Are minisplits a good solution for heating (and cooling) a smallish addition to my 85-year-old house?
I’m in zone 4 (NYC suburb) and the original house is a 2 1/2 story wood framed house heated by gas fired one pipe steam. Cooling is from window units. Our addition (currently rough framed and dryed in) is two stories with an 18′ x 15′ exterior footprint. 3 foot block stem walls make the lower level slightly smaller than the upper. The upper level, which connects to our main floor, will be our new kitchen, and the lower level, which connects to a walkout basement, will be a play/TV room. The main floor of the house will be pretty open with large openings between the kitchen, dining room and living room. The resulting main floor will be just under 1100 sq. ft. The lower level of the addition will have a direct connection with a room that is about 300 sq. ft. The addition is 2 x 6 construction with one inch of XPS on the exterior and planned cellulose in the walls and above the kitchen ceiling. There is two inches of XPS under the addition slab The original house had blown in cellulose retrofitted to the 2 x 4 walls and some other air sealing and insulating work at the rim and in the attic.
Mini-splits seem like a good option because of their efficiency and the fact that they heat and cool. I’d love to have main floor cooling and dehumidifying provided by the ductless rather than installing window units every summer and taking them back out every fall. They also seem like a more streamlined option compared to trying to add on to the steam system, or adding a new small hydronic zone, or both. Neither of which would offer improved cooling.
Does my situation sound like two mini-splits, one up and one down, would be a viable option?
I know that the rooms themselves are likely too small for any size unit. Does the open floor plan change that significantly?
I would welcome any advice from someone who has experience with this kind of setup. Does the thermostat for the steam get set back a few degrees? Would I need to relocate the thermostat out of range of the mini-split?
Thanks in advance
GBA Detail Library
A collection of one thousand construction details organized by climate and house part