Ducted Mini Split installed in encapsulated crawlspace

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ChrisM

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We are thinking of installing a ducted Mitsubishi Mini Split in our encapsulated crawlspace. It is always between 55 and 70 degrees depending on the season has no vents and is setup as part of the house envelope. Would this create a problem such as adding humidity? Our attic is not part of the conditioned space and gets extremely hot in summer and freezing in winter so we are not considering it as a possibility.
 
In the AC mode it would dehumidify the space as any humidity in the crawlspace would condense on the coils and drained off. In the heating mode it wouldn't add humidity to the space. You don't list your location, are you in a humid area? A dehumidifier might be all you need in your crawlspace. They do put out some heat year round. How big is the crawlspace and what kind of volume of space are you looking at? Here crawlspaces can literally be a crawlspace or in my neighbor's case at the tallest point 14' high, sloping up to 2' because of the slope of his yard.
 
In the AC mode it would dehumidify the space as any humidity in the crawlspace would condense on the coils and drained off. In the heating mode it wouldn't add humidity to the space. You don't list your location, are you in a humid area? A dehumidifier might be all you need in your crawlspace. They do put out some heat year round. How big is the crawlspace and what kind of volume of space are you looking at? Here crawlspaces can literally be a crawlspace or in my neighbor's case at the tallest point 14' high, sloping up to 2' because of the slope of his yard.

It's about 450 sq ft and about 4' high located in the Hudson Valley NY about 90 miles north of NYC. It can get very humid in the summer in July and August but by late August things start cooling off. This ducted system is meant to heat and cool the above dining room, kitchen and living room all open space.
 
OK, so you're not looking to condition the crawlspace. In my area (central NC - hot and humid) crawlspaces are very common. Most are vented but many are starting to encapsulate them. Here a dehumidifier would be all that would be needed in a encapsulated crawlspace to keep humidity in check. It would likely work as well in your area. Assuming by encapsulating your crawlspace walls are insulated and the ground is covered completely with 6mil plastic or possibly a slab with plastic under it. Vents are kept closed in an encapsulated crawlspace.

Putting your mini-split in the crawlspace should not cause any problems. Many of our HVAC systems are located in our crawlspaces. The compressor unit is outside. We also have a system here called a "gas pack" which is a combined gas furnace and AC unit in one outdoor unit. The conditioned air is ducted into the house through a hole in the foundation. They use these on homes with low crawlspaces.
 
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