You are looking for a way to lower your heating bills, and every article you read says insulation is the answer. But when you go to the home center, you see rolls of fiberglass batts for $0.50 per square foot and machines for blowing loose fiberglass into the attic. You are not sure whether you need batts or blown-in material, or whether the cheapest option is actually the right choice for your particular home and situation.
Fiberglass is a common type of fiber-reinforced plastic using glass fibers (Wikipedia), and fiberglass insulation is the most widely used insulation material in North American homes. The fiberglass insulation cost ranges from $0.50 to $2 per square foot for materials, depending on whether you choose batts or blown-in, the R-value, and the application area. Installation labor adds $0.50 to $1.50 per square foot for professional installation.
This guide covers fiberglass insulation cost for batt and blown-in types, the cost differences by application area, and how to budget for your project.
Batt vs Blown-In Fiberglass Insulation Cost
The first choice in fiberglass insulation is between batts and blown-in. Batts are pre-cut rolls that fit between standard stud and joist spacing. Blown-in insulation is loose fiberglass that is blown into place with a machine. The cost and performance differences are significant.
| Type | Material cost per sq ft | Installed cost per sq ft | R-value per inch
|
| Fiberglass batt (R-13) | $0.50u2013$0.80 | $1u2013$2 | R-2.2 to R-2.7 |
| Fiberglass batt (R-19) | $0.60u2013$1 | $1.20u2013$2.20 | R-2.2 to R-2.7 |
| Fiberglass batt (R-30) | $0.80u2013$1.20 | $1.50u2013$2.50 | R-2.2 to R-2.7 |
| Blown-in fiberglass | $0.50u2013$1 | $1u2013$2 | R-2.2 to R-2.7 |
Fiberglass batts are generally cheaper per square foot for the same target R-value when comparing the material cost alone for your project. A bundle of R-19 batts covering 50 square feet costs $30 to $50. The same R-value in blown-in fiberglass costs $25 to $50 for the material, but the blown-in material covers a larger area because it is less dense.
Blown-in fiberglass has an advantage in irregular spaces. It fills around wires, pipes, and framing better than batts, which must be cut to fit. The air sealing performance of blown-in fiberglass is better because the loose fibers settle into gaps that batts leave open. For attics with complex framing, blown-in insulation is the better choice despite the similar cost.
Fiberglass batts are much easier for DIY installation compared to blown-in insulation. No special installation equipment is needed for batts beyond a sharp utility knife and a straightedge to cut them to size. The batt is cut to length and pressed into the cavity between studs or joists. The downside is that improperly installed batts — compressed, gaps left unfilled — perform significantly below their rated R-value.
Fiberglass Insulation Cost by Application Area
The fiberglass insulation cost varies by where it is installed. Attics, walls, crawl spaces, and basements each have different requirements and cost factors that affect the total price.
Attic insulation with fiberglass is the most common application. Attic batts cost $0.80 to $1.20 per square foot for R-30 material alone. Professional installation adds $0.50 to $1 per square foot. Blown-in attic insulation costs $0.50 to $1 per square foot for material. A typical 1,000-square-foot attic with R-49 requires about 20 inches of fiberglass and costs $400 to $800 for materials alone, or $800 to $1,600 installed.
Wall insulation with fiberglass batts costs $0.50 to $0.80 per square foot for R-13 material fitting standard 2-by-4 walls. R-15 batts for 2-by-4 walls cost $0.60 to $1 per square foot. For 2-by-6 walls, R-19 or R-21 batts cost $0.70 to $1.20 per square foot. Wall insulation in new construction is installed before drywall. Retrofitting walls with blown-in fiberglass through holes drilled between studs costs $1.50 to $3 per square foot installed.
Crawl space insulation costs $0.60 to $1 per square foot for R-19 batts installed between floor joists. The batt must be held in place with wire stays or insulation supports. Crawl space walls can be insulated with R-13 batts at $0.50 to $0.80 per square foot. A vapor barrier is recommended over the crawl space floor in addition to the insulation.
Basement wall insulation costs $0.60 to $1 per square foot for R-13 batts in framed walls. Fiberglass batts should not be installed directly against concrete basement walls because moisture causes mold growth. A framed wall with a vapor barrier is required before installing batts in basements.
R-Value and Thickness — How They Affect Price
The R-value and thickness of fiberglass insulation directly affect the cost. Higher R-values require more material and thicker insulation, which costs more per square foot.
The U.S. Department of Energy recommends R-49 insulation for attics in most climate zones across the country, R-13 to R-21 for walls depending on the climate, and R-25 to R-30 for floors located above unheated spaces like garages. Achieving R-49 with fiberglass requires about 16 to 20 inches of material. Achieving R-13 requires about 3.5 inches — the standard 2-by-4 wall cavity depth.
