Basement wall assembly in climate zone 3A
I’m finishing my homes basement and have been reading on GBA and FHB around the issues and approaches for resilient and efficient assemblies. Below are some facts about my situation:
Climate Zone 3A, new house built in 2016, daylight basement with 3 poured concrete walls and one 2×6 framed, wall height 9′-6″.
As i’ve mentioned, I’ve been reading pretty extensively and think the approach I’m taking is sound, but as Martin mentioned on a recent FHB podcast, I don’t want my imperfect understanding to lead to big problems down the road. Some of the articles I’ve read: “How to Insulate a Basement Wall,” “Calculating the Minimum Thickness of Rigid Foam Sheathing,” and “Combining Exterior Rigid Foam with Fluffy Insulation.”
I’ve attached a diagram of the wall assembly I’m planning to use , but in short I’ll be insulating the interior of the concrete wall with 1″ rigid foam with taped seams, 2×4 wall tight against the foam with R15 fluffy insulation, 1/2″ drywall. My primary objectives with the walls and floor, in order of importance, are: 1. Moisture and condensation resistance, and 2. Energy efficiency.
I think if I’m reading the “Calculation the Minimum Thickness…” article, in my climate zone 1″, or even 1/2″ of rigid foam is fine. Since I’m planning to put fiber insulation in the wall cavities, I also have to consider the ratio of the rigid:fluffy insulation. The “Combining” article doesn’t have a entry for climate zone 3 (hottest zone listed is marine 4), but if I use the first entry of 16% as a conservative minimum ratio, my R5(or 4.2)/15 comes out to be 25-21%, so that looks good also.
Anything I might be missing or misinterpreting? This is a great forum and thanks to everyone (Martin especially) for sharing their knowledge.