James Kachadorian’s simple yet highly effective house design ideas have served him well since he got involved in passive solar technology in the mid-1970s—first as founder of Green Mountain Homes, more recently as author of the popular how-to book The Passive Solar House: Using Solar Design to Heat & Cool Your Home.
Snow still fills the fields in Woodstock, Vermont, on an early spring day. Though the morning sky is overcast, it’s light and cheery in the dining room of the home where Jim Kachadorian ’61 lives. Outside, the temperature is a raw 38 degrees. Inside, the furnace is off. Warmed with just a bit of help from the kitchen’s wood-burning stove, it’s a cozy 70 degrees.
This lovely, comfortable home is one of Kachadorian’s original passive solar designs, built in 1980. Perhaps one of its most striking characteristics is that it doesn’t look solar. There are no shiny photovoltaic arrays glinting from the roof, no gadgets or machinery to harvest the sun’s energy, not even a telltale plethora of windows—just thermally smart siting and construction, and a concrete foundation so innovative it was patented.
Inspired by crisis
Before he wrote The Passive Solar House, Kachadorian and his small staff at Green Mountain Homes sold the company’s passive solar kits. His wife, Lea, drew renderings of 12 basic designs for the brochures. Between 1976 and 1990, Green Mountain structures (300 in all) sprang up as far south as the Carolinas and as far west as Kansas.
After the patent on his solar slab foundation expired in 1990, Kachadorian focused on his book. “I wrote it so anyone could use my solar slab idea to help harvest the sun’s free energy,” he says. “I hope it might play some small role in transforming the nation’s appalling energy policy. Our foreign policy has been dictated by oil for far too long. Today, Iraq has the second largest oil reserves in the world, which is, of course, why we are at war there. The irony is that we have the technology to turn this situation around. We could do it if we took half the money we’re spending on the Iraq war and invested it in energy efficiency.”
This ex-Army officer, who served in Germany from 1962 to 1965, was not always so passionate about energy efficiency. In fact, he was making a handsome living in the early 1970s as general manager of a New Hampshire–based home construction business. “We sold Post and Beam luxury homes— expensive playhouses,” he says of the energy-hungry constructs. “I shared the industry opinion that home producers were not responsible for heating system design. Our homes had single-glazed windows and patio doors. R-13 wall and R-20 roof insulation was considered more than adequate.” [Today’s standard homes have R-20 wall and R-32 roof insulation.]
“Like most other people, I didn’t get serious about renewables and energy efficiency until the oil crisis hit,” he says, referring to October 1973, when OPEC jacked crude prices by 70 percent to punish the United States for its pro-Israeli stance in the Six-Day War. Then came the oil embargo, when the price per barrel reached $27 in New York City; it had been under $3 the previous summer.
“When I reflected on how Americans were living—the 70-mile-per-hour speed limits, the inefficient cars and homes—it was obvious to me that as a country we had forgotten the basics of good energy management,” he says. “I felt I needed to do something about it. I no longer wanted to sell big energy-guzzling houses to rich people.”
Air grilles located in the first riser of the stairway discharge warm air collected at the second floor ceiling.
It can’t be done. Or can it?
Kachadorian had long been interested in solar energy. He studied it on his own in 1974, growing excited about the prospect of designing a simple, affordable, passive solar house. But as excited as he was about Green Mountain Homes, he found his unconventional ideas were not embraced by the heating design community.
“When they heard that heat was to be stored in the home’s foundation at a temperature no greater than comfortable room temperature, they told me, ‘This can’t be done. Remember Newton’s Law of Heat Transfer: heat only moves from hot to cold.’ They thought my design would suck heat out of the living space.”
But his passive solar home does work, and he proved that from the start with a model in Royalton, Vermont. A team from the Thayer School of Engineering at Dartmouth College independently monitored the prototype’s energy use, concluding that “the purchased energy requirements were quite low and the percent solar is well above 40.”
If there’s a watchword for Kachadorian’s passive solar design, it’s to keep it simple. Used well, standard building materials—concrete, windows, patio doors—become the literal building blocks of the naturally heated home.
The solar slab is the basement-less foundation for the house and employs the same kind of concrete blocks that are used to build foundation walls in many new homes. But Kachadorian lays them on their sides with the holes lining up horizontally, forming air passages running north to south. When concrete is poured over these blocks, it bonds to them, making a huge concrete “radiator.” Vents are built into the slab to allow air to circulate through the home.
Kachadorian’s understanding of traditional radiators inspired the solar slab design. The ample surface area of baseboard radiator fins allows the hot water inside to transfer its heat to the air. Similarly, air circulates through the solar slab’s “fins” (the concrete blocks) whenever the sun shines. As heat is transferred into the home by the south glass or by heat transfer through the wall, air alongside the south wall rises. Warmed air is pulled out of the ventilated slab into the home, and cooler air along the north wall drops into holes along that wall. This thermo-siphoning continuously pulls air through the solar slab.
An efficiently constructed solar house works in concert with the solar slab. Good insulation, tight seals, proper ventilation, and enough windows—but not too many—all work together to make the solar system hum.
Inside the house, sunlight passes through the glass in the form of short-wave energy. As it strikes interior objects, the light is trapped as long-wave energy, or heat. This is why Kachadorian warns against excessive glazing; too many windows would overheat the house on sunny days. The energy absorbed through windows and patio doors is either consumed by the heat demand of the home, or absorbed by the solar slab.
At night, thermo-shutters on the largest windows keep the heat in, allowing the house to remain warm as the solar slab surrenders its stored heat into the cooler living space. The shutters’ interior insulation—one inch of foil-faced urethane—reflects heat back into the room. Stops allow the shutters to fit tight, eliminating reverse thermo-siphoning at night.
An efficiently constructed solar house works in concert with the solar slab. Good insulation, tight seals, proper ventilation, and enough windows— but not too many—all work together to make the solar system hum.
A brighter future
Kachadorian’s book contains detailed instructions on how to orient the house on the site, determine the optimal square footage of glass, calculate the proper size and depth of the solar slab, and figure the optimal size for the backup heat source. The second edition, due out later this year, will include a CD of his Solar Prediction Program, which automatically fills out the worksheets that form the basis of each home’s design.
Will his book change the way the nation’s homes are built? “Well, it certainly can’t hurt,” Kachadorian muses. “Our oil binge will have to end because the price will keep going up. We can’t drill our way out of this mess,” he adds, referring to Congress’ recent vote to consider oil exploration in Alaska’s National Wildlife Refuge. Rather than open up more land for drilling, he suggests a 100 percent tax on every barrel of imported oil, “to be devoted to developing alternative energy sources. If we did this, we would see an instantaneous boom in alternative energy.”
While he’s been discussing his ideas on this cool spring morning, Kachadorian’s 25-year-old passive solar home has remained at a steady 70 degrees—even with the sun now shining brightly.
Gazing at the glistening snow in his backyard, the civil engineer makes another prediction. “I saw what happened in the ’70s; people got scared, and we started making our homes more energy efficient. When fuel costs so much that we can no longer afford it, we won’t be able to ignore this mounting problem. We’ll wake up.”firstname.lastname@example.org
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Last modified: Aug 25, 2005, 13:40 EDT