How much does it cost to insulate an attic?

Reviewed by Frank Compagnone remodeling expert. Written by Fixr.com.

Heat naturally flows from warm areas to cool ones. This is true of every space, including your home and attic. This means the energy heating your home may be transferred to an uninsulated attic, where it can escape outdoors. A superheated attic can transfer heat to your living spaces in the summertime, causing your air conditioner to work overtime. That is why having a properly insulated attic is important.

According to the U.S. Department of Energy, a properly insulated home and attic can save 10% to 50% off your home’s power bill. Insulating your attic can have other benefits, such as preventing ice dams from forming in the winter and slowing your roof’s deterioration from heat in the summer.

Many places in the attic can be insulated, and you can use many insulation types. The national average cost to insulate an attic is $2,000 to $3,250. Most homeowners pay around $2,500 to fully insulate a 1,000 sq.ft. attic with a mixture of fiberglass batts and blown-in cellulose. This project’s low cost is $500 to add fiberglass batts to a partially insulated attic. The high cost is $10,000 to install spray foam insulation on all areas of a 1,500 sq.ft. attic.

Attic Insulation Cost

Attic Insulation Cost per Square Foot

You can insulate an attic in several ways and types. Most people pay between $2 and $3.25 a square foot for attic insulation, but the full range is $1 to $7 a square foot fully installed. Several factors influence the final cost per square foot, including the insulation type, whether the attic is partially insulated, and how accessible the various areas are.

Insulate a 1,000 Sq.Ft. Attic

The full cost range to insulate a 1,000 sq.ft. attic is $1,000 to $7,000, with most people paying between $2,000 and $3,250. 1,000 sq.ft. is one of the most common sizes for attics. Insulation can be added to the floors and walls between joists. It can also be added to the roof deck’s underside. It is common to use batts between joists, blown-in insulation to cover the floors, and spray foam may be used in walls or on the underside of the roof deck.

Attic Insulation Cost by Type

Many insulation types can be used in the attic. The most common types are batts and blown-in insulation, but spray foam and foam board are also effective in specific areas. You have other options to consider in finished attics, such as rigid board cork insulation for another layer of insulation. Each type has considerations and costs.

Installing Batt Insulation in an Attic

The average cost to install batt insulation in an attic is $500 to $1,500. Batts are a type of blanket insulation commonly used in attics. They can be made of fiberglass, rockwool, or sheep wool. They consist of loose insulation fitted and held by paper or metallic facing. They are sized to fit between joists on floors and ceilings. They come in multiple depths or thicknesses for a range of insulating values.

Blow Insulation in an Attic

The average cost to blow insulation into the attic ranges from $1,750 to $5,500. Blown-in insulation is loose-fill material. It can be made of cellulose, fiberglass, or rockwool. The loose material is blown via machine into cavities or onto the attic floor. When insulating the attic wall cavities, use dampened cellulose insulation. Otherwise, you can use fiberglass, rockwool, or cellulose to insulate the attic floor.

Attic Foam Board Insulation

The cost to install foam board insulation in an attic averages $2,500 to $7,500. Foam board insulation can be made of a few materials, including polystyrene XPS and EPS, extruded polystyrene, or expanded polystyrene. It can also be made of polyisocyanurate or ISO. All three materials do a good job of adding insulation to the underside of your roof deck and some areas on the attic walls. This can also be a good option in some homes to add beneath the attic flooring. It is important to combine this material with a vapor barrier because it leads to moisture issues in some installations.

Spray Foam an Attic

The average cost to install spray foam in an attic is $2,500 to $12,000. Spray foam is liquid insulation that solidifies on contact with the substrate it is installed on. At this point, it expands to many times its size. Spray foam does a superior job of insulating areas like the underside of roof decks and hard-to-reach areas around pipes and corners. It can be added to traffic areas or used in combination with other materials. It can be found in different formulas, some of which are more eco-friendly than others.

A lot of times when you see a roof turning black, it’s actually because the shingles are heating up so much that they start to turn black and stripe up the roof. Whenever somebody starts to do spray foam insulation in their attics, their goal is to keep the air in and not let any hot air come in. But unfortunately when that happens, it seals the deck. What they do is they spray in all your vents, all your soffits, and then that doesn’t allow your roof to breathe, so your shingles will start to burn, which affects the roof warranty. You can spray foam your attic to keep the air cooler, but it still needs to go in and out. It still needs to have the ability to breathe.

Frank Compagnone, roofing expert

Installing Rigid Board Insulation in an Attic

The cost of installing rigid board insulation in an attic ranges from $4,000 to $15,500. Rigid board insulation is not common in attics. This is usually cork insulation that may be added to finished spaces as an extra layer. It is added to finished wall and ceiling spaces, so it is not common in unfinished attics. Cork and other materials like it can add a lot of insulation per inch. It is more costly than some types and limited in use.

