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Efficient whole house dehumidification in a humid area?

 
master steward
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My little part of the world historically only gets too hot and muggy about 10 days a year.  Therefore our house doesn't have an air conditioner..  Unfortunately we're going to tally our 10th day of hot and crappy weather tomorrow with a 7 day forecast of more heat and humidity.  So I'm starting to consider our options.

Is there some magical new technology out there to achieve dehumidification without all the infrastructure/cost/energy use of an air conditioner?

I have central heat so adding a coil to the furnace would be very workable.  I do have a cold pond at my disposal that I might be able to tap into.  But I'm also curious about options that would work for people without a pond.
 
pollinator
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sounds like you're headed in the right direction:  coil or radiator with cold water cycling through it inside your central air. Since you'd condense a great deal of water, I'd make a summer by-pass for your central air, tilt the condenser radiator/coil in the by pass to collect the water into a pipe with a low pressure check valve to drain it away into a planter or some other use.

of course you need to build a test model first and see at what CFM you get the best dehumidification

For those with out a pond, they could find out how deep in the earth they need to go to hit 50F and go another ten feet deeper...this way, they now have a heat sink bigger than your pond.
 
master pollinator
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Hi Mike,

While we dont have "Air You Can Wear" like southern Mississippi and Louisiana,  humidity hits big time, here in southern Illinois, around July 1st and sticks around into Sept.  This is not to say that we dont have serious humidity before and after those dates.  I understand your frustration with the humidity, but I question the cost ( time and money ) vs return.  I suspect that by the time you finish the project, the humidity will be gone.
 
pollinator
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That level of humidity causes all kinds of mold problems with modern building materials and methods.  It isn't just about comfort.

With a cold pond and forced air, a water coil sounds like the easy answer..

There are a lot of commercial buildings using in floor cooling.  Mainly to kill the solar gain from the sun shining through big glass onto marble or polished concrete floors.  It works great as long as you don't cook the floor below dew point.  Still use forced air for humidity control.

Earth tubes can dehumidify, but you have to get them just right or they can mold, too
 
Mike Haasl
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Thanks Orin, I could set up a test out by the pond to see if it would work.  The pond is very small but very cold so I think it's spring fed.  It, and the wet woods adjoining it, drain through a culvert into a nearby lake.  I could also then test if I would pump too much heat into the pond over time.

John, no worries, I'm intending this to be a long term solution.  This current heat wave is just long enough to make me get a bit more serious about it.

And for those who are, no doubt, thinking that my little problems are nothing compared to the southeastern US, a city I used to live near in eastern WI hit a dew point of 90F in 1995.
 
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Hi Mike;
Here's an out of the box response for you....   Western Montana has similar environment to N. Wisconsin (less cheese though)  only, average summer humidity is %20 or so... very nice.
If that is something you can't bring yourself to do, then... I recommend a small bedroom wall A/C unit to let you sleep in comfort.
I grew up on the east coast,  ave. hot summer day temp was 98 F humidity %98... night time it "cooled to 88 F  with %98 humidity except for a hour or two around 4 am when the ocean breeze would waft inland for a short while....pushing the heat and humidity back towards the midwest.  
Mainly it was a hot miserable place and I moved west as soon as I could.
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Mike Haasl
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I lived in Utah for 7 years and really came to appreciate the low humidity.  The baking sun wasn't my favorite but you can't have everything.  I looked into moving West a few years ago but couldn't afford it.  Our current place is perfect except on these days.  Plus the bugs.

All the windows are casements (crank out) so I can't just pop in a window unit.  

I waded into the little pond today and tried to get a temperature measurement.  It was near the surface which is clearly warmer than the bottom.  But it was 65F.  So I doubt the bottom is anything colder than 50.  And the pond is really small.  So I suspect the spring that I think I have in the woods must not be that much of a spring.  Need to check if there's any flow at the culvert...   We haven't had appreciable rain in the last 10 days.

Now the missus is picking out a spot for central air.  
 
gardener
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Well Mike, it seems like you just ran through the cheap options.  I live in humid country.  We just replaced our central heat pump (does both heat and a/c).  We have an interesting feature where the a/c runs at low level so as to get rid of humidity, even if the heat is not terrible.  This is a fairly efficient way to make your house more comfortable.  But you do have to install central ac.

