Sizing a Minisplit Heating System
Long time reader, first time poster. I’m grateful for this website, I’ve learned a lot and appreciate all the resources.
I’m hoping to get some advice around sizing a system to heat a 1987, 2,200 sq ft colonial in Dover, NH 03820. We have an oil boiler on it’s last legs and I would like to decarbonize our home by going to mini-splits (plus the added benefit of AC + air filtration), and a hybrid HWH .
We are going through the NH Saves insulation program which to improve the envelop of the home. I’m not sure what details would be helpful in this regard, but the sealing work should get the house from 2950CFM to 2000CFM50, and the major insulation pieces will be having rigid foam insulation/spray on rim joist for the basement and blown in cellulose for the attic.
We also paid to have an energy study done by the auditor & insulation contractor to help size a heating system for the home. He is BPI certified and, if relevant, uses TREAT software . I have in hand (attached) the heat load needs for our home (after insulation/sealing work).
The auditor’s position is that although great, mini-splits are not cost effective as an option to heat our home since “To do it right, you’d need to spend between $25-28K”. Over time, my relationship with the auditor has soured and I’m looking for advice/second opinions. I’ve found installers who can do minisplit systems that can serve the heat load on paper, but when I spoke of them to our auditor – he said the price is too low/a red flag because he knows what these systems cost.
I know it is an oversimplification, but I’m stuck on having found a system/installer/price that serves the ~49K BTU needs of the house (Fujitsus, operating down to -15 deg), versus his adamant position it’d be insufficient/unsuccessful based on the price (no system details discussed).
He will not assist further in system design unless I’m willing to spend the amount he projects and/or he GCs the project. To me, this is a red flag, but I also acknowledge he’s an industry professional with many years of experience in the area, so he could be right.
I’ve attached a very crude layout of our home (excluding basement — the greatroom/garage is on a slab fyi). I’m researching folks in my area who might be able to provide a second opinion and thought I might try and seek some advice here as well.
Any advice on what to consider, how to approach would be greatly appreciated.
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