Crawl space vapor barrier and insulation

opiesche · 12-23-12, 09:10 PM

Hi all,

After installing my radiant floor heating system, I'm now looking at the need to treat my crawlspace. First, insulate betwen floor joists in my crawl space - I think I've got that part handled (fiberglass roll insulation with the facing pointing up, wire supports, done).
Secondly, I'll need to install a vapor barrier on the ground. There seems to be a lot of conflicting information out there, so I'd appreciate some advice

My house is in northern california (dry, hot summers, humid cool winters) on a vented 2' crawl space with a dirt floor. There's currently no vapor barrier. From everything I've read, I should use at least 6mil poly sheeting with as low a perm rating as I can find. Overlap seams by 8-12 inches, tape together - so far so good. Where I'm getting differing opinions is on how to treat the foundation walls with the vapor barrier. Some people say to leave it 6" away from the foundation walls. Some say to run it halfway up and tape or glue it to the wall. Some say to run it all the way up the wall to the sill plate (which other people argue against because, they say, it will make moisture from the ground wick up the foundation wall into the sill plate).

What have people here done about crawlspace vapor barriers, and what are your experiences?

Thanks!
Olaf

12-23-12, 09:10 PM	#1
opiesche Helper EcoRenovator Join Date: Jul 2012 Location: Rohnert Park, CA Posts: 99 Thanks: 4 Thanked 14 Times in 9 Posts	Crawl space vapor barrier and insulation Hi all, After installing my radiant floor heating system, I'm now looking at the need to treat my crawlspace. First, insulate betwen floor joists in my crawl space - I think I've got that part handled (fiberglass roll insulation with the facing pointing up, wire supports, done). Secondly, I'll need to install a vapor barrier on the ground. There seems to be a lot of conflicting information out there, so I'd appreciate some advice My house is in northern california (dry, hot summers, humid cool winters) on a vented 2' crawl space with a dirt floor. There's currently no vapor barrier. From everything I've read, I should use at least 6mil poly sheeting with as low a perm rating as I can find. Overlap seams by 8-12 inches, tape together - so far so good. Where I'm getting differing opinions is on how to treat the foundation walls with the vapor barrier. Some people say to leave it 6" away from the foundation walls. Some say to run it halfway up and tape or glue it to the wall. Some say to run it all the way up the wall to the sill plate (which other people argue against because, they say, it will make moisture from the ground wick up the foundation wall into the sill plate). What have people here done about crawlspace vapor barriers, and what are your experiences? Thanks! Olaf