Basement Insulation Options – Vapour (Vapor) Barrier
I am currently building an addition on the back of a 95 year old house in Toronto, Canada.
-My new basement walls are 10” CMUs, of which about feet are above grade and five feet below grade. The exterior of the below grade portion is covered by a semi-flexible hard plastic membrane for waterproofing.
-The carpenters have framed my basement walls with 2×4” lumber, and on the interior face of the concrete walls have placed Typar housewrap – wrapped over the top plate and under the bottom plate of the interior lumber walls to act as a bulk water barrier.
– My contractor is now planning to add R12 fiberglass batts between the 2×4”s and then cover with a 6-mil poly vapour barrier. Over that will be 1/2” gypsum drywall.
Everything I have read that is published by the Canadian government or Canadian energy boards recommends an interior vapour barrier.
Everything I have read on this site or in the in-depth articles put out by BSC strongly recommend against interior vapour barriers, especially below grade.
Can anyone offer any insight? Since, where I live, we heat our home for about 7-8 months a year and use A/C for about 2-3 months a year, my primary concerns are
a) if I do not have a vapour barrier on the warm side of the insulation, will the resulting/potential wintertime condensation on the cold basement walls result in significant mold and mildew on the lumber and drywall?
b) if I do have a vapour barrier, will I have issues with water (vapour or liquid) migtrating in through the floors and walls being trapped in the wood framed walls, and resulting in mold and mildew?
p.s., The 2×4 walls were built only about 1/2” off the concrete walls, so there is no room for XPS or EPS panels, so short of paying through the nose for spray foam, fiberglass batts seem to be my only option