green building blocks
Whether you prefer making mud bricks by hand or consider yourself
a modern mason, there is an eco-friendly option for you.
By Jane Mahoney
Ask any New Mexican about residing in an adobe house and watch him get dewy-eyed—even if he has never actually lived in one. Adobe, that simple mix of dirt and water, is the quintessential Southwestern abode—warm in the winter, cool in the summer—a welcoming shelter of thick plastered walls.
“Adobe has a mythical feel about it,” says builder David Peterson of David C. Peterson Construction, who has worked with the medium for a quarter-century. “You can feel the very mass.”
The old New Mexican standby, which, unfortunately, has evolved from the building material of the masses to that of the affluent, has some stiff competition these days among builders looking at alternatives to wood frame construction. Concrete-filled panels, foam-like building blocks that stack like Legos, and straw bales have made significant inroads among the various masonry systems used in the construction of exterior walls today. Concrete block is a contender, too, particularly in commercial applications.
Some builders pay the new products what they regard as the ultimate compliment when they say, for example, that an E-Crete home “feels” just like its well-built adobe counterpart. Some claim it’s superior.
“Looking back through the history of architecture, the buildings that last and shape culture and tradition are masonry structures,” says Kent Beierle, a co-owner and designer with Environmental Dynamics, Inc., an Albuquerque firm specializing in sustainable design. “It is one of the oldest building mediums and remains one of the most common and permanent approaches to construction.”
Green building proponents, in particular, can find a wide selection of masonry materials and systems that tout the use of recycled waste products, emit no toxic chemicals, provide superior insulation and thermal mass, and are bug-proof and nonflammable to boot.
While the U.S. Green Building Council loosely defines green or sustainable building as the practice of creating healthier and more resource-efficient models of construction, personal interpretations of that goal by builders, architects, and homeowners vary greatly. Are you more interested in saving fossil fuels or timber? How important is water conservation? Are you determined to utilize recycled or waste materials? Is your top priority to avoid materials that may emit harmful chemicals?
Then, there’s that whole sticky wicket of “embodied” energy, the sum total of energy expenditures along a material’s life. This is all the energy required to extract, manufacture, and transport a building’s materials, as well as that required to assemble, finish, and maintain it.
In the end, the selection of the “green” building block material used in the construction of a home comes down to the owner’s personal choices, admittedly based on emotion as often as facts. There are ardent advocates for each system. A straw bale enthusiast may overlook the non-green aspects of the post and beam superstructure required by the state of New Mexico. Another builder won’t flinch at the large amounts of costly steel and concrete poured into an insulated concrete form (ICF) structure. They like the way materials go together. They’re happy with the feel of the final product.
“I am fond of telling clients that there is no Holy Grail building material,” says Beierle. “No one product will meet all your expectations.”
To help consumers make choices, Beierle tells his clients to develop a list of their priorities then helps them to evaluate the options. Consider not only the cost and composition of the product, but also its durability, thermal properties, availability, toxicity, sound control, flammability, and the possibility of recycling the unused products. Is the material compatible with the design of the house? Can it be used to create the curves and arches of your dream home? Is the material suitable for the environment where it will be built?
That said, Su Casa takes a look at some of the most popular masonry systems available in the Southwest today—new products as well as adobe, that old favorite.
Insulated concrete form (ICF)
ICFs are hollow blocks or panels generally made of insulating foam that are stacked into the shape of a building’s walls. This simple lightweight, modular formwork remains part of the structure even after the hollow portions are filled with steel rebar and concrete. The sandwiching of a heavy, high-strength material (reinforced concrete) between two layers of a light, high-insulation material (recycled foam) creates a sculptable wall with superior R-values and mass, good sound control, and strength. Units are factory-molded with interlocking edges that allow them to fit together like children’s blocks.
The biggest drawback, according to Beierle, is that the ICF systems rely on large amounts of concrete and steel, both high embodied energy and costly materials.
The rising price of lumber, however, leveled the playing field for Placitas builder Eric Merryman, owner of ENM Homes, who is now embarking on his second ICF home constructed of Perform Wall Panels System, a product manufactured in Juarez, Mexico. With his family, he lives in the first home.
“Phenomenal” is his one-word description of life in an ICF home, where the solid walls provide warmth and block the noise and impact of howling canyon winds.
“It’s an earthy, grounded house,” Merryman says. “You can just tell this house is here to stay. It’s like walking into an old church with big, thick walls. This house feels like it’s been here for centuries.”
As a builder, Merryman marveled at exterior walls that went up in two days. As an artist, he reveled in being able to take a rasp and sculpt rounded corners and bullnose finishes into the foamy panels and add stone ledges as one-of-a-kind awnings. As a conservationist, he chose the product because it is made of recycled polystyrenes or plastics that are ubiquitous in our culture and nonbiodegradable.
Common ICF brand names are RASTRA, Reward Wall, Perform Wall, PolySteel, and Amvic, and you can visit the Insulating Concrete Form Association at forms.org for information.
