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Crawlspace dehumidifier - needed or not?

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7.8K views 5 replies 6 participants last post by  joe954  
#1 ·
I am doing some work in my crawlspace and it is starting to look really nice, if such a word can be used for a crawlspace. It all started with sagging piers and girder. The house is from the 60's and there is only one girder supported by 4 piers. There was rain water coming into the crawlspace and making a mess. A sump pump was installed and now the crawlspace seem to be stabilized. 10 24" footings will support two girders, one on each side of the old one. I got rid of all the crap that was there, left by others in the past few decades. I bought two crawlspace fans, rated at 220CFM each one. These will be installed soon.

Even with all improvements, the crawlspace is still damp and smells musty. I was wondering if a dehumidifier would be too much or not. Would it bring any real benefits, since all HVAC equipment is in the attic? The CS is not encapsulated. I was thinking of getting the remote panel so I would not have to go down to have access to it, but it seems these dehumidifiers need to have the filter changed every 3-4 months. Does that mean that once a dehumidifier is in the CS, I'd have to go down anyway 3-4 times a year? As I already have a sump pump installed, the drainage for the dehumidifier would be fairly easy. This is the type of dehumidifier I had in mind:

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#3 ·
There's no point of putting a dehumidifier in an un-encapculated crawl - the ground needs a vapor/moisture barrier.

A dehumidifier without that would just run and run and burn up a lot of electricity, never really controlling the humidity.

Ventilating a crawl is counter-productive in summer in a humid climate, just bringing in more humidity.
Ventilation is good in dry.low humidity weather.

Once encapsulated, close the vents to outside and put a dehumidifier down there.
 
#6 ·
Do you have the correct number of vents? Are they clean or are they covered with plants. There are calculators online that will tell you how many square inches or feet of vent space that you need for the square footage of crawl space that you have. The mistake that many people make is to cover the existing opening that they have with screen or some other material to make them look nice and prevent critters from coming inside. The problem is that the screen or covering will reduce the amount of air that can pass through. Don't use window screen. My guess is that window screen will reduce the opening by at least 30%. Use hardware cloth. Another problem that I have seen is that an addition will be added to the house and a vent or two will be eliminated and the house will now have a dead air space. A fan can help in this situation.