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DIY Guy
Join Date: Jan 2011
Location: Mpls,MN
Posts: 315
Thanks: 2
Thanked 17 Times in 17 Posts
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![]() I am at the point in deciding how to plumb/control the hydronic radiant floor in my new addition space. It is three loops(200' ea) of 1/2" non-ox pex laid in concentric sq spirals from outside to center going from 6" spacing on outside to 12" in center where less heat is needed in a 15x30'(open space plan) slab of 4" of hi density concrete with lots of rebar(as it is an arched suspended 1st floor over a full basement) I chose this pattern because the first third of the south side of the slab is mostly window with direct passive solar exposure and I want the fluid path flow to move some of that heat gain to non exposure floor area to even floor heating.
Exterior walls are true R50 except S wall which is mostly hi perf windows and thermal covers that are about R20 total, ceiling is R80. Double wall construction on three walls only a single 3/4 top plate that only continuous wood inside to exterior(all other areas have at least an 1 1/2" hi R thermal break. South wall with so many windows this could not be accomplished practically but is the area that receives the most solar gain so not as critical a heat loss area. Every exterior joint was glued or caulked with a continious 8mil vapor barrier is unpenetrated (except windows and doors) so air infiltration is minimal. Fresh air will be my biggest heat load and some type of air to air is planned. So I see two choices for heating the floor, the most simple being a single pump with on demand(thermostat) or a continuous running pump with hot water injected as needed. I think the second choice adds the advantage of moving solar gain heated fluid around and would only require the addition of a injection valve to the plumbing?? I plan to use an off peak elec water heater to supply hot water for now as our COOP has reduced off peak rates. The slab easly has capacity to hold enough heat to make it thru a nightly cycle heating pattern. I see the continuous pump option as the floor heated the most evenly but I want to keep the system as KISS as possible. One other possible choice I can think of is the continuous pump and have the water heater ON just off-peak(controlled by thermostat). So much of the info on hydronic system controls quickly get into much more complex systems than than what I have that it is not easy to determine what is required for the most simple. I don't see the need for the $1000. plus control panels from hydronic suppliers for my needs. Am I wrong in my thinking? |
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