I am about to finish my basement. The previous owners insulated the foundation walls with fibreglass batt insulation and have subsequently drywalled all the foundation walls. Can I leave this insulation in place? Or, do I need to rip it out along with the drywall and replace with spray foam?
The way it was done is fine...as long as they put tyvek or typar between the concrete and the insulation.
Working from the inside of the house towards the concrete the order should be as follows; drywall, vapour barrier, insulation, typar.
Unfortunately, there is nothing on the wall just batt insulation against concrete.
Thanks for the help, my next question is... is it necessary to install an HRV or would an exhaust fan suffice? If it is necessary, any idea of cost?
I personally would recommend removing the batt insulation with no bearer, replace with spray foam, it works well in our wet climate, A dehumidifier in the basement also will help, run it on a timer set to run 1 hr every 8 hrs monitor how much water it produces you may need to increase run time if needed.
I would strongly advise against finishing a basement that has the outside walls already finished by someone else. I would hate to see anyone endure the most expensive stages of finishing a basement ie flooring, millwork, electrical, mechanical, etc. while simply relying on the least expensive stage as proper.
The vapor barrier makes the outside walls critical components of a finished basement system from a performance standpoint. If it is not providing a 100 per cent air seal in the walls and joist ends (which is almost impossible with poly) you may end up with condensation or frost behind the insulation on your concrete walls or rim joists in the cold months of the year = long term damage and health risks.
I would only finish the basement if I removed all the previous work to foundation, examined the foundation walls, and started from scratch with new framing, spray foam insulation, and certified electrical.
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