Ever notice how your floors feel like ice in January? Or maybe your energy bills keep climbing while your comfort stays stuck in neutral? You’re not the only one dealing with this.
Here in Central Kansas, picking the right crawl space insulation can make all the difference. Two options get talked about most: spray foam and fiberglass. Both have their fans, but they work in totally different ways.
We’ve tackled hundreds of crawl spaces across Wichita, Hutchinson, and the surrounding area since 2011. We’ve seen what works and what falls apart when Kansas humidity rolls in.
Let’s walk through what each option brings to the table.
Spray Foam Insulation Overview
Spray foam seals tightly. It stops air leaks and keeps moisture out, two problems that plague crawl spaces in our region. Closed-cell spray foam is what we use most often below grade because it doesn’t just insulate. It creates a barrier that water can’t penetrate.
Key features of spray foam insulation
Closed-cell spray foam delivers an R-value between R-6.5 and R-7 per inch. That’s nearly double what fiberglass offers per inch of thickness.
The material expands to fill every crack and gap as it’s applied. Once it hardens, it forms a rigid, airtight seal that blocks both air movement and moisture intrusion.
This barrier stops pests from sneaking in through tiny openings. Rodents can’t nest in it as they do with fiberglass batts.
Spray foam lasts 80 to 100 years when installed correctly. That’s often longer than the home itself will stand.
Benefits of spray foam insulation for crawl spaces
Air sealing is the game-changer. A properly sealed crawl space can cut energy bills by 15% to 20%. In Central Kansas, that matters year-round. Our winters can drop below freezing for days, and our summers bring heat and humidity that creep into every unsealed space.
Spray foam doesn’t absorb water. When condensation forms or ground moisture rises, the foam stays intact and keeps performing. Indoor air quality improves, too. Mold spores and musty odors stay out of your living space because the crawl space stays dry and sealed.
Many homeowners notice warmer floors in winter within days of installation. Your HVAC system doesn’t have to work overtime to compensate for drafts.
Drawbacks of spray foam insulation
Cost is the first hurdle. Spray foam runs $1.50 to $3 per square foot for closed-cell applications, roughly three times the cost of fiberglass. Installation requires trained professionals with specialized equipment. Mistakes during application can leave gaps or cause the foam to cure improperly.
Removal is tough. If you need to access plumbing or wiring later, cutting through hardened spray foam takes time and creates a mess. Repairs to the foam itself require calling in a pro.
Fiberglass Insulation Overview
Fiberglass batts are a budget-friendly pick for crawl spaces. They’re easy to find, simple to install, and have been used in homes for decades. We see them in older crawl spaces across Central Kansas all the time. But easy doesn’t always mean effective.
Key features of fiberglass insulation
Fiberglass batts deliver an R-value between R-3.5 and R-4 per inch. That’s about half the thermal resistance of closed-cell spray foam. The material is lightweight and comes in pre-cut rolls. You can cut it to fit between floor joists with basic tools.
It’s non-combustible, which is a safety plus near electrical wiring and furnaces. Fiberglass won’t catch fire the way some foam can if installed incorrectly.
Benefits of fiberglass insulation for crawl spaces
Price is the big draw. Fiberglass costs between $0.30 and $1.50 per square foot, making it the most affordable insulation option. DIY installation is possible for handy homeowners. Weekend warriors can knock out a crawl space with batts, a utility knife, and a stapler.
If you have a bone-dry crawl space with no history of moisture issues, fiberglass can do its job. But that’s a big “if” in our climate.
Drawbacks of fiberglass insulation
Moisture is fiberglass’s worst enemy. The material doesn’t absorb water like a sponge, but it holds moisture within its fibers. Once damp, fiberglass loses its R-value and becomes a breeding ground for mold.
We’ve pulled out countless batts in Central Kansas crawl spaces that looked like science experiments. Gravity causes sagging over time. Heavy, wet insulation pulls free from fasteners and ends up on the crawl space floor, leaving joists exposed to cold air.
Pests love it. Mice and insects burrow into fiberglass batts to build nests. That ruins the insulation and introduces health hazards from droppings and odors. Air leakage continues even with fiberglass in place. The material slows heat transfer but doesn’t seal gaps like spray foam does.
Spray Foam vs. Fiberglass: Performance Comparison
These two materials couldn’t be more different when you put them side by side. Let’s break down how they stack up on the metrics that matter most.
Moisture resistance and air sealing
| Insulation Type | Moisture Resistance | Air Sealing Ability | Common Issues in Central Kansas |
| Spray Foam (Closed-Cell) | Excellent moisture barrier. Resists water intrusion and prevents condensation. Ideal for humid or encapsulated crawl spaces where moisture control is critical. | Seals gaps, cracks, and penetrations thoroughly. Reduces outside air infiltration and improves indoor air quality by blocking allergens and odors. | Stops Kansas humidity from creeping in. Prevents cold drafts in winter. Creates a long-term air seal when applied correctly. |
| Fiberglass Batts | Poor moisture control. Absorbs and holds water easily. Can trap moisture and promote mold growth. Best used only in dry, well-ventilated spaces. | Minimal air sealing. Air leaks persist, especially near band joists and around penetrations. Susceptible to pest pathways and odors. | Mold growth after the Kansas spring floods. Pest nests are common in crawl space corners. Draft complaints continue even after installation. |
R-value and thermal efficiency
R-value tells you how well a material resists heat flow. Higher numbers mean better insulation.
