Questioning my logic…GSHP, ASHP, radiant?
I’m in the planning/almost ready to break ground stage of a new home and I’m beginning to question my sanity when it comes to figuring out the right approach for heating & cooling.
The home is:
North end of Climate Zone 5
Main Floor: 1700 sq ft + 1000 sq ft garage, vaulted ceilings through much of it
2nd Floor: 1100 sq ft (2 bedrooms, 2 baths, living room) primarily over the garage
Basement: 1700 sq ft, partial walkout + 1000 sq ft shop under the garage (separated from the rest of the basement)
Walls: R30+ (2×6, 2″ XPS outside, 2lb SPF for sealing + 1/2lb SPF for cavity fill)
Roof: R50 (similar construction to walls. thermal envelope at roof. vent-over roof deck)
Windows: Double-pane, energy star rated
Garage is insulated to the same R30 walls, plus a deceptively-rated “insulated” garage door with typically mediocre air sealing.
Basement Walls: R10 for the time being. Will be finished eventually to R20-30. Really won’t be used much until it’s finished. Shop under garage will be insulated to R10-20.
Natural gas is a $30k proposition to have the main extended to my property, but electric is readily available
Garage and shop space under garage need to be heated, but only to 60 deg max
Main floor will have a Tulikivi soapstone fireplace for ambiance/backup heating (or primary heating on some days)
The master bedroom is on the main floor and we prefer to sleep in a cold room. As in our bedroom windows are open if the temp is over 20F outside. Typical morning bedroom temps are in the upper 50s in the winter. Yes, the master bedroom will be insulated from the rest of the house. Yes, this drives some sort of zoning. Radiant floor heat in the master bath is thus mandatory, hydronic or electric.
My previous thoughts:
Radiant floor heating on the main floor because of the comfort level it brings (warm under foot). We’ll have “Wood” flooring throughout the main floor. Carpet upstairs.
Seems natural to go with a Ground Source Heat Pump/Horizontal Loop Geothermal since I’m 100% electric, looking for efficiency, and there’s a rebate that could be appealing.
Hot water at least in part from the GSHP (almost free at that point, right?)
Of course, after reading several threads, I’m second-guessing that.
Radiant drives 2 delivery systems, which drives $$
Geothermal, especially the one quote I have is OMG expensive
Radiant might not be THAT warm underfoot if the house is that well sealed.
As I said, I have one lone quote right now. He said he did a Manual J and came back with over 60k for the house, plus about 20k for the garage and 20k for the shop for heat, and almost 50k for cooling. 11 tons total in the equipment , split between 2 units, and a 12 ton loop. At roughly $1 per heating btu, there’s absolutely no way that’s happening.
So now I’m reading and wondering. Seems like my project is paralleling Kent’s project from a couple of years ago, except in comparison I’m thinking the Manual J numbers for mine are way past being in left field: https://www.greenbuildingadvisor.com/community/forum/mechanicals/33963/why-must-hvac-decisions-be-so-complex-or-geothermal-worth-it
Ground Source? Air Source? Mini Split?
Mix of the 3?
Ditch the radiant entirely except for the bathrooms?
Could a mini-split unit heat & cool the garage and shop? (shop won’t need cooling being in the basement)
Thanks in advance for any advice!
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