Ashburn, VA

How much does crawl space insulation cost?

$1.00 – $4.50 cost per square foot
$500 – $3,700 average total cost

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February 15, 2022

Reviewed by Tom Grupa and 3 expert insulation installers on HomeGuide.

Crawl space insulation cost

Crawl space insulation costs $1.00 to $4.50 per square foot or $500 to $3,700 on average. Spray foam insulation under a house costs $2 to $5 per square foot. Replacing insulation in a crawl space adds $1 to $2 per square foot for old insulation removal.

Crawl space insulation cost
Square feet Cost to insulate the walls* Cost to insulate the subfloor
700 $330 – $1,500 $700 – $3,150
1,000 $420 – $1,900 $1,000 – $4,500
1,200 $450 – $2,000 $1,200 – $5,400
1,500 $480 – $2,200 $1,500 – $6,800
2,000 $540 – $2,400 $2,000 – $9,000
2,500 $600 – $2,700 $2,500 – $11,300

*Based on a 3' high crawl space

Average cost to insulate a crawl space

The following table shows the average cost to insulate a crawl space:

Average cost to insulate a crawl space
Average cost to insulate a crawl space

Average cost to insulate a crawl space
National average cost $1,800
Minimum cost $320
Maximum cost $10,000
Average cost range $500 to $3,700

Cost data is from research and project costs reported by HomeGuide members.

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Cost to install insulation under house by type

Installing insulation under a house costs $500 to $3,700 on average, depending on type and location.

  • Insulating the subfloor and rim joists is best in vented spaces.
  • Insulating the walls and rim joists is ideal in closed, unvented areas.
  • Insulating the subfloor, walls, and rim joists are recommended in cold climates.
Cost to install insulation under house by type
Insulation type Crawl space location Cost per square foot Total cost installed*
Closed-cell spray foam insulation Walls + subfloor $2.00 – $5.00 $850 – $6,700
Rigid foam board Walls $1.20 – $3.70 $500 – $1,600
Rigid foam board Subfloor $1.20 – $3.70 $1,200 – $3,700
Blown-in Subfloor $1.00 – $2.80 $1,000 – $2,800
Roll and batt (fiberglass, rockwool) Subfloor $0.90 – $1.40 $900 – $1,400

*Average total for a 1,000 SF crawl space with 3' high walls.

Contractor installing board insulation in crawl space
Contractor installing board insulation in crawl space

  • Rigid foam board can be expanded polystyrene (EPS), extruded polystyrene (XPS), or polyisocyanurate (Polyiso, ISO).
  • Roll and batt insulation may be fiberglass, Rockwool, natural fibers, or plastic. Roll and batt is best reserved for subfloors in dry, conditioned spaces.
  • Fiberglass batt insulation is the most common but the most problematic in vented crawl spaces. Fiberglass comes loose over time and also absorbs moisture, reducing its insulating value and potentially causing mold and structural damage.
  • Blown-in insulation is not typically recommended for crawl spaces but may be useful in spaces too tight for other insulation.

Spray foam insulation for crawl space cost

Spray foam insulation costs $2 to $5 per square foot on average for a crawl space. Spray foam insulation under a house works best when combined with rigid foam board insulation. Closed-cell spray foam is ideal for sealing subfloor gaps and insulating and sealing the floor joists.

Closed-cell spray foam insulation pros and cons
Pros Cons
  • Long-lasting
  • Does not lose its R-value over time
  • Creates a moisture barrier
  • Provides an airtight seal
  • Adds strength to foundation walls
  • Inert material – not a food source for bacteria, mildew, or mold
  • More expensive than fiberglass
  • Requires professional installation
  • Difficult to remove if needed for future repairs
  • May trap moisture
  • May shrink over time in areas with extreme temperature differences
  • Requires time to cure
Closed-cell foam is preferred for crawl spaces because it has a higher R-value per inch and provides a moisture barrier. Open-cell foam allows moisture in and is better for above-grade applications.

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Crawl space insulation cost calculator

Crawl space insulation cost calculator
Factor Cost per square foot
Insulation materials $0.50 – $3.20 
Installation labor $0.50 – $1.30 
Total cost to install $1.00 – $4.50 

The following factors affect the cost of crawl space insulation:

  • Area size – The square footage and wall height affect the material and labor required.
  • Accessibility – Ease of access affects the labor cost. Jobs in hard-to-reach areas typically take longer to complete.
  • Type of insulation – Roll and batt insulation is cheaper than rigid foam board. Spray foam is the most expensive.
  • Faced vs. unfaced – Faced insulation batting costs $0.10 to $0.25 per square foot more than unfaced insulation and contains a vapor barrier.
  • Geographical location – Homes in climates with extreme temperature changes require thicker insulation, which costs more.
  • Vented vs. unvented space – Insulating a vented crawl space may require additional sealing to meet current building codes.
  • Old insulation removal – Removing and disposing of old insulation costs $0.75 to $2.00 per square foot.
  • Preparation – Spray foam requires a clean and dry surface. Cleaning and preparation may increase the labor time.
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Cost to insulate crawl space walls vs. underside of the house floor

Insulating crawl space walls costs $420 to $1,900 on average for a 1,000 square foot space with 3' high walls. Insulating the underside of the house floor in the same space costs $1,000 to $4,500.

