Magazine article Sunset

Building Tomorrow's Home: Energy Efficiency Is the Driving Force Behind Six New Construction Techniques

Magazine article Sunset

Building Tomorrow's Home: Energy Efficiency Is the Driving Force Behind Six New Construction Techniques

Article excerpt

Greener pastures are on the horizon for residential construction now that homeowners, architects, and builders can choose environmentally friendly ways to build or remodel. Standard-dimension softwood lumber (2-by-4s and 2-by-6s) used in conventionally framed houses is being challenged by a new generation of alternative building materials: 10-foot-long modules of polystyrene and cement; straw bales; broad panels that sandwich thick layers of insulation between sheets of a plywood-like engineered wood product; solid walls made from a sprayed mixture of earth and cement; lightweight, hollow foam blocks; and steel studs.

These new materials perform best along the exterior walls of houses, but that's also where they must battle for acceptance. To prove themselves, they must be economically competitive with traditional "stick-building" techniques. At present they are slightly more expensive on initial construction costs, although the rising cost of lumber and increased familiarity with the new building processes have narrowed the gap. Lower long-term energy costs, speed of construction, aesthetics, and the satisfaction of using "green" products are where these materials really shine.

We followed the construction of six Western houses that each used one or more of these new building systems. They show that environmentally friendly architecture can appear in many guises, from thick, plastered walls to vinyl siding.

Rastra

It's called rastra: a precast forming system using long modules made of recycled polystyrene and cement that contain cavities for rebar and concrete. Despite their massive appearance, the 10-inch-thick, 15-inch-tall, 10-foot-long blocks weigh only about 150 pounds and can be glued together horizontally or vertically. The polystyrene and air gaps in the block add insulative properties and, when sealed, give a 10-inch-thick wall an R-value of 36, more than twice that of traditionally framed walls.

This system forms the curving walls of Phyllis Hunt's home in Napa, California (above). The interior feels like a giant kiva; the house blends Southwestern and Native American architecture with passive solar design. It notches into the slope and orients the two-story main room toward the south. In winter months, low-angled sunlight stores its energy in the mass of the colorful concrete floor and the thick plaster coating the Rastra. In summer, the overhanging roof and trellises shade the interior.

ARCHITECT: Craig Henritzy, Berkeley (510/526-8602)

RASTRA: Environmental Building Technologies, Santa Barbara (805/6842060); supplied by InteGrid Building Systems, Berkeley (510/845-1100)

BUILDER: Cloutman Construction, Kenwood, CA (707/833-2812)

Straw bales

Sunset first reported on straw-bale building in April 1995, and since then the technique has become increasingly popular, with good reason. No other manufactured block or panel can compete with this natural, annually renewable resource when it comes to low cost and high energy efficiency. (The typical straw bale measures about 23 by 15 by 40 to 50 inches and costs about $3.50 delivered to the site.) Although many homes have been built with straw bales providing the structural framework, the most common practice is to build a load-bearing post-and-beam system out of wood, then insert the bales between the posts, using them as insulation and wall surfaces. When sealed with plaster or stucco,a 2-foot-thick straw-bale wall has an R-value of almost 50!

Straw bales are also fast and easy to build with; they're earthquake, termite, and fire resistant; and they add an attractive massiveness to walls. The house shown at left started with a frame of recycled redwood trusses that rest on posts made of vertical wood I-beams the width of a straw bale. The house uses bales for most of its walls, but includes a wood-framed section for the bathroom. "Out of practicality, I don't believe in running plumbing in straw bales," says architect David Arkin. …

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