I was going to recommend a window unit, but I guess your windows will not accommodate.

BTW, how is the heat & humidity at night.  My wife’s grandparents lived in the tiny town of Prentice, WI.  We once left there and drove straight south to Southern Illinois.  We arrived at about 9:00pm and the temperature was still about 90 degrees with probably 80% humidity—Yuck!  I certainly hope you don’t have to experience that kind of heat and humidity.

Eric
 
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Slight side shoot of this topic, the water from AC, dehumidifiers or "condensation" is mostly "pure H2O" (OK, so dust is likely to land also). Being able to save some of it in jars to put it to good use has its place. I use it in my iron, as our house water is high in minerals, and we try to get 50% of our clothes washing water to be condensation water as it's soft and will wash better with less soap. Hubby saves it up for when he needs to change the anti-freeze in the vehicles. If something needs to be seriously clean, he'll splurge and buy bottled H2O, but for most uses, we save what we produce.
 
R Scott
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But they still can use lead solder in AC equipment so don't drink it unless you test it.
 
Mike Haasl
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Yes Eric, Prentice isn't all that far away from here.  Normally when it's hot and humid for a couple days, we have a less humid spell (independent of the temps) and on those nights we open up and cool/dry off the house.  Carefully monitoring inside vs outside dewpoint and opening windows normally gets us through but this stretch is starting to get to us.  Low temp Wed is supposed to be 69 and humid.

Good idea Jay!  I have a floor drain near the furnace that they'd probably plan to use.  But I'd be interested in a condensate pump or storage system.  Maybe then I'd do a grey water system for that and the laundry room...

 
gardener
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As an FYI you can buy portable AC units that work well with crank out type windows. The AC unit sits on casters in the room and there is a water pipe and intake pipe that attaches to a flat piece that goes in the window (remove the screen). Depending on the window size, you may need to cut a few boards/pieces of plastic for it to fit. My dad and my grandma both have them.

Similar to this:
https://www.bestbuy.ca/en-ca/product/danby-portable-air-conditioner-14000-btu-white/13328819

For cheaper/less energy intensive solutions... I keep a small burlap bag of clay cat litter in my car to reduce condensation on the windows in the spring and fall. I have always wondered if a larger scale version might help with humidity.

Do you have a dehumidifier in a basement? I would be tempted to bring it upstairs and try it out.

There is also always the "northern labrador" solution... a HUMIDIFIEr, filled with ice before bed and left running with a fan pointing the air to the bed :)
 
Mike Haasl
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Aha, that's a new one to me Catie, thanks!  I'd have to figure out the drain since I'd want it to run continuously.  

We do run a dehumidifier in the basement and sometimes upstairs in this weather.  The issue is that it puts the heat back into the room.  So it ends up a bit drier and a bit hotter.  

I don't think I want to do anything that adds any more humidity, even if it's associated with icy goodness.
 
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Look into split units.  They cost considerably less than central air and are DIY friendly. I'm considering one to replace our worn out central air.
 
pollinator
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Catie George wrote:As an FYI you can buy portable AC units that work well with crank out type windows. The AC unit sits on casters in the room and there is a water pipe and intake pipe that attaches to a flat piece that goes in the window (remove the screen). Depending on the window size, you may need to cut a few boards/pieces of plastic for it to fit. My dad and my grandma both have them.
Similar to this: https://www.bestbuy.ca/en-ca/product/danby-portable-air-conditioner-14000-btu-white/13328819


Unfortunately, the units that don't stick out the window tend to be loud and quite inefficient.
https://www.youtube.com/watch?v=_-mBeYC2KGc
 
gardener
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I was also going to suggest those portable floor units. I've seen some that are pretty powerful and quiet enough for office use. For a few weeks of crazy summer humidity I can't imagine installing a split (or worse, central air). Just a good-sized dehumidifier unit and a fan should make things much more tolerable.
(we have major humidity problems, but in the winter. Mold everywhere, condensation on the windows. We run a large dehumidifier every day, even when we don't have heaters running. Luckily in summer it's much less humid and I like the heat.)
 