Attic Insulation Price by Material

Many materials can be used in attic insulation. Each type has pros, cons, and costs. Some are easy to install DIY, while others need professional installation at all times. Each can be used in different ways, so consider how you intend to use it based on where it is installed. Costs below are for average attics of roughly 1,000 to 1,500 sq.ft.

Fiberglass Attic Insulation

The cost of fiberglass insulation for the attic averages $300 to $1,000. Fiberglass is one of the most popular materials for attic use. It comes in batts and loose-fill, blown-in insulation. Fiberglass is made of thin fibers coated in glass. The fibers trap air, providing insulating properties. Fiberglass is easy to install and can be installed DIY.

Cellulose Attic Insulation

The average cost of cellulose for the attic is $600 to $3,500. Cellulose is a material made of wood pulp. It frequently contains a large amount of post-consumer recycled content, such as newspapers. Cellulose is treated to be flame retardant and insect resistant before installation. It can be installed in wall cavities or covering the floor. It comes in two types - damp for vertical installation and dense pack for the floor and other areas.

Polystyrene Attic Insulation

The cost of polystyrene attic insulation ranges from $1,000 to $9,000. Polystyrene is a foam insulation type. It can be found in spray foam and foam board. It can be expanded or extruded, which changes the material’s properties and how well it insulates. Extruded polystyrene insulates better, and while both are flame retardant, expanded polystyrene can melt, and extruded does not. Polystyrene can cover the underside of the roof deck and floors and walls in the attic.

Rockwool Attic Insulation

The cost of rockwool insulation for the attic is $1,400 to $3,200. Rockwool or mineral wool is made of fibers spun from recycled slag or silica. It can be found in loose-fill and batt insulation types. It is denser and insulates better than fiberglass. It contains silica, so it should only be handled by professionals due to the risk of inhaling dust. There is no danger in having the material in your home once installed.

Sheep Wool Attic Insulation

The cost of sheep wool for attic insulation averages $1,500 to $4,200. Sheep wool or real wool is available in batt form. Wool has a high insulating value and is completely renewable and biodegradable. This makes it good for homeowners who want a truly eco-friendly material. It can be installed DIY and used to fill spaces between joists in the floor and walls. Sheep wool is usually faced with paper on one side.

Cork Attic Insulation

The cost of cork insulation for an attic is $3,000 to $10,000. Cork insulation typically comes in rigid boards. Cork provides superior insulating values per inch than many other materials. However, it is expensive and not commonly used in unfinished areas. It is most commonly added as an additional insulating layer to interior spaces. This includes adding it to walls and ceilings in finished rooms. It can be used in the attic once the space has been finished.

What Is a Good R-Value for Attic Insulation?

The R-value is the amount of resistance for thermal transfer a material possesses. The higher the R-value, the better it insulates. The amount of insulation you need is dictated by the material’s R-value and the climate-determined R-value you need in your attic. Climates with very cold winters need a higher R-value than areas with moderate climates. This means that areas with extreme temperatures or cold zones have higher costs to insulate an attic.

As a general rule, Energy Star recommends insulating to a minimum of R-38 in most attics. However, you may get better results by consulting your climate zone recommendations. Below are the recommended climate-zone-based R-values for the attic.

Labor Cost to Add Insulation to an Attic

The cost of labor for adding insulation to an attic varies depending on the material. Labor costs range from $0.25 to $2.50 a square foot for most insulations. Expect to pay between $250 to $2,500 in labor costs for the average attic, but most people typically pay between $500 and $1,500 for labor out of a $2,500 average total.

The one exception to these costs is spray foam. This material is applied so differently than other insulations that labor is calculated by the hour rather than the square foot. Installing spray foam costs $50 to $100 an hour. Most attics take 6 to 8 hours to insulate, resulting in an average labor cost of $300 to $800 for spray foam.

Cost to Replace Attic Insulation

If your attic insulation is old, degraded, or disturbed by pests, you may want to consider replacing it. Removing old insulation has a cost range of $1 to $3 a square foot. This is in addition to the average costs of adding new insulation to the attic. For an average 1,000 sq.ft. attic, the costs to remove the insulation are $1,000 to $3,000 plus the average costs to install new insulation, giving a total of $3,000 to $6,250 for most attics.

If the insulation is in good condition, you do not need to remove it to add more. You can add more insulation to your existing attic insulation to bring your R-values to the recommended total.

Faced vs Unfaced Insulation Attic

When determining the insulation type to use, consider if the insulation is faced or unfaced. Typically, all types fall into one of the two categories. Faced insulations include foam board and batts, while unfaced include spray foam and loose-fill. The facing can be brown kraft paper, metallic foil, or vinyl. It holds batt insulation and can act as a vapor barrier, preventing moisture from moving from one space to another. Faced insulation is helpful for exterior walls because it prevents moisture build-up. It can also be helpful to hold insulation for easier installation. Costs for both overlap because the two types come in many materials. One is not necessarily better than the other, but if you have moisture issues, facing can prevent moisture from penetrating the areas the insulation is applied to.

