Zone 4 basement remodel: how much insulation is enough?
I’d like to insulate the basement on my central Virginia home to save on energy costs, and so I can more comfortably use it as a home office this coming winter — when I expect I will again be working from home, just like I’ve done since mid-March of this year. It’s a walk-out with a shady yard; one wall below grade, two are half below grade, and one (southern) is above grade; all walls are cinderblock. It is currently unconditioned, though I’m considering opening a register in one of the ducts. I’ll probably put interlocking foam mats on the concrete floor for now. I’m also insulating the rim joists myself (foam board + great stuff + rock wool barrier). My budget is limited ($5K tops). I’m also a half time single parent working from home with little childcare this summer (thank you COVID) so my time for DIY is at a premium.
I’m considering Insofast, with additional concrete fasteners. This would be R10 continuous which meets code for below grade mass wall in an unconditioned basement. The other option is 2″ XPS foam board, frame, batt + drywall. Significantly more work, and slightly more expensive.
My question is, would this be sufficient in practice to be reasonably comfortable? Mostly looking for perspective from folks who’ve done something like this in this zone.
Thanks in advance for any advice, comments, or experiences!
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