The Insulation Under Your House Is Probably Failing
Go look under any older Baltimore home and you will see the same thing. Fiberglass batts stuffed between the floor joists, sagging, falling, or gone completely. Some hang by a thread. Some lie in a damp pile on the ground. Moisture is the killer — fiberglass soaks up crawl space humidity like a sponge, gets heavy, and drops. Once it is on the ground, it insulates nothing and starts growing mold.
Bad crawl space insulation hits you three ways. Your floors are cold in winter because there is nothing between you and the cold air below. Your energy bills are high because your furnace and heat pump work overtime. And your pipes are at risk, because the same cold that chills your floors can freeze a water line on the coldest nights.
Where the Insulation Should Go
This is the part most contractors get wrong. There are two schools of thought, and the right one depends on whether your crawl space is vented or sealed.
Sealed crawl spaces: insulate the walls. Once a crawl space is encapsulated, it becomes part of the house — a semi-conditioned space. The right move is rigid foam board on the foundation walls and the rim joist. The whole space stays mild, the floors stay warm, and the insulation is up on the walls where moisture cannot hurt it. This is the modern best practice and what we recommend with every encapsulation.
Vented crawl spaces: insulate the floor. If the space stays vented, the insulation belongs between the floor joists, up against the subfloor — with a proper support system so it cannot fall. We use insulation that handles moisture better than old fiberglass, and we fasten it so gravity cannot win. We also seal the rim joist, which is one of the leakiest spots in any house.
What we do not do is mix them up. Insulating the walls of a vented crawl space wastes money. Stuffing batts into a damp space without fixing the moisture first is throwing insulation away. Moisture control always comes before insulation — see our moisture control page for why.
The Rim Joist: The Leak Everyone Misses
The rim joist is the wood board that caps the ends of your floor joists, sitting right on top of the foundation wall. In most older homes it is barely insulated — sometimes just a thin batt, sometimes nothing. It is also full of gaps where pipes and wires pass through. All that cold air pours in right at the edge of your floors, which is why the floors are coldest near the outside walls. Sealing and insulating the rim joist is one of the highest-value jobs we do. It is a small area with an outsized effect on comfort.
Our Process
Step 1 — Free inspection. We check the current insulation, measure moisture, and decide whether the space should be sealed or stay vented.
Step 2 — Written estimate. Wall insulation or floor insulation, rim joist sealing, and any moisture work that has to come first — itemized.
Step 3 — Remove the old. We pull out the failed batts, wet material, and debris, and haul it all away.
Step 4 — Fix moisture first. If the space is damp, we handle drainage, vents, or a dehumidifier before any new insulation goes in.
Step 5 — Install. Rigid foam on walls for sealed spaces, or supported floor insulation plus rim joist sealing for vented spaces. Everything fastened to stay put.
Step 6 — Verify. We check the coverage, confirm the space is drying, and walk you through what was done.
What Good Insulation Feels Like
The change is immediate and you feel it with your feet. Floors that were cold in January feel normal. Rooms over the crawl space hold their temperature instead of swinging. The furnace runs less. On the coldest nights, pipes are safer because the space around them is no longer freezing. It is one of those upgrades you notice every single day.
Frozen Pipes: The Winter Risk
Baltimore gets cold snaps that freeze pipes in uninsulated crawl spaces. A burst pipe can flood a crawl space and cause thousands in damage. If your crawl space has a history of freezing, tell us during the inspection — we will prioritize pipe insulation and heat protection along with the main job. Our winter guide covers what to do before the cold hits.
Every project is different — contact us for a free written estimate.
Call (301) 679-9193 or send the form below for your free crawl space inspection.