Roxul against the wall is asking for mould.

I could quote another leading building scientist (Ph.d) who told me that in person. (But since Roxul is one of his clients, he'd rather I not!)

One room, have him rip it out and do it right.

BTW, the foam should be attached directly to the wall as tightly as possible. And, before you do so, run at least two lines of caulking or glue horizontally on the wall. The most recent research from the Canada Mortgage and Housing Corporation has shown that otherwise, convective air currents between the foam board and wall will reduce the effectiveness of the insulation. Seal any gaps with handheld foams such as Great Stuff.

The foam is the vapour barrier, so you don't need to add poly behind the drywall unless some behind- the-times building inspector says so.

Worthy, I'm thinking Roxul in the cavity in front of the XPS - and before doing so foam seal all the gaps in the cavity where the XPS meets with the framing. Try to stop air movement through wall to the air gap behind the wall.

If that is not a good alteratnive to ripping out the wall do you feel there is an alteratnive to ripping out the framed room?

No poly will be added. Already cleared plan specs with inspector which is simply XPS attached to concrete wall and then floating wall away from the XPS. He said thats the way he would do his basement - no poly vapor barrier

If you add batt insulation between the studs you will HAVE to have a vapor barrier just behind the drywall. Otherwise the warm moist air from the basement could cool enough to condense before it hits the foam vapor barrier.

Vapor barrier just scares me - I feel like their will be moist warm air trapped behind the vapor barrier just behind the drywall. Perahps its not a correct assumption.

I'm not an expert on this topic so hoping you guys can provide some insight on what I should or shouldn't except as a resolution. Meeting with contractor in the morning to advise on what needs to happen going foward as well as the room already constructed.

Here's the suggestion for exactly the situation from the last above-noted link:

"WHAT TO DO IF THE BASEMENT IS ALREADY BUILT WITH AN AIR SPACE BETWEEN THE CONCRETE AND THE INSULATION

Taking a cue from the CMHC recommendations to use horizontal glue lines behind ridged foam panels to stop the rise and fall of air on the cold side of the insulation, you can make one single horizontal air block that is quite effective. About 4 feet up the wall you should be close to the soil grade on the outside. Below this level the soil retains some of the basement heat – above this line the concrete does almost nothing to stop the heat loss, leaving the inside face of the foundation below zero most of the winter.

If you carefully slice open the wall paneling (don’t cut through the studs) at about 4 feet from the floor exposing about two inches, you can then run a knife through the insulation (foam or batts) right down to the air space. Pull out that plug of insulation carefully and set it aside. When you can see the wall, or the moisture barrier on the wall, use the spray foam in a can to fill up the two inch strip behind the insulation. Be sure to spray behind the studs if they do not touch the wall. This should create two separate compartments behind the insulation – one relatively warm on the bottom and the other cold on the top, but neither with a large temperature difference from top to bottom. That will stop the air looping.

Put back in your insulation, even put on the slice of paneling you removed. You can either use drywall tape to smooth out the wall, or a piece of trim to look a bit like an old chair rail. You might even want to do this whole operation a bit lower than 4 feet so that it really is at chair rail height. "

That way, you can add insulation between the studs and then drywall, no vapour barrier necessary.

I didn't catch that link at first - good read by the way.

I'm still trying to visualize the application of spray foam --> fill up the two inch strip behind the insulation. I think they simply want a ledge of foam half way up the wall behind the insualtion to keep the convention loop from depostiing condensation in the sills.

Maybe I have misunderstood the design but why isn't the insulation covering waterproofing on the outside of the foundation wall? Is this a renovation?

Lower level finish in basement in a newer construction home. 2” XPS on outside of fondation. Subsoil is all sand with excessive draining qualities.

Is there waterproofing on the outside of the wall (not just dampproofing)?

Damp proofing is all you get around here - water under the bridge at this point

I'm just trying to understand your concern regarding and interior moisture barrier. Its not something that is easily dealt with on the inside of a foundation wall.

When I have dealt with it, I used high density spray foam on the concrete.

Thanks RES....That would have been my number 1 choice - it seems like that is everyone's number once choice.

It was too costly so we opted to adhere the XPS panels directly to the concrete - that seems to be the number two accepted choice.

Now that the panels aren't adered and attached to the framed wall - an air gap exists between XPS and bare concrete - its not clear what to do.

The contractor was going to contact the local Building Science representative to address.

Welcome further comments and we'll keep the thread posted!