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Old 10-04-13, 11:18 AM   #11
AC_Hacker
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Default Mold Need Warmth, Moisture and Food...

If you look at my Mini-Loo project, you will see that my whole bathroom is only slightly larger than the shower you want to enclose, so the Mini Loo actually is an enclosed shower. The lessons I have learned there apply to what you want to do.

In my case, I didn't want a ceiling exhaust fan unless is was absolutely necessary. I have been using the Mini Loo for about a year and a half and things are working out well.

In the summer, when the air is warm and relatively dry, I just open the little Mini Loo double hung window (which I intentionally mounted very high on the wall), and convection does it's thing. In the winter, when it is cold and humidity is higher, I set a fan on the floor and let it run (also with the window open) until everything is dry... then I close the window.

I was warned by many people who were in possession of good sense and much enthusiasm, that not having an exhaust fan would result in the Mini Loo becoming a hideous mold garden.

However, previously I had read about the concerns that must be addressed in building a home for someone who is extremely allergic to the presence of mold... I learned that mold needs three things to grow: warmth, moisture, and food (not so different from the three things required for a fire to burn).

Quote:
In an initial experiment that began in January 2004, researchers used a small panel of wallboard -- which is very porous -- soaked in water and injected with non-toxic fungal spores. In one month's time, those spores germinated as the wallboard was kept in a high-humidity environment. Mold thrives in damp wallboard because of its paper-based encasing, DeJesus explained.
http://www.gtri.gatech.edu/casestudy/detect-hidden-mold

So, in these houses, non-organic studs in the walls are used (steel studs), and non-organic wall board is used (sheet rock is covered on 2 sides with paper which is pre-digested wood pulp, ready to become a mold explosion). [EDIT: I just came across a gypsum wall board that is covered in a non-cellulosic material and should be better at mold prevention] There is a type of wall board that is not covered with paper... it's not even gypsum based (gypsum isn't really the problem, it's the paper), it's something else. The green sheet rock is almost no better than regular sheet rock. In my opinion, the previously mentioned type of wall board, or something similar should be use in all bathrooms.

Here is a Fema paper on post-flood mold remediation. Essentially a bathroom, and even more a shower stall, repeats the mold-growing conditions that flood victims are faced with... only on a daily basis.

But back to the Mini Loo... In building the Mini Loo, I knew that I couldn't prevent warmth, or moisture, but I could prevent food (anything organic). So the ceiling of my Mini Loo is cementitious tile backer board, Hardibacker in my case.

The Mini Loo is warm and moist, but there is no mold food... therefore, no mold at all.

Regarding the fan... where is your fan exhausting to? Is it dumping the moisture into your attic? Could be a future problem if it is.

Also, for your fan to properly exhaust a sealed shower, you will need to provide air in. In the case of my Mini Loo, it has a curtain door which obligingly opens sufficiently at the bottom after showers, to allow moisture to naturally convect out the window.

I think that the humidity sensor idea is really great, just great. The ground moisture sensor idea will not work, it uses a different principle. You need an airborn moisture sensor... they can be found for cheap on ebay... and the Arduino stuff you already know how to do.

To recap...

Since you will be concentrating your moisture and mold producing conditions into a smaller space, you need to:
  • Change out shower ceiling sheet rock to tile backer board, or equivalent
  • Provide source for air in
  • Go with a moisture sensing exhaust fan

-AC

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Last edited by AC_Hacker; 10-04-13 at 12:09 PM.. Reason: make things more good...
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Old 10-04-13, 11:23 AM   #12
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Thanks for those insights AC.

The fan exhausts outside.
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Old 10-08-13, 01:59 PM   #13
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I would highly suggest to move the fan out side of the shower for several reasons.
1. The extra moisture can rust the parts and cause the shaft to rust in place later causing the motor to over heat and die, or if the wires are to small it could cause a fire.
2. Having it on eliminates the reason to seal the shower since you are removing the warm air.
3. It is against code. At least it is in KY.

I would plexy the whole top of the shower and walls so the whole area would be sealed. That way the moisture will all be contained the the shower and you should not have worry about mold as long as your grout is not cracked (you might want to seal it). With the moisture being contained the air will reach it saturation point allowing the rest to collect on the walls and ceiling that will then drain. If the ceiling is slightly pitched it will not collect but run down the wall.

If you have not checked this out take a look at Cozy Low-Energy Shower
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Old 10-09-13, 08:55 AM   #14
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That instructables is one of the things that made me want to do this in the first place. Its a good write up.
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Old 09-28-15, 05:46 PM   #15
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Did you ever enclose your shower? I'm thinking about doing two of mine.

I wish Plexiglas wasn't so expensive
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Old 10-08-15, 07:26 PM   #16
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Make sure to red guard the areas that you enclose before you tile them. Do not try to keep them painted the whole interior should be as waterproof/vaporproof as possible.

The proper fan is a humidity sensing in line fan. It will keep the humidity level below 60%.

IMO all bathrooms should be required to have humidity sensing fans or have the fan tied to the light switch. The latter is code in some places as few people actually turn the fan on and it needs to run for a while after you get out of the shower.
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Old 10-10-15, 10:10 AM   #17
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I'm not sure how environmentally friendly it is but Kilz or Zinsser primer does the job. I did a stubborn mildew spot over our shower and its been mildew free for 15 years. Other uses besides the obvious, on fire damaged houses, really water damaged from the firehose, here they Kilz primer the framing that isn't replaced. This also makes it easy to identify houses that had fires. If I recollect correctly there is a similar additive that can be mixed into any paint.
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Old 10-10-15, 01:25 PM   #18
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Kilz is OK but not as a primer on bare material. (There are bare drywall versions though) It has a nasty habit of peeling off in sheets.

The best stuff out there is BIN but it's quite pricey. One quart usually costs almost as much as one gallon of kilz. It's a shellac based primer so it uses denatured alcohol as the carrier. It dries fast too. Make sure to check the date on the bottom of the can as it does age quickly. It does not brush well but perfect coverage isn't as important as other primers so it doesn't have to be an even solid white when done, just covered.

There are specific aerosol mold killing primers that the commercial painters use on restaraunt remodels. Not sure the brand though. And yes there are additives to put in the paint. Dunnow how well that works in the real world hough.

As for environmentally best choice. Personally I will go for the product that will do the best job and last the longest. Even if that product has some nasty stuff in it or processing issues it's still the greener choice because it keeps the structure out of the landfill longer and you aren't rebuilding it. Basically the longer you can keep it in service the better it is overall. Just look at the big picture. Have seen too many use the "green" product only for it to fail and have to do it again which defeated the purpose.
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Old 10-12-15, 08:55 AM   #19
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Nope, I never got around to actually doing it. Its still on the 'want to to' list though.
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Old 10-12-15, 09:31 AM   #20
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One easy trick is to prime all new sheet-rock surfaces with an oil based primer. Some of the ones mentioned above in posts work well, but steer clear of Kilz as a primer. I have also seen it come off in sheets (along with the finish paint).

When I redo bathrooms, I have had to often tear out old rotted sheet-rock. When it is that bad, I try to use DuRock (cement board) as the base. It is absolutely impermeable to water vapor and holds tile very well.

If I don't have the time/resources to do tile (at that point) I have used the inexpensive plastic shower boards from HD/Lowes that work well. Very quick to put up.

Redoing bathrooms sucks as you often need to use it while you are redoing it. My wife has "claimed" one bathroom here and I get the other dumpy one. God help me if I tread in "her" bathroom or god forbid that I take a shower in there. I am likely not the first spouse that has noticed women's claim of a bathroom.

Hang in there.


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