Clark
Basic Member
Posts:248
 |
| 24 Apr 2010 10:20 AM |
|
What's the best way to control the indoor humidity in an ICF (or any ultra-tightly-built) house in spring time? I noticed that on these rainy spring days here in northern Illinois, the indoor humidity levels rise close to the outdoor levels if I ventilate the house with the HRV at the recommended ACH. Turning the HRV off only helps temporarily. Outdoor relative humidity is typically in the range of 60 - 70% at outdoor spring temperatures in the 60's and 70's. I'd like to maintain an indoor relative humidity of ~50% for comfort and to protect my hardwood floors. I have central air conditioning, but it's not usable this early in the season to depress humidity levels. Is a separate dehumidifier the only answer?
Clark |
|
|
|
|
|
|
TexasICF
Advanced Member
Posts:622
|
| 24 Apr 2010 11:48 PM |
|
If you just built your home out of ICF then a bit of humidity is normal and wood floors are one of the sources of moisture realease as well as internal wood framing and etc. For this scenario a temporary dehumidifier is works fine. If you've been in your home for more than a month or two and you are having moisture problems then you are likely over-tonned. Do you have a sealed attic (I assume you do) and how many square feet per ton of air do you have? Regards. |
|
|
|
|
jonr
Senior Member
Posts:5341
|
| 25 Apr 2010 07:52 PM |
|
I would just use a dehumidifier - put it in the HRV intake air stream where humidity is highest.
|
|
|
|
|
cmkavala
Veteran Member
Posts:4327
|
| 26 Apr 2010 08:06 AM |
|
Clark ;
you can try running the air handler in the fan on mode 24/7 it will help draw out humidity and circulate air |
|
| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
|
|
Clark
Basic Member
Posts:248
|
| 26 Apr 2010 10:42 AM |
|
It's been over a year since the ICF walls were poured and the interior partitions erected, so the internal humidity sources have long since stabilized. The hardwood floors were installed in February when the interior relative humidity was in the low 40% range. The flooring was acclimated to the house for over a month before installation. I always run the air handler 24/7 at low speed for improved ventilation, and it's too early to start using the central air conditioner. When the outside humidity drops below 40%, I open up the house to the dry air, but any benefit is temporary. I have since connected up a standalone dehumidifier, but it's noisy and when the HRV is ventilating the house, the dehumidifier runs constantly (not very energy efficient, I'm sure.)
jonr, your suggestion to put a dehumidifier in the HRV's intake sounds like a good idea. Are these in-line duct units? Any recommendation on a particular unit?
Clark |
|
|
|
|
cmkavala
Veteran Member
Posts:4327
|
| 26 Apr 2010 11:00 AM |
|
Clark;
anything under 60% is accepatable |
|
| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
|
|
cmkavala
Veteran Member
Posts:4327
|
|
Clark
Basic Member
Posts:248
|
| 26 Apr 2010 12:52 PM |
|
Posted By cmkavala on 26 Apr 2010 11:00 AM
Clark;
anything under 60% is accepatable
That depends. From a health safety standpoint, yes. But, most solid hardwood flooring manufacturers recommend maintaining indoor humidity between 45%-55% year round. Flooring planks will expand under high humidity conditions. The wider the plank, the more pronounced the swelling. Since my floors were installed at an acclimated humidity of 40%, I'm concerned about allowing the indoor humidity to rise to 60% because of the potential for damage (cupping, nails loosening, buckling.) Had I installed an engineered hardwood floor, the effect of humidity variation would have been minimized. Live and learn, I guess. |
|
|
|
|
jonr
Senior Member
Posts:5341
|
| 27 Apr 2010 11:14 AM |
|
I have solid hardwood floors (oak and tropical hardwoods) and I let the air humidity range from 30% in the winter to 90+% with the windows open in the summer. The effects are minor - a few small gaps in the winter and no permanent damage.
No particular recommendations for an in-line duct dehumidifier. Just make sure that it is designed for the air flow rate you expect to put through it.
|
|
|
|
|
Clark
Basic Member
Posts:248
|
| 27 Apr 2010 05:54 PM |
|
jonr, that's encouraging. I guess the hardwood flooring manufacturers are being overly conservative in their recommendations. Do you happen to know when your floors were installed and what the ambient relative humidity was? How long was the material allowed to acclimate? My daughter's floors were installed in the summer when the humidity was fairly high. In the winter, when the indoor humidity drops to <30% the floor boards shrink enough to open cracks wide enough to insert a dime. No permanent damage, either, but certainly not desirable.
In my case, the floors having been installed in winter, when the boards swell in the higher spring and summer humidity, there's no space to expand into, putting a lot of stress on the boards and fasteners. So far, I'm okay dehumidifying the air with a portable dehumidifier. I just want to be sure my expensive hardwood floors aren't damaged for lack of attention to indoor humidity levels. In my mind, permanent damage includes the floor developing squeaks. |
|
|
|
|
jonr
Senior Member
Posts:5341
|
| 27 Apr 2010 09:22 PM |
|
I don't know about the oak, but I would guess it was installed in winter. The tropical hardwood was done in winter with a 1 month acclimation. No squeaks on either one. I have seen other houses with larger gaps in the winter - they were probably installed in the summer. |
|
|
|
|
TexasICF
Advanced Member
Posts:622
|
| 27 Apr 2010 11:02 PM |
|
60 is too high for comfort. But... I still suspect you are overtonned.... " Do you have a sealed attic (I assume you do) and how many square feet per ton of air do you have?" Regards. |
|
|
|
|
cmkavala
Veteran Member
Posts:4327
|
| 28 Apr 2010 06:53 AM |
|
Posted By TexasICF on 27 Apr 2010 11:02 PM
60 is too high for comfort. But... I still suspect you are overtonned.... " Do you have a sealed attic (I assume you do) and how many square feet per ton of air do you have?" Regards. I agree, it is acceptable from a health stand point, but not for comfort or wood flooring. If the HVAC is over sized, they could try running the air handler motor on a lower speed if it has that option on it. This is a constant error made by inexperienced HVAC contractors that are affraid of undersizing and having complaints later of insufficient cooling, but in a tight house it would be better for the system to run all day in hot humid weather, at least it is getting rid of humidity, ERVs will not help in lowering humidity |
|
| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
|
|
Clark
Basic Member
Posts:248
|
| 28 Apr 2010 08:00 AM |
|
Posted By TexasICF on 27 Apr 2010 11:02 PM
60 is too high for comfort. But... I still suspect you are overtonned.... " Do you have a sealed attic (I assume you do) and how many square feet per ton of air do you have?" Regards.
