Crawl Space Insulation
- Licensed & Insured
- 5-Star Rated
- Local Business
- Transferable Warranty
Spray Foam Crawl Space Insulation for Mid-Atlantic Homes
Best Buy Waterproofing installs crawl space insulation for homeowners across Maryland, Virginia, Washington DC, Pennsylvania, Delaware and West Virginia. We use closed-cell spray foam, applied to the foundation walls and rim joists or to the underside of the floor depending on how your crawl space is built. Closed-cell foam does three jobs at once: it insulates, it acts as an air barrier and it resists moisture. That makes it well suited to the damp, below-grade conditions found in crawl spaces, where traditional fiberglass batts tend to absorb water, sag and fall out of place.
Mid-Atlantic weather is hard on crawl spaces. Humid summers push moist air under the house, clay and silt soils hold water against the foundation, and freeze-thaw winters send cold air across the floor above. Uninsulated or poorly insulated crawl spaces show it with cold floors, drafty rooms, musty odors and damp framing. Our crawl space insulation work includes air sealing at the rim joists and penetrations, and it pairs naturally with crawl space encapsulation for homeowners who want the space fully sealed and dry.
Signs You Need Crawl Space Insulation
Insulation problems in the crawl space are usually felt upstairs first. Look for these signs.
Cold floors in winter
Floors over the crawl space feel chilly because heat escapes through uninsulated framing.
Drafty rooms
Air leaks at rim joists and vents pull outside air under the floor and into rooms.
Sagging fiberglass
Batts hanging down or lying on the ground have stopped doing their job.
Wet or moldy insulation
Fiberglass that holds moisture can feed mold and keep joists damp for long periods.
Rising energy bills
Heating and cooling work harder when the floor system leaks air and heat.
Pests and odors
Gaps around the rim joist let insects, rodents and musty air into the home.
Our Crawl Space Insulation Solutions
Closed-Cell Spray Foam on Crawl Space Walls
In a sealed or unvented crawl space, we insulate the foundation walls rather than the floor above. Closed-cell spray foam is sprayed directly onto block, brick, stone or poured concrete walls, where it bonds to the surface and fills uneven joints. The result is a continuous layer that insulates and blocks air and moisture at the same time. Because the crawl space then sits inside the insulated envelope of the house, it stays closer to indoor temperature, which helps prevent condensation on pipes, ducts and framing.
Closed-cell foam is the below-grade choice because it resists moisture. Open-cell foam absorbs water and is not suited to crawl space walls.
Rim Joist Insulation and Air Sealing
The rim joist, the band of framing that sits on top of the foundation wall, is one of the leakiest spots in many homes. It has seams, gaps at the sill plate and penetrations for pipes, wires and vents. Rim joist insulation with closed-cell spray foam fills those gaps and covers the wood in one step, so air sealing and insulation happen together. That reduces drafts, keeps the floor above warmer and closes common entry points for insects and rodents.
We also seal around access doors and other penetrations in the crawl space, so the insulation is not undermined by air leaks elsewhere.
Insulating Vented Crawl Spaces
Not every homeowner is ready to seal the crawl space. If your crawl space stays vented, we insulate the underside of the floor instead of the walls, applying closed-cell spray foam between the floor joists. This keeps heat in the living space above and adds an air and moisture barrier at the floor, which helps with cold floors and drafts.
During the inspection, we explain the difference between insulating the floor and the walls and recommend the approach that fits your home.
Removing Failed Fiberglass
Many crawl spaces across the region still have fiberglass batts between the floor joists. In damp conditions, fiberglass absorbs moisture, loses its insulating value and often sags or falls to the ground. Wet batts hold moisture against the joists and can feed mold. Before installing spray foam, we remove old insulation that has failed, clean up the area and check the framing for damage.
If we find rot or sagging floor joists, we let you know and can address the framing as part of the same project.
Pairing Insulation With Encapsulation
Crawl space insulation and crawl space encapsulation work best together. Encapsulation covers the floor and piers with a sealed vapor barrier, closes the vents and adds a dehumidifier to control humidity. Spray foam on the walls and rim joists completes the seal and insulates the space. Together, they turn the crawl space into a dry, conditioned area instead of a damp pocket of outside air under the house.