Autoclaved aerated concrete (AAC)
Autoclaved aerated concrete is a manufactured building block made of all-natural raw materials. Developed in 1914 (and used in residential and commercial buildings for decades in Europe and Asia), AAC is made of Portland cement mixed with lime, sand, recycled fly ash, water, and aluminum powder or paste poured into a mold. The reaction between aluminum and concrete causes microscopic hydrogen bubbles to form, expanding the concrete to about five times its original volume. The aerated concrete is cut to size and steam-cured in a pressurized chamber known as an autoclave. The resulting block is lightweight, nontoxic, noncombustible, and provides an excellent sound barrier. It’s available in varying thicknesses and spans, easily stacked with Thin-set mortar, and uses little concrete and steel compared to ICFs.
AAC is a sculptable wall system ready for plaster or stucco without preparation. According to Beierle, an eight-inch thick wall is approximately equivalent to an insulated 2x6 frame wall’s R-value. One drawback, says the designer, is that the material is not recommended for below-ground construction unless the blocks are first waterproofed.
“This product is better than adobe,” says Santa Fe’s William Szczech, a distributor for E-Crete and owner of Life-Style Homes. “It gives you a solid wall that’s already insulated. It gives you thickness and breathability. You can sculpt and carve it. It’s absolutely the most fireproof material you can build with. Insects can’t live in it, and it’s very soundproof. It’s a green product—an Energy Star rated product. Lots of products have Styrofoam or petro-based products in them. E-Crete has none.”
While both AAC and ICFs are more expensive than wood-framed houses of 2x6 construction (estimates vary from “slightly” higher to nearly double the cost of building walls), builders gain savings in eliminating the labor and product costs associated with installing insulation. AAC and a few of the ICFs generally require no prepping for plaster or stucco. The future energy savings are also more substantial. While some builders might be unfamiliar with the building process, both AAC and ICF systems can be readily mastered with far less skill, for example, than that needed to lay traditional clay brick.
Common AAC brand names are E-Crete (made in Casa Grande, Arizona), FlexCrete, and Aercon. Visit the Autoclaved Aerated Concrete Products Association at aacpa.org for information.
To form straw bales for construction, the straw from wheat is baled then stacked as blocks. Stucco is applied as a finishing material.
What’s not to like about straw bale houses? This natural and nontoxic product, after all, is an inexpensive agricultural byproduct with good availability. It’s also a good insulator.
The trouble is, says Beierle, the straw bales are considered insulating infill. Because the state of New Mexico does not allow load-bearing straw bale walls, a timber post and beam superstructure must be constructed, as well. Other possible drawbacks are that the thick walls require a larger footprint, and the flammable bales can only be used aboveground. The walls can be susceptible to moisture deterioration, as well as insect or rodent infestation. Still, straw bale has its enthusiastic advocates who consider the product as the most affordable and natural choice in sustainable masonry systems.
“We’ve done several straw bale homes, and they’re wonderful,” concedes Beierle. “It does have its place.”
He advises straw bale builders—many of them do-it-yourself homeowners—to make sure that the bales remain thoroughly dry in all stages of transportation, storage, and construction. The site itself should be well-drained. Pay special attention to the detailing near grade and around penetrations. A concrete block stem wall, for example, can prevent the rodent problems. Well-sealed penetrations for electrical outlets can deter insects.
“If it’s done carefully, straw bale is a fine way to go,” Beierle says.
These sun-dried bricks are composed of sand, clay, and occasionally straw and gravel. Stabilized blocks also contain asphalt emulsion.
“I can take a pile of dirt, water, a hoe, and a wheelbarrow and build a house. That’s pretty green,” says adobe advocate David Peterson.
Adobe construction is a dying art, Peterson laments, a victim of Southwestern architectural styles that have morphed into gargantuan Tuscan-style McMansions.
Adobe homes offer thermal mass and the ability to absorb cool night air or daytime sunlight and smooth out large swings in a home’s interior temperature. What adobe walls don’t offer, however, are high insulation values. It’s why some adobe builders such as Peterson choose to add a layer of rigid insulation to the exterior of an adobe wall prior to applying stucco, and why builder Eric Merryman uses adobe in interior spaces (rather than exterior walls) to function as a storage wall for direct gain sunlight.
In an ironic twist, handmade adobe is inexpensive, but purchased adobes are quite the opposite. It’s time-consuming to make adobes and to lay them. Smaller than ICF and AAC blocks, adobe construction is a slow process, but a forgiving one as mud can be used to level out the courses. “It’s expensive and slow, and there’s no way around that,” says Peterson. “But the thrill I felt driving up to an adobe home I was building 25 years ago, well, I still feel that.”
Adobe works well as a structural bearing wall. It’s noncombustible, offers good sound control, and the nonstabilized blocks are nontoxic, according to Beierle. On the other hand, adobe can be susceptible to moisture degradation, and it’s often less durable than other masonry options.
Throughout the world, the remains of our ancestors’ structures are of stone and clay, monuments to the lasting power of masonry. In the end, the crumbling buildings are among the few physical remnants a culture leaves behind.
“Build smart, and build to last,” advises Beierle. “Build something that expresses who you are and leaves something of value for future generations. Nobody wants to live in an ugly or stupid house that slowly makes them ill while costing them money.”
Freelance writer Jane Mahoney resides in a fixer-upper in Albuquerque’s South Valley and frequently writes about home builders and real estate issues for the Albuquerque Journal.