Ducted heat pump retrofit
We have a 1200sqft, single story (with basement) in Zone 6 (northern New England). Built in the 1950s, it’s been upgraded with insulation (R60 attic, blown fiberglass in the 2×4 walls, foamed rim and basement) and air-sealing. Blower door is 3.87ach50, Manual J heat load ~35,000btuh (attached).
We have a single 18000 btuh minisplit (Fujitsu ASU18RLF/18RLXFWH) in the combined kitchen/living/dining area.
We would like to remove our old oil system entirely, since it’s failing anyway.
We received a quote for a ducted unit to cover the remaining rooms (two bedrooms and bathroom). The indoor unit would be mounted in the basement, with vents coming up through the floors. The contractor is proposing a Mitsubishi SEZ-KD18NA4 (specs attached).
I’m concerned by the listed minimum temp as -5F (we see -20F a few times every winter) and the listed rating at 17F dropping to 13,000btuh. Think this unit plus the 1:1 unit we have could cover the whole house? Should we consider a different unit? or add electric baseboards to supplement as needed? Any thoughts on ducted units would be appreciated.
Thanks in advance,
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