Replies

1. 
   ohioandy | Sep 24, 2017 08:43pm | #1

   45-50% is not necessarily too high, and you're certainly not likely to see any condensation on windows this time of year. But this is a good question for this forum, and it's been discussed often, with some consensus and some controversy. For good advice you'll need to provide more information: where approximately is your house located; how well was it constructed--that is, was it built to modern energy codes that require measuring airtightness; describe any mechanical ventilation (bath/kitchen/whole house fans, HRV or ERV, fresh air intake in furnace ducting); how many people live in the house; how much water does your dehumidifier produce in a day--and has that been consistent. One very good starting point, too, is to get yourself an accurate hygrometer, preferably a sling version with a wet bulb, in order to obtain reliable measurements.

2. GBA Editor
   Martin Holladay | Sep 25, 2017 04:11am | #2

   Melsie,
   It sounds like everything in your house is just fine, but it wouldn't hurt to provide the information that Andy suggested you provide -- especially if you are worried.

3. Expert Member
   Dana Dorsett | Sep 25, 2017 08:25am | #3

   45-50% is in the "ideal for human health" zone in charts developed by the health professionals. eg:

   https://amshieldcorp.com/wp-content/uploads/2014/03/optimum-relative-humidity.jpg

   http://www.jeanscotthomes.com/wp-content/uploads/2015/01/humidity_chart.jpg

   http://www.webwhispers.org/newspics/dec00/4HUMCHA.JPG

   (Unlike wood sheathed framed houses) with an ICF house you don't have to worry about wintertime moisture accumulation inside the walls. Concrete can not grow mold, and neither will EPS, nor is there any significant air movement from the conditioned space into the concrete or EPS.

   For the record, where are you located (by US DOE climate zone, or ZIP code)?

4. 
   SwitchgrassFarmer | Sep 25, 2017 08:56am | #4

   I have an ICF foundation and a fair amount of concrete and masonry elsewhere. The first full winter here the humidity was comfortable. By winter two I was drying laundry inside to keep the humidity from going too low. I attribute that change to the building materials continuing to dry over time.

5. 
   user-1072251 | Sep 25, 2017 11:39am | #5

   You're into the humid months of your first year, when the concrete, drywall, paint and wood are all still drying out. As Andrew says, your humidity levels should go down by next summer. First year in any new house will be more humid.

   Did you do a blower door test? Anyone with a tight house, and ICF's might qualify, should have a ventilation system to provide fresh air.

6. Expert Member
   Dana Dorsett | Sep 25, 2017 11:48am | #6

   Bob: I was assuming the ducted heat pump was also providing the ventilation air (a common setup, and a reason for cycling the air handler every hour) but since MELSIE didn't state that explicitly I could be wrong.