solve a debate about a humid crawl space and mildew

7 years ago

First, I live in central Wisconsin ... we had legendary rain last summer. Now on to the issue ...

I have a large crawl space under a part of my house, which is a mid century modern built in 1958. The hvac mechanical and hot water heater is in there. The furnace has a fresh air intake but the combustion intake is interior. The floor is sand. The crawl space is extremely humid (80%+) even with a dehumidifier running constantly. Parts of the floor stay damp but no standing water.

There is no mildew or mold on the beams in the space or on the subfloor above it. However, mildew grows on anything that is stored down there and we have had mildew in parts of the living space above the crawl space.

We want to do something to 1) eliminate the mildew problem and 2) reduce the humidity in the living space. Because we live in Wisconsin, we ultimately plan to insulate the ceiling of the crawl space to prevent us from losing so much heat in that spot.

Numerous individuals have weighed in on the issue and we have two general opinions. Please comment with your thoughts.

One side of the debate believes that encapsulating the space is a decent solution that will reduce humidity in the crawl space and improve the air quality in the living space ... most importantly, this side of the debate believes that encapsulating the crawl space will eliminate the mildew problem in the living space.

The other side believes that encapsulating is overkill. This side prefers venting the space or adding either a dehumidifier exchange to the furnace or adding more dehumidifiers in the living space. This side believes that encapsulating the crawl space will not resolve the issues in the living space.

What do you think?

adding dehumidifier(s) to the living space will help.

encapsulating the crawl space will help.

venting the crawl space will help.

Featured Answer

partim

7 years ago

last modified: 7 years ago

My parents' crawl space is vented to the outside. It has a concrete floor. And even so, we don't store anything (cardboard, fabric) in there that would mildew, or it starts to smell musty and so do the rooms above it. It's not meant as a storage space.

Tatts' referral to a useful site was helpful. Your response was rude.

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Comments (9)

tatts
7 years ago
This isn't a Design Dilemma. You are in the wrong forum. You might as well be asking baking questions in a forum about cars.

Do this: Google this old house mildew crawl space.

This Old House has covered the topic in detail as have a lot of other sources.
Lyndee Lee
7 years ago
Start outside and see if you can modify drainage patterns to keep water from that area. Then, proceed with a concrete floor for the craawl space
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PRO
Brian Gannon
7 years ago
Believe it or not a simple light bulb is a great source to dehumidify a space.
hazelcraddock
7 years ago
You could start with thick 20 mil plastic over the sand floor. If you do insulate the ceiling of crawl space then your plastic will have to be just under that insulation at floor joist. So yes, encapsulation. And don't store anything in the crawl space. I also live in central WI in a ranch style - with a concrete floor. Unless I run AC, dehumidifier in basement, and two box fans in basement to circulate air in summer, the basement will smell musty. I used to open the basement windows to let some non humid fall fresh air in, but with the deep exterior window wells it really didn't help. Anything important is stored in plastic bins, no cardboard boxes.
User
7 years ago
A conditioned crawl space is the best approach.
Gargamel
7 years ago
There is lots of info on crawlspaces on Building Science website
PRO
Patricia Colwell Consulting
7 years ago
You need to undestand what is rude and waht is actually helpful , this is a design forum the question you asked is really not a design question so he is trying to get you some help.
chiflipper
7 years ago
Is a vapor barrier in place? If the sand is in direct contact with the soil that is your problem. It's a big job to correct this omission; sand must be moved aside, heavy plastic sheeting laid (with the seams taped), sand moved back. The sheeting is placed such that it continues up the walls. As always, proper grading to direct any water away from the exterior perimeter.