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RachWashState 09-06-2013 03:33 AM

Insulate Basement Knee Wall
My basement has a short cinder block wall that is interior and on the other side is a sloping crawlspace away from my basement. I found the best video that solved my problem. How to insulate the wall.

Just do not understand why the guy has to lay a top blue insulation board on top his pony wall then have another one go under the pony wall onto his concrete?

Just wondering if I need to frame in my pony wall or knee wall?

I want to place the Owens insulation tight up against the cinder block wall and partial 3 foot knee wall. Next lay treated wood on floor then steel frame on top of treated wood tight to Owning 2" insulation. Finally sheet rock.

Gary in WA 09-15-2013 10:15 PM

Are you East or West of the mountains? Closest large city?


RachWashState 09-17-2013 03:17 AM

Portland Oregon.

Gary in WA 09-18-2013 04:29 PM

Fig. 1 and 2 is the best way to insulate the basement wall. Air-tight coverage; 1' square grid of foam compatible adhesive on backside of f.b., canned foam or caulk around perimeter of rim f.b. If you use the "search" white box at top of every page, many posts will list the proper way.

Coastal side of mountains requires R-2.5 to prevent condensation in cavity;

You would need that thickness XPS to prevent condensation and R-13 (f.g.) in the wall to meet your energy code requirements OR just R-10 (2"XPS) as listed without a frame wall/cavity F.G. insulation. Need to run wires?

PS. the video wouldn't play for me. Foamboard under the frame wall is a thermal/air/capillary break;

RachWashState 09-20-2013 11:40 AM

Gary, thank you!
Fig 1 and 2? Would like to see.

The video is Basement walls by Todd Fratzel, but not to sure what he has on the other side of his wall.

Mine is in interior wall with crawlspace on the other side. Crawlspace slopes to the other wall.

Gary in WA 09-20-2013 07:48 PM

I am so sorry, I forgot the link;

Fb requires gluing for an air barrier against basement air condensing on the cold concrete wall; The wall assembly must prevent any significant volume of
interior air from reaching the cool foundation wall. Thus it
must have an effective interior air barrier or a method of
elevating the temperature of potential condensing surfaces
(such as rigid insulation installed directly on the interior of
concrete or masonry surfaces). From;


If still interested and need further proof, lol; "Roads to failure" and "Air movement";


PS. the above-grade portion of crawl-space interior wall needs insulation, if outside vented. Add a weatherproof door between the two.

RachWashState 09-24-2013 02:48 AM

Thank you!

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