[Greenbuilding] dehumidifying bathrooms - makeup air?

[Reuben Deumling]

Well I've always thought that it was the quintessential thermodynamic
insult; a means of converting the highest quality energy carrier (back)
into, well, heat: something that in theory and practice a large pile of
leaves can produce.

I'm aware that as a customer who's utility tries hard to convince him that
the electrons piped into his house come from wind turbines, the heat losses
that dog the above conversions when starting with a fossil fuel are
reduced, but nevertheless I can't shake the loathing I feel when
contemplating such an expensive and fragile technical system all to warm up
the air.

On Sat, Dec 16, 2017 at 2:31 PM, Michael O'Brien <obrien at hevanet.com> wrote:

> What’s the issue with electric heat?
>
> Best, Mike
> Sent from my iPhone
>
> On Dec 16, 2017, at 11:23 PM, Reuben Deumling <9watts at gmail.com> wrote:
>
> 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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