Basement – Building Sciences Method
I’m south of Boston (cold in winter) and in the process of finishing my basement according the FHB article / Building Sciences method (http://www.taunton.com/finehomebuilding/PDF/Protected/021169078.pdf)
Here’s my question: rather than apply foam directly to the rim joist, can I run my 2″ Dow XPS from the floor all the way to the ceiling, i.e. to the bottom of the first-level floor? I would run it between the floor joists and seal all gaps in that fitted area with foam and Tyvek tape – basically, a 96″ floor to ceiling run right up past the internal foundation wall with cutouts to accommodate joists. The reason for this is two-fold: 1) it’s more straightforward, i.e. I don’t have to work around utilities to get back into the joist area; 2) I have this design approved by the building inspector, because it shows a *continuous* vapor retarder (the foam has a perm rating of 1.0 per inch).
The cold joist is still protected from the warm air I will create in the basement space in winter, but there would be a 12″ pocket between the joist and the edge of the foam (which I can stuff with existing fiberglass). Is this OK?
Thoughts?
BTW, this is a re-post from another thread, where I think I caught the topic too late in the conversation to generate responses. Thanks.
Replies
Seems ok at first read, as long as the foam is covered completely by the walls that I assume you will be building. Foam can't be left exposed, must be detailed with a fire retarder (ie: drywall).
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Got it - thanks. Stud wall and paperless Sheetrock will cover the foam; I am leaving the cavities between the studs empty; drop ceiling to follow. The 2" XPS is R-10 and meets code for basements in these parts.
If I remember your other post correctly, you're planning on running/attaching your studs up to your ceiling joists and not having a top plate. Is that right?
If so, I think you need to have some kind of fireblock that prevents fire from quickly going from wall to ceiling directly.
You're right. Point taken and thanks.
What do you mean by utilities? Wiring is probably fine. Anything with water in it (hot water or steam heating, water supply or drains) is likely to freeze.
Good points - I should have been more clear: HVAC ducts, electrical, fresh air venting for hot water and furnace. Nothing carrying water.