I bought an old home (over 50 years old) where the basement foundation was made of blocks. I'm planning to finish the basement myself and definitely could use advise from the experts.
I notice existence of efflorescence sporadically on the basement walls but did not find any cracks nor water penetration from the outside. I'm planning to put 3/4" durofoam insulation on the walls and fiberglass on top of it.
1. Should I put vapour barrier on the walls before the durofoam?
2. Can I put vapour barrier again on top of the fiberglass insulation? I'm planning to cover the walls with gypsum drywall and was told not to put the vapour barrier on top of the insulation.
I would greatly appreciate your advice!
Any amount of efflorescence means there is now or at least has been some water infiltration. Remove the efflorescence and monitor for a year to see if it returns or at least through one spring or rainny season. If it does not then you may not have a water problem at all. But if it returns then you do have a water problem and hiding it behind a developed basement will cost you later. You really should solve that problem first.
Q1. All vapour barriers must be on the warm side of the insulation. Within 1/3 of the R Value. Otherwise moisture from the interior of the home will have the chance of condensing on the vapour barrier.
Q2. 2 layers of vapour barrier is unrequired and will possibly trap moisture between the layers. Also see answer to Q1.
Your concern is not lost on us. We work with a top quality home inspection company for many of our projects as well as basement sealing specialists.
We recommend 2lb Spray Foam. At 1.5" it is a vapour barrier and moisture barrier. It is rated at R6 per inch. We only use the best product called Polar Foam which is 5% Soy.
I hope this helps you.
Eco Insulation York
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