Ductless vs. Ducted Heat Pump Sizing and Costs
I’m getting quotes for 2 whole-home heat pumps in my MA two-family house. To receive the generous MA rebate, in short, all heated and partitioned rooms need a heat source. This means $24,000 in rebates.
I’ve calculated the empirical heat load for a few seasons per the GBA article (https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler). The total heat load of this old, leaky, uninsulated home is max 60,000 BTU/hr. This is broken out into:
– Unit A 1000 sq ft Heat Loss (without insulation): averages ~26,000 BTU/hr, but has gone up to 32,000 BTU/hr
– Unit B 1200 sq ft Heat Loss (without insulation): averages ~32,000 BTU/hr
I will be getting insulation throughout the home via Mass Save, which is required for the heat pump install rebates. All installers know this, and the quotes I’ve received all include 36k BTU in Unit A, and Unit B ranges from 42k BTU-54k BTU. That’s a total of up to 90k BTU/hr for 2200 sq ft. The biggest quote actually came from the recommended heat pump installer of a leading GBA contributor (go figure).
The sizes are mostly driven by the “heat source in every room” Mass Save requirement.
Now, my gas boilers (hydronic) are both on their way out, and I’d love to make sure I’m covered on the coldest of cold days. I also know that 2 new high efficiency mod con boilers will cost at least $35k total, and they will not give me cooling in the summer. I’m willing to pay, but these 80-90k BTU/hr systems on a post-insulation 2,200 sq ft home seem like heat pump insanity. Heck, that’s still 50% bigger than my pre-insulation need!
Would ducted systems make this sizing issue mostly go away?
The cost before rebates for these systems is about $60,000 (about $35k after rebates). I was informed that a ducted system would cost more, but I don’t have a sense of how much more. Could anyone offer some guidance on how much a ducted system might cost and/or what the major drivers of cost are versus a ductless system?
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Replies
Adding ducts is the cost driver, it’s labor intensive vs drilling holes in your walls. However, a lot of contractors can do it and you can look outside the typical Mitsubishi, Fujitsu, etc installers to the ones that install Tranes, etc.
Does electric baseboard count as a heat source? I’d use that for the smallest rooms over a ductless.
Yes, I could do electric baseboard in the smaller rooms, but I don't know if I'd still qualify for the 12k in rebates per unit. Worth investigating though... I'll look into it.
The balance would be…does a simpler system cost less than the expensive system with the rebates.
Ducted VRF seems like the way to go here. You still get most of the benefits of ductless/VRF efficiencies but satisfy the MassSave requirements and don't have to use oversized heads in small rooms. You will give up some room-by-room zoning control but you gain the ability to add whole-house filtration, dehumidification, or even a retrofit ERV addition (won't be optimal unless you install dedicated supply and return ducts just for ERV).
Yes the ducted systems work better when you have several smallish rooms.
Yes it will likely cost more money.
The biggest cost the most refuse to accept is you must make space inside your home for the air handler about the size of a small closet near the center of the small rooms. Other time you can make the space by lowering the ceiling in the hallway upstairs.
Walt
In a retrofit situation I think your better might be high velocity. Installers in areas with radiant heat are used to working with these and installing to get air conditioning. It can be done without major demo and rework. The equipment is not cheap but in this case it will save a fair bit of labor. There is no reason why you can't add a heat pump outdoor unit to one.
There are now hyper heat outdoor units that can pair with a two stage high velocity air handler (ie https://www.shareddocs.com/hvac/docs/1010/Public/00/01-DLS-019-CA-01.pdf look at the High Heat AB series) so it is a pretty straight forward "standard" install.
This gets you heat and air conditioning to all your rooms without any of the issues of a multi-zone system.
Sometimes the installer won't feel comfortable the heat pump handling the heat load when cold (this is really a non issue in zone 5 with hyper heat units), in this case you can add a hydronic coil or strip heater to make them feel better and avoid oversizing the heat pump.
We spent ~$42k installing three ducted mini-split systems (one per floor) in the Boston area. We had already removed the entire hydronic heating system. We had a third-party design (Manual J, S, etc.) in-hand when quoting it. We had a quote for less, but that contractor couldn't source the equipment we needed, and had a third quote for a few thousand more.
Keith, I'd love to know the name of your contractor if you could share or give strong clues as to who it is.
I've gotten another quote with more of the same. All quotes are 6.5-7.5 tons of ductless minisplits for 2200 square feet, post Mass Save insulation. Stop the madness.
Send me an email and I will share the contractors referenced. [email protected]