Dave Hinz wrote:



Doesn't make sense. You're using that energy to heat the shop. The
water heater, presumably, is in the shop. So the heat that leaks out of
the water heater, well, heats the shop. Which is what it's for.

I am going to disagree slightly with this, and everyone else who is
saying the same thing.
Yes the heat goes into the same overall space, and results in the same
average air temp, but how it is getting there makes a difference.

The radiant floor is heating from the floor up, heating him, and his
equipment.

The stray loss heat, is mostly convective, and while it heats the air
immediately around the tank, is convected upwards and out of the part
of the space you really want to heat.

In my shop space this would make a big difference.

jk