Basement insulation question
I’m building a house in Zone 5 (southern CT). The house will have a full basement with spray on waterproofing. There is no sub-slab foam. The builder budgeted for 2″ of XPS (with dimpled moisture facing) on the sub-grade exterior of the foundation walls, but NOT the above grade portions. There will be a footing drain running to daylight and a shed water system to catch storm water running off of our house (2 foot overhangs; no gutters). The soil is sandy loam and drains well.
The basement will likely contain a heat pump water heater and propane furnace backing up our air source heat pump.
Based on my reading here and due to budgetary constrains, can I forego the exterior foundation foam, with an eye toward insulating the basement via the interior side (floor and walls) with rigid foam at some later date? As I understand it, if I were to install the foam below, but not above grade, there is not much value in the insulation due to the exposed portion of the foundation wall. We do not have the funds to spring for exterior foam under the slab and above grade (and related finishing costs). I could use the savings from the foam elsewhere. Anyway, please let me know your thoughts. Thanks.
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