Passive-Solar Gem Wins Green Award

The New Mexican

Santa Fe architect Mark Chalom and builder John DiJanni won the Su Casa magazine/Build Green New Mexico Award for Green Home of the Year and a Gold certification from Build Green New Mexico.

But according to Richard Bechtold, the owner of the award-winning house in the Eldorado area, they “just squeaked by” on the rating for the award.

Chalom, who worked closely with Bechtold and DiJanni on the design and construction of the home, said the rating systems used by Build Green New Mexico and the national LEED (Leadership in Energy and Environmental Design) certification apparently don’t acknowledge the energy benefits of passive-solar design. The Bechtold house was designed to take full advantage of the sun with solar panels to heat water, and south-facing glass and trombe walls to heat the home.

A trombe wall is a specially designed and built structure that essentially “pumps” warmth into the house on winter nights. It is a thick wall of concrete or adobe – “thermal mass” – with a dark surface facing the sun and with an air space and glazing on the outside. During the day, the thermal mass slowly absorbs solar warmth, while the air space helps prevent its loss back through the glass, then the warmth is slowly released into the room at night.

In a similar but less efficient manner, south-facing windows maximize wintertime solar gain, the warmth absorbed by the thermal mass in concrete or brick floors. In the Bechtold house, this solar gain is accentuated by the fact that Chalom designed the interior walls to be constructed of heat-absorbing adobe.

Traditionally, the surface of a trombe wall facing the outside of the house has been painted black – and DiJanni even had good results in the past simply finishing it with the darkest stucco he could find. On the Bechtold project, Chalom increased the efficiency of the trombe walls by applying a selective-surface film on the thermal mass.

“We’ve done trombe walls with adobe, which is 6,000 years old, and selective-surface film, which is space-age,” Chalom said during a December visit to the house. “The film absorbs 95 percent of light that hits it, and only gives up 6 or 7 percent back out.”

The bottom line on all of these strategies was to cut down energy consumption for heating in the wintertime. Bechtold said the team’s main objective was energy-efficiency.

Chalom has long experience with energy-efficient design. “I used to work with William Lumpkins, who designed his first solar adobe home back in 1935,” he said. “I lived in a geodesic dome when I came here in the 1970s. I’m a Bucky (the visionary architect and inventor Buckminster Fuller) freak. Always have been. I met him a number of times. I even understand his books. I’d spend months trying to figure out three pages.”

And what’s the impact of that passion for Fuller’s principles and designs?

“Well,” Chalom said, “I’m not afraid of technology.”

DiJanni has used trombe walls for more than 20 years. “You tried to use patio-door glass, the standard size, so in my home we had a couple of trombe walls that were about three feet wide and seven or eight feet tall. I used
12-inch, concrete-filled concrete block behind those panels and those worked incredibly well.”

DiJanni has been in business for more than three decades in the Santa Fe area. “My company (Custom Homes by John DiJanni) has always gone for south-side solar gain and we’ve always built very tight homes with extra insulation, but the Bechtol house has just taken the whole concept to the nth degree,” he said.

Asked if building “green” or sustainably has long been a priority, he said, “When we first got into it, building solar homes in the late 1970s, it wasn’t labeled green. I do hope this trend continues. It seems like with the new administration coming in, there will be a big emphasis on green building.”

The builder lamented that the incentives for owners to do passive-solar design waned after the 1970s. “At the time, there were very favorable state and federal tax credits and once those expired and energy was cheap, the public moved toward bigger homes and more amenities.”

In written materials about the Bechtold project, Chalom notes that the desire was for a house that relied primarily on the sun to provide lighting and the majority of the heating load. The orientation was chosen to maximize passive-solar heating in winter and to take advantage of the natural prevailing wind direction to provide cooling and ventilation.

“We bought the lot in 1997, but we had talked to Mark before that,” Bechtold said. They looked at the advantages of walls made from insulating concrete forms such as Rastra, as well as adobe and adobe/frame. They decided on the latter, using adobe to provide thermal mass inside the house and wood-frame exterior walls insulated both with continuous rigid foam and blown-in icynene.

Electricity and gas are saved through the use of solar panels to heat water for the house. Small photovoltaic panels drive the pump for the heat-transfer solution in the solar hot-water panels.

Water conservation was another imperative for Bechtold, Chalom and DiJanni. All rainwater from the roof is directed to a buried, 10,000-gallon cistern; this is primarily used to flush the toilets. Landscaping plants are watered with household wastewater treated with aerobic-digester technology.

The use of local adobes and locally built cabinets and doors aided the Santa Fe economy and cut material-transportation costs.

Regarding the sustainable-home certifications, the Build Green and LEED rating systems seem to be based on the dominant, American paradigm: frame houses with forced-air heating. Chalom is assembling hard evidence of the efficacy of passive-solar heating.

Bechtold said he last filled his 500-gallon propane tank on Jan. 10, 2007. He was planning on filling it again this Jan. 10 so they could compare energy use for an entire year to the Build Green standard.

The Bechtold house is tremendously heat-efficient in the winter. During a visit on Dec. 11, the owner said the heat didn’t come on the previous night, with a low temperature in the 20s. But however well the trombe walls and other passive-solar features work, they don’t figure into the LEED or Build Green New Mexico rating systems.

“We got into a big fight over the trombe walls with the rater,” Chalom said. “He put them in as windows, because there’s no way to enter them as trombe walls. Also, the system is not doing anything about energy coming in. They’re not looking at the advantage of heat gain in the winter; they only look at the cool escaping out of the windows in the summer, and they’re assuming you have air conditioners.”

“I think Build Green is mostly looking at a mass market where there are certain things you can do to make a standard home energy-efficient, and using green materials, but I totally agree with Mark,” DiJanni said.

“In the Bechtold case, saving money was not the primary focus. The couple (Richard and Susan Bechtold) put out a fair amount extra over a normal home that would have served their purposes the same in terms of floor plan and amenities, just because they felt it’s the right thing to do. Unfortunately that’s pretty rare.

“It’s kind of like recycling,” DiJanni said. “You go to a lot of effort sorting things and you’re not getting anything back, just the satisfaction that you’re doing the right thing.”