Case file — Leesburg, Loudoun County, VA. One of the 25 jobs in our 250-home series. New here? Start with our open letter.
At a glance
| Location | Leesburg, Loudoun County, VA |
| The problem | Humidity and air movement, without the water intrusion that drives a full sealed system |
| The fix | Both vents sealed, rim joists insulated, a dehumidifier with a condensate pump — and deliberately no floor or wall encapsulation |
| Time on site | One day, plus an extra hour and a half for conditions found on site |
What we left out, and why
Every other crawl space in this series got a sealed barrier across the floor. Most got one carried up the walls as well. That system is the centrepiece of crawl space work, it is what the photographs look impressive for, and it is the largest line on the invoice.
This crawl space did not get it.
Not because the homeowner declined it. Because the conditions did not call for it, and installing it anyway would have been selling a system rather than solving a problem.
What the space actually needed
Both vents sealed. Two foam inserts, cut to the openings. This is the single highest-value thing you can do to a crawl space in this climate, and it costs almost nothing. An open vent turns the space into outdoors; a sealed one lets everything else work.
The rim joists insulated. About 90 linear feet, cut to fit each pocket. The rim joist band is the biggest uninsulated surface left in most houses, and in a crawl space it is also the place where the most air moves.
A dehumidifier. A 70-pint-per-day unit with a MERV 11 filter, rated to 2,200 square feet — comfortably more capacity than this space asks for, so it cycles rather than running flat out.
A condensate pump, so the water that unit pulls out of the air is carried away instead of being dumped back onto the ground beneath the house.
Seal the air, insulate the gap, control the humidity, remove the water. That was the whole problem, so that was the whole scope.
When you do need the barrier
To be clear about where the line is, because we are not arguing that encapsulation is oversold in general. It is the right answer often.
You need a sealed floor and wall system when the ground itself is the moisture source — bare soil giving off vapour continuously, day after day — or when there is standing water, or mold that will come back the moment humidity rises again. The Bethesda crawl space in this series needed the full system for heat loss as much as for moisture, and the Accokeek one needed a drain under it before the barrier could even go down.
What you do not need is the same system quoted for every house because it is the one the salesperson has a brochure for.
The extra hour and a half
The plan includes additional crew hours for conditions found on site.
That line exists because crawl spaces are not fully knowable from the hatch. You get under there, you find something that adds time, and there are two ways to handle it: absorb it quietly and rush, or put it on the plan and do it properly.
An hour and a half is not a dramatic overrun. It is what honest scheduling looks like written down.
The test of a crawl space company
Ask for a quote and see whether what comes back is shaped like your house or shaped like their catalogue.
If every crawl space gets the same five line items regardless of what is under the floor, the diagnosis is not doing any work. This job had four line items because the space had four problems. That is the only reason a scope should ever be the length it is.