The House on Hummingbird Hill: Radiant heating and cooling

A key part of the house is its radiant heating-cooling system. Hidden in the plasterboard walls are 150 finned copper tubes circulating heated water. Solar panels on the roof provide the heat source for the house, while a pair of thermally actuated valves control house temperature.

It is a gravity-driven radiant-heating system, possibly the first one in the history of mankind. It keeps the house within a few degrees of set point without using any pumps, electrical controls or electricity.

Most radiant systems are installed in the floors. This one is installed in the walls so no air bubble can stop it. Additionally, the Weingartens were able to put more tubes beside windows to balance heat flows and keep the house more comfortable. Have you ever stood next to a cold window and felt a chill? That's what they were designing against.

The system, now that it's set, should operate silently for years, using no power.

The placement of the copper tubes, even though they're concealed under plasterboard, is marked by a clever system built into the baseboard and bookshelves above.

The photo below gives a close-up of fin and pipe while the one, above right, shows the fins gradually vanishing into the wall. For more on how it got from exposed fins to hidden fins, see Sheetrock Party.

Finally, take a look at the device at lower right. It is the mechanical thermal control for the heating-cooling system. When the temperature rises above a preset level, the lever throttles down a valve several feet below it to nearly close the piping bringing heated water into the fin system. The device is generally used to open and close greenhouse windows....