You’re likely to find insulation rebates plus those for energy efficient doors and windows, appliances and more. “

Thank You for Reading

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