Energy Source Builder

To Save Trees, Cut Wood

The forests of North America looked vast and inexhaustible to European settlers. Timber from these forests built towns, railroads and factories. What looked infinite then, looks limited now. To the modern population, forests are more than just wood mines, where a resource is extracted. Forest lands provide clean water, recreation and a wide assortment of consumer products for a fast-growing human population. Forests also help to keep the global climate in balance by processing excess carbon dioxide into oxygen. The relative importance of timber production is declining as these other forest values gain importance.

The U.S. uses twice as much wood as other industrial nations, according to the Wood Reduction Clearinghouse. It takes about one-and-a-half acres to grow the dimensional lumber for a typical American home. That doesn't count another 10,000 sq. ft. of panel products, such as plywood and oriented strand board (OSB). Wood use is projected to double over the next few decades. There's little hope that the forests can meet the increasing demands.

Some builders are looking for ways to relieve demand on forest lands and prepare for the inevitable limitation to wood supply by reducing the amount of wood used in construction. A report published by the Natural Resources Defense Council (NRDC) estimates that wood use in home construction can be reduced by 30 percent through reduction, recycling and material substitution. There are a many ways to cut wood use without compromising structural stability or building durability. Many of these ideas will also save you money.

The techniques mentioned here may require products or materials that you won't find at the local lumber yard. Because of space limitations, it's not possible to list sources of supply for all these products. However, suppliers are listed in a comprehensive database called the Oikos Product Directory. Words printed in italics can be used to search the directory. See the side bar for details.

Reduce Waste

Check your material take-offs for excessive waste factors. Plan on making better use of cutoffs and scraps. Then drill the idea into your crews.

Make it easy for the crew to use scraps by keeping it organized next to the stack of new lumber. That way carpenters don't have to search the entire site for suitable scrap.

 

Streamline Framing

wall framing

Advanced framing has been promoted for many years as an energy saving technique, but it started as a way to save money by reducing lumber use. Advanced framing, also called Optimum Value Engineering, eliminates framing elements that aren't structurally necessary. Develop house plans on a 2-foot module to maximize lumber and sheet materials. Locate windows and doors on this 2-foot module to reduce cripples and king studs. Space other studs 24-in. on-center instead of the standard 16-in. spacing for all one- and two-story designs. Eliminate headers in gable end walls, where there is no roof load and carefully size headers where they are needed. Gypsum board supports are metal clips, plastic flanges or blocks of scraps that provide backing for drywall. These supports replace the lumber used simply to hold up drywall. (Advanced framing was described in detail in the Dec. 1991 and Feb. 1992 issues.)

Plate-connected trusses have replaced stick framing for virtually all roofs. Now some builders are using open web wood trusses for floor framing. Not only do they use less wood, trusses also span greater distances, shrink less, resist floor squeaks and allow ducts to run through the floor cavity.

Engineered lumber, such as glue laminated beams, I-joists and finger jointed studs, also makes better use of wood fiber than dimensional lumber. These products offer all the advantages of plate-connected trusses, except the ability to enclose ducts. However, these products use large amounts of chemical adhesives, which may be cause for concern.

Substitute Materials

Builders have a greater range of choices for building materials than ever before. It's now possible to find non-wood substitutes for many common applications. Recycled plastic lumber is well-suited for outdoor furniture and decks. Linoleum, ceramic tile and stone can be used for flooring and countertops. Interior doors are made from pressed wood composite. Straw board, made from agricultural waste, substitutes for particleboard in carpet underlayment, cabinet carcasses and shelves. Most straw board uses adhesive that doesn't contain formaldehyde.

Use Reclaimed Wood

Giving wood a second life is now a growth industry in the U.S. Salvagers dredge logs from the bottoms of rivers and lakes. Others carefully deconstruct old barns, factories and schools. Large beams are re-milled into flooring or trim. The quality of reclaimed wood often exceeds anything available in the current market.

