cost to blow insulation in attic

Last Updated: Wednesday, January 12, 2022

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How Much Does it Cost to Insulate the Attic to R50?

	Low Estimate $0.30 – $0.40 cents / sqft	Average Cost Estimate $0.45 – $0.60 cents / sqft	High Estimate $0.55 – $0.95 cents / sqft
Insulation Type	Cellulose Bags	Cellulose Bags	Cellulose Bags
R-Value	R30-49	R35-60	R40-60
Amount Needed	9-14 Inches	11-18 Inches	14-18 Inches
Ease of Access	Average	Average	Average to Hard
Prep Work Required	Minimal	Average	Average to High
Installed By	DIY	Pro	Pro
Cost of Tools & Supplies	$50 – $75	None / Included	None / Included
Permits, If Required	$0	$0	$0

Sections: Overview | Product Costs | Installation Cost | DIY or Pro | Web Compare | Shared Pricing

Overview of Blown In Attic Insulation

Adding attic insulation has the highest return on investment of any home improvement project, according to a respected annual building industry survey. The most recent data shows that attic insulation raises home sale prices by 107% of its cost. If you don’t sell, attic insulation quickly pays for itself through lower energy bills.

How much insulation does your attic need? R-value, or resistance value, is a measurement of how resistant material is to heat transfer. The higher the R-value, the better the insulation value. The US Department of Energy’s Energy Star program details the R-values recommended for each climate zone in the US.

The recommended R-values are:

• Zone 1 R30-R49 | 9 – 14 inches of insulation.
• Zones 2 & 3: R30-R60 | 9 – 18 inches.
• Zone 4: R38-R60 | 11 – 18 inches.
• Zones 5-8: R49-R60 | 14 – 18 inches.

If there is already some insulation in your attic, measuring it will help determine its R-value. Also check our spray on insulation estimates to get an idea of those costs. Fiberglass insulation has a value of R2.2 to R2.7 per inch. Cellulose insulation’s value is R3.2 to R3.8 per inch, or an average of R3.5 per inch of thickness. It’s OK to mix insulation types, for example, using blown cellulose over fiberglass batts. However, if the old insulation is wet or shows signs of mold, it should be removed. Of course, wet or moldy insulation indicates a roof leak or poor attic ventilation, issues that should be resolved before adding fresh insulation.

In this Costimate, we’ll help you estimate the costs for insulating your home with blown-in insulation. You’ll learn how much you need, how to measure the current r-value, as well as estimating how much it will cost to reach a higher level of efficiency based on the various factors that affect cost. We’ll also share a comparison table of other leading websites and what they estimate the costs will be, before sharing actual costs of homeowners like yourself.

Blow-In Insulation Cost Details

Insulation Cost Factors

Besides the size of your attic and how much insulation you add, the main factor that will affect cost is who does the work:

• DIY or Pro – Professional blown insulation costs break down to about 67% for material and 33% for labor. The 33% you save by doing it yourself will be slightly offset by the cost of renting an insulation blower and purchasing goggles, dust masks and a ladder, if needed.
• Amount Needed – Obviously, the more insulation you need in your attic, the higher the material costs will be.
• Existing Insulation Condition – If your existing insulation is old, compacted, wet, or damaged in any way, now is the time to replace it. Doing so will cost a bit more right now, but assure proper insulation and save money in the future.
• Prep-Work Required – While doing this project, you’ll want to seal around all ceiling and roof gaps. If you have a lot of pipes, stacks, flues, etc that pass through your attic, expect a bit of extra time for preparation.

Cost of Cellulose Insulation and Supplies

Before the cost per bag of insulation will mean anything, you must determine how much insulation is needed. Some home improvement sites have an insulation calculator like this one at Lowes but you can figure it out quickly using the information and equation below.

Cellulose insulation is sold most often in bags weighing about 20 pounds that will cover 40 square feet with R19 insulation. So, here’s how much you’ll need to achieve the desired R-value for your zone:

• R19 –1 bag per 40 square feet (5” deep)
• R30 –1.5 bags per 40 square feet (7.5” deep)
• R38 –2 bags per 40 square feet (10” deep)
• R49 –2.5 bags per 40 square feet (12.5” deep)
• R60 –3 bags per 40 square feet (15” deep)

1). Divide the number of square feet in your attic by 40.

2). Multiply the result by the number of bags needed per 40 square feet to achieve the desired R-value.

For example, if you wanted an R38 upgrade in a 1,200 square foot attic:

• 1,200/40 = 30
• R38 = 2 bags per 40 square feet
• Therefore, 30 x 2 is the equation, so you’ll need 60 bags of insulation

The list below tells you the R-value of the attic insulation you currently have, so you’ll know how much to add.

• Fiberglass insulation: R2.2 to R2.7 per inch
• Cellulose insulation: R3.2 to R3.8 per inch
• Rock wool/mineral wool: R3.0 to R3.3 per inch
• Cotton insulation: R3.4 per inch

Now, here are your costs:

• $25-$50 | Insulation blower per half day or full day (with refundable deposit of $200-$275)
• $6.25-$7.25 | 40lb bag of loose-fill cellulose insulation
• $8.50 – $12.00 per can | Great Stuff, or other spray foam product.
• $60-$85 | Delivery charge (Optional)
• $85-$115 | Aluminum step ladder to access the attic
• $5-$20 | Pack of 5-10 disposable dust masks
• $20-$40 | Reusable all-purpose safety mask
• $4-$7 | Light-duty safety goggles

Free rental: Some retailers offer free blower rental with the purchase of a minimum number of bags. For example, The Home Depot currently gives one day of rental with the purchase of 20+ bags.

Permits, Inspection, and Related Costs

Permits and Inspection Cost

• $0 | No permit is required for insulating your attic

Installation Cost and Time

As we noted, the cost of hiring a professional for attic insulation is roughly half the cost of the insulation. In the scenario we gave earlier, the cost of insulation would be about $400, and the labor would approximately $130, plus any travel time the company may charge for a small job like this.

Of course, pros consider the depth of the insulation required to achieve the desired R-value when estimating jobs. In other words, the more insulation/higher R-value they are adding, the higher the estimate. With that in mind, expect estimates to be in this range:

• $0.55-$0.95 (55-95 cents) per square foot | Professional installation of attic insulation

Blown In Attic Insulation Time Schedule

• 6-8 hours | Attics up to 1,200
• 8-12 hours | Most larger attics

DIY or Hire a Pro?

I’ve had the unfortunate pleasure of adding insulation to our current home. We have 1820 square feet of attic space and it only had 8 inches of insulation when we moved into our zone 4 home that was built in 1977. I added an average of 10 inches to reach the desired R60 rating, which was easy enough with a rented blower, but very tiresome and messy. We changed our gas furnaces (2) out at the same time, so calculating ROI was not an option, due to higher efficiency units.

• Good DIY project if you have easy access and help.
• You’ll need to get dirty. Very dirty.
• Expect heavy lifting and bring a few helpers.

The Family Handyman has a great DIY resource if you plan to do this yourself.