The house is a 2100 sf ranch with vented attic. The A/C is 1.5 ton, the smallest I could get. The AHU has a variable speed fan (First Co) with a low speed for humidity reduction.
I don't see a problem controlling humidity in the house once hot summer days arrive. My question was how best to maintain comfortable and safe humidity level during cool rainy spring days. From the responses so far, my only solution is to install a dehumidifier in the air intake from the HRV. In-line dehumidifiers are expensive, it seems ($800-$1000.) I'm not sure I want to spend that kind of money for something needed a couple months a year. |
|
|
|
|
cmkavala
Veteran Member
Posts:4327
|
| 28 Apr 2010 08:57 AM |
|
get a couple od small $100. portable dehumidifiers |
|
| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
|
|
ICFconstruction
Veteran Member
Posts:1324
|
| 30 Apr 2010 08:26 PM |
|
Have the windows open on a dry day. |
|
| Brad Kvanbek - ICFconstruction.net |
|
|
sasanoa
New Member
Posts:6
|
| 01 May 2010 08:02 AM |
|
Interestingly enough, if I recall correctly, the new EPA rules on indoor air quality are going to require New homes to have a relative humidity of 35%. I think they are spending way too much time in their fossil fueled offices running the AC and dictating lifestyle choices to others. How many of them have lived in South Florida with no AC?
|
|
|
|
|
Clark
Basic Member
Posts:248
|
| 01 May 2010 08:24 AM |
|
I can now see why the choice between installing an ERV vs. an HRV becomes an issue in some climates. Right now, an ERV would give me the ventilation I need while keeping the indoor humidity in check. There's no ventilation mode on my HRV that is optimized for the months of April and May. The intermittent mode that works so well in winter (HRV turns on when the humidity rises above the set point) is useless in spring. Does anyone have an HRV with an outside air humidity sensor and mode where the fan turns on when the outside humidity drops to a certain level? This would be preferable to opening the windows on a dry day because, here in Chicagoland, dry spring days are usually cold spring days. And, unlike an open window, an HRV can also filter out dust and pollen. |
|
|
|
|
Geo junkie
New Member
Posts:11
|
| 03 May 2010 12:17 PM |
|
The science is pretty straight forward. Humidity is moisture in the air and relative humidity is the amount of moisture present as a percentage of the moisture the air can hold at a specific sensible temperature. Therfore, to reduce the relative humidity you must place the warm, moist air in contact with a surface that is colder than the dew point of the air os it will leave the air and accumulate ont eh cold surface. This is commonly done with a refrigerant cooled or water chilled air coil. However, when the war moist air is passed across the cold coil it not only removes the moisture, it also reduces the sensible temperature of the air; often to far for comfort. So a typical dehumidifyer "reheats" the air to bring the temperature back up. The heat used to reheat the air comes from the heat that is removed to cause the moisture to collect on the air coil and reduce the temperature. It's all a part of the refrigeration process.
Some High efficiency Central Air Conditioning systems have a "dehumidification mode". You might contact your equipment installer to find out if your system has this option. It basically runs the blower at a reduced speed to allow for the coil temperaure to be just above freezing to remove the most moisture as theair passes. The other "downside" is that the air temperature coming from your supply registers is quite cold too. It may cause some drafts.
Sizing of a dehumidification system can be done by a QUALIFIED and COMPETENT HVAC contractor who will measure the indoor conditions and the volume of the home. From this, they can determine the amount of moisture removal needed to maintan the indoor relative humidity at appropriate levels during these cool, wet periods.
AprilAire makes a whole house dehumidifyer that you can connect into the ducting associated with your HRV. However, you must realize that running a dehumidifyer is not an inexpensive proposition. Dehumidification is a process of cooling and moisture removal and then reheating. So you are paying to take heat and moisture out and then paying to put just heat back.
These are just some things you should keep in mind.
Good luck! |
|
|
|
|
Clark
Basic Member
Posts:248
|
| 03 May 2010 08:49 PM |
|
My take on this thread so far is that there is no automatic humidity control system commercially available and in common use to address this problem. I'm not sure if many people even see it as a problem. I would like to maintain an indoor relative humidity between 40 - 50% year round (40% in winter and no more than 50% at other times.) To do so requires a lot of attention on my part. The process is anything but automatic. In winter, I can set the humidity set point at 40% and the HRV does a good job of maintaining that humidity level automatically. In summer, I set the indoor temperature set point at 72 and the A/C keeps the humidity in range as long as I don't run the HRV too much. In spring, neither approach does the job, so I have to run a dehumidifier to reduce the humidity level, again with the HRV off for the most part. All of this requires a lot of attention and awareness on my part. Furthermore, I'm not getting enough ventilation of the house as indicated by my high radon levels. Not good! Is this rocket science or what? |
|
|
|
|