Replies

1. 
   Peter Yost | Jan 28, 2019 03:07pm | #1

   Hi Steve -

   I just checked in with longtime high performance architect and GBAer Steve Baczek and he says that he dimensions the rough opening in the concrete as much as 12 inches to be absolutely sure that he can dimension IN with wood rather than dimension OUT with a concrete saw...

   He then insulates the roughed in wood framing with as much rigid as he needs.
   And here is a general GBA reference on high performance window wells:
   https://www.greenbuildingadvisor.com/article/urban-rustic-a-light-down-below

   Peter

2. Expert Member
   Akos | Jan 28, 2019 04:48pm | #2

   Steve,

   I find stopping the interior wall about 1' bellow the rough opening much more pleasant. It makes the window look larger and takes away from the "bunker" feel of deep basement windows.

   You can run rigid all way up the concrete to the bottom of the rough opening and drywall over it. It essentially makes a 2 step window sill.

   If you have space to run the rigid all the way around the window, it will be better insulation wise but will take away from window area.

   Typically here the drywall return just runs from the stud rough opening right out to the J mold on the window with just the vapor barrier between the drywall an the concrete.

3. 
   airfix | Jan 29, 2019 08:57am | #3

   Peter,

   Thanks that's what I was thinking but I'm not sure I have space for 10" all around because of the location of window close to a corner.

   I suppose the surface finish of the concrete when you dimension out with a saw cut is much harder to air seal than when dimensioned correctly with a window buck during pour.

   Good article on window wells.

   Amos, I want to run my foam around the inside of the r.o. I was originally thinking I would run the bibs as well to ensure I have enough insulation to prevent condensation on the inside of the rigid foam and to minimize thermal bridging.

   I'm assuming when Peter says as much rigid insulation as necessary he means to prevent condensation?

   Steve

1. Expert Member
   Akos | Jan 29, 2019 10:55am | #5

   Steve,

   Condensation will form on the cold surface, so that is your concrete foundation (which doesn't mind). As long as your vapour barrier is well sealed, you shouldn't have a problem with moisture if you run the drywall directly over the foam. The drywall in that area will be a bit colder than the interior space, provided your interior RH is reasonable, shouldn't be a problem. I have the non foam version (foundation, vapour barrier, small air gap, drywall) at a rental and never had issues with it.

4. 
   airfix | Jan 29, 2019 09:03am | #4

   Peter,

   One more thought. What does Steve Baczek do to finish the outside of the 10" framed in rough opening? Does he trim it out with siding?

   Steve

5. 
   russelln2009 | Dec 22, 2022 09:50pm | #6

   Hi Peter and Airfix,

   I'm in a similar situation with a house I just started building. We will have a few Schuko windows installed in the foundations and I'm trying to figure window placement within the 12" thick foundation & interior wall assembly.

   My plan is to cut the concrete RO about 8 1/2" bigger than the window and build it back in with a (2) 2x4 and a 3/4" buck surround. This will give me some space to build up the insulation on the interior concrete shelf that is left depending on where the window is installed. The 2x4 interior walls will be held off the foundation walls 2" which will be filled with closed cell spray foam (along with the cavity between the studs).

   What would be the best positioning for the window within the overall assembly?