Crawl Space Dehumidifier Recommendation needed

[frule]

I'm in East Tennessee. It's very hot/humid here, especially in the summer. Most properly encapsulated spaces here 
require a dehumidifier to keep the relative humidity at 50%. We also have much ground water and that contributes much moisture even in well-sealed spaces. It's virtually impossible to completely keep humidity out of a crawl space due to the stack effect, regardless of the encapsulation. I have installed wireless hygrometers around the space to monitor the RH.

That said, there are many months where the dehumidifier does not run. Several studies were done at Oak Ridge that detail
enclosed spaces and the need for "conditioning".

Fred

[Mr_Mike]

Fred, does your crawl space exchange air with the rest of the house. My understanding is that if you seal, you must exchange air with the rest of the house. Since the house air is conditioned, no unique equipment is needed in the crawl space.

I'm unfamiliar with conditioning the crawl spacewithout house air exchange. Neil's link shows exchanging air with the house.

I intend on converting my east tennessee home to a conditioned crawl space when I move in in two years. I have not yet figured out the best method of providing air exchange. I'll either use forced air from the furnace or provide a fan. I am convinced the existing vented crawl space is very poorly vented and the path of least resistance is to just convert to unvented.

I'll do a radon test first to see if I need to provide some exterior air exchange as well.

[frule]

It can be done that way, but most spaces are kept as separate as possible. TVA did an energy assessment (check into this,,,it saves $$ and is free) and recommended sealing all penetrations into the living space. The company that did the encapsulation
had already done this anyway. I really want as little air from the crawl space to enter the living area as possible. Some incorporate  HVAC air  into the system, but I can't see doing that.

Basically, most feel it best to have as little air from the crawl space to enter the living space as possible.Simply put, seal off as much outside air as you can So, you put down a vapor barrier on the "floor" of the crawl (usually is dirt) and extend the vapor barrier to the top of the concrete block foundation walls. It also goes up any piers about 2 feet. I used 6mil poly sheeting. If you have much traffic through your crawl, you can use 10-12 mil or just double the 6 mil which is cheaper. All vapor barrier seams are overlapped by 12 inches and taped. The walls are first insulated with foamboard (I used 1" which works well). All exterior penetrations are sealed (vents are permanently closed and sealed with foam board). I left the rim joists untouched (not insulated) to allow the termite guy a way to inspect.

I removed all of the fiberglass between the floor joists. Nothing else is done to the floor. You must use a dehumidifier if you do this, or you will get mold. I think I'll get a Sante Fe as it's a USA made product from a long-standing company. Avoid the Horizon dehumidifiers (Chinese junk in my book ....mine failed after 3 years....and no response at all fom the company to try and get repairs done under warranty).

This is an easily enough DIY job. The companies that do this can be really expensive and it's not rocket science at all.I'll never have another vented crawl space. We had a cool night. It's 39 degrees otside and 67% humidity. In the crawl space its 68.7 degrees and 44% RH with the dehu not even running..

Come see me when you get to E. Tennessee! Im near Townsend in the foothills of the Smokies.

Fred

[Robert Adams]

I prefer that method. I'd rather run a dehumidifier than have air exchanging with the living space. 

     I'm looking at a few units locally but only about 3 to really choose from. The problem is its not cold enough for heat not warm enough for ac so the indoor humidity isn't dropped below 69% in weeks. 
       Makes the house feel stuffy and promotes growth of stuff to make you sick.

        Will end up running the ac for a bit to remove the humidity then furnace to warm it back up. Lots of commercial units can run both at the same time because of the humidity problems here.

[EricU]

the Sante Fe is a little on the rich side from me.  In another thread, someone mentioned they got an open box special, but didn't mention the dealer.  Anyone have dealer recommendations?