Durable basement wall insulation techniques

Chad Johnson Published: March 25, 2019, 8:33 p.m.Last updated: April 27, 2019, 12:24 p.m.

I live in climate zone 5 in USA and plan to frame basement walls roughly 3” away from concrete and then place mineral wool between the studs.  I do not plan to apply any vapor barrier to the concrete or between the studs and drywall and the mineral wool has no vapor barrier.  Is this space between concrete and studwall a terribly idea if walls are already dry and mold free? the exterior of the basement walls has 2”  of foam on them so any warmer air from finished basement would permiate through mineral wool to the wall but air space would or should allow for dry out no?

Thoughts on that specific method?  Any research on it or seen it before fail or do fine?

Responses (1)

Ecohome April 4, 2019, 3:47 p.m. Reply

Hi Chad, 

I wouldn't go so far as saying it was a 'terrible' idea, but I don't think it will do what you hope it will. A 3-inch cavity wouldn't help it dry out in anyway since the only direction it can dry is inwards and that wouldn't change by leaving a space. It's great that you have insulation on the exterior, along with reducing heat loss that will reduce the wetting of the concrete, but it will still likely have an endless source of moisture unless it is protected underneath the footing as well, which I doubt.

Myself I would prefer to have a membrane against the interior of the concrete wall to prevent the concrete from drying inwards. And I would either move the stud wall against it and enlarge the space a bit, or, I would use that space to add some rigid insulation (which itself will act to slow or stop the inward migration of moisture. Here is our page on basement finishing that may help.