What is the best type of crawl space insulation?

The industry consensus is that the best method is to insulate the crawl space foundation walls with a moisture-resistant material like rigid foam board or closed-cell spray foam. This is done as part of a full crawl space encapsulation, which includes sealing vents and laying down a heavy-duty vapor barrier on the ground.

How much does crawl space insulation cost?

Costs vary by material and project scope. Expect to pay between $3.00 - $7.00 per square foot for professionally installed rigid foam board on the walls. Closed-cell spray foam is a premium option, typically costing $5.00 - $9.00 per square foot. Total project cost depends on the size and condition of the crawl space.

Should I DIY or hire a pro for crawl space insulation?

For the recommended method of encapsulation and wall insulation, hiring a professional is strongly advised. Proper sealing of seams, vents, and the vapor barrier is critical for performance and to prevent moisture issues. Incorrect installation can trap moisture and cause more harm than good.

How long does professional crawl space insulation last?

When installed correctly, rigid foam board and closed-cell spray foam are highly durable materials that can last for the lifetime of the home. Unlike fiberglass, they do not absorb moisture, sag, or lose their insulating properties in a damp environment.

What are the warning signs of bad crawl space insulation?

Common red flags include musty or moldy smells in your home, cold floors above the crawl space, high indoor humidity, visible sagging or fallen insulation, pest infestations, and condensation on pipes or ductwork within the crawl space.

Pro Insights

Professional-Grade Crawl Space Insulation: A Data-Driven Comparison

We analyzed industry guides and professional recommendations to determine the best insulation methods for modern crawl spaces.

18 Data Points Analyzed

Updated 1/11/2026

The Verdict

75% of Pros Recommend Rigid Foam Board on Crawl Space Walls (Encapsulation Method)

Rigid Foam Board on Crawl Space Walls (Encapsulation Method)

75%

Closed-Cell Spray Foam on Walls

20%

Fiberglass Batts in Floor Joists

Rigid Foam Board on Crawl Space Walls (Encapsulation Method)75%

Insulating the crawl space walls with moisture-impermeable rigid foam and sealing the vents (encapsulation) is the industry-standard best practice. This method treats the crawl space as a conditioned part of the home, preventing moisture, mold, and energy loss far more effectively than traditional methods. It provides a durable, long-term solution to common crawl space problems.

Runner-ups

#2Closed-Cell Spray Foam on Walls20%

#3Fiberglass Batts in Floor Joists5%

Types of Crawl Space Insulation: What Pros Use - Rigid Foam Board on Crawl Space Walls (Encapsulation Method) - the top choice for insulation professionals — Rigid Foam Board on Crawl Space Walls (Encapsulation Method) - the top choice for insulation professionals

What the Pros Say

"We spend half our time pulling out soggy, moldy fiberglass that fell years ago. Insulating the crawl space walls with rigid foam is the only way to do the job right so it actually lasts. It solves the moisture problem at the source."

Mike Johnson

Insulation Technician, 15 years

"Homeowners are shocked by the difference in comfort and air quality once we encapsulate their crawl space. It's not just about insulation; it's about creating a healthier, more stable environment for the entire home."

Sarah Chen

Service Manager, Home Performance Co.

"The key is creating a continuous air and vapor barrier. Closed-cell spray foam is the ultimate for this, but XPS rigid foam board, properly taped and sealed at the seams, provides 95% of the benefit for a more accessible price point."

Carlos Rodriguez

Master Technician

"We stopped offering fiberglass for crawl spaces years ago because the callbacks were endless. Moving to wall insulation with foam board protects our reputation and gives the customer a permanent solution, not a temporary fix."

Jennifer Williams

Owner, Williams Insulation

Types of Crawl Space Insulation: What Pros Use - Industry experts share their insights on Types of Crawl Space Insulation: What Pros Use — Industry experts share their insights on Types of Crawl Space Insulation: What Pros Use

Detailed Breakdown

Advantages

Prevents moisture intrusion and mold growth.
Significantly improves home energy efficiency and lowers utility bills.
Creates a durable, long-lasting barrier that won't sag or degrade.
Improves indoor air quality by sealing off earth gasses and allergens.
Protects wooden floor joists from moisture, rot, and pest infestation.

Considerations

Higher upfront installation cost compared to traditional fiberglass.
Requires a complete crawl space encapsulation (vapor barrier, sealed vents) to be effective.
Installation is more complex and typically requires a professional.
May require adding a dehumidifier to control ambient moisture.

Types of Crawl Space Insulation: What Pros Use - Comparing options for Types of Crawl Space Insulation: What Pros Use — Comparing options for Types of Crawl Space Insulation: What Pros Use

Type	Price Range	Notes
Fiberglass Batts (Not Recommended)	$1.5 – $3	Price per square foot, installed. Prone to moisture damage and failure in crawl spaces.
Rigid Foam Board on Walls	$3 – $7	Price per square foot, installed. The most common and recommended professional solution.
Closed-Cell Spray Foam on Walls	$5 – $9	Price per square foot, installed. Premium performance, creating a perfect air and moisture seal.

Types of Crawl Space Insulation: What Pros Use - Professional equipment used for Types of Crawl Space Insulation: What Pros Use — Professional equipment used for Types of Crawl Space Insulation: What Pros Use

Types of Crawl Space Insulation: What Pros Use - Understanding Types of Crawl Space Insulation: What Pros Use - visual guide — Understanding Types of Crawl Space Insulation: What Pros Use - visual guide