I'm reaching the end of the design of a new radiant heat system and I was hoping to get some feedback and ask a few (probably dumb) questions!
The project is a gut reno/addition - we bought a ~2400 sq ft house built in 1953 and basically removed everything but the foundation/unfinished basement. We are adding a second floor and expanding a couple rooms. It is now 3,500 sq ft with a second story. I have attached simple floorplans.
So far, here's what I have for radiant heat design:
--Total heat loss of the home is 105k BTUh.
--Looking at open system design.
--The plan is to do a thin-slab pour on the first floor - the current flooring has been taken down to the concrete panels (they didn't use wood - very sturdy). The second floor will be run between the joists with metal heat fins.
--I'm looking at four zones, two on the first floor, two on the top floor. The zones will be:
Zone 1: 780 sq ft (630 with piping - no pipes under showers, in closets, etc). Heat Loss of 17K. Consists of Master br, master closet, master bath, 1st floor guest bath and bed.
Zone 2: 1,145 sq ft (857 with piping). Heat loss of 40K. Consists of living room, dining room, kitchen, entryway, sun room, mud room.
Zone 3: 800 sq ft (750 with piping). Heat loss of 18K. Consists of den, office, laundry room.
Zone 4: 750 sq ft (700 with piping). Heat loss of 12k. Consists of two upstairs bedrooms, 2 bathrooms, and loft.
Equipment I'm looking at so far:
Takagi TH3DV-NG on demand water heater
Everhart 1/2" oxygen barrier PEX tubing
Rifeng stainless steel manifolds
Grunfos stainless steel variable speed pumps
--My circuits can only be 300 sq ft, where does that measurement start and end? From manifold back to manifold, or from water heater and back?
--My water heater and zone pumps are going to be located in the basement. That's pretty far from the top zones. Should I move the manifold for the circuits upstairs? If I do that, how does it impact my 300 ft circuit length? Do I need to add the copper distance from the pump to the manifold to the circuit? What's best practice between moving manifolds and "homerunning" as I've heard it called?
--In my master bedroom zone, the master bedroom itself is looking like it will require more flux than I think should be planned to output. It will take 41.77 btuH/sq ft, but the other parts of the zone (hallway, master closet, master bath, second bedroom) will require much less than they are suppled. To what extent should I assume that the heat will move from adjacent areas separated by interior walls? The bedroom itself has a crawlspace below it, no structure above it, 9ft ceilings, and a 16ft wide window wall. Should I just keep the same 10" tube spacing throughout the zone and maybe adjust the flow rate up slightly in the circuits going through the master bedroom and down for the other circuits, and then plan on having to use a secondary heat source in there, or can I safely micromanage the flooring to get it warm enough without having the flooring get too hot or the flow rate too fast?
--How should I account for heat loss from the unfinished basement, which I wasn't planning on heating? That area is included as a source of heat loss, but there is nothing in that area to offset - should I just apply that heat loss to the rooms directly above it?
Thanks so much for any assistance or insights!