Crawl Space Insulation in Beaverton, OR

Crawl space insulation matters more in Beaverton than many homeowners expect. A lot of the city's ranches, split-levels and two-story homes sit over vented crawl spaces, and from November through February the air down there is cold and wet. If the floor above is uninsulated, or the batts have fallen, you feel it in cold floors, drafty rooms and higher heating bills. If the ground is not covered, moisture from the soil adds a musty smell and can soak whatever insulation is left.

What we usually find

• Fiberglass batts between the floor joists that have sagged or dropped onto the ground
• Torn, bunched or missing plastic ground cover
• Standing water after heavy rain, often from downspouts or grading
• Ducts that are disconnected or uninsulated
• Rodent nests in the batts and droppings on the ground cover
• Open rim joists along the foundation

Each of these affects how insulation will perform, so the estimate starts with a full crawl through the space when access allows.

Ground cover first

In a vented crawl space, a continuous ground cover of polyethylene sheeting keeps soil moisture from evaporating into the space. We remove damaged plastic and debris, lay new sheeting with overlapped seams, and run it up the foundation walls where needed. Standing water is a separate problem; if water collects after storms, the source (downspouts, grading or a high water table) needs to be dealt with, and we tell you that before insulating.

Insulating the floor

For a vented crawl space, the insulation goes in the floor framing, against the subfloor. The current Oregon code calls for R-30 under floors in new construction, and the Department of Energy suggests R-30 for an uninsulated floor in our climate zone. Batts only work if they stay in full contact with the subfloor, so we hold them up with wire supports or netting rather than relying on friction. Where framing is irregular or plumbing and ducts are in the way, rigid foam board or closed-cell spray foam can do a better job.

Rim joists and ducts

The rim joist is the band of framing that sits on the foundation all the way around the house. It is often the biggest air leak in the crawl space. We seal and insulate it with closed-cell foam or cut-to-fit foam board sealed at the edges. If ducts run through the crawl space, we note any disconnected or crushed runs; reconnecting and insulating them is usually worth doing while we are under the house.

Vented or encapsulated

An encapsulated crawl space is sealed from outside air, with a heavy liner on the ground and walls and insulation on the foundation walls instead of the floor. It can make sense for some homes, especially where ducts and equipment are in the crawl space, but it costs much more and changes how the space has to be ventilated or conditioned. HomeGuide lists encapsulation at $3,000 to $15,000. For most Beaverton homes, a good ground cover, a properly insulated floor and sealed rim joists solve the problem for far less.

Rodents under the floor

If mice or rats have nested in the batts, the contaminated insulation is removed and bagged, and the area is sanitized before new insulation goes in. Openings around pipes and vents should be sealed so they do not move back in; we can coordinate with your pest control company.