HVAC guys / crawlspace humidity question

[tanto]

We just bought a “new to us” home and it is pier and beam construction, 1966. The previous owner took the liberty of installing new blowers underneath the home in the crawl space, one for the east side, one on the west. The blowers are wired to humidistats so they will cycle on and off to ventilate the space as needed. My question is, what setting should they be set to in order to do their job efficiently? There is a knob on the humidistat that has different humidity percentages listed as well as an “on” and “off” location on the knob. Any help would be appreciated!
-home is located in Dallas, Tx. for reference.


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[tanto]

up

[Throwin Darts]

I think mine is set on 60%. I can check later when I get home.

[Rat]

So, are they dehumidifiers or just fans?
Is the crawl space encapsulated?
Is there any air transfer from the main house into the crawl space?
Is there any supply air (from the HVAC system) into the crawl space?
Is the HVAC equipment and/or duct work located in the craw space?

I need answers to these before I can give you the correct answer for your application.

[tanto]

So, are they dehumidifiers or just fans?
Is the crawl space encapsulated?
Is there any air transfer from the main house into the crawl space?
Is there any supply air (from the HVAC system) into the crawl space?
Is the HVAC equipment and/or duct work located in the craw space?

I need answers to these before I can give you the correct answer for your application.

Crawlspace is not encapsulated. (I assume that there is...no air transfer from main house to crawlspace, no supply from HVAC to crawlspace) and duct work is located in crawlspace.

Thanks

[8mpg]

Crawlspace is not encapsulated. (I assume that there is...no air transfer from main house to crawlspace, no supply from HVAC to crawlspace) and duct work is located in crawlspace.

Thanks

I just had the whole underside of my house sprayed with 2" of closed cell spray foam due to air leakage. I had a bit of an "old house smell" in my house after being completely remodeled 3 years ago. Its AMAZING how much air is coming from under your house and inside your house. We really noticed it when they were spraying the foam. I read online that up to 40% of the air inside your house can be from under your house and now I believe it.

My floors are pier and beam, 1x6's laid diagonally, 3/4" OSB and wood floors in most of the house, bedrooms carpet and tile bathrooms. The smell is gone, our closet isnt as cold as it used to be compared to the rest of the house and the floors are much stiffer. I'd vote to encapsulate to the minimum.

[tanto]

HVAC guys / crawlspace humidity question

I'd vote to encapsulate to the minimum.

Okay good to know, we may budget for this eventually. What did it run you cost wise? What’s the sq ft of your home?





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[8mpg]

I'd vote to encapsulate to the minimum.


Okay good to know, we may budget for this eventually. What did it run you cost wise? What’s the sq ft of your home?





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I paid $4k for a 2000 board feet. So I went above and beyond what most people would do. Its $1.13sqft per inch of closed cell. I got a bit of a discount going 2" and have used the company before. So my house is only 1600sqft but I had them spray foam the joists as well. Normally they only do the floor bottoms. This is a technique recommended by Joe Lstiburek (godfather of building science).

A cheaper technique but achieves the same goal is to spray foam the foundation walls (closing all vent holes) and laying down plastic on the ground as a vapor barrier. You add in plastic expense but way way less spray foam ($1000 or so in my case). I wasnt crawling around under the house for a day or two trying to neatly lay down plastic, tape all the seams etc. So I just spray foamed the floor deck and joists.

If you are bored, read this article from Joe Lstiburek:

https://buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces

[Rat]

Unfortunately you are in the worst possible situation for dealing with a crawl space; existing structure and not encapsulated.

Encapsulation is the best method, but there are other, les effective but better than what you have ways of dealing with it.

I wish I could share my hundreds of hours of training on this with you, but I can't. Instead, here are a few articles to get you going.

https://www.energyvanguard.com/blog/...rawl-Space-Air

Basically, unsealed crawl spaces and fans are the absolute worst options. Turning the fans off and sealing the crawl space will give better results; just turning the fans off will be better!

Get yourself a digital hygrometer, preferably one that can read remotely, and keep an eye on the RH in the crawl space; fans on, fans off, sealed, etc.

If you have a bulk water problem you will need to get that fixed first, the above article explains that as well.