The balance between cool and warm means that even a passive solar house should include heating and cooling mechanisms. Rather than use anything that takes power, we’re setting up a couple of other options.
Windows are the natural cooling mechanism. We have sash windows on every wall so these can be opened to create cross-drafts. If you open a window low on one side and high on the other, this creates a natural draw to pull the air across a room.
For heating, we’re constucting a Kiva-Rumford Fireplace (That’s Inky standing on the adobe hearth, in front of the arch built–you can see the top of the fireplace throat). The Rumsford comes from a Count Rumsford who designed a fireplace that would easily draw the smoke up and out of a room. This is done with two things: a shallow and tall fire chamber, and a “throat” above that which narrows, pulling the smoke up and into a smoke chamber. This is married to the traditional Southwest Kiva design that marries the fireplace to the adobe walls, so that the heat moves from the fireplace into the adobe—the idea is to warm the adobe so that it will give off heat for a longer period of time. You get more heat for your burn.
The constuction of the hearth was simple enough—adobe onto the concrete foundation. Then the firebrick went up for the fire chamber. The tricky part was building the arch to frame the fire chamber.
This is where a workshop at Southwest Adobe paid off. The two tricks to builing the arch were to 1) cut out an arch guide from wood and 2) use more narrow adobe bricks as you start the arch curve. We also adobe mud that was a little more stiff to help add strength. And, for the arch guide, this was built with blocks that could be knocked out at the bottom, easily dropping the guide (so you don’t have to worry about pulling out your bricks when you pull out the guide). Plans from Jim Buckley’s site on a Kiva-Rumford were also helpful, and the fireplace elements (fire brick, throat, damper, smoke chamber, flue) all came from Builders Materials in Albuquerque. (They know their stuff, too–they sold us exactly enough fire brick to make the fire area!)
The fireplace will be finished up with more adobe and cob to give it a lovely, organic curved shape. We’re putting in a couple of nichos as well (up high where the temp is lower so items will not be affected by intense heat). It will be finished with plaster, colored clay, and a final polished coat of mud plaster with a milk casin. Before then, however, we’re going to test it with a fire, just to make sure everything works as designed.