Eric Hanson
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Tereza,

How does a floor model ac unit work?  I mean the heat has to go somewhere.  Does it heat water which is then poured down the drain or used to wash dishes, bath water, etc?

Or are you talking about a floor model dehumidifier?  Those also work well but unfortunately they dump heat right into the house.  Frustrating.

Eric
 
Eric Hanson
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Catie,

I had never heard of a casement style window mount ac unit.  That sounds like a brilliant idea in this circumstance.

Eric
 
Tereza Okava
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Sorry if that was not clear. ON the floor, not in the floor.

Typical Brazilian construction generally isn't too compatible with the traditional boxy window AC units (unless you're in an apartment building that has a specific "socket" to plug one into). These mobile units may not be optimal but they're what we have.
 
Eric Hanson
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Tereza,

That is an interesting design.  I was wondering where the ac dumped heat.  When you said floor mount I was imagining some boxy unit sitting on the floor unconnected to anything but an outlet.  In that situation the only outlet for the heat seemed (in my imagination at least) to be a little jug of water that would then get emptied someplace.

But I can see that the floor mount is indeed an air-to-air unit and I have to say that I actually like window mount interface much better than a window mounted ac unit.  I have set those up before but I always feel like I am going to accidentally drop the ac out the window while getting it in place.

Very nice!

Eric
 
Tereza Okava
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Eric Hanson wrote:boxy unit sitting on the floor unconnected to anything but an outlet.


those exist here too but don't seem to make much sense -- my dehumidifier is like that, but since I use it in the winter it works out just fine.
 
Eric Hanson
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Tereza,

A problem with a dehumidifier in Mike’s case is that the unit generates a considerable amount of heat.  Basically a dehumidifier is simply an ac unit that uses the cooling coil to condense water.  Given that all ac units merely move heat and not generate cold, the dehumidifier will indeed condense water from air (and nice, high quality, very pure water at that), but will also pump heat right back into the air.

My mother used to run a dehumidifier in our basement (2 dehumidifiers actually) and they did take out humidity but they also pumped out heat—in the summer no less.  The basement was not as humid, but neither was it the cool retreat it once was.

Eric
 
Mike Haasl
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Related to the mini splits, I already have central heat so I'd only be upgrading it to central air.

My worries with the portable air conditioners is their output.  Looks like they're best suited to a large room, not an entire house.  But if they're efficient enough, two or three of them may be cheaper than a/c.
 
Eric Hanson
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Mike,

Given your climate I wonder if you would only need 1-2 units.  I get 4-5 months per year where I need to have the ac on.  You mentioned that you recently were expecting to get a low of I think 69 degrees and high humidity.  Do you know how high the humidity?  I am just thinking that if you only have a few days a year with uncomfortable heat and humidity then maybe a relatively cheap option is warranted.

Right now our outside temps are about 95 degrees and about 57% humidity.  The temperature will likely fall to 80 degrees tonight with humidity getting even higher.  I realize that we all get accustomed to a temperature and humidity profile.  

I have a kinda funny story from several years ago.  It was the heat of summer and my family and I were at the airport in Minneapolis (my family is from Minnesota).  A group of us had to cross a large parking lot under a baking sun (well over 90 degrees) in very high humidity (I would guess close to 90%) while carrying luggage.  Most of us were Midwesterners and while the walk was definitely uncomfortable, such experiences are common for us and we all breathed a great big sigh of relief once we all stepped into a large, air conditioned elevator at the end of our jaunt.  Most of us rejoiced in the cool air, but one poor woman looked like she was going to die.  I am not exaggerating, she looked awful, close to death.  From out of nowhere she stated that she thought it was humid when she woke up that morning in Nevada and the humidity was 30%!  The rest of us just laughed.  I stated that I could not remember the last time the humidity was as low as 30%.  The poor woman just had no experience in any even remotely high humidity areas.  I imagine it would take some time for her to acclimate to Midwestern humidity.

Mike, I live at the intersection of the Midwest and the South.  But I do miss the climate of more northerly latitudes, and strange as it may seem, I miss a real winter.