Attic Insulation Removal Cost

If your insulation is old or in the way of new construction, you may want to remove it. Attic insulation removal costs between $1 and $3 a square foot, depending on the type and how much. Costs can be higher if your insulation contains asbestos or other hazardous materials. Insulation does not need to be removed if you plan on adding more - it only needs to be removed if it is in the way or contains things like mold or asbestos.

Structural Insulated Panels for Attics

Another method of adding insulation is to use structural insulated panels or SIPs. SIPs are essentially plywood and insulation sandwiches used to build with. While they are not a good choice for adding insulation to your existing attic, SIPs can be used to better insulate the space while you build if you are building an attic addition. SIPs create a tight building envelope because they do not have empty cavity walls. The average cost to build with SIPs is $10 to $12 a square foot for the addition.

How to Know If Your Attic Needs Insulation

You can determine if your attic needs insulation in several ways. The first is look and measure. Most homes need a minimum of 10” to 14” of insulation on the attic floor. If you find less than this, you may need to add more.

Other signs are harder to pinpoint and measure but can be obvious if you are looking for them. The first is ice dams forming on your roof in the winter. If your warm air is escaping into the attic, it melts the snow on your roof, where it runs to the edge and re-freezes.

Another sign is temperature variances between floors. If the rooms just below your attic are harder to keep warm in the winter or are getting very hot in the summer, it can be a sign of needing more attic insulation. Feeling drafts in these areas can also be a sign.

Finally, speak to your neighbors. If your energy bills are higher than other homes in your area that are about the same size, it can be an indicator that you need additional attic insulation.

Attic Insulation Blown-In vs Batt

Two of the most common attic insulation types are blown-in and batt. Blown-in insulation can be made of cellulose, fiberglass, or rockwool, while batts can be made of fiberglass or rockwool. Both can be added to many areas of the attic. Batts are most commonly added to the space between joists in floors and walls, and blown-in is most commonly added to the attic floor. Of the two, batts are generally the least expensive method and easiest to DIY. Blown-in insulation can let you get deeper amounts of insulation quickly, which can increase your R-values substantially. You can use both in the attic to insulate different areas, and many people choose this route.

Attic Insulation Fiberglass vs Cellulose

Two of the most commonly used materials in the attic are fiberglass and cellulose. Both are easy to install and used to cover the floor and some wall cavities. Fiberglass comes in batt and blown-in form, while cellulose comes in two forms of loose-fill - damp and dense pack.

Of the two, fiberglass is generally considered to be easier to install. Fiberglass does not settle, but cellulose can, which decreases its insulating properties over time. However, cellulose has a higher R-value than fiberglass, making it a better choice for reaching recommended R-values quickly. Of the two, fiberglass is generally less costly.

Enhancement and Improvement Costs

Energy Audit

If you are unsure whether your attic needs more insulation or what areas to insulate first, an energy audit may help. During an energy audit, a thorough study of your home is conducted. Areas where you are losing the most energy are identified to address those first. An energy audit typically costs $145 to $420.

Soundproofing

Adding insulation can improve acoustics and act as a soundproofing agent. If you want to add more soundproofing, this can be done with additional acoustic-absorbing material. The average cost to soundproof a room is $1,000 to $2,500.

Mold Remediation

If your attic has had leaks or moisture problems, you may have mold growing in the area or affecting the insulation. Before you can add more or new insulation, you must deal with the mold first. Mold remediation costs between $1,500 and $3,500 and removes mold from the area.

Humidity Repairs

Your attic may have higher-than-average humidity levels. This is particularly true in the warmer months. Humidity causes mold growth or settling in cellulose insulation. Adding a dehumidifier to your attic can address this issue. Dehumidifiers cost from $100 to $1,000, depending on the size and type.

Additional Considerations and Costs

• Vapor barrier. While previous recommendations were to use a vapor barrier with your insulation, this is currently not recommended. Vapor barriers may trap moisture in your attic rather than allowing it to evaporate. Trapped moisture can cause mold, mildew, and other problems.
• Storage decking. If you want to place decking over your attic floor for storage, it is recommended that you insulate first, and then lay the decking down over the insulation.
• Rebates. Federal and state rebates and credits are frequently available for adding insulation. Speak to your contractor about what may be available.
• Regulations. Building regulations can dictate where and how you insulate parts of your home. Speak to your contractor to ensure your new insulation meets code.
• Vents. Ventilating your attic is also very important. Ventilation keeps air moving, preventing it from superheating and potentially transferring heat to your home.
• Asbestos. If your home was built before 1990 and your insulation looks grainy with shiny flecks, it may contain asbestos. You should have this tested before removal and call an asbestos abatement team if necessary.