If the crawl space takes on water, we recommend crawl space waterproofing first, so the space is dry before it is sealed and insulated.
Our Crawl Space Insulation Process
Free Inspection
We check moisture, air leaks, existing insulation, vents and framing in your crawl space.
Your Recommendation
We walk you through what we found and what we recommend, with a firm price.
Spray Foam Application
Our in-house crew preps the space, applies the foam, lets it cure and checks coverage.
Warranty Protection
Your crawl space insulation is backed by a transferable warranty that stays with the home.
Why Homeowners Choose Best Buy Waterproofing
Crawl space insulation works best when it is planned alongside moisture control, and our one team handles both. Homeowners across the Mid-Atlantic have trusted us with their crawl spaces since 2017.
- Serving homeowners since 2017: Our team has focused on crawl space, waterproofing and spray foam work across the Mid-Atlantic since 2017.
- Licensed and insured: We are licensed in Maryland, Virginia, Washington DC, Pennsylvania, Delaware and West Virginia, and fully insured.
- One in-house team: Spray foam, encapsulation, waterproofing and structural repairs are handled by our own crew.
- Free inspection and financing: Inspections and estimates are free, and financing options are available for qualified homeowners.
- Transferable warranty: Your warranty transfers with the home, which adds peace of mind if you ever sell.
What Affects the Cost of Crawl Space Insulation?
We don’t quote crawl space insulation from a price list, because every crawl space is different. You get a firm price after a free inspection.
Area to insulate
Wall height, perimeter length or floor area sets how much foam the job needs.
Walls or floor
Sealed crawl spaces get wall insulation; vented ones get insulation under the floor.
Old insulation removal
Wet or fallen fiberglass must be removed and the area cleaned before spraying.
Air sealing needs
The number of gaps, vents and penetrations affects rim joist and air sealing time.
Access and clearance
Low or tight crawl spaces take more time to prepare and spray.
Moisture problems
Standing water or high humidity may call for waterproofing or encapsulation first.
Crawl Space Insulation FAQs
Why use closed-cell spray foam in a crawl space?
Closed-cell spray foam insulates, seals air leaks and resists moisture in one layer. Crawl spaces are damp, below-grade spaces where fiberglass tends to absorb water and fall down. Closed-cell foam bonds to the surface and holds up in those conditions, which is why it is the material we use for crawl space insulation.
Should I insulate the crawl space walls or the floor?
It depends on whether the crawl space is sealed or vented. In a sealed crawl space, we insulate the foundation walls and rim joists, which brings the space inside the home’s envelope. In a vented crawl space, we insulate the underside of the floor. We recommend the right approach after the inspection.
What is rim joist insulation?
The rim joist is the framing that sits on top of the foundation and surrounds the floor system. It is full of seams and gaps that leak air. Rim joist insulation with closed-cell spray foam covers that wood and fills the gaps, combining insulation and air sealing in one step.
Does crawl space insulation replace a vapor barrier?
No. Spray foam on the walls and rim joists insulates and seals, but the ground still gives off moisture. A sealed vapor barrier on the crawl space floor handles that. For full moisture control, we pair crawl space insulation with encapsulation, which includes the liner, vent sealing and a dehumidifier.
Will crawl space insulation make my floors warmer?
In most homes, yes. Cold floors over a crawl space usually come from heat escaping through the floor and outside air leaking in at the rim joist and vents. Insulating and air sealing the crawl space keeps it closer to indoor temperature, so the floors above feel warmer in winter.
Do I need to leave the house during installation?
Spray foam needs a curing period after it is applied, and the crawl space should stay closed off during that time. We explain how long to stay out of the area and any steps to take before we start. Our crew handles prep, application and cleanup.
Do you install spray foam in attics or walls?
No. Our spray foam work is focused on below-grade spaces: crawl spaces and basements. That is where closed-cell foam’s moisture resistance matters most and where it fits with our waterproofing and crawl space repair services.
Related Services
Popular service areas: Baltimore · Washington, DC · Arlington · Alexandria · Columbia · Frederick · Silver Spring · Wilmington · All service areas
Ready for Warmer, Drier Floors?
Schedule a free inspection and we will check your crawl space, explain what we find and recommend the right insulation plan. We serve homeowners across Maryland, Virginia, Washington DC, Pennsylvania, Delaware and West Virginia.