[Greenbuilding] dehumidifying bathrooms - makeup air?

Tue Dec 19 10:21:39 CST 2017

Clay is remarkable in buildings. Years ago we developed a clay paint (basically clay, chalk, casein) that was used in a lot of projects. It was incredibly durable but would waterspot or stain if splashed heavily. Avoided using it around wet areas (kitchens, baths). Ok on a feature wall that wasn’t prone to splashing. In bathrooms I often used cement stucco finishes (generally smooth polished). 

I experimented with wax paint which was quite amazing as a phase change material – quickly modifying temperature (great in kitchens). Quite a variety of traditional materials that are well suited to various purposes and rooms. 

From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Lynelle Hamilton
Sent: Tuesday, December 19, 2017 6:24 AM
To: greenbuilding at lists.bioenergylists.org
Subject: Re: [Greenbuilding] dehumidifying bathrooms - makeup air?

Stephen, where do you get the clay you're planning to use?  I'm not near doing the bathroom yet, but would like to use it.

Thanks,

Lynelle 

On 2017-12-19 9:19 AM, Stephen Collette wrote:

Hello Reuben and all 

Yes, Reuben, there are building materials that have been used since time immemorial that can safely manage moisture generated without resulting in damage and ultimately mould growth. Hygroscopicity is the rate at which moisture can be adsorbed by the material. The greater the hygroscopicity, the greater the rate it can take moisture in, and release it. Materials that have high rates of hygroscopicity are unbaked clay, unfinished wood and cork for example. Hygric buffering capacity is the term that looks at how much water the material can safely store/hold/then release before it fails. Again, a higher value means it can hold more. The Lstiburek/Carmody book Moisture Control Handbook made mention (if I remember correctly) of a steel stud with drywall building holding something like 5 gallons of water, while a brick building could hold 500 gallons safely. Brick being fired cannot hold anywhere near as much as unfired clay, which is used in plaster or unfired adobe in your case in your bathroom. 

I have some slides, but I can’t upload them to the group so send me a PM and I’ll send them to you.

Cheers

Stephen

Stephen Collette 

BBEC, BBNC, LEED AP, CAHP, BSSO

Principal

Your Healthy House 

Indoor Environmental Testing & Building Consulting

http://www.yourhealthyhouse.ca

stephen at yourhealthyhouse.ca

705.652.5159

On Dec 18, 2017, at 2:00 PM, greenbuilding-request at lists.bioenergylists.org wrote:

Stephen,
that is so fascinating. I deeply appreciate these insights and reminders of
things we (or at least I) had forgotten. One question right off - materials
that store and release moisture - are these categorically different from
the materials we regularly see harboring mold? Like caulk, latex paint,
drywall? I'd be delighted to pursue these ideas!

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