Trusted Crawl Space Insulation Nationwide
Crawl space insulation is the layer of foam, batts, or board installed on the walls or under the floor of the shallow space beneath your house. It keeps cold air and damp from working their way up into your floors, which is why a well-insulated crawl space makes the rooms above it feel warmer and the heating bill smaller. We’re Thistledown Attic Insulation, a Cedarwell-family company founded in 2003, and we’ve spent more than two decades earning trust by writing the price down before any work starts and cleaning up like the house is our own. Every call is answered by a live person, 24 hours a day, at (909) 768-6501.
Crawl Space Insulation
Crawl space insulation is the thermal and moisture protection applied to the foundation walls, the underside of the floor, or both. You need it when floors over the crawl space feel cold underfoot, when pipes freeze or sweat down there, or when your energy bills keep climbing and the attic is already in good shape. Thistledown Attic Insulation installs rigid foam, closed-cell spray foam, and fiberglass or mineral wool batts, and we choose the product after we have seen the space with our own eyes. Crawl space insulation typically falls between $1,200 and $5,500 depending on square footage, how tight the access is, and which material fits the job. Removal of old insulation or a ground vapor barrier adjusts that number, and nothing gets added after the fact. If the attic needs attention too, see our attic insulation page.
Why the Crawl Space Gets Ignored
Nobody goes down there, so nobody notices when the batts have fallen to the dirt or the foil facing has peeled away. Yet a bare or failing crawl space leaks heat all winter through the floor. We photograph what we find so you can see it from the comfort of your kitchen.
Clean Work in Tight Spaces
We lay protection at the access hatch, wear shoe covers inside the house, and bag every scrap of waste. The hose and tools go through the crawl space door or a window, never across your living room floor.
Vented vs. Sealed Crawl Spaces
A vented crawl space has openings in the foundation that let outside air move through. In that setup the insulation belongs between the floor joists, tight against the subfloor, so the heated part of the house is separated from the cold space below. A sealed or conditioned crawl space closes those vents, puts a heavy vapor barrier on the ground, and insulates the foundation walls instead. Both methods work, and each one fails when it is installed in the wrong kind of crawl space. Putting wall insulation in a space with open vents wastes money, and stuffing batts between joists in a damp, sealed space invites mold. Thistledown Attic Insulation checks the vents, the grade around the foundation, and the humidity before recommending either approach, and your written estimate states which one we chose and why.
Floor Insulation Between the Joists
For vented spaces we fit batts or rigid board snugly against the subfloor and hold them with wire supports or fasteners so they do not sag. Gaps around pipes and wiring get sealed, because a small hole leaks as much air as a missing section of insulation.
Wall Insulation for Sealed Spaces
For sealed spaces we fasten rigid foam or spray closed-cell foam to the foundation walls, then run the vapor barrier up the wall and seal the seams. The result is a dry, steady space that protects the floor system from rot.
Vapor Barriers and Moisture Control
A vapor barrier is a heavy plastic sheet laid over the crawl space soil to stop ground moisture from rising into the air and into your insulation. You need one when the dirt floor is bare, when the plastic already down is torn or shifted, or when you smell mustiness near the access door. Thistledown Attic Insulation installs reinforced polyethylene, overlaps the seams, and seals it to the walls and piers so water vapor has nowhere to go. A vapor barrier typically adds $600 to $2,200 depending on the size of the space and how much debris has to be cleared first. We write that line into your estimate separately so you can see exactly what it costs.
Fix the Water First
Insulation over standing water is wasted. If we find pooling, a leaking pipe, or a gutter dumping at the foundation, we tell you before we install anything. Sometimes the best first step is regrading or a downspout extension, and we say so plainly.
Why Dry Insulation Lasts
Wet fiberglass loses most of its R-value and can hold moisture against wood for years. Keeping the crawl space dry is what lets the material do its job for decades instead of a few seasons.
Materials We Install
Rigid foam board is a strong fit for foundation walls because it resists moisture and holds its shape over time. Closed-cell spray foam seals air leaks and insulates in one pass, which suits irregular framing and tight corners that board cannot reach. Fiberglass and mineral wool batts remain a practical choice between joists in vented spaces, as long as they are supported and kept dry.
We install products from Owens Corning, Johns Manville, Knauf, Rockwool, CertainTeed, Icynene, and Demilec, and we follow each manufacturer’s published installation guidelines so product warranties stay intact. If a builder specified a certain brand, tell us and we will match it.
Removing Old or Damaged Insulation
Old crawl space insulation is often soaked, compressed, or chewed by rodents, and new material should never go over it. Thistledown Attic Insulation removes the failed layer, bags it, and carries it out through a protected path before any new work begins. Removal typically runs $800 to $2,500 depending on the amount of material and the level of contamination, and it appears as its own line in your written estimate. The same crew can also handle insulation removal in other parts of the house when you need it.
What We Look For Under There
We check for rotted joists, rusted pipe straps, pest nests, and signs of past leaks. If something needs a plumber or a carpenter, we tell you honestly and will not insulate over a problem that will keep getting worse.
Air Sealing the Floor System
Insulation slows heat, but it does not stop air. Gaps around plumbing, ductwork, and the rim joist let cold air blow straight into the house, and a tight job starts by closing them. We seal penetrations with foam and mastic before the insulation goes in, which matters most in older homes with many holes drilled over the years. Pairing crawl space work with attic air sealing gives you a house that holds its heat from the bottom to the top, and a combined plan is often cheaper than two separate visits.
