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7 Reasons You Should Have Spray Foam Insulation in Your Crawl Space

image of molding and falling insulation

Originally posted 7/16/20, updated 8/6/21

When you’re a kid, sliding across hardwood floors in your socks is fun.  And let’s be honest, sometimes it’s fun when you’re an adult, too!  But what is NOT fun is being forced to wear socks because your floor and your feet are both cold. 

Insulation is supposed to help maintain your home’s temperature.  It’s meant to block out drafts and hold the cooled or heated air inside.  But like many things, all insulation methods are not created equally.

Acculevel is a foundation repair company, which at first glance may not seem like the most relevant source of information about insulation.  However, one of our primary services is repairing crawl spaces.  And we have seen many, many examples that clearly illustrate why fiberglass insulation is a bad fit for crawl spaces.   We want you to avoid the pitfalls that come with the wrong insulation type, because they can be frustrating and expensive to repair.


Why You Should Not Use Fiberglass Insulation in Your Crawl Space

At one time, builders thought insulating the crawl space with fiberglass batting was a sound practice.  Unfortunately, time has shown us that this is a terrible idea.  It frequently comes loose and falls out of place, which is frustrating and wasteful.  It’s not insulating anything when it’s falling to the ground!

wet crawl space with molding insulation falling downThis photo was taken by an Acculevel project advisor during a routine estimate appointment.  This is clearly the “before” picture.  The “after” is below.

But where it stays in place it can actively cause damage to your wooden flooring structure.  This is because the batting absorbs and holds water, much like a sponge.  Since this itchy sponge batting is attached to your joists, beams, and subfloor, the moisture gets “shared” with those wooden components.  Over time, if the fiberglass batting absorbs enough water, it can become too heavy for the fasteners and fall out of place.    


A Damp Flooring Structure Is a Major Issue 

Damp boards make an appealing home for insects like termites.  Termites like softer wooden surfaces because it’s easier for them to chew.  The insulation itself can be an enticing location for larger pests looking for nesting materials.  And both surface types- damp wood and insulation- can develop a variety of molds.  None of these things are what you want in or around your home! 

Mold and water contribute to how quickly wood rots.  As your wooden joists and beams decay, your floors will begin to sag.  The only way to fix sagging floors is to repair or replace the damaged boards. 

All of these issues can be costly to repair.   In the last 12 months, the average cost to repair sagging floors is about $5600, and the price range for mold treatment is $2100-$4200.  We don’t have pricing for extermination services, but if you have molding and sagging floors, we know you’re going to pay at least $7700 for repairs. If you don’t have these problems yet, then replacing your damaged or failing fiberglass insulation with spray foam is an excellent preventative measure. 

photo of earlier crawl space, now repairedThis photo was taken by an Acculevel team member, after repairs to the crawl space were completed.  They removed the old insulation, installed spray foam along the outside walls, and replaced the failing wooden supports with adjustable steel jacks.


If you have questions about waterproofing, sagging floor issues, or unpleasant odors in your crawl space, check out our comprehensive Crawl Space Repair Guide for Homeowners!

What Is Spray Foam Insulation? 

At Acculevel, we use a formula that combines two different components.  Once mixed, these create a solution that can be sprayed onto any clean, dry surface.  (Full disclosure: we use products from Better Energy Store.

The spray begins as two liquids, but through the mixing process it becomes a wet foam.  Immediately after spraying, the foam expands- filling every gap or crack along the way.  It hardens as it dries, and becomes a solid, lightweight insulation that blocks out anything outside your home.  

Diagram of flooring structure

In our industry, spray foam is applied to spaces between floor joists, along band boards (or band joists), or along the walls if you are planning to finish your basement.  We have also used it to seal off crawl space vents.  

close up of spray foam A close-up of spray foam installed along the band boards. This picture was taken by an Acculevel crew member after the crawl space repairs were completed.


