Boiler with Hydro Air vs New Multi-Head Mini Split

ILikeEmOlder · March 23

I’m still working hard to find the best setup for a client with an existing propane-fired boiler and electric resistance baseboard heating (no central cooling).

CZ6. Building heat load of roughly 35K BTU/hr at 1F. 2-story house with single-story addition.

Viessmann Vitodens boiler in the basement (connected to Vitocell indirect WH) currently serves the entire 1st story and addition via a mix of underfloor and under-the-subfloor radiant. Second story is heated via electric resistance baseboard.

So, we’re down to the following options for heating the 2nd story:

A) Add a hydronic air handler to the attic, fed by the existing boiler. Future plan would be to add a cased evap coil to the hydronic air handler for cooling.

B) Install a Mitsu ductless multi-head mini split heat pump.

I’m inclined to go with option A, but I know that option B has its merits.

Option A would include new ductwork and some drywall patching (to accommodate the new piping to the attic). The drawback (as I see it) is that the ducts will be in an unconditioned attic, and I will have to build a “room” in the attic to house the air handler.

Thoughts?

Jamie Hall · March 23

Option A.

pecmsg · March 23

Heat pumps are a small % over straight A/C. Get the heat pump. Use it on the shoulder seasons. When that NE wind blows and the thermometer drops switch to Hydro.
now if your in an area where the art can get below freezing glycol will have to be used.

Hot_water_fan · March 23

ducted heat pump in the attic. You can use the hydro coil or just use a furnace.

hot_rod · March 24

Boiler with Hydro Air vs New Multi-Head Mini Split

ILikeEmOlder

Mar 23, 2025

I’m still working hard to find the best setup for a client with an existing propane-fired boiler and electric resistance baseboard heating (no central cooling).
CZ6. Building heat load of roughly 35K BTU/hr at 1F. 2-story house with single-story addition.
Viessmann Vitodens boiler in the basement (connected to Vitocell indirect WH) currently serves the entire 1st story and addition via a mix of underfloor and under-the-subfloor radiant. Second story is heated via electric resistance baseboard.
So, we’re down to the following options for heating the 2nd story:
A) Add a hydronic air handler to the attic, fed by the existing boiler. Future plan would be to add a cased evap coil to the hydronic air handler for cooling.
B) Install a Mitsu ductless multi-head mini split heat pump.
I’m inclined to go with option A, but I know that option B has its merits.

Option A would include new ductwork and some drywall patching (to accommodate the new piping to the attic). The drawback (as I see it) is that the ducts will be in an unconditioned attic, and I will have to build a “room” in the attic to house the air handler.

Thoughts?

If it is not based on $$, At some point it becomes a personal preference choice. Some like minis, others swear by ducted systems, and at mini splits :)

ILikeEmOlder · March 25

https://forum.heatinghelp.com/discussion/comment/1849763#Comment_1849763

Let’s say that $ is an important consideration…which way would you go then?

DCContrarian · March 25

Another vote for a ducted minisplit.

Kaos · March 25

+1 For ducted. If you are in a place that needs cooling, hydro air makes no sense as you still need to buy an AC unit.

Wall mount mini splits seem like a good idea on paper but have issues. Each head needs periodic cleaning as the filters are useless. The drains occasionally plug up and cause flooding. Multi splits are near impossible to size to feed bedrooms without significant oversizing which creates comfort and efficiency issues. When my multi split dies, it is getting replaced with a ducted unit.

Boiler with Hydro Air vs New Multi-Head Mini Split

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