[RichTibo]

Hi,
Hopefully someone can advise me what to do.

I moved into my new construction home in July 2012 with an unfinished basement.
The basement walls are all insulated except for the bottom 12 inches. There is the framing done as well as vapour barrier all over the insulation going down to the floor. I have been preparing to put up drywall, but I noticed some moisture on the floor under the VB and if I peel it back a bit the wetness is on a certain area of the wall as well. There is no accumulation of water that I could see, but it is quite wet and it gives off a misty/moldy smell. I'm not sure if this is normal because it is a brand new house. We also just had a week of -40 C weather, it might be a factor to consider?

I don't want to drywall and trap it in if there is an actual problem in the foundation and it could cause mold to grow on the drywall I install.

Any thoughts on what the wetness is and what should I do?

 

[Gary in WA]

Could be some of the wetness from the pour at construction or could be some condensation from the humidity in the basement; http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

http://www.buildingscience.com/docu...merica-high-r-foundations-case-study-analysis

Where are you located?

Gary
PS. welcome to the forums!

 

[RichTibo]

It seems mostly like condensation. Can this be a problem for dry walling?
I'm located in Ottawa, on, Canada.

 

[laser_jock]

vapor barrier below grade - BAD!!!

You got to get those vapor barriers out of there...

according to buildingscience and others, vapor barriers below grade (below ground level) are causing basement finishes to fail with mold and mildew behind the barrier, especially if it is airtight. concrete is permeable, and water from the soil outside is constantly pushing through it, even after the concrete has fully cured. new construction is adding rigid foam to the outside of foundation walls, and perimeter drains, before backfill. recommended finish methed now for older construction is R-10 2" rigid foam glued (Liquid Nailed) to the concrete, then followed by stud wall and R-21 fiberglass (no vapor barrier). the blue foam is semi-permeable, allowing the concrete to breathe and dry out, and the R-30 is enough to keep humid living space air from condensing onto the concrete surface.

I also added new HVAC supplies and returns in my basement, along with a humidistat (with outside temp sensor) and humidifier in the air handler. in the cold months, this keeps the basement air at a comfortable humidity without going too high. the humidistat can start the air handler on its own. after three years now no mold or mildew.

i found special carpet padding for the concrete floor as well - 5/8" thick, but no vapor barrier on it either.

link to report - with full color pictures! (mold behind vapor barriers in basements): http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems (note they don't call it out by name, but drylock can also be a bad move)

Excerpt:
Requirements for Interior Basement Insulating Systems
Any interior basement insulating wall system must have the following properties:
• It must be able to dry to the interior should it become wet since the below grade portion of the wall will not be able to dry to the exterior during any time of the year. This precludes an interior polyethylene vapor barrier or any impermeable interior wall finishes such as vinyl wall coverings or oil/alkyd/epoxy paint systems.
• The wall assembly must prevent any significant volume of interior air from reaching the cool foundation wall. Thus it must have an effective interior air barrier or a method of elevating the temperature of potential condensing surfaces (such as rigid insulation installed directly on the interior of
concrete or masonry surfaces).
• Materials in contact with the foundation wall and the concrete slab must be moisture tolerant; that is the materials should not support mold growth or deteriorate if they become wet. However, moisture tolerant materials are not necessarily capillary resistant. That is, some materials may tolerate being wet without blocking the passage of liquid water through the materials. A capillary break must be placed between these materials and moisture sensitive materials.

 

[Gary in WA]

"Great minds think alike....."---lol. See first link in post #2, above.

Gary