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Humidity Help

2K views 2 replies 3 participants last post by  Hands-on 
#1 ·
So I have taken some measurements:

Basement @ 65 degF, 65% Humidity
Living Space @ 80 degF, 67% Humidity

I did some calculations:

Basement is approximately 6400 ft^3
Living Space is approximately 19200 ft^3

So I estimate less-than 30 pints (3.75 gallons) of water in the air throughout the whole house.


Some more facts:

The living space is two stories (slightly hotter on the second floor, but no more than 1 degree). I have sealed the living space fairly well. Sealed the outlets, light fixtures, attic hatch. The windows and doors have good seals. There is ~18 inch insulation (R-54) in the attic. The exterior walls are 2x4s with batts of R-13. I have not been running the A/C. Also, the A/C is way oversized so it does little good in controlling the humidity levels. I have also not had the windows open (much) because of unseasonably hot temperatures (>95 degF during the day, >70 degF at night). With the hot weather I am really happy the temperatures inside have stayed around 80 degrees, but I cannot control the humidity.

The basement is completely unfinished. There is a sump pit, but no sump pump. The pit always contains about 4-8 inches of water. I pump it out occassionally, but it fills back up to this 4-8 inches within an hour. Even during heavy rainstorms it just sits happily at this 4-8 inches. Nothing else exciting down there.

The house was built in fall 2007, so it is fairly new.


My problem is I have been running two dehumidifiers (one in the basement and one in the living space) constantly (24/7 minus time to empty the water bucket)for the past 2 weeks and the humidity sits around 65% in both areas. I know the dehumidifiers are working because I am emptying the water buckets once a day in the basement and nearly twice a day in the living space.


Any thoughts/clues/questions/experiments to try and control the humidity level? I would really like to get it down to the 50% range.

Since the house is not even three years old could it still be the house drying out? That is the only thing I can come up with, unless I have a major leak somewhere that I missed.


One more thing.

Outside during the day (right now) is ~90-95 degF with 60% humidity. Outside during the night is ~72-75 degF with 99% humidity. I could run the A/C, but like I said it is over sized so it will get the house back to 74-78 degF before it affects the humidity levels.


Thank you.
 
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#2 ·
A. Run the A/C.
With the dehumidifiers going, and the A/C, you get a lower humidity in your first and second floor areas.
B. Seal your basement from your first floor.
Look for the holes where they ran your electric wiring through, and caulk them.
C. Pump a sump pump in that pit.
Your basement floor is probably bleeding a lot of moisture through. Not enough to show wets spots on it. But enough to raise the humidity. May want to consider an epoxy sealer for your concrete floor.

Your floor bleeds a lot of moisture from the basement to the first floor also. So address the basement humidity issue.

Your total moisture content in your air at the temps and RH you posted is less then 3 gallons. And if you removed ½ gallon, and no moisture came in. Your RH would be 55%.

So you either have a very high infiltration rate.
Or:
You cook 18 hours a day.
The other six hours you wash the dishes.
You wash the floors way to often.
You have several, or one really large aquarium with no cover.
Your bathroom exhaust fan doesn't work, or you don't use it.
Your kitchen exhaust fan doesn't work, or you don't use it.
You have 10 to 20 people in your house most of the time(somebodies gotta eat all that food).

Thats just some possibilities.

PS: Might want to slow the blower of your A/C so it removes more moisture.
 
#3 ·
Outside during the day (right now) is ~90-95 degF with 60% humidity. Outside during the night is ~72-75 degF with 99% humidity. I could run the A/C, but like I said it is over sized so it will get the house back to 74-78 degF before it affects the humidity levels.
If you aren't running A/C and the humidity outside is 60 - 99%, are you opening the windows? Even if you aren't, you are still pumping the house full of moist air through opening doors, infiltration, etc. If everything is sealed and you don't have water leaks your only other option is mechanical dehumidification; it may take more dehumidifiers. Your mechanical unit will help dehumidify some, but (oversized or not) most of the new units have little latent (moisture in the air) capacity. Have you considered adding dehumidifiers? If you are comfortable with the temperature and don't want to air condition, that would seem to be the best option. Look at the capacities of the dehumidifiers; you may want a larger commercial type one.

Good luck!
 
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