I recently sat down with Kristof Irwin, P.E., of Positive Energy to talk about how to cool a house with chilled water. The system works with radiant panels that are installed on the ceiling - not hard against the ceiling, but decoupled from the mass so they can change temperature quickly as chilled water is piped through the panels.

These are architectural panels that could be free standing on a ceiling or wall. These panels are more suited to a commercial installation. In a residence, special drywall panels can also be used to mimic a conventional drywall ceiling. In both cases, tubes are pre-built into the backside to distribute chilled water over the ceiling area.
These are architectural panels that could be free standing on a ceiling or wall. These panels are more suited to a commercial installation. In a residence, special drywall panels can also be used to mimic a conventional drywall ceiling. In both cases, tubes are pre-built into the backside to distribute chilled water over the ceiling area.
This is the back of a drywall radiant panel. The tubes are embedded in metal to spread the cold out to a larger surface area.
This is the back of a drywall radiant panel. The tubes are embedded in metal to spread the cold out to a larger surface area.

Radiant cooling works on the same principle as radiant heating: Radiant energy is absorbed by a body (human or a building mass) across a distance; it doesn't move through the air (that's convection) or through the molecules of a material (that's conduction); radiant energy moves from a body of higher temperature to a body of lower temperature through space.

Radiant heating is easy to understand. Just step into the hot afternoon Texas sun and you’ll feel that radiant energy heating you; step into the shade and you are immediately cooler. Radiant cooling works exactly opposite from that.

The blue on the IR image on Matt's phone clearly shows the cooler temperature of the radiant cooling panel.
The blue on the IR image on Matt's phone clearly shows the cooler temperature of the radiant cooling panel.

With radiant cooling, we are creating a big cool mass on the ceiling, and the heat from our bodies, as well as from warm window surfaces and from warm wall surfaces in the room, radiates outwards and is absorbed by the cold panels. This lowers the temperature of the building and of our bodies. Our bodies and the wall surfaces are the warm bodies, instead of the sun. While not nearly as warm as the sun, our bodies and building surfaces still radiate heat as long as there is a colder body that will absorb the heat.

This is how drywall radiant ceiling panels look before they are mudded. The piping (seen to the right on this experimental installation at the Positive Energy offices) would be buried in the ceiling and panels skim coated, so it would look like an ordinary drywall ceiling and you'd never know there were radiant panels inside.
This is how drywall radiant ceiling panels look before they are mudded. The piping (seen to the right on this experimental installation at the Positive Energy offices) would be buried in the ceiling and panels skim coated, so it would look like an ordinary drywall ceiling and you'd never know there were radiant panels inside.

In the video below, I discuss with Kristof how this idea might be implemented in a home, where it can provide even, quiet cooling with no registers to be seen anywhere and no fans blowing air and dust around.