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-   -   newbie basement insulation/vapor ?'s (http://www.diychatroom.com/f19/newbie-basement-insulation-vapor-s-60905/)

bergerdude 01-03-2010 11:51 AM

newbie basement insulation/vapor ?'s
 
Hi,
I have been looking at many threads and I realize opinions vary on the subject of vapor barriers and insulating a basement.
Chicago 3yr. old, below-grade basement, builder white vinyl/fiberglass wrap (ugh) to 6" within floor.
Darkening areas near floor perimeter in summer (will "dry" when sprayed with isopropyl alcohol). Residual "sandy" material in several areas.
That being said, basement floor has never been fully cleaned to see if this returns. A few plastic-taped-to-floor tests for water droplets with no moisture seen.

I have a few questions though:

IF one insulates with 2" foam insulation sheets glued to the wall.
1) If there ever is a leak, how difficult is it to peel this stuff off the wall, especially considering it may have been attached with liquid nails and you may be working through a finished wall with a relatively small hole?
This is what worries me most about doing the "proper" insulation.

2) Drylok or no drylok? Just when I thought I knew what to do, I read a post saying drylok will inhibit any moisture wicking and force it to wick into places you don't want, like the floor? True, or probably rubbish?

I have read through the .pdf's on building science or what-ever the links were. IN SPITE OF THIS I was thinking of doing this:

REMOVE builder insulation, may cut into strips and reuse.
Preventative epoxy all wall ties (have had 3 leak during the build)
Drylok the walls and floor.
Insulate the rim joists with caulk and 2" foam board.
Leave walls bare>1-2" air space>insulation between studs>plastic barrier>drywall.

In my case where the builder probably skipped the vapor barrier where the wall meets the floor and moisture may be wicking through, it seems to make sense to drylok and allow airspace in case moisture does come through anyway.

I know there is new science about this, however I really am uncomfortable with any insulation directly on the poured wall.

At least if a crack develops and starts to seep, there "may" be enough air space to allow the moisture to evaporate, no?
I realize any real leak will have the potential to create mold.

Thoughts? And sorry for the long-winded questions!

Berg

jaros bros. 01-03-2010 01:01 PM

So you want to trap the moisture inside the wall behind the sheetrock? Not a good idea. The goal is to try to mitigate how much moisture even gets to the concrete. Good backfill, perimeter drains, sloped ground, and rain gutters that move the water away from the foundation help do that. If you are still having significant amounts of water, some of the above work never got done.

You are right in thinking moisture will get behind the sheetrock. The purpose of not having the vapor barrier is to allow for the small amounts of moisture that do come through to diffuse and escape.

bergerdude 01-03-2010 02:48 PM

Quote:

Originally Posted by jaros bros. (Post 375856)
So you want to trap the moisture inside the wall behind the sheetrock? Not a good idea. The goal is to try to mitigate how much moisture even gets to the concrete. Good backfill, perimeter drains, sloped ground, and rain gutters that move the water away from the foundation help do that. If you are still having significant amounts of water, some of the above work never got done.

There is not a "significant" amount of water. I have only seen some evidence of possible wicking of the water...sand, some staining. Never any liquid water.

Yes, I am trying to do my best to correct mistakes that the builder (now out of business...go figure) did. The foreman was also an idiot. Quantity not quality was their motto.

The wicked moisture...if trapped would be between the insulation and the cement wall, in the 1-2" airspace. I would have a vapor barrier behind the drywall, in front of the insulation in the studwall...or how it has been done for years. This would prevent the warm interior air from contacting the cool air of the cement wall.

Maybe I made it confusing. Two things everyone deals with, there is wicked moisture through the cement wall, and there is condensation caused from interior warm air hitting the cool cement wall.
The vapor barrier between the studs and the drywall prevent the air from mixing.

The wicked moisture coming through the cement wall will hopefully be handled by drylok, and any residual coming through the porous cement will, unfortunately....reside in the 1-2" airspace.
This seems to be the change in thinking from years past of having a vapor barrier to not having ANY vapor barrier today.
The summer months has water gassing through to the interior....with possibly no where to go.


Would everyone agree that the white vinyl fiberglass insulation tacked to the cement needs to go?

Would NO vapor barrier then be better?
And without no vapor barrier are you forced to use the foam sheets on the cement wall?

Also, would any "trapped" moisture between the cement wall and the insulation/drywall>moisture barrier evaporate up into the home through the floor/ceiling above?

Has anyone else considered/wrried about wall ties creating a path for ground water?

The history of my foundation does not give me a warm/fuzzy!

Thanks,
Berg


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