OT--Home crawl space ventilation

Jiles · Jul 1, 2015

I live in Alabama and have a large, tall crawlspace in about 3/4 of my home with 1/4 unfinished basement.
I use a dehumidifier in the basement and was just wondering if I should leave the crawlspace vents closed or open?
Crawlspace smells a little musky closed or open, and I have a lot of items stored there.

Russ from MN · Jul 1, 2015

Most crawl spaces need to be ventilated, if is connected to a basement that you are dehumidifying then you probably could just vent it to the basement. We have a similar situation, close to a lake, high water table so we have a power vent with a heat exchanger that runs in the daytime year around. I also installed a duct full length of the crawl space to circulate air, it's about 60 ft long with a small fan on the end.

Goose · Jul 1, 2015

We have a 4' crawl space under our house rather than a basement because of a high water table. We have 6 vents with shutters that automatically open and close at 40 degrees temperature.

Texasmark1 · Jul 1, 2015

Gotta ventilate it for two reasons: mildew and summer attic heat. If you don't have a gabled roof with end vents then you need to put
some eave vents in and turbines or power ventilators near/on the peak of your roof. If using the eave vents, ensure that the attic
insulation isn't blocking air flow off. If you have 6" or more insulation is usually requires removal of the outer edges adjacent to the
vents.

rustyacres sd · Jul 1, 2015

Have a full finished basement here in SD and in the summer with the humidity it always feels damp. Humidifiers work somewhat. I just installed a radon mitigation fan (can use
something similar. and some pvc pipe. Also used an adjustable fan speed controller. Seems to have helped immensely. It is now more comfortable in the basement then upstairs right
now due to the high humidity. Wish I could figure how to get the pics to show right side up. Can also see in the one photo of the speed controller

Geo-TH,In · Jul 1, 2015

If Alabama is like Indiana, Don't vent. I have a rental house with a basement.
Basement walls are below dew point temp. Tenant wants to open back door which lets
warm moist air in the basement. When warm air hits cold concrete blocks, condensation
forms, musky smells even damp carpet of floor.

I have three homes with half basement half crawl. Dehumidifiers may not be enough if
you have air leaks. I keep mine dry with a central ac and a dehumidifier.

This time of year, Indiana nights temp gets below dew pt. Grass is wet. I even noticed
a few metal buildings this morning with dew on the outside walls.

When I headed to town this morning, my front window was fogging up on the inside. So I
turned the defroster on which also turns on the AC. It cleaned off the fogging in the
inside, but soon after condensation formed on the outside of window.

I think many people don't understand how dew point and relativity humidity works.

jacks · Jul 1, 2015

I live in a humid climate and my crawl space used to stay wet all
summer. Moisture forming and dripping everywhere. I blocked off the
foundation vents with insulation board and installed a 1" pipe from
the heat pump supply duct to discharge into the crawl space.
Eventually this displaces the humid wet air and the crawl space will
dry up. This is assuming that you don't have a problem with moisture
coming up into the crawl space from drainage problems outside the
house. My crawl space stays dry now year around, even during humid
summer weather.

bison · Jul 2, 2015

I have a 3' crawl space under my entire house, there's only a sheet of black poly as moisture barrier on the ground. The space air can ventilate at various points into the house trough 6 unused registers that are not hooked up to the furnace plenum that is located in the crawl space.There is no outside vent leading into the crawl space
In the 22 years since we build the house we never had a moisture problem or a bad or musty smell either in the crawl space or coming into the house trough the registers.

OT--Home crawl space ventilation

Jiles

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Russ from MN

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Goose

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Texasmark1

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rustyacres sd

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Geo-TH,In

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jacks

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bison

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