DEhumidifiers: one or two?
Zone 5, 2 story residence, forced hot air/AC. This year’s particularly wet/humid summer has been ideal for mold growth. The structure has neither AC or any source of heat and have been doing my best to keep fans on and windows/doors open to thwart mold growth. The newly poured concrete slab in the basement is a not helping. I want to install a dehumidifier, regardless of the current issues. The basement is NOT ducted. Basement is actually larger than the first floor foot print with basement extending under covered-attached porches.
What is the best way to set up a whole house dehumidifier?
The way I see it, either one large unit, I would likely need at least a 200 pint/day unit, ducted return to return, tapping into the house’s ducting system. Issue is, basement is not ducted. Possibly either an electric damper and humidistat that controls where the unit draws from. Or maybe two 90 pint units, one designated for basement alone, other for the house. What do you think? Maybe other better alternatives I am missing?
Regards
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Can we assume the tidal of your post is an error and you are asking about dehumidifiers?
Generally a dehumidifier is a tool of last resort and best avoided if at all possible.
The real question is what is the moisture source and how can you deal with the source?
If your moisture source is a rubble stone foundation you may have no other options.
If it is new construction moisture a dehumidifier is not a bad idea for a few months.
Please take the time to read this article
https://www.greenbuildingadvisor.com/article/all-about-dehumidifiers
Walta
Last thing I need, more humidity!
I added DE-. Tnx
The source is the high humidity in the air, house is shaded amongst tall oaks, my neighbor's roof is moss covered, it's where we live. This summer's rain making it worse.
I'll read the link.
Thank you
Sal,
I'm somewhat confused. You wrote that your house has "forced hot air/AC." So far, so good.
Then you wrote that "The structure has neither AC or any source of heat and have been doing my best to keep fans on and windows/doors open."
If you have AC, as stated in the first quote, then you should close all of your windows and use your AC. If you refuse to do that, it's hard to know if your house has a humidity problem. Moreover, it doesn't make much sense to buy two new expensive dehumidifiers if you have AC equipment that you aren't using -- and if you are leaving the windows open.
Sorry Martin, I should have of clarified, I am in construction and have been for a while as I am doing it mostly on my own. So its HVAC ducted, eventually forced hot air and AC. Given the long pauses between phases (it's very well insulated -rigid outsulation XPS 1.5" and internal fiberglass R-21 in the bays so walls dry to interior - and sealed, all nooks and cranneis caulked/foamed, all plywood sheathing taped, XPS panels caulked and taped, electrical and plumbing roughed out, ) I find myself in a situation where inside hygrometers measure relative humidity consistently above 90% in basement, 1 st floor and 2nd floor. I have increasing concern for a mold outbreak. Basement had some OSB sheets I used to cover pallets with stone, covered in mold growth. I worry about the exposed wood framing. Since my understanding of dehumidifiers (or I am reading too much Ultra-Aire literature and watching Risinger's commercials/video's) is such that they serve to increase comfort and lower AC costs. Our area is VERY humid in the summer months, thus I am thinking of getting one (or two) into the structure ASAP. Additional thoughts, maybe start with setting up one non-ducted dehumidifier in the basement (its about 1600 sq ft), and monitor how it affects the hygrometer readings on the first and second floor.
An aside, I did it all, applied an elastomeric capillary break between footing and poured concrete walls, laid down Stego 15 mil vapor barrier under slab, exterior poured walls were primed and I applied Grace's bituthene membrane with 4" overlap. It was last summer in August, the stuff seems to have melted onto the walls, I was hoping for a dry basement, no such outcome so far. Still the slab exuding moisture? The ambient temp differential with the slab causing condensation? One thing I did not do, lay down rigid foam insulation below the basement slab.
But do not want to distract from the AC issue. I appreciate your comments and used much of what I Iearned on this site and buildingscience.com to build it, despite local contractors skepticism and sometimes flat out ignorance.
Thanks
I think you need to condition the air in your building.