7 Reasons You Should Use Spray Foam Insulation in Your Crawl Space 

  1. Spray foam insulation gets into even the smallest cracks, which thoroughly blocks air flow from the outside.  This means no more drafts under your home- and no more cold floors!
  2. Because the air flow is completely blocked, this eliminates one of the ways pollen gets into your home.  This is an immediate improvement in air quality, which anyone with allergies will be thrilled to hear.
  3. Eliminating drafts and pollen particles will also improve your HVAC performance.  A more efficient heater/air conditioner runs less, and reduces utility costs.
  4. Spray foam insulation repels moisture, which eliminates a source for mold to grow.  This is another win for air quality.  Keeping moisture out also helps prevent leaks.
  5. Since spray foam sets up to a hard, dense material, it deters both insects and larger pests.  Sure, if a raccoon is determined to claw its way through spray foam it probably can.  But most pests don’t want to work that hard when there are more accessible spaces nearby.
  6. It adheres to the surface where it is installed, no fasteners needed.  It also conforms to the exact space it’s in.  This keeps it from deteriorating or falling.  The life expectancy of spray foam insulation is 80+ years. 
  7. The R value of spray foam insulation is double that of fiberglass batting.  The R value of fiberglass batting is 2.8-3.9; spray foam’s R value is 5.5-7.12.  The “R value” is how effective a material is at preventing heat transfer.  The higher the number, the more effective the surface.

Please keep in mind that R-value is not always the best way to measure a material.  If you have multiple layers of an insulator, you can have a high R value.  But if there are still gaps or drafts through those materials, you will still have cold floors.

image of molding and falling insulationThis photo was taken by an Acculevel project advisor during a routine estimate.  Some of the fiberglass insulation is falling, and what has stayed in place is beginning to mold.


What Are the Drawbacks of Spray Foam Insulation?

There are only two significant drawbacks to spray foam.  

Cost: Spray Foam is More Expensive

By far, the biggest negative is its initial cost.  At Acculevel, spray foam insulation is $12.08 per linear foot.  For comparison’s sake, fiberglass insulation averages about $1 per square foot.  

Something to consider:  our $12.08 per linear foot includes labor AND materials.  The price of fiberglass insulation is something I researched, averaging out prices at a variety of hardware stores.

Dear Reader, I must admit: comparing square footage to linear footage was embarrassingly hard on my brain.   If you are in the same boat, let’s row together:

Let’s assume the walls of your crawl space are 60 feet by 25 feet.

Sq footage = 60 x 25 or 1500

Linear footage= 25+25+60+60 or 170

This means you can insulate the entire crawl space with fiberglass insulation for $1500.  Or you can insulate the entire perimeter with spray foam for $2054.


Spray Foam Insulation Does Not Move

The other potential problem with spray foam is its permanence.  If you decide to build an addition to your home, and need to access the wall of your crawl space?  You will have to manually scrape the foam off the affected surface.  It can’t be pulled down or easily cut away.  


Are You Ready to Insulate Your Crawl Space with Spray Foam? 

You’ll want to find an experienced, reputable contractor to work on your home.  If you live in Indiana or the surrounding areas, call Acculevel!  One of our friendly customer care representatives will schedule a free appointment for you.  Our knowledgeable project advisors will evaluate your home and provide a written estimate, valid for 12 months. 

If you don’t live in our service area, please make sure you verify that your contractor is insured and accredited by the Better Business Bureau.  

Not familiar with the process of finding or meeting with a contractor?  We offer a free downloadable guide of questions to ask a contractor.  This can help you interview and vet companies,to find the best fit for you and your home repairs.    


Kelly Kater

Over her twenty year career, Kelly has worked in a wide variety of fields: secondary education, nursing, biology, elder care, the postal service, multicultural development, and academia. She has developed a skill for translating industry-specific jargon into everyday language. Her goal is to share the knowledge and experience of the Acculevel team with homeowners, in a way that is both engaging and informative.

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