  • Insulate the subfloor and rim joists when the crawl space is vented.
  • Insulate the walls and rim joists when the crawl space is unvented or contains HVAC ducting.

Crawl space insulation prices by R-value

R-value is the measurement of a material's heat resistance. The higher the R-value, the better the insulator. The recommended R-value for crawl spaces depends on the climate and local building codes.

Crawl space insulation prices by R-value
R-value Foam board Closed-cell spray foam Roll and batt
R-6 to R-7 $1.00 – $1.80 $1.50 – $2.50 $0.70 – $1.00
R-12 to R-14 $1.50 – $2.50 $2.00 – $3.80 $0.90 – $1.20
R-18 to R-21 $2.20 – $4.00 $3.00 – $4.50 $1.00 – $1.30
R-22 to R-30 $2.80 – $4.60 $4.00 – $5.50 $1.10 – $1.50

*Cost per square foot installed.

Insulation R-value recommendations
Insulation R-value recommendations

Labor cost to install insulation in crawl space

The labor cost to install insulation in a crawl space is $0.50 to $1.30 per square foot on average, depending on the insulation type. Batting is quick to install. Spray foam needs more prep time but installs faster than foam board, which requires sizing, cutting, and sealing each piece.

Crawl space cleaning and repairs

Crawl space cleaning and repairs cost $500 to $8,000, depending on the condition. Repairs may include vent and foundation repair, mold removal, pest control, and more. Cleaning and repairing the space is essential to ensure the new insulation does not mask underlying problems that could worsen over time.

Crawl space vapor barrier or encapsulation

Crawl space encapsulation costs $3,000 to $8,000 on average and is recommended for homes in areas with high moisture levels. Installing a vapor barrier costs $1,200 to $4,000. When using unfaced fiberglass insulation, lining the crawl space first with a vapor barrier adds a layer of moisture control.

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DIY cost to insulate a crawl space

The DIY cost to insulate a crawlspace is $150 to $700 on average. Hiring a professional is recommended to ensure there are no water damage or pest issues, all gaps are sealed, and the new insulation is installed correctly.

Effectively insulating a crawl space includes:

  • Getting rid of all water sources
  • Removing old insulation
  • Insulating the walls instead of the ceiling
  • Sealing all vents, gaps, and hatchways
  • Using mold-resistant, waterproof insulation
  • Sealing rim joists with boards or closed-cell spray foam
  • Installing a vapor barrier on the floor
  • Removing any built-up moisture with a dehumidifier once the installation is complete

Frequently asked questions

Should a crawl space be insulated?

Yes, a crawl space should be insulated. Uninsulated crawl spaces are a common source of unconditioned air infiltrating the home. Cold floors, high energy bills, and freezing or bursting pipes are signs the home needs better crawl space insulation.

What are the benefits of insulating a crawl space?

Benefits of insulating a crawl space include:

  • Prevents cold floors and drafts along the baseboards
  • Improves indoor air quality and comfort
  • Reduces energy bills
  • Keeps out pests and rodents (closed-cell spray foam)
  • Adds a moisture barrier (closed-cell spray foam)
  • Prevents frozen pipes

What R-value for crawl space floor insulation?

The recommended R-value for crawl space floor insulation is R-13 to R-30, depending on the home's geographical location. The colder the climate, the higher the recommended R-value.

What is the best type of insulation for a crawl space?

The best type of crawl space insulation is a combination of rigid foam and closed-cell spray foam. Both types provide insulation and an air and moisture barrier when adequately sealed. The best place to install the insulation depends on accessibility and whether the space is vented or unvented.

  • Vented – Insulate the subfloor or crawl space ceiling with rigid foam. Seal subfloor gaps and rim joists with spray foam and insulate ductwork and pipes before installing the subfloor insulation.
  • Unvented – Use sealed rigid foam on the crawl space walls. Use spray foam to air seal and insulate the rim joist. In cold climates, insulating the subfloor is also recommended.

Can you use spray foam insulation in a crawl space?

Spray foam insulation can be used in a crawl space. Still, many experts recommend against using it as the only insulation because it makes future underfloor repairs challenging to access.

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Tips for hiring an insulation company

Before hiring an insulation contractor to insulate your crawl space:

  • Get at least three estimates to compare.
  • Look for pros experienced in crawl space insulation.
  • Browse their reviews on HomeGuide and Google.
  • Select companies that are insured, bonded, and have been in business for more than five years.
  • Ask for references.
  • Avoid selecting the lowest quote as quality may suffer.
  • Get a detailed estimate, contract, and warranty in writing before the work begins.
  • Never pay in full before the project starts. Use a payment plan instead for work completed.

Questions to ask

  • Are you licensed, bonded, and insured?
  • How long have you been in business?
  • What experience do you have with crawl space insulation?
  • What type of insulation do you recommend for my crawl space, and why?
  • How long will the installation take?
  • What is and is not included in the estimate?
  • What additional costs should I expect?
  • How long should the insulation last?
  • Is there a warranty, and if so, what does it include?
  • Are there rebates available, and do you apply for them?

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