Crawl Space Insulation in Montgomery, AL

Crawl space insulation is essential for energy efficiency and floor comfort in Montgomery,

Alabama homes. However, traditional insulation methods often fail because of the high

humidity in crawl spaces. Understanding the right insulation for your crawl space prevents

mold, rot, and wasted energy.

Problems with Traditional Fiberglass Batt Insulation

Many Montgomery homes have fiberglass batts installed between floor joists, with the paper

facing toward the living space. This method fails for several reasons. First, fiberglass absorbs

moisture from the crawl space, becoming heavy and sagging or falling out. Second, wet

insulation has almost no R‑value. Third, the paper facing can grow mold. Fourth, rodents and

insects love to nest in fiberglass. Montgomery Foundation Repair Co removes thousands of

pounds of failed fiberglass insulation every year. If your crawl space has fiberglass between the

joists and you have high humidity, that insulation is likely doing more harm than good.

Insulating the Crawl Space Walls (Not the Floor)

The best practice for crawl spaces in humid climates is to seal the crawl space and insulate the

foundation walls, not the floor. This approach keeps the crawl space within the home’s

conditioned envelope. Montgomery Foundation Repair Co installs rigid foam insulation

(extruded polystyrene or polyisocyanurate) on the interior crawl space walls, typically 2 inches

thick for R‑10 to R‑13. The insulation is glued and mechanically fastened, then covered with a

vapor barrier or a fire‑rated covering. This method keeps the crawl space warmer in winter and

cooler in summer, reduces energy bills, and eliminates floor drafts.

Insulating the Floor When Encapsulation Isn’t Done

If you choose not to encapsulate your crawl space, insulating the floor is the next best option.

However, you must use moisture‑resistant insulation. Closed‑cell spray foam applied to the

subfloor from below is ideal because it seals gaps and resists moisture. Alternatively, rigid foam

boards can be cut to fit between joists and sealed with spray foam. Montgomery Foundation

Repair Co does not recommend fiberglass or mineral wool for floor insulation in vented crawl

spaces—they will eventually become wet and useless. Any floor insulation should be

supported with wire or netting to prevent sagging.

Vapor Barrier and Insulation Together

Insulation alone does not solve moisture problems. Even the best insulation will be

compromised if your crawl space has standing water or 90 percent humidity. Montgomery

Foundation Repair Co always addresses moisture first (with drainage, vapor barrier, and

dehumidifier) before installing insulation. In a fully encapsulated crawl space, the vapor barrier

protects the insulation from ground moisture, and the dehumidifier keeps air dry enough that

condensation does not occur on the insulation surface. This combination provides decades of

reliable performance.

Frequently Asked Questions