Discovered 440 square foot crawl under basement! Help!!

[ekrig]

A dehumidifier will need a place to dump the water is pulls from the air. That said, there are dehumidifiers with built-in pumps which can push that water up to a discharge point higher-up. In any event, kind in mind that most likely the dehumidifier will need to be accessible because you need to do maintenance on it (e.g., for cleaning air the filter, fans, and purge any algae in the water tank and/or lines) at least a couple of times a year. Will that be practical in your case? I mention the issue of maintenance because this is what I have to do with the dehumidifier in my basement. Perhaps those are non-issues in your case, but I'd double-check.

Personally, I don't like the idea of deep window wells and adding vents as that creates an entry point for humidity. One could turn that idea around, much like what @dsteinhorn mentioned, and have the duct to pull air from the crawlspace through the living area above it. If you do it along a corner or by thickening a short wall and then frame and drywall around it, then it will look just like a feature of the house. That's how the AC air is pushed to the upper story in my house. Ideally, you still need an air intake.

It seems that the crawlspace have foundation walls around it; on some or all sides? Is there a basement? And, if so, a basement wall adjacent to it? If so, that would be a great place for another vent with a fan pushing air to the crawlspace by pulling from the basement.

Without lots of additional pictures and details about what exists and doesn't and general space constraints, it is hard to be more specific.

 

[Steve123]

How old is the house ?

 

[dsteinhorn]

I’m confused as they seem to think we need to have a place for the water the dehumidifier collects to go. So they are proposing we core through the foundation to make a drainage hole to the yard. Is there a way to install a dehumidifier without having to core through the foundation for a drainage area???

Look at the video I sent. A pump to drain the collection pan would lift the water up to wherever it can drain in the house. I will take a litlte McGivering because you have a suboptimal structure to work with. But, there are solutions

 

[PJB12]

We looked into encapsulating and also spoke with some inspectors and owners. The problem is that if there is one, small void or damage, moisture will readily come in. Moisture from the crawl will permeate the house. Plus, the crawl is now super sealed. No air will exchange.

Alternative-
Maybe you can turn the craw space into part of the Conditioned Space of the house.
A portion of our house is on a crawl and, for many reasons, venting was not the appropriate solution. We made it part of the conditioned space.

A) Carefully wash away any growing things and either sanitize or, if you want more certainty, disinfect.
(Ideally, hire the fungus & mold mediation out to a pro)

B) Remove sharp rocks from the floor.

C) Lay plastic vapor barrier that is 0.006" thick or thicker to cover the floor, lapping up the wall 6" or so.
Don't do the entire walls. (See** below)
Overlap sheets' joints by about 6" and tape with vapor barrier tape.

D) Use insulation specifically for basements. Start at the subfloor above and run it down the walls and
stop when it is about 2 feet( See *** below) onto the floor. Don't worry about the batt's vapor barrier laying on
the floor plastic. It's only about 2 feet onto the plastic sheeting and the ends are open.

E) Seal the seams between bats with vapor barrier tape.

** One can also use vapor barrier on the floor and walls. Then use non-vapor barrier basement insulation over it.

*** Where you live, the 2 feet onto the floor guideline may be different. In the Detroit area, it is the distance where
heat getting to the floor stops being emitted or conducted to the walls.

Optional:
For more insulation, add perforated radiant barrier across the batts and the floor. (Must be perforated and must be 100% uncoated aluminum: Must have 19mm or larger gap on one side)

The humidity level in the crawl will soon match the humidity level of the rooms above. If you want more ventilation, you can put floor type heating registers in the floor above at opposite ends of the crawl space. We did not do this.

Our crawl is now the same temperature and humidity as the rooms above. (And the floors are warmer in winter.) When corrected for degree-days, our heating costs are lower. (Heat used to go into the crawl and out the brick walls.)

Paul

PS: Radon Note
If you have radon entering the crawl space, if done well the above treatment should seal the soil & walls against penetration to the air in the crawl space. You will have to do at least one 90-day test before starting and at least a month after finishing to find your results.

 

[Ron Van]

This guys worth watching. Crawlspace Ninja.

 

[lucyonfire]

I guess I should have clarified, exterior grade, because venting requires flow.

Were it I, and the exterior grade is lower than the floorjoist system, I'd cut in a couple foundation vents and a selectively controlled fan at the underfloor access.

Agree with you

 

[PJB12]

Your first post mentioned encapsulating and installing a dehumidifier. You can use a condensate pump to remove the dehumidifier water, but you're still not replacing the air in the space. It'll be dead air.

Plan B-
Can you dig down to the wall from outside and pipe a vent to above grade? Use two- Intake and exhaust at opposite ends.
This is done in sky scarpers that have 2, 3, 4 or more basements below grade.

The pipes probably will naturally convect on their own, but if they don't change enough air for you, add a very low CFM in-line fan. I'd use at least 6" PVC pipe so it is waterproof and a reasonable size. If the 6" doesn't keep up, add a second pair.
At 6" you can also get Schedule 30 PVC so it's lighter to handle.


Make the end in a U-Turn to keep rain & snow out. Screen the opening for bugs.

Ideally, you'd encapsulate the crawl first to prevent new moisture.

No matter what you do, Please check for radon.

Paul

 

[lucyonfire]

Found very helpful thread!