Does anybody know what a reasonable temperature for a crawlspace would
be? I recently put two dehumidifer units in my crawlspace (along with
a couple box fans to circulate air), as I've had major problems with
moisture down there. I have all the crawl space vents sealed.
However, the temperature in the crawlspace is now running about 8-10
degrees hotter than it had been. It was running around 68 degrees.
Now it is consistently up around 76-78 degrees. I guess this is
because the dehumidifers heat things up. The humidity level in the
crawlspace is now under control, the RH has been staying around 45-47%
(it had been running around 80-90%). But I'm concerned about the
temperature running higher. Is this anything I should worry about?
What would be the ideal temperature and RH for a crawlspace?

dblho39 wrote:
Does anybody know what a reasonable temperature for a crawlspace would
be? I recently put two dehumidifer units in my crawlspace (along with
a couple box fans to circulate air), as I've had major problems with
moisture down there. I have all the crawl space vents sealed.
However, the temperature in the crawlspace is now running about 8-10
degrees hotter than it had been. It was running around 68 degrees.
Now it is consistently up around 76-78 degrees. I guess this is
because the dehumidifers heat things up. The humidity level in the
crawlspace is now under control, the RH has been staying around 45-47%
(it had been running around 80-90%). But I'm concerned about the
temperature running higher. Is this anything I should worry about?
What would be the ideal temperature and RH for a crawlspace?

Hi,
RH is function of temperature. So looks like nothing really changed in
your crawl space. My cabin has crawl space where furnace, water heater,
well water tank are located. It's cool in summer, warm in winter down
there and no moisture problem just with natural vent. Furnace draws
fresh air from outside thru insulated duct. The floor of crawl space is
dirt and it's dry, it;s almost dusty.

dblho39 wrote:

Does anybody know what a reasonable temperature for a crawlspace would be?

Close to the soil temp? I suppose most people don't care.

I recently put two dehumidifer units in my crawlspace (along with
a couple box fans to circulate air), as I've had major problems with
moisture down there.

Where does the moisture come from? Rainwater? A floor with no vapor barrier?

... the temperature in the crawlspace is now running about 8-10
degrees hotter than it had been. It was running around 68 degrees.
Now it is consistently up around 76-78 degrees. I guess this is
because the dehumidifers heat things up. The humidity level in the
crawlspace is now under control, the RH has been staying around 45-47%
(it had been running around 80-90%).

So the water vapor pressure in the crawlspace air used to be about
0.85e^(17.863-9621/(460+68)) = 0.594 "Hg, and now it's about
0.46e^(17.863-9621/(460+77)) = 0.436 "Hg. That's progress.

It used to contain 0.62198/(29.921/0.594-1) = 0.0126 pounds of water per
pound of dry air, and now it contains 0.62198/(29.921/0.436-1) = 0.00920.
This is called the absolute humidity or humidity ratio, and it does not
depend on temperature.

I'm concerned about the temperature running higher. Is this anything
I should worry about?

I guess not, but you might worry about your electric bill.

What would be the ideal temperature and RH for a crawlspace?

I'd say just keep the RH below 60% to avoid mold.

Nick

ADD COMPLETE VAPOR BARRIER! Plastic seal edges and double thickness of
10 mil plastic.

Make certain no extra water is getting dumped under home things like
route downspouts well away from area! Adding a ground water drain under
and away from home with gravel under house can be used for tough or
standing water situations...

OPEN ALL VENTS and add more vents so air flows easily under home!

REMOVE AND FORGET about dehumidifiers, they arent needed in this
application and will just increase your electric bill dramatically!

If your really intent on spending money on electric add a ventilating
fan with humidistat so it only runs when the humidity is high!

I don't think the box fans are necessary since you already have the
dehumidifier.

see: http://www.advancedenergy.org/buildi.../crawl_spaces/

I assumed you've already followed Advance Energy's recommendations to seal
up the crawl space and have a good vapor barrier installed.

I have two crawl spaces -- each with it's own dehumidifier. the larger
space has a double vapor barrier and maybe runs one or two degrees higher
than before [66-68 degrees] while the other crawl space is quite a bit
smaller and runs about 72-78 degrees -- the second has only a single layer
6mil plastic vapor barrier. both spaces are sealed up pretty tight though
and the floors above them are also pretty heavily insulated.

I keep the RH set below 50% on both -- below the level for dust mites.

I think the higher temp is from the dehumidifier having to work harder
because of the lack of a second vapor barrier and the heavy insulation keeps
the heat in.

"dblho39" wrote in message
ups.com...
Does anybody know what a reasonable temperature for a crawlspace would
be? I recently put two dehumidifer units in my crawlspace (along with
a couple box fans to circulate air), as I've had major problems with
moisture down there. I have all the crawl space vents sealed.
However, the temperature in the crawlspace is now running about 8-10
degrees hotter than it had been. It was running around 68 degrees.
Now it is consistently up around 76-78 degrees. I guess this is
because the dehumidifers heat things up. The humidity level in the
crawlspace is now under control, the RH has been staying around 45-47%
(it had been running around 80-90%). But I'm concerned about the
temperature running higher. Is this anything I should worry about?
What would be the ideal temperature and RH for a crawlspace?