Crawl Space Insulation in Charlotte, NC
704 Crawl Space Pros is a crawl space encapsulation and moisture control company serving Charlotte and the greater metro, NC. Crawl space insulation is the job most often done twice, because the way it is usually done first does not survive a Carolina Piedmont summer. If you have fiberglass batts stapled between your floor joists and they are sagging, dark, or lying on the ground, that is not a fluke — it is the predictable outcome of putting an air-permeable insulation in a humid, vented space.
Why fiberglass between the joists fails here
Batts between the floor joists insulate the floor above but leave the crawl space itself outside the building envelope — vented, humid, and at outdoor dew point. Fiberglass is air-permeable, so humid air moves straight through it. When that air reaches the cool underside of your subfloor it condenses, the batts absorb the moisture, they get heavy, and gravity does the rest.
Once they fall, they sit on a dirt floor wicking ground moisture, and the paper facing feeds mold. We remove a lot of insulation that was installed correctly to the letter and still failed, because the assembly it was installed into was the problem.
Insulate the walls, not the joists
In a sealed crawl space the insulation belongs on the foundation walls. That brings the crawl space inside the conditioned envelope — the space stays close to house temperature, the dew point problem largely disappears, and there is no air-permeable material sitting in a humid airstream.
Rigid foam board against the block, sealed at the seams and held off the ground, is the usual approach. It is paired with sealed vents and a barrier over the floor, because wall insulation in a still-vented crawl space is insulating against outdoor air that is already inside.
- Remove failed batts, contaminated facing, and anything already on the ground
- Seal the vents and lay the reinforced barrier first — insulation last, not first
- Rigid board on the walls, held off the floor and sealed at the joints
- Band joist and rim area sealed, which is where a surprising share of the air leakage is
What it changes, honestly
The energy claim worth making is the measured one: the North Carolina field study behind the state's 2004 code change found closed crawl spaces used over 15% less heating and cooling energy than wall-vented ones across twelve identical homes. That is the assembly as a whole, not insulation alone.
The more immediate change most people notice is floor temperature in winter and the smell in summer, both of which come from the crawl space no longer being a vented, damp buffer between the house and the ground.
Crawl Space Insulation questions
Should crawl space insulation go on the walls or between the floor joists?
On the walls, if the crawl space is sealed — which is what we recommend in this climate. Insulating between the joists only makes sense if the crawl space is staying vented, and a vented crawl space in the Piedmont is the underlying problem rather than a condition worth insulating around. Wall insulation brings the space inside the envelope; joist insulation leaves it outside and puts an absorbent material in the humid air.
What does crawl space insulation cost in Charlotte?
It is usually quoted as part of the encapsulation rather than alone, because insulating a still-vented crawl space is work that will need redoing. As a line item, removing failed batts and insulating the foundation walls typically falls within the $4,200 to $13,500 full-system range depending on wall area and how much old material has to come out. We quote removal and new insulation separately so you can see both.
Do I have to remove the old fiberglass?
If it is wet, sagging, mouldy, or on the ground, yes — it is holding moisture against the wood and there is no way to make it work in place. If it is dry, intact and you are not sealing the space, it can sometimes stay. In practice, in Charlotte, most of what we find under houses is in the first category.
Is crawl space insulation the same as encapsulation?
No, though they are usually done together. Encapsulation seals the space — barrier, vents, humidity control. Insulation controls heat flow. You can encapsulate without insulating the walls and still get most of the moisture benefit; insulating without sealing generally wastes the insulation.
Not sure which of these your crawl space actually needs? The Charlotte cost guide breaks the whole system down component by component, and the cost calculator runs those same figures against your own square footage.
Related services
Crawl space guides
Musty air, sagging floors, or moisture under the house?
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