[Greenbuilding] dehumidifying bathrooms - makeup air?

[Stephen Collette]

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 <http://www.yourhealthyhouse.ca/>
stephen at yourhealthyhouse.ca <mailto: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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