[Greenbuilding] dehumidifying bathrooms - makeup air?

Reuben Deumling 9watts at gmail.com
Sat Dec 16 16:23:42 CST 2017


True, Though electric heat is about the last thing I'd be inclined to
welcome ;-)

The dehumidifier is an ingenious device, to be sure. Especially when you
can pipe the condensate through the wall. But I guess I'm spooked by
something akin to a refrigerator running that much.*

* of course I don't know how much it would actually run as I've not tried
it in the living space and don't know its duty cycle, but my hope is that
there might be a (passive?) way to accomplish some of these goals without a
compressor running a lot of the time....

On Sat, Dec 16, 2017 at 2:15 PM, Michael O'Brien <obrien at hevanet.com> wrote:

> Hi, Reuben—
>
> A dehumidifier removes heat from water and leaves it in the space. They
> have a COP of about 1.2 (last I checked), so you could think of it as a
> supplemental heater.
>
> Best, Mike
> Sent from my iPhone
>
> On Dec 16, 2017, at 9:13 PM, Reuben Deumling <9watts at gmail.com> wrote:
>
> I'm going to piggy back onto a seven year old thread full of interesting
> insights on essentially the same subject.
>
> Here's my situation:
>
> 650 square foot single story Craftsman with R13 dense pack cellulose walls
> heated entirely with a wood stove (no outside air source) in PNW
> where--unlike many of you--our humidity mostly occurs in the winter. We
> have not hitherto had either a bathroom fan or a vent hood over the kitchen
> stove. I've been meaning to install both forever, but the complexities of
> managing the humidity this earlier thread hints at have kept me from
> actually buying any hardware or making much progress otherwise.
>
> I'm expecting to install both an exhaust fan for the single bathroom and
> one for the kitchen stove, and that part is straightforward enough, but my
> worry is that in the winter my fans may in use end up drawing high humidity
> outside air into the house through cracks around the exterior doors or
> windows(?) diluting any hoped for effects from the fans.
>
> Sidebar: minor evidence of mold can be found--with some scrutiny--in the
> tile grout in the bathroom, some on firewood pieces that cured outside and
> are brought inside, as well as on the underside of our daughter's cheapie
> mattress. The urgency around reviving this project is related to a hope
> that some of this potential for mold growth could be reduced.
>
> Oh and I have a(n Energystar-qualifying) dehumidifier as well, but have
> only run tests with it in the basement so far and am not excited about the
> electricity implications of running it continuously or for long
> stretches....
>
> Any and all insights and suggestions are as always welcome and appreciated.
>
> Reuben
>
> On Mon, Oct 25, 2010 at 6:48 PM, elitalking <elitalking at rockbridge.net>
> wrote:
>
>> ----- Original Message ----- From: "John Straube"
>>
>> Short answer again.
>>> ERVs do not dehumidify. The reduce the load on the dehumidifier when and
>>> only when it is lower RH indoors than a outdoors.
>>>
>>
>> Yes.  Then if there is not another process to condense the vapor out of
>> the air such as air conditioner, dehumidifier, or desicants, then there is
>> no benifit to latent heat transfer.  However, when you mechanically dry the
>> interior air, the ERV will preserve the value of that dehumidification.
>> Right?  Strategies of night flushing cooler high relative humidity at night
>> does not qualify.
>>
>> Eli
>>
>>
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