Permanently Installed Bathroom Dehumidifier

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Molo

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Hello,
We would like to permanently install a dehumidifier in our bathroom that drains into the tub unit with a concealed hose.
Does anybody know of a permanently installed ceiling mounted residential dehumidifer or are we limited to placing a floor mount style on a shelf to gain the elevation needed for draining?
A search of the web hasn't resulted in much other than commercial units, but maybe that's what we'll have to use.

Thanks in Advance
 

Jadnashua

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While it's one more thing...you could utilize a condensate pump. Before I talked my mother into central air, on really hot days, she had a portable ac unit. I had to run its output to a small condensate pump, since it didn't work well pumping itself out the window.
 

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What is the real problem that you are trying to solve? The normal solution for humidity in bathrooms is to exhaust the air outside. It then pulls drier make-up air from the rest of the house. It works a lot more quickly than a dehumidifier, costs less to run, and doesn't add heat to the bathroom.
 

Jadnashua

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FWIW, in the winter, I don't typically use my exhaust fan, because that bit of extra moisture in the house doesn't hurt. Your situation may be different. I do use mine in the summer, since the humidity tends to be higher, and would make the a/c run more. But, if you can't or don't leave the room open when done, without something, that high humidity can cause problems. A dehumidifier is like running an a/c unit, but exhausting the waste heat back into the room rather than outside...not ideal.
 

Dana

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A Panasonic Whisper Green high-efficiency bathroom fan (eg: the FV-05-11VKS1 , but there are others, some with lights, etc) with the optional FV-CSVK1 humidity/condensation sensor control is usually good bet for managing peak bathroom moisture automatically, with low annual power use, low wintertime heat loss, and very low maintenance.
 

Molo

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What is the real problem that you are trying to solve? The normal solution for humidity in bathrooms is to exhaust the air outside. It then pulls drier make-up air from the rest of the house. It works a lot more quickly than a dehumidifier, costs less to run, and doesn't add heat to the bathroom.

A bath fan is a challenge to install because there is living space above plus attic and it is a brick clad home.
 

Dana

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It's neither rocket science nor expensive to make a reasonably clean 4" hole in a brick veneer without ruining the whole thing. It can even be done DIY while in drag!

Take your time to avoid having to replace big chunks of brick, and make sure to air seal the wall to the vent on the interior side (can foam usually works), and make it water tight to the brick on the exterior side (any decent quality polyurethane caulk does it, but avoid "self leveling" types for wall applications.

For a REALLY clean hole through the brick you can buy a 4+" masonry hole saw bit for about $30-80, provided you have access to a heavy duty half-inch chuck high torque/low-speed drill motor (like the Milwaukee Hole Hawg or similar) to run it. It's an expensive drill motor to buy, but they're rentable. A lighter duty half-inch drill motor could do it in a pinch, but it's a PITA if the drill is too wimpy or higher speed/lower torque.
 
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Molo

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It's neither rocket science nor expensive to make a reasonably clean 4" hole in a brick veneer without ruining the whole thing. It can even be done DIY while in drag!

Take your time to avoid having to replace big chunks of brick, and make sure to air seal the wall to the vent on the interior side (can foam usually works), and make it water tight to the brick on the exterior side (any decent quality polyurethane caulk does it, but avoid "self leveling" types for wall applications.

For a REALLY clean hole through the brick you can buy a 4+" masonry hole saw bit for about $30-80, provided you have access to a heavy duty half-inch chuck high torque/low-speed drill motor (like the Milwaukee Hole Hawg or similar) to run it. It's an expensive drill motor to buy, but they're rentable. A lighter duty half-inch drill motor could do it in a pinch, but it's a PITA if the drill is too wimpy or higher speed/lower torque.

Thanks for the vote of confidence. You mentioned one of my specific apprehensions regarding vapor barriers. My concern is introducing moisture to the currently uninsulated wall cavity of the 100 year old home. I can certainly create a moisture barrier between the interior space and the room, but will moisture condense on the warm pipe inside the wall cavity? It seems as if the entire pipe would need to be insulated. Maybe I can reach into the wall cavity with an expanding foam nozzle and insulate the entire exterior of the pipe....
 

Dana

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If the studwall cavity is uninsulated there are few drying issues, but it's good to keep bathroom air from entering to find colder surface onto which to condense. In most cases it will be generally safe to blow cellulose into those cavities, but more information about the material stackup of the wall, window flashing, etc. is necessary to address that. (A competent insulation contractor would be able to assess the relative risks.)

Moisture never condenses on warm things (pipes, wood, or bricks), only materials colder than the dew point of the proximate air. The dew point of bathroom air peaks pretty high during showers (which is why even the not-so-cold mirror will fog up), but typical heated/conditioned room air will have dew points between 35-40F during the winter, 55-60F during the summer. The mold risk issue is from cold wood sheathing accumulating excessive moisture from air leaks or vapor diffusion from the interior over the winter.

As long as your vent pipe is air-sealed well from the interior where it passes into the studwall portion it won't create a problem. Far more moisture will move through the wall from air leaks than from vapor diffusion alone- vapor barriers aren't needed in an uninsulated home, but air tighness still matters. If there is wood sheathing on the exterior of the studs, with an air gap between any tar-paper (or even bare plank) and the brick it won't need a vapor barrier even after insulating in much of NY state, but it may in the coldest ZIP codes. Again more information is needed to make that call.

Note: Bath exhaust ventilation depressurizes the bathroom relative to the outdoors when running, so during the winter it will be pulling dry wintertime air through minor leak points rather than than driving humid bathroom air into the wall, which is good. In summer it hardly matters, since outdoor air dew points are rarely above the temperature of the indoor surfaces in NY even when it's pretty muggy out.

Plumbing in exterior walls can present a freeze problem in colder climates if there is more insulation between the pipe and the warm interior than there is between the pipe and the cold exterior. Be sure to assess that carefully too before insulating- sometimes it's easier to leave the stud bays with the plumbing uninsulated.
 

Molo

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Thanks for the detailed response Dana. Im still wondering if a dehumidifer is more effective at keeping a bathroom dry than a bath fan and would love to read your thoughts on the subject.
 

Dana

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In winter a bath fan can take the humidity down to even unhealthy levels if you run it a high rates 24/7. In summers during the very peak humidity days with outdoor dew points north of 70F it might not, unless you're also air conditioning the house.

A room air conditioner (anywhere on the same floor) or central air conditioner would be the right solution to enabling the bath fan in summer. A dehumidifier converts the latent heat of vaporization of the water in the air and turns it into sensible heat, which is the LAST thing you want do do in summer! (The additional heat is fine in basements, which are cooler.)
 
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