Fiberglass batts are manufactured in standard thickness sizes for common R-values needed in residential construction: R-13 batts are 3.5 inches thick for 2-by-4 walls, R-19 batts are 6.25 inches thick, R-30 batts are about 9.5 inches, and R-38 batts are about 12 inches thick. The cost increase from R-13 to R-19 is about 20 percent. From R-19 to R-30 is about 30 percent. From R-30 to R-38 is about 25 percent.
An insulation contractor with 20 years of experience explained: “The biggest mistake I see with fiberglass is people buying the wrong R-value for their climate, or compressing the batt into a cavity that is too shallow. Compression destroys the R-value. A compressed R-19 batt performs like R-11 insulation or even worse in some cases. Always buy the right thickness for the cavity space you are filling.”
Labor Costs for Fiberglass Installation
Labor costs for fiberglass installation add $0.50 to $1.50 per square foot to the total project cost. The labor rate depends on the type of insulation, the accessibility of the space, and the complexity of the installation.
Batt installation labor by a professional crew costs $0.50 to $1 per square foot. A professional crew can install batts in a standard attic in one to two hours per 500 square feet. The work involves unrolling the fiberglass batts into the attic, cutting them to the proper length with a knife, and fitting them tightly between the ceiling joists without gaps. Wall batt installation takes longer because each cavity must be measured, cut, and fitted individually.
Blown-in installation labor by a professional crew costs $0.50 to $1 per square foot, similar to batts. The equipment cost is included in the contractor price. A crew of two can blow insulation into a 1,000-square-foot attic in one to two hours. The machine operator on the crew feeds the fiberglass material into the hopper while the second person up in the attic directs the hose and makes sure the material is distributed evenly across the entire space.
Retrofit installation work — which involves drilling holes in existing finished walls and then blowing loose fiberglass into the wall cavities — costs $1 to $2 per square foot in labor alone. This is the most time-consuming fiberglass installation because each stud cavity must be accessed individually, filled, and the holes patched.
Disposal of old insulation material that is removed before installing new fiberglass adds about $50 to $200 to the total project cost. If the existing insulation must be removed before installing new fiberglass, the removal labor adds $0.50 to $1.50 per square foot depending on the type and condition.
Fiberglass vs Other Insulation Costs
Fiberglass is the cheapest insulation material per square foot but has lower R-value per inch than other options. The comparison below shows fiberglass against other common insulation types at R-49 for attic applications.
| Insulation type | Cost per sq ft at R-49 | Air sealing | DIY possible
|
| Fiberglass batt | $1.50u2013$2.50 | No | Yes |
| Blown-in fiberglass | $1u2013$2 | Partial | Yes, with rental machine |
| Blown-in cellulose | $1u2013$2 | Partial | Yes, with rental machine |
| Open-cell spray foam | $1.50u2013$3 | Yes | No |
| Closed-cell spray foam | $4u2013$8 | Yes | No |
Fiberglass is the most affordable insulation option available on the market today and offers the best overall value for homeowners who are working with a limited budget for their home improvement project. The lower R-value per inch means more thickness is needed, but the material cost of fiberglass is low enough that the total installed project cost remains significantly lower than using spray foam material for the same application. The main trade-off with fiberglass is that it does not provide air sealing like spray foam does, which means air leaks around the insulation can reduce the effective R-value of your installation.
Frequently Asked Questions
How much does fiberglass insulation cost per square foot?
Fiberglass costs $0.50 to $1.20 per sq ft for materials. Installed cost is $1 to $2.50 per sq ft including labor.
Which is cheaper, fiberglass batts or blown-in?
Both cost about the same for materials. Batts are easier for DIY. Blown-in fills irregular spaces better and provides slightly better air sealing performance.
How much does it cost to insulate an attic with fiberglass?
An attic with R-49 costs $400 to $800 for materials. Installed cost is $800 to $1,600. Blown-in is most common for attics.
What R-value fiberglass is best for an attic?
R-49 is recommended for attics in most climates. This requires about 16 to 20 inches of fiberglass insulation, depending on the specific product R-value per inch.
Can I install fiberglass insulation myself?
Yes, batt installation is a common DIY project. Blown-in requires a machine rental. Both are straightforward but require protective gear — gloves, long sleeves, and a dust mask.
How long does fiberglass insulation last?
Fiberglass insulation lasts 20 to 30 years. It does not rot or attract pests, but it can settle over time and lose R-value if compressed or exposed to moisture.
Is fiberglass cheaper than cellulose insulation?
Fiberglass and cellulose cost about the same per square foot. Cellulose has a higher R-value per inch but can settle more over time. Fiberglass does not absorb moisture like cellulose.
How much does professional fiberglass installation cost?
Professional labor costs $0.50 to $1.50 per square foot. Total installed cost with materials is $1 to $2.50 per square foot depending on R-value.