Use Certified Wood

A growing number of lumber companies are submitting their forest management practices to the scrutiny of third-party certification agencies. These agencies confirm the use of sustainable forestry practices and the distribution chain that moves the lumber to market. This assures consumers that wood is accurately represented. Some of the first companies to adopt certification have been practicing sustainable forestry for decades. (To find companies selling certified wood, use the Oikos Product Directory's Power Search and select "sustainably harvested" from the Environmental Benefits list.)

Certified wood substitutes directly for conventional dimensional lumber. It can be framing lumber, decking or panel products, such as plywood and OSB (oriented strand board). According to the NRDC report, costs in California can range from several hundred dollars less than conventional materials to a few thousand dollars more. In general, expect certified wood to add cost.

Find Alternative Structures

foam block

If you want to take a really big bite out of wood use, replace the basic wood frame with something else.

Insulated concrete forms are skyrocketing in popularity. These stay-in-place concrete forms also serve as insulation, although the amount varies significantly among the products. ICFs are easy to erect on site and create houses that are tight and quiet. Most ICFs are made of expanded polystyrene, which uses pentane foaming agent that doesn't harm ozone.

Autoclaved cellular concrete is used extensively in Europe and is available in some parts of the eastern U.S. The manufacturing process creates tiny voids in the concrete giving these lightweight blocks an insulating value of R-8 to R-10. The blocks can be cut with a standard saw blade. Because they are considerably larger they lay up much faster and reduce labor costs.

Insulated structural panels have been available for 20 years. The most common form is the foam core panel that sandwiches several inches of foam insulation between half-inch-thick sheets of OSB. Some panels use a steel frame with foam insulation fitted to block thermal bridging through the framing. One unique panel uses straw board in the middle instead of foam insulation.

Steel is often mentioned as a wood alternative, but it comes with advantages and disadvantages. On the positive side, it contains some level of recycled content, although it's difficult to know exactly how much. On the down side, thermal problems continue to plague steel framing. A one- to two-inch layer of rigid insulation is required to reach an insulation level equivalent to a wood-framed wall. Plus, many of the steel buildings tested for air leakage have shown poor results&emdash;generally much worse than wood-framed buildings.

Find More Alternative Structures

straw bale

The options above fit well into the current professional home building process. Other options nearer the fringe are gaining momentum, too. Small, independent professionals and owner-builders are preparing for the future by looking to the past. They are reviving old building techniques in search of greater environmental harmony.

Straw bale homes have been built in Europe and across the American plains for centuries. Bale walls have an extremely high insulating value--up to R-60. Bales are stacked--usually by a group of friends and neighbors in a barn raising atmosphere--to form the walls of the building. Most straw bale homes are single story with a conventional foundation and roof. Straw bale walls can be built to support a roof load, but many projects rely on a post-and-beam structure and use bales to fill in as highly-insulated, non-structural walls.

Rammed earth buildings date back to the middle ages in western Asia. In this technique, temporary forms are filled with specially mixed soil. The soil is compacted by hand or with the aid of a compressor- driven tamper. The forms are stripped and set up for the next wall section. The foundation and roof generally use typical materials and methods. The high-mass walls effectively even out the daily temperature swings in hot climates.

These alternative structures often require more labor than wood-frame construction and lend themselves to owner-builders. However, a number of builders specialize in these methods.

Decisions, Decisions

There is no shortage of options for reducing wood use or adopting less wood-hungry building systems. Here are some sources of additional information that will help you investigate the options. The NRDC report, titled Saving Wood, Saving Money, Saving Trees: A Handbook for Professionals, will be available from NRDC by calling 415-777-0220. The report will offer detailed information on ways to reduce wood use in frame construction, including cost and savings estimates for the California market. Another good source of information is Construction Waste Management published by the NAHB Research Center. The Wood Reduction Clearinghouse can be reached at 202-387-8030.

This article appeared in Energy Source Builder #54 December 1997,
©Copyright 1997 Iris Communications, Inc.

Searching for Sources

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