The headline numbers
| Scope | Typical cost |
|---|---|
| Full professional encapsulation, national average | ~$5,500 |
| Typical range, most homes | $3,000 – $15,000 |
| Per square foot (basic → extensive) | $3 – $10 |
| Basic vapor-barrier-only job | $2 – $4 / sq ft |
"Encapsulation" bundles several jobs: sealing the ground and walls with a heavy vapor barrier, sealing vents and air leaks, conditioning the air (that's the dehumidifier), and handling any liquid water (drainage or a sump). Quotes vary wildly because the bundle varies wildly — always ask for the itemized version.
The itemized breakdown
| Component | Cost | Notes |
|---|---|---|
| Vapor barrier material (20 mil) | $0.50–$0.70 / sq ft | The 10-vs-20-mil upsell is real but modest at material level |
| Crawl space dehumidifier, installed | $1,000–$3,000 | Unit alone: $300–$2,000 — see below |
| Sump pump, installed | $200–$4,000 (avg ~$1,200) | Only if liquid water shows up |
| Labor share of the total | 50–70% | The crawl-height tax: low clearance = slow work = money |
Where the money hides
- Labor is half to two-thirds of everything. A 2-foot crawl height can nearly double the labor line versus a 4-foot one. This single fact explains most quote spreads.
- Pre-existing problems bill separately. Mold remediation, standing water, old debris removal, and rotted insulation all get their own line items before encapsulation proper begins.
- The dehumidifier markup is the easiest line to audit. Contractors commonly install units like the AlorAir Sentinel HD55 or Argendon Shield 60 ($459 (list $589) retail) — if the quote's equipment line is triple the retail price, ask why.
What you can safely DIY
A vapor-barrier-plus-dehumidifier job on a dry-ish, accessible crawl space is realistic weekend-warrior territory: barrier material for a 1,500 sq ft space runs roughly $750–$1,050, seam tape and hardware another couple hundred, and a proper crawl-space dehumidifier $460–$1,300 street. Call it $1,500–$2,500 DIY versus $5,500+ professional — the delta is that labor share, which you're paying yourself in sore shoulders.
Where DIY stops being smart:
- Standing water or active seepage — that's drainage engineering, not plastic sheeting. Fix water before sealing anything.
- Mold beyond surface spotting — remediation has its own safety rules.
- Structural surprises — sagging joists and termite damage found mid-job are why pros carry contingency lines.
- Combustion appliances in the crawl space — sealing changes airflow; a furnace or water heater down there needs a pro's makeup-air math.
Is it worth it?
For genuinely damp crawl spaces: usually yes, and not for resale-brochure reasons. Sealed, conditioned crawl spaces stop feeding moisture into the floor above — that's less mold risk, less musty smell, less cupped hardwood, and HVAC that isn't fighting a swamp under the house. Energy savings are real but modest; think of them as a rebate on the comfort fix, not the reason to do it. The honest "not worth it" case: a dry, sealed, low-humidity crawl space that some salesman wants to encapsulate anyway. Measure first — if it holds under 60% RH on its own through summer, spend your $5,500 elsewhere.
Sizing the dehumidifier for a sealed space
Once sealed, the space needs a right-sized unit — undersized runs constantly, oversized short-cycles. Our sizing calculator does the AHAM-chart math for your exact square footage and dampness, in both pint standards, and shortlists units that actually cover the space.