By Alicia Kellogg
This article first appeared in Spring 2008 Su Casa
- Larry Gorman of Building Energy Solutions conducts a blower door test at a One Earth Design house built to the Passive House energy standard. Photograph by Joaquin Karcher
- This compact, super-insulated, airtight home exhibits typical characteristics of a Southwestern Passive House. Designed by One Earth Design in Taos, the home has passive solar orientation and adobe thermal mass at the interior walls. Photograph by Joaquin Karcher
- This home in Arroyo Hondo, New Mexico, features a “frost-protected shallow foundation” with a thickened edge slab that is seamlessly wrapped in insulation to eliminate cold bridges to the ground. The home, designed by One Earth Design, also is built to the Passive House standard. Photograph by Joaquin Karcher
Conservation strategies: WATER
A critical issue in the arid Southwest, water conservation has significant potential for savings. A properly installed gray water system uses water twice—potable water for drinking and showering is reused for landscaping, says Steve Hale of Hale and Sun Construction. Roof-water harvesting systems catch rainwater with gutters and a downspout. The collected water is stored in underground tanks and pumped back to the house to flush toilets, water the garden, or wash the car, explains Joaquin Karcher of One Earth Design. Designing roof slopes that concentrate runoff to one area, where water can be directed to plantings or captured in a cistern, is a conservation method that builder Ed Paschich of Ed Paschich Homes employs.
Collection techniques aside, in terms of water conservation, Paschich suggests thinking beyond the lawn to xeriscaping, or using regionally appropriate plants. Having grass all over your property is nice, but it doesn’t fit anymore, Hale explains. The new mindset includes choosing small lawns rather than an expanse of grass and porous ground cover rather than surfaces that contribute to runoff problems.
Design that makes a difference: PASSIVE SOLAR
Passive solar home design remains an important element of green building, particularly in the Southwest. Rotating a house can make it 20 percent more efficient by orientation alone, says Ed Paschich of Ed Paschich Homes in Albuquerque.
“The big idea is that the sun provides far more energy than we need to keep our houses warm,” says architect Bruce Warren Davis. The questions are how to catch the energy when you need it for warmth and how to avoid it when you don’t—essentially, how to obtain energy when you want it. Retaining this heat involves insulation and the thermal storage necessary to keep the heat longer term.
Davis advocates simple solutions: passive solar heating, daylighting, and natural cooling, which he says provide a good return on the money invested and are good for the environment. These techniques require awareness of the environment and involve considerations such as how the location and orientation to the sun influence aspects such as window placement.
Mass, or sheer weight, is one of the most significant issues in natural heating and cooling, Davis says. “In the Southwest, climate is frequently extreme, but we also have the great resource of massive materials.” Masonry walls composed of materials like adobe, brick, stone, or concrete—including autoclaved aerated concrete (AAC) or Rastra—work with the passive solar heating aspect of a home’s design. If these materials do not have their own insulating qualities, Davis insulates them.
Quentin Wilson, who teaches adobe construction at Northern New Mexico College and is president of the board of directors for the Adobe Association of the Southwest, calls adobe “the world’s best storage material for passive solar heat.” Heat can be collected through measures like glass on the south side of an adobe house elongated east and west. The heat is stored in the adobe and distributed by the walls.
Careful design comes into play. Your land might have an incredible view to the west, but a full west wall of windows does not make sense if you want to be serious about sustainability, Davis says. He recommends thoughtfully and judiciously admitting sun into your home, understanding that this involves more than obvious considerations such as the view. Natural lighting strategies include skylights and windows that are carefully placed and have some kind of adjustable covering, while strategies for controlling the sun include awnings or deciduous trees or vines to shade the house in summer and admit sun in the winter.
Architectural designer Joaquin Karcher of One Earth Design takes a different approach with the Passive House standard, which was developed in Germany, practiced in Europe, and now is being introduced to the United States through the Passive House Institute U.S. A Passive House uses 80 percent less energy to heat than a standard home by creating a super-insulated, airtight structure that minimizes heat loss and then maximizes free gains through passive solar, according to Karcher, who has researched Passive House design for the Southwestern climate and notes that he is the only Passive House designer in New Mexico.
“The building achieves deep energy savings through the envelope alone,” Karcher says. The home has triple-glazed windows with Styrofoam-insulated frames, is appropriately oriented, and has the proper ratio of south-facing glass to its footprint. A Passive House is tested with specific energy-modeling software and results in a home heated by the amount of energy supplied by a hair dryer. (Passive Houses are heated with a small heating element tied to the ventilation system called a heat recovery ventilation system, or HRV.) According to Karcher, a Passive House costs 5 to 10 percent more to build—which is recovered by utility savings—and a small photovoltaic system can help make up for the home’s already-low energy consumption, working toward carbon neutrality.
Natural adobe, made with a mixture of clay and sand, requires little energy to produce, little energy to build with, and at the end of the building’s life returns to dirt. “I would say that adobe is the standard by which anything else is measured,” says Quentin Wilson, adobe construction instructor at Northern New Mexico College in El Rito, New Mexico, which he describes as the country’s only full-time adobe program. “Very little energy is required to create adobe.”
