wrote:

... Some buildings have chilled beams and ceilings for cooling.

So do many many cold rooms of various applications. Ever hear
of static-coil ammonia systems ?

No. I'm mainly interested in houses, altho I've read that a 70 F low-e
ceiling can reduce ice rink melting by 10 watts/ft^2...

They do not work primarily by raidant absorption, they work mainly by
convection currents.

Cool air falls...

If you were to put the coils at the floor instead of the ceiling, they
wouldn't work worth a ****.

There would be more cool surface, but maybe less cooling, with no slow
ceiling fan.

... a cool floor would make more sense, since warm air rises. A slow
ceiling fan with an occupancy sensor and a room temp thermostat could
stir up some floor air as needed for comfort.

And thus, it is no longer a radiant system, it is convective.

Most of the cooling might be convective, but consider that a) a ceiling
needs well-distributed cool sources in order to have a large radiant or
convective surface, but we might cool an entire floor with a single point
source, since cool air falls, and b) a slow ceiling fan can provide more
air velocity for useful low-energy cooling, allowing a higher room air
temp for the same comfort, and c) a radiant cool floor can allow a higher
air temp, for the same comfort, and d) with a slow ceiling fan, it's easier
to turn off the cooling when nobody's in the room.

Nick