What happens when you call
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A real person answersNo phone trees – you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Signs Your Crawl Space Needs Attention
- Cold floors in winter. If bare feet on the kitchen or living room floor feel like a skating rink, heat is escaping downward. Missing or fallen insulation under the floor is the usual cause.
- Frozen or sweating pipes. Pipes in an uninsulated crawl space freeze in a cold snap and drip condensation in humid weather. Both lead to damage that costs far more than the insulation would have.
- A musty smell from the floor vents or hatch. Damp air from the crawl space travels up into the house. That smell usually points to moisture, a torn vapor barrier, or mold on the subfloor.
- Insulation hanging down or lying on the ground. Batts that have dropped no longer touch the subfloor and do almost nothing. Rodent nests are another sign, since mice and rats love loose fiberglass.
- Heating bills that keep rising. When rates and habits have not changed, the cost often traces back to the crawl space and attic, the two places heat leaks the fastest.
Our Process, Step by Step
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Initial call and honest conversation. You reach a live person at (909) 768-6501, any hour, any day. We ask about cold floors, smells, pipes, and what your energy bills have been doing. No script, no voicemail tree.
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Crawl space inspection with documentation. A uniformed technician arrives at the scheduled time, puts on shoe covers at the door, and protects the path to the access hatch. We check vents, moisture, existing insulation, and the condition of the framing, and we photograph everything we find.
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Written price before any work. You get a specific written quote that names the product, the R-value, the square footage, and the total price. That number is what you pay, even if the job takes longer than we expected.
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Careful installation with the Cedarwell Care Promise. We install to the exact spec in your quote, ask before moving anything in your home, keep noise down when children are sleeping, and seal the work area as we go.
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Cleanup, photo proof, and the Done Right Promise. We remove our materials, photograph the finished crawl space, and leave the access hatch clean. Then you’re covered by our 365-Day Done Right Promise: if it’s not done right, we make it right, no debate, no fine print.
How Much Does Crawl Space Insulation Cost?
Most crawl space insulation projects across the country fall between $1,200 and $5,500 for a typical single-family home. Batts between the joists sit at the low end, while closed-cell spray foam or rigid foam on the foundation walls runs higher because the material costs more and the application takes longer. A ground vapor barrier typically adds $600 to $2,200, and removal of old, damaged insulation adds $800 to $2,500 depending on contamination.
What moves the price is mostly square footage, access difficulty, the insulation type, and whether moisture or air sealing work is needed. You avoid overpaying by hiring a contractor who crawls in, measures, and writes down a specific number before starting, rather than one who quotes a wide range and “sees how it goes.” Every free estimate from Thistledown Attic Insulation includes the inspection, the measurements, the written price, and the product recommendation. Call (909) 768-6501 and you’ll have your exact number before anyone picks up a tool. If you also want to compare loose-fill options for the attic, read about blown in insulation.
Where We Work
Thistledown Attic Insulation serves homeowners and businesses across the United States through local crews who carry the same Cedarwell Care Promise into every home. Our teams arrive in uniform, cover floors before they walk, explain prices before they work, and photograph the cleanup before leaving. Wherever your crawl space is, the standards don’t change. Start from our home page to see everything we do.
Frequently Asked Questions About Crawl Space Insulation
Crawl space insulation is the material installed on the walls or under the floor above your crawl space to slow heat loss and keep the space from swinging with the weather. It can be rigid foam board, spray foam, or batts held in place with fasteners, and the right choice depends on whether your crawl space is vented or sealed. Done correctly, it makes the floors above warmer and cuts the load on your heating system.
Most crawl space insulation jobs fall between $1,200 and $5,500 depending on square footage, access, and the material chosen. Adding a vapor barrier or cleaning out old, damaged insulation raises the number. Call (909) 768-6501 and you get the exact price in writing before any work starts.
It depends on how the crawl space is vented. A vented crawl space usually gets insulation between the floor joists, while a sealed, conditioned crawl space gets insulation on the foundation walls with a vapor barrier on the ground. We inspect first and tell you which approach fits your home, not the one that is easiest for us to install.
Most single-family crawl spaces take one day, and larger or heavily damaged ones take two. If old insulation has to come out or standing moisture has to be dealt with first, we put that timeline in the written estimate. You will know the schedule before we arrive.
Insulation alone does not fix a wet crawl space. We check for standing water, ground vapor, and vent problems, and we install a vapor barrier where it is needed so the insulation stays dry. If mold is already present we tell you and handle it in the same written plan.
Every job is backed by our 365-Day Done Right Promise. If it is not done right, we make it right, no debate and no fine print. Manufacturer warranties on the insulation products apply as well, and we install to each product’s published specs so they stay valid.
Schedule Your Crawl Space Insulation Service Today
Call (909) 768-6501 and a live person answers, any hour, any day. Tell us what you notice at floor level and we’ll schedule an inspection with a background-checked technician, give you a written price before any work starts, and back the whole job with our 365-Day Done Right Promise. The estimate is free, the cleanup is photographed, and the number you’re quoted is the number you pay. Call us today.
Written by Neil Barron, Owner at Thistledown Attic Insulation, serving homeowners across the United States since 2003.