Conditioning with dehumidifiers and no AC will lower the dew point in the building but it will also heat the building maybe to the point to the point that will not be comfortable to work inside.
I think you should get your building “closed in” and run the AC and a dehumidifier and get the humidity below 60%.
What is your zip code?
Matt Risinger has several YouTube videos about how they deal with their oppressive humidity.
https://www.youtube.com/user/MattRisinger
Walta
Without knowing any more details I would consider getting 70pint/day portable dehum and let it run in the basement. Humidity is easier to keep even without ductwork and fans than temperature. Don't set it any lower than necessary since it will just heat up the air in place of humidity. I leave my basement dehumidifier set to 55-60%rh (older house without any poly under the slab or moisture breaks between the footings and walls.) It's helpful to have a condensate pump model, or a drain nearby otherwise it will spend have it's time just sitting there with a full tank.
Upstairs consider some sort AC, portable if you have too (But get one that has balanced ventilation inlet and exhaust hoses, not just an exhaust). You might not keep temperature at setpoint but you should be able to keep humidity under control.
Also, a heatpump style water heater can make a contribution and the energy is put to good use instead of wasted.
I agree, just get a cheap standalone unit for now and see what happens.
You don't need 200 pints a day removal rate though for a while your going to be removing whats ingrained so empty frequently or drain automatically.
Very high interior humidity should be avoided - dehumidification should be standard in most of the US. The humidistat will ensure that it doesn't run when it isn't needed. The thermostat and AC will ensure that it never overheats the house.
It's so much less expensive to use portable (vs central) dehumidifiers that you should try one per floor with interior doors left open.
Sal,
If you follow Jon R's advice, be sure to close the windows and doors.
Sal,
It sounds like you've got your building shell complete, but the HVAC is not yet running, and that its' been in something like this condition for about a year, correct?
You will see general statements that it sometimes takes a year or so for construction moisture to dry out of a building. Ignore them. In your case, it could take decades. You have a very tight building shell, a humid outside environment, and no conditioning in the building to remove moisture. This is why you are routinely seeing 90% humidity in the house and, yes, that is not a good thing.
But you are on the right track. Dehumidifiers will certainly do the trick for you. I would go ahead and purchase two and make sure that they are set up for self-draining, as recommended by others above. You may or may not need to continue using them once the initial moisture load of the house is removed, and once the HVAC is running regularly, depending on your climate, house envelope, living conditions and preferences, etc. Many, or most basements need dehumidification regardless of construction type and other conditions.
You also seem to express some frustration that you are not yet seeing the benefits of a "dry basement." Don't worry. From your description, you do (or will) have a dry basement, once the construction moisture dries out. There are literally tons of water stored in poured concrete and until that moisture dries out, you will have humidity issues. It is once the interior moisture dries out that all of your exterior moisture defenses will start to pay off.
Set up the dehumidifiers and let them run for a month or two at 55% or so. Get the HVAC running in time for colder weather, and use it. Make sure any outside ventilation you've got is running, once the weather cools off (assuming things dry out in your area). Then see how things are going.
Your description is 100% accurate Peter, thanks. I appreciate everyone's above input. I already got a stand alone portable dehumidifier running at 50% setting. Looking to order a 100 pint basement-designated dehumidifier and will transfer the portable 70 pint to the second floor. Read Dana's input on the Therma-Stor stuff in one of of the many comments sections. Interesting, most efficient does not always seem to be the right answer.
I plan to drop a 50,000 BTU pellet stove in the basement this Fall. Really looking forward to firing that up and drying some of this moisture. I've been reading lots on new construction moisture and appreciate the huge water load. Finding mold growing on the OSB panels freaked me out. I rented a fumigator and bombed the structure with 3 gallons of concrobium rotating it through all the rooms. As the temps drop, the humidity will follow and that should also help. It was a particularly bad summer. Looking forward to the day my effort and investment yields the dry basement I envisioned.
Thanks Guys.