Hawthorne: Crawl Space Encapsulation & Vapor Barrier
A 1,450 sq ft dirt crawl space at 78% humidity, with mold on the joists and floors that never got warm.
Location
Hawthorne, Portland
Service
Crawl Space Encapsulation
Duration
3 days
Completed
April 28, 2025
The situation
The owners called about a musty smell in the bedrooms. The source was underneath: bare soil, collapsed batt insulation lying in the dirt, 78% relative humidity (opens in a new tab) and visible growth across the floor joists (opens in a new tab) . The stack effect (opens in a new tab) carried it straight upstairs.
What we did
Full clean-out and disposal, antimicrobial treatment of the joists, a 20-mil reinforced liner sealed to walls and piers, rim-joist air sealing and insulation, and a dedicated dehumidifier draining away automatically.
The outcome
Humidity now holds at 47%. The odor is gone, ground-floor rooms measured 4-6°F warmer through a Portland winter, and the owners reported a clear drop in their heating bill, which lines up with what rim-joist air sealing alone is expected to save.
The framing here was sound, so this was crawl space encapsulation on its own. Where it is not, crawl space repair comes first. The autumn walkthrough tells you which one you are looking at.
By the numbers
| Metric | Result |
|---|---|
| Area encapsulated | 1,450 sq ft |
| Humidity before / after | 78% to 47% |
| Liner thickness | 20 mil |
| Floor temp change | +4-6°F |
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