Best Of

you would need to do a heat load calc to know the exact answer. Are there two tube runs in each bay. Is the problem area over a basement? Bubble foil alone may not be enough insulation.

What temperature is the supply set at? Increasing the supply temperature may be a simple way to increase floor output.

I suspected a single run when you mentioned 3/4 tube.

Can you see the data on the tube? If it is any version of Pex, it should handle 180 f or more.

The heat output limitation will be the floor surface temperature. Stay below 82F for a floor that is comfortable in bare feet. With wide spacing like you have you will see stripes of warm spots right over the tube.

Generally you want at least a 6” fiberglass batt below a system like that.

And no, 1/2” bubble foil is not equal to a 6” batt 😏

There are cases where radiant floor alone will not adequately heat a room or space. 10 delta is fine as @Hot_water_fan mentioned

if the circ has a check, I don’t see why you need the flo check?

The proper way to size a hot water boiler is to do a heat loss calculation for the space. The emitters likely are oversized and the system will heat more evenly and run longer cycles with a boiler that matches the heat loss. The only reason that steam boilers are sized to the installed edr is because you have to more or less fill the whole system with steam to heat all of the emitters (with careful balancing and with 2 pipe systems it can work with less but this is the reasoning to size to the edr).

You should double check that the emitters can output your calculated amount of heat but you don't need to make it bigger than the heat loss.

The boiler can't eject any more than the emitters can emit, so there is no reason to size any larger than that. However, a heat loss calc is still a good idea to possibly be able to downsize the boiler and gain some efficiency.

if you are supplying 180, use the 170 degree column for the fin tube output, that will be the average temperature in the loop, assuming a 20 degree delta design.

The number will be a little more accurate this way.