Need advice on monitoring the humidity in crawl space under house

I need to monitor the humidity in the crawl space under my house. Radio Shack has a unit that you mount inside your house and then place a remote sensor in the crawl space. Has anyone had experience with this unit? Can anyone recommend a better uni?. I like the idea of being able to monitor the humidity inside my house without having to go into the crawl space.
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Why monitor it, it will be high, so what. The radioshack unit im sure only works in a specific temp range. Monitor your house where you live.
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I have a RS model. Works well though I have no idea whether it is accurate. It seems accurate enuf though.... consistent with weather guy on tv. It doesn't stop my wife from asking me how cold it is outside.

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put down a HEAVY plastic vap[or barrier over all the exposed earth, overlap seams and tape well.
the insulate the foor above so pipes cant freeze, and ventilate well the area with lots of vents.
whats up with your crawl space?
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What do you intend to do if you find it's high?

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It is a new house and I plan on installing 6 mil plastic and foam insulation on the block walls. If it is still over 55%, I plan on adding a dehumidifier that is controlled by a humidistat controller.

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A humidifier in a crawl space can freeze up, and you have to make provisions for condensation drainage. Is it possible to connect the humidistat to an exhaust fan?

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Bob, Depending on where you are, an exhaust fan wired to a dehumidistat can be a very ad idea. In this area, the bug companies love to do it. Then the floor joists start to rot and the finger pointing begins.
In most areas it will help in the winter if it does not frreze the pipes. In humid climates, it is about the worst thing you can do.
The OP has the right idea.
The Radio Shack units are reasonably accurate, at least the ones I have checked. They have up to 3 remote sensors. I norm,ally use Hobo Data Loggers from Onset Computer Corp. Then I can leave them in the crawlspace for a couple weeks and download a graph to my computer for a permanent record.
For more information see this link on Crawlspace problems:
http://www.contractingbusiness.com/Classes/ArticleDraw/ArticleDraw.aspx?CIDr53&HBC=GlobalSearch&OAS=&NIL lse
Stretch
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Aha! I was just thinking of doing the same myself to detect when the crawlspace is flooded. There is indeed a remote sensing hygrometer set selling for around $26+shipping mail order. Search for RMR603HGA with froogle. But do your own research. It may or may not fit your needs.
I also did an experiment with a non-remote sensing digital hygrometer. I hung it inside the crawlspace access panel. When the crawlspace is normally dry, it reads about 50%, same as outside. When the crawlspace is wet with puddles, it reads 75%.
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If you're just trying to sense water, Glentronics has a water sensor model # BWD-HWA 'Basement Watchman'. It's 9VDC, solid state, with a 100 dB alarm. Don't remember where I got mine. May have been Grainger. http://www.glentronics.com/water_alarm.htm

normally
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Bob wrote:

If the crawl space has bare earth floor, you should cover it with plastic and provide some ventilation to the outside.
Mark
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add plastic, and additional ventilation to the crawl space.
most dehumdiferes today include a humidity read out.
your least expensive approach is great plastic sheet job, lots of insulation, and a small muffin fan running 24/7 they use nearly no electric but can keep humidity low.
make sure the area is welll drained, with downspouts and all routed all away from house
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I use the Oregon Scientific "Long Range Weather Forecaster with Audible Alert (BAR122HGLA) " partly for the exact purpose that you're referring to. It come with a wireless remote and you can add 2 more channels -- I added the THGR268 which is the Oregon Scientific Wireless ThermoHygrometer Sensor and is the same as the one remote that is included with the BAR122HGLA. Since I have two crawl spaces I have a wireless remote in each plus one outside and then the base station gives me my living space readings.
My crawl spaces are closed off and I have gone through and sealed all the rim joist areas of the crawl spaces as well as my partial basement. As recommended by Advance Energy I also went through and sealed & Insulated all of my ductwork in my crawl spaces. This has made a huge difference in the air quality and comfort in our house!
When you put down your vapor barrier I would suggest you put down two layers of 6mil plastic -- put down one layer that you'll be working on then before you close it up I put down a second layer because no matter how careful you are you are going to put holes in the plastic while working on it.
for a good reference on crawl spaces check http://www.advancedenergy.org/buildings/knowledge_library/crawl_spaces /
I am using dehumidifiers in each crawl space -- in one it has an internal pump that pumps the water out the other space has a simple gravity line. Both work OK.

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I have checked the Radio Shack units and found them to be reasonably accurate. As for using a fan to dry the crawlspace, in Arizona it would work, but not in any high humidity climates. Check this link as well as advanced energy.
Crawlspace problems
http://www.contractingbusiness.com/Classes/ArticleDraw/ArticleDraw.aspx?CIDr53&HBC=GlobalSearch&OAS=&NIL lse
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No experience w/ the RS unit but it seems reasonable
I've used http://www.davis.com for all sorts of sensors with good results
http://www.davis.com/index.asp use humdity as keyword, your'll get a variety of instruments that will do the job
looks like they have units similar to the RS unit but they can monitor more than one location
cheers Bob
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No experience w/ the RS unit but it seems reasonable
I've used http://www.davis.com for all sorts of sensors with good results
http://www.davis.com/index.asp use humdity as keyword, your'll get a variety of instruments that will do the job
looks like they have units similar to the RS unit but they can monitor more than one location
cheers Bob
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