When our early ancestors first discovered fire and learned how to manage its energy, the fire’s radiant heat cooked food and heated water, rocks of a fire ring, people and pets very efficiently. But radiant heat—from a fire or from the sun—does not heat air. Instead, air is warmed by moving across surfaces that have been radiantly heated. You have likely noticed that a single cloud can force you to suddenly become chilled on a day of abundant sunshine. On a cold night, enjoying the warmth of a campfire, you may suddenly become cold when someone walks between you and the fire.
For tens of thousands of years, air was not heated for warmth. Cliff dwellers and pueblo dwellers of the land that would become New Mexico allowed the sun’s short-wave light to strike adobe and rock surfaces, which stored energy that would be released into living spaces as long-wave radiant energy, or heat. Radiant energy warms living spaces efficiently and cleanly without heating the air.
In tipis, an opening at the top allows air to escape, exhausting smoke from the fire below. Wood fire heats rocks, which radiate heat for many hours after the fire has died out. Native Americans used radiant heat from rocks in diverse structures, while European groups built heavy fireplaces that, even in castles, heated massive walls. Builders in Asia heated floors.
Blessed with abundant, free, radiant energy from the sun, people of the Southwest discovered early on that the north adobe wall of a plaza, or resolana, having absorbed solar rays, would release luxurious radiant energy far into the night.
Subsidized, dirty oil and gas encouraged us to forget about radiant energy’s value and usefulness. Forced-air furnaces expel heated air into living spaces. As we know, warm air rises. The warmest air in our homes is not where we are.
During the energy crisis of the 1970s, I became interested in finding a solution to the phenomenon known as the “heat-or-eat dilemma.” Many families living in manufactured homes in economically depressed areas of the Río Grande Valley attempted to heat their homes with firewood. They couldn’t afford propane, nor could propane adequately heat poorly insulated trailer homes. Many families have lost their lives attempting to make it through cold winter nights in highly flammable manufactured homes.
During the energy crisis of the early ’70s, Bill Yanda of Santa Fe, the inventor of the now famous Yanda greenhouse, came to Alamosa, Colorado, where I was living at the time, to share his experience with radiant solar energy. His design incorporated a massive adobe-wall resolana on the north side of a greenhouse. The roof of the greenhouse was insulated to catch the warm air trapped by the “greenhouse effect.” Short-wave energy from the sun passes through glass easily, but as soon as it heats an object, that object reradiates the energy as long-wave radiation. Long-wave radiation does not pass through glass as easily and builds up as heat. Plants in such a greenhouse will thrive, even in freezing air, if they are exposed to the resolana.
Bill Yanda showed us a slide that changed my life. It showed Bill swinging in a hammock in his greenhouse. Outside, snow was deep against the greenhouse glass. Bill was reaching for a beautiful, ripe tomato.
We convened a meeting of neighbors to find a way to solve the heat-or-eat dilemma. Bill North, a rancher, shared his experience of building a simple solar collector to keep water pipes from freezing in his home’s crawlspace. The collector, made of black plastic stapled to his south wall with a layer of clear plastic spaced an inch or so in front of the black plastic, attracted and trapped enough solar energy to keep the pipes from freezing, once pumped under the ranch-house floor with a simple blower. But the most amazing thing about this actually began a quiet energy revolution: The heat under his floor cut his home’s heating bill in half and paid for the solar system in one month!
Thousands of do-it-yourself solar collectors in Bill’s region, the San Luis Valley of Colorado, now pump heat into crawlspaces, turning floors into radiant heat surfaces. The solar heat from the collectors stratifies under the floors. Installed crawlspace insulation—much easier than insulating an entire house!—keeps the heated air under the floor. The solar-heated air is recirculated through the collector, resulting in warmer and warmer temperatures under the floor, and transfers heat to the floor.
I learned that a radiant floor does not directly heat the air of a home. The air is heated secondarily through “scrubbing” radiantly heated objects in the home such as furniture and appliances. I also learned that wood can hold more heat than rock by weight. Wood has a higher “specific heat” than rock! So a home’s wood floor is a perfect place to store solar heat for radiant release.
That same year, 1976, I immediately built a collector onto my house. My wife, Julie, and I decided to first have the solar-heated air directed to a water tank through an inexpensive stovepipe. Once the air heated our water, we could send the air back to the collector in the summer or, in the winter, channel it under our floor. Our $300 heating bills that first winter were reduced to no more than $30! We estimated the payback time on the solar system to have been two months.
I was hooked on radiant energy. Julie and I then built a Yanda-type greenhouse on the south side of our home. The radiant long-wave energy released by the adobe wall of our house kept plants alive all winter, while the air trapped by the fiberglass glazing of the greenhouse was allowed to convectively flow into our living room, bringing not only oxygen-saturated warmth but humidity from the plants. Our children played in mud just feet away from windblown snow piled against the clear greenhouse walls.
By building a no-cost adobe wall in your yard, you can extend your garden’s growing season by four months. On the north side of the wall, you can have chickens roost and improve winter egg production with free radiant heat.
Julie and I have 20 tons of soil compacted over a 1-inch layer of insulation in our home. Not only does this incredible massive flywheel heat our home for days without sun in the winter; in the summer, shaded from the sun, it cools our home magnificently—for free. We don’t need to heat the air in our home, and often on winter days, we have the doors open to the outside enchantment.
One rancher, in the early ’80s, built a collector that still today pumps solar-heated air through 2-inch pipes imbedded in the cement slab of his expansive workshop. He removed the woodstove he thought he would need. As another example, a potato farmer built a system that blows hot air into a rock storage bin under his workshop. He called me one day to say he had his doors open to cool the building down. It was minus 25 degrees outside that morning.
In Española, our nonprofit, the Heart Mind Alliance, has recently conducted free workshops, open to the public, demonstrating how to build the latest version of these do-it-yourself collectors. Much more efficient than those we built in the ’70s, the collectors cost about $700 in materials, including the radiant barrier insulation (about $200 to insulate the perimeter of a crawlspace) to bounce back under the floor over 97 percent of the radiant heat stored in the floor. We hope the state will consider helping to subsidize the cost of these collectors. New Mexico has roughly 400,000 trailer homes. Every year, we lose loved ones to fires as more and more people heat with wood. These are folks who, often, are too poor to pay taxes. But even tax incentives are nonexistent for these home-built systems.
For more information or to obtain our Española Valley Solar Collector construction packet, email email@example.com or visit the websites www.heartmindalliance.org and www.heartmindalliance.com (under construction by NewMexicoVideoServices.com). There, you can find an instructional video with step-by-step construction footage of the Sena family’s solar collector in Ojo Caliente.
Bob Dunsmore has worked as a community development agent and as a grassroots technology specialist in 20 countries. He is the founder of the Heart Mind Alliance, a nonprofit whose mission is to share energy self-reliance information worldwide. He is also a member of the Río Arriba Bioregional Council, a forum for sharing ideas on how to create a regenerative future for the region and beyond. Email firstname.lastname@example.org