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How to insulate a basement bathroom


amatuer's Avatar
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02-19-17, 08:58 PM   #1  
How to insulate a basement bathroom

Greetings all! I've decided to add a bathroom to my basement in a currently unfinished area. Planning on putting up regular 2x4 stud walls along the existing exterior concrete foundation. but what is the best insulation to use? A bathroom could be high -humidity and I know the concrete can bring in moisture also - what's the best way to avoid mold? I live in a cold climate (Wisconsin) so also need it to be as high an R value as possible. I've read about the spray in foam but it sounds like it's not a DIY project - is that true? Are there other alternatives? I'd like to do it myself to save cost. Thanks!

 
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02-20-17, 03:26 AM   #2  
We don't do it in the South, but your application would dictate 1" XPS glued to the concrete walls and the seams sealed with tape. That will create a thermal break between the concrete and your living space. Building the walls out and insulating with Roxul will give an R15 value to the walls, it's about as good as it gets. No vapor barrier on the living side as Roxul is waterproof, vermin proof, mold/mildew proof and fireproof. Of course it is more expensive than fiberglas, but you're only doing it once, right?

 
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02-20-17, 04:58 AM   #3  
A bathroom could be high -humidity
Nope, it will be area of high humidity, you must have good ventilation to remove moisture from showers/baths.

I know the concrete can bring in moisture also
Nope, the water vapor from living/bath area can condense on cold surfaces, the moisture does not come out of the concrete.

Another option, what I have always done, skip the foam, it's extremely expensive, build the wall away from the basement wall a few inches but leave areas above the wall open to the interior. Keeps the wall cavity dry and yes you have some uninsulated areas but the other 98% of wall space is covered.

 
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02-20-17, 06:24 AM   #4  
Thank you both! The bathroom is small to start with so I don't think I can sacrifice a few inches of empty space. But adding 1" XPS shouldn't be a problem. Chandler, what type of tape should be used for the seams?

Marq1 - good point on the humidity, I do plan to add a ventilation fan which should help certainly.

 
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02-20-17, 12:31 PM   #5  
I use Tyvek tape. I am not sure if there is a specified tape for foam or not.

 
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