Making natural adobe bricks by hand requires human energy and the evaporation of water, which usually occurs by sunlight. “The total energy burden can be all human and solar,” Wilson says.
Variants are adobes whose production involves machines to make the mixture, lay the bricks, or transport them, though even then, adobe still has less embodied energy than materials like concrete, Wilson says. However, due to the material’s weight, he discourages transporting adobe bricks long distances.“Hauling adobes more than 50 miles is a crime against the planet,” Wilson says. With several major adobe-producing facilities plus small-production suppliers, he says a person living in New Mexico should be able to purchase adobe bricks from a producer nearby. Making bricks on-site is another option, and taking a class or reading a book such as Adobe: Build It Yourself are good places to start, Wilson adds.
Another variant is adding asphalt to the natural adobe formula to produce a more waterproof, “stabilized” adobe brick. Joaquin Karcher, who co-authored the International Building Code for Adobe, Compressed Earth Block, and Rammed Earth, notes that asphalt-stabilized adobes involve an off-gassing petrochemical, which is why he prefers unstabilized adobe or compressed earth blocks. “Green adobe is an unstabilized adobe,” he says.
Modern foundations and insulation add complexity to the mix. In itself, adobe is difficult to beat, says Bruce Davis of Bruce Warren Davis Architect, but flawed when you compare the entire system to others available today. Ed Paschich, an experienced adobe builder, says although adobe walls are airtight and have thermal mass, the mass requires insulation, which he adds to the outside of the structure. When you add up the time, cost, and energy to build a well-insulated adobe home, he has found that the process is counterproductive when compared to super-insulated frame construction.
Building a properly insulated adobe is more expensive, Karcher agrees. He uses a double-wall adobe system with cellulose insulation between the walls and a new concrete foundation system with high insulation values under the footing and the slab, blanketing the whole house with insulation. Karcher believes that you get more bang for your buck with advanced framing techniques and super-insulated frame walls, which he says far surpass the performance of a single insulated adobe wall.
Even as technology presents new alternatives to traditional methods, adobe advocates continue to spread the word about the most natural building product. If you’re going to work with a professional builder for an adobe home, Wilson advises shopping around until you find someone who shares your building philosophy.
For Wilson, it’s all about using what you have where you are. “If you think about what defines New Mexico architecturally, it’s adobe,” he says.
Green-building tradeoffs: WALL SYSTEMS
Today’s wall systems offer many choices, with varying price tags, benefits, and green tradeoffs. Beyond the standard frame house, advanced framing techniques use less wood and increase the structure’s effectiveness and insulation abilities. Joaquin Karcher of One Earth Design considers frame construction with cellulose insulation made with recycled newsprint the most realistic and cost-effective construction method. “To me, that type of super-insulated envelope is just as green as adobe or strawbale,” he says. “I put them on the same level.”
Frame construction aside, you’ll find a myriad of options distinguished by their quietness, insulating properties, or ease of use—from insulated concrete forms (ICFs) and autoclaved aerated concrete (AAC) to strawbale and adobe.
Green-building decisions are rarely black and white, and products involve various levels of embodied energy for different reasons. “In the right context, strawbale is hard to beat,” says architect Bruce Davis, warning that he has, however, heard of people shipping in straw from miles away—not a green solution because of the embodied energy and pollution involved in transport. He considers rammed earth a good choice in locations such as southern Arizona.
“Different solutions can be most green in different circumstances,” Davis says.
“I believe photovoltaics are the best and most viable way to move us to energy independence in this country,” says builder Ed Paschich, noting that he thinks tax credits are the key to advancing their use. Dollars per watt, photovoltaics are getting closer to the price of regular electricity, he observes. And within the next five years, he believes that the price will be even with or below the cost of grid electricity, which should increase photovoltaics’ use tremendously.
Meanwhile, solar thermal is recommended for domestic hot water and has a three- to five-year payback time, according to Michael Cecchini of Mesa Realty and Kayeman Custom Homes. Solar thermal requires homeowner interaction and maintenance, Paschich adds. He finds photovoltaic systems that are grid tied without batteries to be easier to use—with no interaction from the homeowner required—easier to acquire, and, depending on their size, cheaper than solar thermal systems.
Solar photovoltaics are on the rise, Cecchini says. If you are considering a system for your new home, remember that it should be properly sized to provide a sensible amount of electricity for your home’s size and needs. You will need a site assessment of your home’s electrical panel—upgrades might be required, Cecchini adds. If you are interested in solar options, you can ask an informed home builder and get started with your own research on solar basics and topics such as tax incentives.
Likewise, if you are interested in other alternative energy sources, such as geothermal, which can involve pumping heat from the ground into the house via underground pipes, or wind energy, which might be available for purchase through your local utility company, work with a knowledgeable builder who can help you sort out the options and their viability for your location.