[Greenbuilding] dehumidifying bathrooms - makeup air?

[Reuben Deumling]

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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