Crawlspace, Basement & Water

Crawlspace Floor Insulation:
Missing, Fallen, Torn or Installed Backwards

Cold floors in a Portland house usually trace back to what’s stapled, or not stapled, under the joists.

Russ Motyko, CMI® November 2026 2 min read 523 words

At 50 houses, Russ wrote up the insulation under the floor. The most common title was “floor not insulated” (23 houses). After that came batts installed backwards or with their paper facing exposed, insulation torn up by rodents, and batts hanging down or lying on the ground.

In a vented crawlspace, that insulation is the only thing between the heated house and outdoor air.

No insulation at all

In a Portland house, the floor system had no insulation. Russ’s report noted it can lead to heat loss in winter and heat gain in summer, affecting comfort and energy use. Older Portland homes were often built that way. Floors over a vented crawlspace feel cold underfoot, and the furnace makes up the difference.

Adding insulation under a floor is a common energy upgrade here. Utility and state programs have offered incentives for it at times, and an insulation contractor can say what’s current.

Fallen and sagging batts

Fiberglass batts stay up by friction for a while. Then they sag. Without wire supports or strapping, many end up hanging in loops or lying on the vapor barrier. In a Beaverton house, so much insulation had fallen and was hanging that it limited what Russ could see of the crawlspace. His report recommended re-securing it so the area could be evaluated.

Fallen insulation also hides what it lands on: a pipe leak, a wet spot on the vapor barrier or rodent droppings.

Paper facing the wrong way

Kraft-faced batts have a paper vapor retarder on one side. In a crawlspace floor, that paper generally belongs up against the subfloor, on the warm side. Russ found batts installed with the paper facing down in several houses, and exposed paper facing in a Canby basement ceiling and a Camas crawlspace. Exposed kraft paper is flammable, and the manufacturer’s labeling says it isn’t meant to be left uncovered.

The faced fiberglass post covers this in detail, with photos.

Torn and soiled by rodents

In a Battle Ground house, the underfloor insulation was torn and contaminated by rodent activity. Mice and rats nest in batts, tunnel through them and leave droppings. That insulation is usually removed, the crawlspace cleaned, and entry points sealed before new insulation goes in. The rodent activity in floor insulation post covers what Russ looks for.

Real Inspection Photos

Floor Insulation From Russ's Inspections

Floor insulation findings from Russ's recent reports.

  • Fiberglass floor insulation hanging down between joists in a crawlspace
    Floor insulation hanging down into the crawlspace.
  • Damaged and torn pink fiberglass batts under a floor
    Torn and damaged batts under the floor.
  • Torn floor insulation with kraft paper facing hanging loose
    Damaged insulation with its paper facing hanging loose.
  • Bare floor joists and subfloor in a crawlspace with no insulation
    A floor system with no insulation.
  • Kraft-faced insulation with the paper exposed along crawlspace walls
    Kraft paper facing left exposed in a crawlspace.

See a full sample report

What Russ checks

He enters the crawlspace when it’s safe to move around and looks at the floor insulation’s type, coverage, support and facing, along with framing, plumbing, ducts, wiring, the vapor barrier and signs of moisture or pests. He doesn’t move insulation to see behind it, and areas it blocks are noted as not visible. Findings get a recommendation for a qualified insulation contractor, or for pest and cleanup work first when there’s contamination.

Inspector Checklist
Floor insulation checks
0 of 5 items verified
  • From the crawlspace hatch, look up: insulation between the joists, or bare subfloor?
  • Look for batts sagging in loops or lying on the ground
  • Check which side the paper facing is on
  • Look for supports across the joists
  • Watch for droppings, tunnels or shredded batts
Key Takeaway

Floor insulation was missing, fallen, torn or installed facing the wrong way at 50 of Russ’s inspections. Fallen batts also hide what’s underneath them. An insulation contractor can re-hang, replace or add insulation, and supports keep it in place.

For the rest of what’s under the house, the guide to the crawlspace before you make an offer is the next stop. To set up an inspection, you can book online.

Common Questions

Floor Insulation FAQ

In a vented crawlspace, the floor above is the line between heated and unheated space, so energy codes call for insulation there. A sealed, conditioned crawlspace insulates the walls instead.
The kraft paper vapor retarder generally goes toward the heated side, which in a crawlspace means up against the subfloor. Paper facing down into the crawlspace is a common install mistake. The paper is also flammable and isn’t meant to be left exposed.
Wire supports (often called lightning rods or tiger teeth), twine, mesh or strapping across the joists. Without them, batts tend to sag and fall over the years.
Clean, dry batts can sometimes be re-hung. Insulation soiled by rodents is usually removed, and the crawlspace cleaned, before new insulation goes in.
It blocks the view. In a Beaverton house, fallen and hanging insulation limited how much of the crawlspace Russ could see.
Russ Motyko, Certified Master Inspector, Portland Oregon
Russ Motyko, CMI®
Certified Master Inspector®  |  OR #1898  |  WA #1856

Russ is Oregon City’s only Certified Master Inspector® and a licensed general contractor. He has completed more than 3,000 inspections across the Portland metro and SW Washington. Bilingual in English and Russian, a U.S. Army Reserve Noncommissioned Officer, and owner of Trusted Home Inspections. Learn more →