I am finishing the basement. The basement was already insulated ceiling to almost floor with large blankets of fiberglass covered by a vapour barrier. I have tucked taped and sealed under and in between all the joists trying to make VB air tight.
However at the bottom about 1 foot off the floor the insulation ends and there is a metal band that runs the length of the walls and was used to tack the vapour barrier and insul. to the concrete wall about every 16 inches or so.
This is not sealed tight along all the walls and my question is does it have to be?
I dont see the benefit of the V barrier if it is open or gaping at the bottom.
What would you recommend to seal this bottom strip along the concrete wall ? Is there some sort or caulk type sealant product?
Basement has been very dry for 11 years but want to do it right before drywalling.
Thanks
Mark
Replies
MMcC,
Fiberglass should not be used to insulate the interior of basement walls, because of the likelihood of moisture problems and mold.
The use of a vapor barrier over the fiberglass makes things worse, not better. In general, the looser the vapor barrier over a fiberglass-insulated basement wall, the better. Tightening it up just makes it hold the moisture so the mold grows faster. The best vapor barrier of all is none.
Sorry for the bad news, but the best way to proceed is to remove the existing insulation and to put rigid foam on your wall.
Thanks for your reply ..I'll definetely look into that as I can see that rigid board would be better from a mositure control point of view. Its not a long wall in this case so taking it out is an option
I am confused though as the building code from this part of Canada requires that basements be insulated at least to the frost line (about 4 feet below grade) and fiberglass bat insulation with 6 mil VB seems to be used 99% of the time.
The insulation I am referring to was installed by the original builder and passed by the inspector when we bought the home.
I guess the question remains if I stick with it am I still better to seal it at the bottom rather then let any mositure escape?
Thanks
Mark
Mark,
Learn more about basement insulation at http://www.buildingscience.com. Here is one of their documents:
http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems
"All Building America homes constructed by the Building Science Consortium were initially constructed with interior basement insulation. The approaches used early in the program were interior stud wall framing insulated with fiberglass batts and 'blanket' insulation. ... The experience by the Building Science Consortium with these two approaches has been bad. The Building Science Consortium has concluded that these two approaches are unsuitable for use by the home building industry due to serious problems associated with mold, decay and odors."