Sizing the minisplit: ducted upstairs, ductless downstairs
Firstly thanks for the all the fantastic info you continue provide on HVAC sizing. The information asymmetry between the contractors and the average homeowner is incredible. We are looking at retaining an energy consultants to run manual J and or manual D calcs and I am sure what we outline will reinforce this for you,
We have just purchased a 1910ish Colonial in CT (Zone 5). Single family dwelling two stories with 3 beds and 1 bathroom upstairs and a fairly open plan downstairs. The house has no central ac and uses a forced air oil burner for heat. The home size is 1225 sq ft and was renovated in last ten years- plaster walls; double pane windows, new foam in ceiling in attic floor. There is ductwork in floor downstairs and in plaster ceiling upstairs via unvented attic.
The standard approach seems to have been a walk through before sending us a quote for Mitsu systems. The $ values of the quotes have ranged from $16K to $30K. We rec’d a fourth quote in the $24K range but lost the precise mechanical breakdown.
My CoolCalc numbers (note: I have zero experience doing this) gave me Heating BTU downstairs of 10,951 and upstairs of 25,771
1. I am guessing this is nuts oversizing?
2.Does ducted upstairs and ductless downstairs make sense/right approach? I wasn’t keen to use the old ductwork downstairs.
3. Does 1 register/ductless wall unit downstairs make sense – all contractors initially pushed two on us
4. Per the “Getting the right mini split” article on this site, should we be looking at a Fujitsu over a Mitsu for a house this small?
5. Is a multi split a bad idea ie we do separate outdoor units for upstairs and downstairs?
Thanks in advance.
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