Good day, can someone explain to myself regarding renovating a basement. Recently I had a contractor in a he did some renos on my basement. The main question I have was when he framed the basement walls, he put the framed walls about 2" from the exterior concrete walls. Once all was complete it was then insulating with insulation (roxal) followed by a 6mm plastic vapor barrier before drywall was installed.
Should I be concerned about condensation seeping in.... or is this procedure a good practice. I never had any leaks in my basement beforehand and he also installed a sub-floor which by the way "rocks". Oh yah, I also live up her in Canada (Ottawa). Appreciate any advice/ insight on the topic. Cheers!
No, that's standard practice for insulating a basement concrete wall up here in the 'very cold' zone...I imagine your contractor used 2x4s for the wall studding and filled the spaces between the suds with about 4-5" of Roxul mineral wool insulation, then covered that with the 6 mil poly vapour barrier. By doing all that, he did what I think is the minimum you need for our climate...
You are trying to keep the moist warm air inside your home from condensing on the cold outside concrete, and keeping the heat you produce inside. So he's reducing the air movement with the vb and adding to your confort with the insulation...relatively inexpensively, I'll add.
The next thing to do is to look at the rim joist area; this is where a lot of air escapes your house in the winter and is a source of wasted money. Insulate that real well, by air sealing the wooden beam you see with (ideally) 2" expanded styrofoam caulked and sealed into place. That's all you have to do there.
Having done all that, you are, in fact, reducing the total air movement in the room; this could cause the relative humidity in there to increase and lead to mould in extreme cases only. So increase the ventilation down there somehow to make sure the air get replaced on a regular basis. Could be a fan, a dehumidifier - just something to keep ventilation up. Put a cheap hydrometer down there to monitor the humidity, but normally the humidity is low in winter, so you don't really have to worry about excessive humidity causing problems.
Now that's the plan for up here, not for someone living in other zones...
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