Can You Spray Foam A Crawl Space?

Spray foam is a quick and cost-effective insulation method for roof, ceiling, and other construction projects. The question is, can you also spray foam your crawl space to make your home more comfortable? We’ve researched the topic to provide the answer for you.

Spray foam is highly recommended for crawl spaces, basements, and attics because of its ability to seal gaps, cracks, and holes. It provides a barrier against vapor and air that improves the efficiency and comfort level of your home. That’s not all, it also prevents rodent and pest infestations in your crawl space.

However, the insulation process isn’t as easy as the other DIY projects. Experience and the right equipment are required to get it right. Misuse of the mixture can result in health hazards and damage to your property which can cost you a lot. Continue reading to learn more about important factors and considerations if you plan to spray foam your crawl space.

A technician spraying foam insulation using plural component gun for polyurethane foam, Can You Spray Foam A Crawl Space?

Is Spray Foam Effective?

Providing homeowners with the highest insulation value since 1986, spray foam is one of the superior insulation products available in the market. With heat transfer properties, it reduces HVAC workload by up to 35 percent! Also, it fills the gaps that traditional insulation solutions can’t.

Construction worker spraying expandable foam insulation between wall studs

What is the R-Value of Spray Foam?

This refers to the insulating material's resistance to heat flow. Spray foam has two classifications, the open-cell, and closed-cell, and both have different R values. 


This foam has tiny cells that are left open. As a result, the structure is softer and more flexible. The R-value is R-3.8 per inch with 0.5lb/ft3 density. It is 3.75” thick or greater, as an air barrier.


This one is completely enclosed, preventing air from filling the cells. The R-value is R-7 per inch with 2lbs/ft3 density. It acts as an air and vapor barrier at 1.5” thickness or greater.

How Much Does Spray Foam Cost?

Foam Type Materials/ Board Foot   Installation/Square Foot
Open-cell $0.44 - $0.65 $1.50 - $4.90
Closed-cell $1.00 - $1.50 $1.50 - $4.90
The information presented here has been provided by HomeAdvisor

Typically, spray foam is more expensive than cellulose or fiber insulation, but it’s worth it. 

How Long Does Spray Foam Last?

Technician spraying foam insulation

With proper application, spray foam can last a lifetime. The material sticks extremely well to substrates and maintains rigidity upon drying. Also, it rarely deteriorates.

However, an incorrect application such as un-proportional chemical ratio, poorly prepared surface, and improper amount of spray can greatly reduce the spray foam life. You might also be subjected to off-gassing and foul odor.

Is Spray Foam Safe?

Technician dressed in a protective white uniform spraying foam insulation

Made of isocyanate and polyol resin, spray foam can be hazardous when inhaled before its cured. Also, when applied or used improperly. But with correct installation and curing, it is generally safe for any property and should not cause any health-related problem.

Pros and Cons of Spray Foam

Spraying expandable foam insulation between wall studs

Here are the pros and cons to take into account, if you’re considering spray foam for your crawl space:


Better than any other insulation method

Spray foam provides an air-tight seal like no other because of its expansive nature. If you try it, you'll discover that it fills and seals gaps more effectively than any other insulation method available in the market today.

Reduces electricity bill

Spray foam makes your home more energy-efficient, reducing your electricity bill by up to 30 percent. Feel free to use it with other insulation methods to eliminate unnecessary airflow through your wall or ceiling.

Impermeable to water

It also prevents and absorbs water, keeping your crawl space dry. That said, you never have to worry about floods ruining the foundation of your property.

Deters mold and mildew

Without moisture, spores cannot foster, and that means a mold-free crawl space! Spray foam is also an inert polymer that doesn’t tolerate mold and mildew.

Lasts a lifetime 

Spray foam adheres extremely well to any surface, creating strong bond forms that can last for decades. You can save more money from maintenance, upgrade, or replacement.


It cannot always fill every possible cavity

Spray foam is a flexible solution, but not a magical solution for every problem. Sometimes the mixture doesn’t expand to reach some gaps. When this occurs, your home may not be as efficient during summer or winter due to air and water leakage. 

It can shrink 

Spray foam can indeed last a lifetime, however, houses in extreme temperatures are at risk of deterioration. The material can shrink and begin to pull away from the surface. This can be solved by spraying more foam or installing a new mixture, though.

Requires experience to get it right

The foam quickly cures is the common problem that many installers face with spray foam. When the curing process begins, the mixture starts to fold over itself, creating many unfilled areas that are hard to spot.

If you are not diligent, you might even miss a whole section. Also, pausing for over 30 seconds will get the nozzles clogged. So it's important that you know how to handle it before proceeding.

How to Install Spray Foam?

Spray polyurethane foam for roof

We want to emphasize that when mishandled, spray foam can be hazardous. Generally, it’s best to leave it to professionals with the right training and equipment. But if you really want to try and do it yourself, there are spray foam kits available to purchase.

Click here to see DAP spray foam kit on Amazon.

DIY Spray Foam

  • First and foremost, you must remove the old insulation before you spray foam because it will just get nasty and get in the way.
  • Read the instructions of the product carefully before use. 
  • Check if the canister is hooked up properly and if there’s an issue with the hose as that can ruin the mixture in the tank.
  • The sealant is flammable, so keep it away from flames.
  • Cover the surrounding space with newspaper or drop cloth.
  • Before the installation wear gloves, goggles, masks, eye protection, and other safety gears. 
  • Ensure that the surface is prepared or is dry first; otherwise, the mixture will just fall away.
  • Spray the materials where you want them to be.
  • Avoid pausing for more than 30 seconds or the nozzles will get clogged. 
  • Once the material is cured, remove the excess with a utility knife.

If you want to spray your enclosed wall, please note that the DIY spray won’t work. This usually calls the help of a professional who can look at and assess your property. They can insulate the enclosed wall diligently without tearing down the drywall.

Unless you are confident enough that you can handle it properly, it is advisable not to spray foam yourself.

How Long After Spray Foam is it Safe? 

The Environmental Protection Agency (EPA) recommends staying out of the house for 24-72 hours after spray foaming to let the chemicals off while it cures. Long-term exposure can have a detrimental effect on your health, particularly on your respiratory system. 

What if You Breathe in Spray Foam?

Inhaling spray foam can cause nose, eye, and lung irritation which can lead to runny nose, shortness of breath, and chest pain. Getting in contact with it while it's curing, may cause redness, swelling, and itching.

In case you inhale the chemical, get some fresh air, then wash your eyes with water. Also, brush off the particles of your skin. If the condition is worse, seek immediate medical attention.

Safety Consideration

During an application, proper ventilation can help you avoid breathing the particles. While the spray foam is curing, limit access until the mixture is cured. If you really need to get inside the house, wear protective gear. Also, avoid high heat flame near your crawl space to avoid accidents.


Spray foam is an efficient insulation method for crawl space and the basement. However, the installation and curing process can be difficult. Unless you have a lot of experience to handle it, it’s best to leave it to a professional. Also, remember to wait for 24- 72 hours after spray foaming to prevent any health problems.

If you like this post, you might also like: 

Should I Pour Concrete In My Crawl Space? –

Basement Floor Drain Flooding—What To Do? –

Leave a Reply

Your email address will not be published. Required fields are marked *