| Feature | Spray Foam Insulation (Closed-Cell) | Fiberglass Insulation |
| R-value (per inch) | R-6.5 to R-7 | R-3.5 to R-4 |
| Thermal Efficiency | Creates a tight seal that blocks drafts and cold spots. Heat loss drops measurably. Cuts energy bills, especially in winter. Maintains performance for 80 to 100 years without sagging or settling. | Allows some air movement. Struggles in windy or humid spots. Heat escapes through cracks and seams. Lower impact on energy bill savings. Tends to sag and lose effectiveness within 15 to 20 years. |
| Performance in Humidity | Functions as both insulation and a vapor barrier. Resists moisture intrusion. Helps prevent mold growth under floors. Keeps crawl space air quality stable year-round. | Absorbs moisture from the air and ground. Prone to mildew and mold if the crawl space gets damp. Loses R-value when wet. |
| Best Use Case (from our experience) | Crawl spaces with a history of humidity. Properties needing maximum efficiency and air sealing. Long-term solution for energy-conscious owners. | Dry, vented crawl spaces in arid climates. Budget projects where high insulation values are less critical. Spaces with no risk of water intrusion. |
Durability and longevity
How long will it last? That’s a fair question when you’re investing in your home.
| Feature | Spray Foam Insulation | Fiberglass Insulation |
| Moisture Resistance | Closed-cell spray foam does not absorb water. Prevents mold growth and stays dry for decades. Perfect for humid crawl spaces in Kansas. | Fiberglass traps moisture. High risk of mold and mildew. Damp insulation loses R-value quickly and becomes a liability. |
| Pest Resistance | Creates an airtight seal. Keeps pests like rodents and insects out. No food source or nesting material for critters. | Common nesting spot for rodents. Attracts insects looking for shelter. Pests tunnel through batts and ruin effectiveness. |
| R-Value & Efficiency | R-6.5 to R-7 per inch (closed-cell). Insulates at a higher rate. Holds value year after year without degrading. | R-3.5 to R-4 per inch. Lower insulation value. Sags, settles, and loses efficiency over time. |
| Longevity | Lasts 80 to 100 years when installed properly. Rarely needs maintenance. Bad installation can cut life short, so hiring a trained pro is key. | May last 10 to 15 years, but often less in crawl spaces. Sags, compresses, or falls. Needs frequent inspection and replacement. |
| Maintenance Needs | No maintenance if installed correctly. Permanent solution. Withstands Kansas humidity without issue. | Needs regular checks for water, mold, and sagging. May need to be replaced after severe weather or flooding. Labor costs add up over time. |
Cost Comparison: Spray Foam vs. Fiberglass
Spray foam costs more upfront. Closed-cell applications run $1.50 to $3 per square foot. Fiberglass batts come in at $0.30 to $1.50 per square foot.
That price gap is real. For a typical 1,000-square-foot crawl space, fiberglass might cost $500 to $1,000. Spray foam could run $2,000 to $3,400, depending on wall height and site conditions.
But here’s the thing. We’ve seen homeowners save 15% to 20% on energy bills after spray foam installation. Those savings add up fast. A few hundred dollars a year can pay back the initial investment in five to seven years.
Fiberglass is cheap today but expensive tomorrow. When batts sag or get wet after a spring storm, you’re looking at removal and replacement costs. Those repeat expenses stack up over time.
Spray Foam Insulation for Crawl Spaces
Crawl spaces in Central Kansas face a tough job. They deal with humidity, pests, and wild temperature swings from one season to the next.
We have seen homes with drafty floors and moisture problems that just won’t quit. Using closed-cell spray foam insulation makes a real difference here.
It forms a tight seal on walls and joists, keeping out both water vapor and unwanted critters. No more cold floors or damp crawl space odors traveling up into your living space.
With an R-value of R-6.5 to R-7 per inch, closed-cell foam packs serious insulating power for every square foot covered. Homes and buildings in our area get hit hard by humid summers and bone-chilling winters.
Spray foam handles all kinds of weather without breaking down or sagging over time, as other options might do underneath the house. Professional installation is key. Improper application can create pockets where air still sneaks through.
That’s something we avoid at all costs, using the right tools for each job. Yes, this method comes with a higher upfront cost than fiberglass batts, but solid performance means fewer headaches later on from mold or pest invasions creeping up from below your feet.
Conclusion
Choosing the right crawl space insulation can feel like picking between apples and oranges. Spray foam blocks out moisture, seals tight, and lasts for decades. It’s a smart choice for humid spots in Central Kansas, where moisture and pests are common problems.
Fiberglass saves dollars up front but may invite trouble with mold or pests if things get damp. We always weigh budget, climate, and long-term results before grabbing the tool belt. Picking smart now means fewer headaches down the line and more comfort under your feet every single day.
Contact Advanced Seal Spray Foam for a free estimate or for more details about the best crawl space insulation.
