Green Framing Offers More Sustainable Homes
For those who want a custom home made with more sustainable materials, the choices are rather diverse – many more than the straw, wood and brick of Three Little Pigs fame.
Most of us live in traditionally constructed houses and buildings, but we’ve all heard about the unique homes made out of recycled glass bottles, old tires and all manner of repurposed materials. When architect Wally Geer, owner of Greymar Associates of Ventura, Calif., talks about green framing options, however, he’s thinking more mainstream than experimental.
Geer outlined some proven alternative construction materials and why you might want to consider using them at a workshop at the California Center for Sustainable Energy in San Diego, Calif. The reasons could be as simple as site or construction staging constraints or as complex as environmental and health concerns. No matter the reason, green framing typically results in greater energy efficiency, a longer lasting structure and, if done correctly, higher life cycle and resale values.
One of Geer’s mantras for green framing is “spend now and save later,” giving a nod to the fact that construction will cost more but holding out that savings can make up the difference within a few years with benefits such as lower heating and cooling costs and reduced insurance rates. He says one of the worst reasons for choosing a green framing system is “because your flaky unlicensed brother-in-law claims he is knowledgeable about alternative building.”
Geer discussed the positive and negative attributes for wood, steel, structurally insulated panels and insulated concrete forms and touched on timber, straw bale and rammed earth. Along the way, he emphasized that no matter your choice, “think of the end result – the comfort of your home – not just the structure.”
In Defense of Wood
With an abundant supply and plenty of experienced contractors to choose among, conventional wood framing offers cost-effective and flexible home design options. A step up is selecting lumber with FSC (Forest Stewardship Council) certification, ensuring it was grown in an environmentally responsible, socially beneficial and economically viable way. Wood’s drawbacks are well-known, ranging from termites, rot and mold to low fire resistance, aging and inconsistent quality. You can get pest resistant treated wood, but the chemicals can be a health problem for sensitive people. With wood framing, it’s difficult to get any added, long-term benefits.
Bugs Don’t Eat Steel
Steel house framing is gaining popularity in the U.S. largely because it eliminates the possibility of termite damage, a serious problem nationwide, but particularly worse in warmer climates across the southern states and Hawaii. Stronger and longer-lasting than wood, steel stands up well to windstorms and earthquakes and can’t catch fire, all of which lower homeowner insurance rates.
Steel framing comes in two basic types: light gauge and red iron. Light gauge (or galvanized) steel, not to be confused with steel wall studs, is a thinner and more flexible version of the heavy steel used to build skyscrapers, bridges and ships. It is recyclable and available with a high percentage of recycled material. Red iron framing uses heavy gauge steel I-beams on wider centers and often comes in pre-welded kits, with holes in place and each member numbered for quick, bolt together assembly. Sometimes red iron framing is used just for weight-bearing structural purposes and then mixed with wood, light gauge steel or other materials.
Unlike wood, steel costs somewhat more and has some design constraints, Geer explained. The biggest difficulty is that it requires architects and construction teams familiar with steel construction as well as knowledgeable mechanical, plumbing and electrical subcontractors. Another problem is that steel is an excellent conductor of heat, so steps must be taken to isolate it with construction techniques and extra insulation.
Building with Sandwiches
Looking much like big ice cream sandwiches, structurally insulated panels (SIPs) are 4- to 6-inch-thick foam core sheets covered on both sides with laminated plywood, drywall sheets or other surface materials. SIPs can be assembled up to three times more quickly than wood framing and come in standard-sized sheets as well as factory prepared custom sizes that have precut doorways, windows and wiring outlets. Their high-insulating power means HVAC systems can be downsized and ductwork minimized. Adding to their green value is their durability and lack of job site waste.
Again, finding designers, contractors and subs who are familiar and comfortable with SIPs may be difficult; and there are potential building department issues because inspectors may not know about them. Conversely, SIP construction presents opportunities for home designers and builders to become the local specialists, Geer advised.
Pour It in Place
There’s no such thing as a completely fire-proof building, but insulated concrete forms (ICFs) offer about the best fire protection available to a homeowner. Similar to oversized Lego bricks, ICFs are lightweight foam blocks with hollow cores reinforced with steel or plastic bracing into which concrete is poured and left to cure. The foam remains on the concrete, and wiring and plumbing are installed in channels cut into the foam with interior and exterior materials added on top. The resulting walls provide super high insulation values, great soundproofing and unmatched protection from storms, earthquakes and fire.
Like SIPs, ICFs come with a somewhat higher price tag and the need for specialized designers and contractors. In combination with renewable energy generation and energy-efficient systems, ICF homes can quickly produce a positive payback in energy savings and provide a higher sales value, especially where wildfires are a concern.
Alternatives beyond Mainstream
If green framing means “back to nature” to you, then there are several methods that may be appealing, Geer said, including timbers, straw bale and rammed earth. Timber framed homes offer larger interior open spaces than conventional wooden frames because the load of the home sits on massive frame posts without the need for interior load-bearing walls. Most timber framed homes are factory prebuilt structural systems that are assembled onsite and offer unique natural wood looks.
Using straw and grasses to build homes goes back to prehistoric times, but with the advent of machine-made straw bales their use for home construction took off in the early 1900s, particularly in the northern American plains. The bales, commonly wheat, rye or oats, are typically stacked in rows, tied together and covered with stucco, plaster or a mix of earth and clay. The bales may be load-bearing or, more typically, a wooden frame supports the structure with the bales serving simply as terrific three-foot-thick insulation. It the walls are not sealed properly and water collects inside them, the bales will rot and require replacement, Geer warns.
Among the oldest building materials are rammed earth walls, which are made by pouring a mixture of sand, gravel and clay, often with a stabilizing substance, into a temporary framework that serves as a mold for the shape and size of each wall section. The mixture is compacted, or rammed, with a long pole, or more efficiently by powered tampers, to add strength. To help withstand weathering and earthquakes, wood or steel rebar can be used for reinforcement; however there are many still-standing ancient rammed earth structures around the world.
What Makes a Green Home?
The primary goals of green framing are to use environmentally friendly materials and to create less waste, resulting in a home that will use less energy, water and natural resources while providing healthier conditions for the people living inside. There is no one magic solution to green home design, Geer points out, but the key is to not stop with green framing – it’s only one component within a whole host of decisions that make up a high-performance, sustainable home.
photo: Arlington County.
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