[Greenbuilding] dehumidifying bathrooms - makeup air?

Sat Dec 16 16:56:10 CST 2017

Reuben: Why do you continue to disparage electric heat? Now that high efficiency solar PV panels are available, the site efficiency of all-electric homes is much much higher than the systems you continue to promote in Trumpian fashion.

     Since the winter of 2015, we have been heating our house on Long Island, New York with tiny ECO 11; an 11 kW tankless water heater that cost $209.99 at home depot. It was installed to replace a Keltec C150, which now costs over 7 times as much.  Our system is illustrated in Fig. 2 of Rocky Mountain Institute’s Home Energy Brief #5 WATER HEATING  @ http://gfxtechnology.com/RMI-HE-5.pdf.

   You should stop misleading people.

Yours truly,

Dr. Carmine F. Vasile

________________________________
From: Greenbuilding <greenbuilding-bounces at lists.bioenergylists.org> on behalf of Reuben Deumling <9watts at gmail.com>
Sent: Saturday, December 16, 2017 5:23:42 PM
To: Green Building
Subject: Re: [Greenbuilding] dehumidifying bathrooms - makeup air?

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<mailto: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<mailto: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<mailto: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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