Crawl space insulation
Fallen fiberglass under the floor is one of the most common things a contractor finds in a Bluegrass crawl space. Fixing it the right way depends on whether the space is vented or sealed.
Crawl space insulation keeps the floors of your Lexington home warmer in winter and helps control moisture in summer. Contractors either rehang or replace insulation between the floor joists, or, in a sealed crawl space, insulate the foundation walls instead and leave the floor open to the conditioned space.
Floor insulation or wall insulation?
In a vented crawl space, the insulation goes between the floor joists, held tight against the subfloor. In a sealed crawl space, the space is treated as part of the house, so the foundation walls and rim joists are insulated instead. The model code's unvented crawl space options for exhaust and conditioned air supply both assume insulated perimeter walls.
Signs your insulation needs attention
- Batts hanging down or lying on the ground
- Insulation that's wet, compressed or stained
- Cold floors over the crawl space in winter
- Pipes that come close to freezing on cold nights
- Evidence of rodents nesting in the insulation
Why fiberglass falls down here
Fiberglass batts soak up moisture from humid summer air. As they get heavier, the wire supports or staples give up and the batts sag away from the subfloor, leaving a gap that does little to keep the floor warm. In Lexington's climate, with humid summers and freezing nights in winter, that means a damp crawl space in July and cold floors in January.
What drives the cost?
- Removing and disposing of the old, wet insulation
- Square footage of floor or wall area
- Material type: fiberglass, rigid foam board or spray foam
- Rim joist sealing and insulation
- Whether it's part of a larger encapsulation
The contractor you're connected with sets the price after an inspection.
Fix the moisture first
New insulation in a damp crawl space will end up just like the old insulation. If the reason it fell is humidity or water, it's worth dealing with that first. That may mean a new ground cover, a full encapsulation, or drainage work.
Common questions
Should I insulate the floor or the walls of my crawl space?
Floor insulation belongs in a vented crawl space. If the crawl space is sealed, the foundation walls and rim joists are usually insulated instead.
Why does crawl space insulation keep falling down?
Usually because it absorbs moisture and gets heavy. Fixing the humidity problem keeps new insulation in place.
Does crawl space insulation work need a permit?
It depends on scope and jurisdiction. Ask the contractor, who can check with Lexington's Division of Building Inspection or your county office.
Towns this covers
Related services
- Crawl space encapsulation
- Vapor barrier replacement
- Crawl space dehumidifiers
- Floor joist and sill repair
For the Kentucky code, karst and radon background, see the Lexington crawl space guide.
Damp smell, cold floors or a sag you can feel underfoot?
One call puts you in touch with a crawl space contractor who works in Lexington and the surrounding Bluegrass counties.