Single minisplit for AC?
Looking for feedback on adding AC to a ~1600 sq ft ranch in central NJ. Current setup is a window unit in the bedroom and a 1980s 220v beast of a wall unit in the dining room. Together they do all right in those worst weeks but for the most part we’ve just been toughing it out. I’m on a well shaded lot and the house stays reasonably cool during the summer, but also a bit damp. So hoping to dehumidify with the AC and of course cool the place down during the hottest weeks of the year.
1960s construction, plaster walls with foil-faced fiberglass batts of indeterminate insulation value. Similar on the ceiling, plus R-30 insulation unfaced batts I added on top, running perpendicular to joists. Original single pane double hung aluminum frame windows, with storm windows. Solid doors. Garage and bedroom ends of ranch are gable ends with no overhang, front and back of house have 18″ or so roof overhang. Front of house (kitchen in front) faces roughly NE.
Heat is primarily from a Jotul F55 wood stove, supplemented by hot water baseboard and Burnham MPO-IQ65 oil boiler when it gets under 20 or we’re not home to feed the wood stove. Not really looking to heat with the mini split but might be a nice option to have during shoulder seasons.
I did a room by room heat loss calc using coolcalc.com and came up with 53k btu heating and 21.5k btu cooling. Floor plan, square footage and cooling btu numbers are attached. I did the one bath together with the adjacent hall and the other together with adjacent den just to keep things simple. Also of note is the high living room btus due to 80% of that wall being glass.
That turquoise box on the drawing is where a 2’x2′ whole-house fan is located. I was thinking a simple solution would be to replace it with a ceiling cassette mini spit in the neighborhood of 18k btu/hr. Seems like it would possibly be a little undersized, but only on the worst of days. Given how well we’re getting by now, maybe close the doors to the unused bedrooms and it’d be fine. My better half and I occupy the home and I expect it to remain that way for the foreseeable future. I understand this would require open bedroom doors for air circulation but that’s how we do it with the wood stove and it works fine for us.
I have a full basement so plenty of room down there to run ducts, but I’d really rather not. Don’t want to cut a bunch of holes in my beautiful wood floors or lovely plaster walls, and I hate banging my head on basement ductwork. 4:12 roof so not much room up there. I did consider a ducted mini split centrally located in the attic, with short runs to the bedrooms. Not sure it’s worth the hassle of ductwork for marginally better air circulation, and then I’d have to figure out returns, ducts in uninsulated space, etc. Again I’m designing for the two of us and it’s predominantly the kitchen, living room and bedroom 1.
Thoughts about this plan, or other options I should consider? Thanks in advance.
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