Eric
 
Mike Haasl
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Wed night is supposed to be 74 with a dew point of 67 and humidity of 72%.  It's fine if that's outside but it will likely be that on the inside as well.  

Similar story Eric, our wedding was in July and outdoors.  It was 95 and 95% humidity.  The in-laws and officiant were all from Utah.  It wasn't pretty.  I think the pastor had two drips of sweat a second coming off his nose dripping on his book.  I think it was ruined after soaking up all that sweat...  To make it worse, the reception was at a ski resort.  They aren't known for having good a/c at ski resort lodges.  We told people to dress casually but the poor groom and groomsmen were dying in their tuxes.
 
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Hi
I suggest a ductless mini split if it is only about humidity. Those floor AC units that vent to the out side take their air for cooling the condenser coil from inside the house and that air comes from out side via all the cracks in a house. That outside air is humid. The floor unit will cool but as far as efficiently dropping the humidity in the house, i suspect they may not.

Here in Kansas City, I have AC but still am not getting the humidity down for a couple of months of the year due to a wet basement. A ductless mini split but not the most efficient one since those sacrifice sensible cooling for latent to increase rated efficiency.

The pond water would need to be less that 50 degrees F to work, but maybe an excuse to drill a well?
 
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Relatively new to forum. Are there places here that teach you how to implement some of the strategies being discussed here? Folks are talking as if everyone here has a PhD in construction and I've got no clue how to patch in an extra coil or a low pressure valve etc without potentially destroying my heating system in the process! There's such a huge array of info that it's kind of overwhelming and hard to figure out where to get started. I'll look around for some "getting started" topics, but this thread applies to my loving situation in Western Mass and is active now so I thought it'd be worth an ask.
 
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A ductless minisplit is really the right tool for this job.  They're very energy efficient and give you a winter heating option in addition to summer cooling and humidification

You can leave your central heat in place and use the minisplit as a supplement - it has its own thermostat you can turn on or off independent of central heat system.

There are now ~$800 DIY versions you can install yourself if you're handy, to avoid the markup of a contractor doing a full-service central air installation

https://www.homedepot.com/p/MRCOOL-DIY-Gen-3-12-000-BTU-22-SEER-ENERGY-STAR-Ductless-Mini-Split-Air-Conditioner-Heat-Pump-w-25-ft-Install-Kit-115-Volt-DIY12-HP-115B25/311900316
 
Mike Haasl
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Welcome D.W.!  I'm not sure where you learn about these things.  One way is to post about your proposed project and hope that other folks who do know how to do it, will chime in and give you guidance.  Otherwise there's the other places on the internet like youtube to learn about adding coils or other things.  I don't know much either which is why I started the thread.

Thanks Davis, I didn't realize there was a DIY friendly approach for mini splits.  The room that needs the dehumidifying the most (master bedroom) also happens to be farthest from the wood stove and could use some winter heat.  When I follow that link and put it in my cart it says $1400 though.
 
pollinator
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Mike Haasl wrote:Related to the mini splits, I already have central heat so I'd only be upgrading it to central air.

My worries with the portable air conditioners is their output.  Looks like they're best suited to a large room, not an entire house.  But if they're efficient enough, two or three of them may be cheaper than a/c.



The floor models are portable, so you could move between rooms, you could take the AC to bedroom at bedtime. The hot air duct isn't insulated, so best to keep it as short as possible

In our rental, there's a big (24KBtu/hr) window unit mounted through the wall.

We had our own central AC unit replaced a few years back, and the installer had 0% financing ( air handler is in the attic, completely separate from our oil fired hydronic heat system). Might be a way to soften the blow of your central AC upgrade or a ductless mini-split installed?
No lost floor space or restricted use of windows, wintertime storage, fewer filters to clean/replace...

Also, 2 or 3 AC units with all the plastic in the cases, ducts/baffles, versus adding AC coil in existing system plus condenser outside?
 
pollinator
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You might want to look at this.  A tiny bit of cooling with dehumidification.  If you can add cooling from a pond you should be able to make this more efficient.

 
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