HELPS BUILD A GREEN HOME
In 1998, the Certified Forest Products Council (CFPC) joined with Habitat for Humanity and talk-show host Oprah Winfrey to sponsor the construction of a 1040-sq.-ft. house in Beaverton, Oregon, applying some of the latest environmental innovations in materials and residential building methods. Since its inception in 1976, Habitat for Humanity has erected about 70,000 sturdy, affordable homes around the world, but this is the first to feature certified forest products while addressing a wide range of environmental concerns. The collaboration serves as a case study for builders, homeowners and developers interested in improving their built environment while fostering a legacy of environmental responsibility.
Winfrey started the ball rolling by challenging corporate America to sponsor a Habitat house in each of her shows 205 broadcast regions. CFPC joined with the Willamette West Habitat for Humanity affiliate in suburban Portlandone of about 1,300 Habitat affiliates across the countryand solicited donations of money and certified materials from member companies. Habitats successful formula combines volunteer community labor, donated materials, flexible loan terms and the "sweat equity" provided by prospective homeowners. In this case, the new resident invested 500 hours of labor in Habitat house constructionnot all of it on her own homeeven as she fulfilled her duties as a single mother and a swing-shift hospital worker. The equity of her job-site labor will be applied in lieu of a down payment for a 20-year, interest-free mortgage. Following standard procedures, Habitat serves as lien holder for the duration of the mortgage, after which the homeowner assumes all equity in the property.
Community service is the cornerstone of every Habitat construction project, but the unique partnership between CFPC and Winfrey signifies a broader commitment to environmental stewardship as embodied in certified forest products. This commitment was enhanced by design and material decisions that relate to a wide variety of environmental issues. Toxic off-gassing and indoor air quality were addressed through the use of latex paints and water-based floor finishes, which contain low levels of volatile organic compounds. Industry-standard, synthetic nylon floor coverings were substituted with carpeting manufactured from recycled post-consumer plastic (polyethylene terephthalate or PET)the same material that has lately been appearing in recycled outerwearand the resilient flooring is linoleum instead of vinyl. (Linoleum is a natural, bio-degradable product, comprised chiefly of linseed oil, resins, wood and cork flour with a jute matrix.) Energy use in the home will be reduced by increased insulation and the installation of a high-efficiency furnace.
Showcase for certified wood
As with all Habitat projects, the walls and roof of this home testify to the hard work and community spirit of an extensive volunteer network. A number of CFPC members donated time and materials to the cause. These contributions showcase wood harvested from independently certified sources in compliance with Forest Stewardship Council (FSC) criteria. Certified dimensional lumber and plywood included in the framing package was donated by the Collins Companies and the Harwood Foundation. Interior finish materials include character-grade, tongue-and-groove, certified maple flooring from Plaza Hardwoods and Endura Wood Products, certified maple moldings from Colonial Craft, certified birch window trim and in-floor heating registers (also from Endura). The collaboration of three CFPC members led to the production of a line of cabinets by the Neil Kelly Company using certified ash veneer and trim. Portland-based Environmental Building Supplies served as a local distribution point for these certified wood products and provided CFPC the opportunity to introduce many other environmentally preferred building materials in this demonstration home.
Two other major components of the building feature alternative wood-based fiber products that are environmentally preferable to conventional materials. Fiberglass insulation was replaced with sprayed cellulose insulation, which is comprised of recycled and renewable wood fibers and employs nontoxic borate compounds to achieve fire-retardant and pest-resistant properties. The project also uses a hardboard siding manufactured by Collins from forest thinnings and sawdust. The hardboard includes some certifiable materials but does not meet the FSCs current standard of 70-percent minimum certified content. As certified forested acreage increases and the logistical challenges of integrating manufacturing residuals from multiple sites are offset by greater efficiencies of scale, hardboard is likely to become available in an FSC-certified form.
The wide array of certified forest products and other "green" building materials featured in the CFPC/Oprah Winfrey house were wedded to a variety of resource-efficient design and construction strategies. These "advanced framing" techniques (collectively known as Optimum Value Engineering or OVE) were developed by the research laboratory of the National Association of Home Builders. They are fully compliant with local building codes and received the active endorsement of the Washington County building department.
Advanced framing techniques achieve the twin goals of reducing the amount of framing lumber required to build a house while increasing the percentage of insulated area, without compromising the structures physical integrity. The reduction in framing materials yields construction cost savings on the front end, and the improved thermal performance generates cost savings for the homeowner throughout the life of the structure.
The single largest efficiency gains were the result of changing the placement of floor joists, wall studs and roof rafters to a 24-in. on-center layout, from the traditional 16-in. pattern thats common throughout much of North America. Reduced labor costs are also realized through the transportation, handling and installation of fewer framing members. Whats more, the change to 24-in. centers simplifies carpentry math and reduces costly errors.
Further gains were generated by addressing subcomponents of the framing package. These fall into three general categories: partition wall backing, corners and nail backing. Instead of using three full-length studs to form a U pocket wherever a partition intersects a wall, advanced framing allows the use of three short horizontal blocks between two studs, thus forming a ladder to secure wall partitions. Blocks are spaced to provide a nailing surface at the seam and mid-point of interior wallboard materials. Ladder blocking can be installed after the walls have been raised, requiring less precision in layout. This speeds exterior framing and provides good pick-up work for laborers after the initial blitz of wall framing.
Exterior wall intersections offer opportunities for efficiency through the use of two-stud L corners or a single stud with nail backing clips. Nailing clips are often used to replace solid-wood nailing blocks throughout a house. If solid wood is used for backing purposes, resourceful use of cut ends and their careful placement to support interior sheet goods can go a long ways towards reducing total lumber needs.
Advanced framing can also save time and materials during jobsite layout. For example, if doors and windows are placed so that one or both side-framing members align with the 24-in. pattern in the walls, savings result through the use of fewer studs. Careful sizing of headers above wall openings according to specific load-bearing requirements also minimizes the tendency to overbuild with unnecessary framing materials. In general, the change to a 24-in. layout also takes better advantage of the structural properties of other building components, such as plywood, which is engineered to accommodate a 24-in. span.
Wood-use reduction, labor efficiencies and cost savings are not the only dividends realized through the application of advanced framing techniques. Significant energy savings also result from the increased insulation in the homes exterior shell and the reduction of thermal "bridging" (conductive heat loss) through the use of fewer framing members and such innovations as insulated headers above doors and windows. (Lumber has an R-value of only about R-1 per inch of wood thickness, while insulation values range from R-3.5 to R-8.3 per inch. An advanced-frame house using R-19 insulation has been shown to provide thermal performance equivalent to a conventionally framed house with R-21 insulation.) Uninsulated pockets in a building shell greatly reduce its overall thermal performance. Advanced framing techniques minimize uninsulated pockets by employing single or two-stick corners and ladder bridging at partition intersections. Similar energy savings result from using roof trusses with cantilevered overhangs or by framing rafters to ensure that the full insulation loft is maintained at the intersection of the roof and exterior walls.
The use of certified forest products, in combination with advanced framing techniques, provides a model of environmental stewardship and an appropriate use of forest resources. Linked with efficient design strategies and other material substitutions, such tactics can greatly improve the quality of mainstream housing while contributing to a sustainable economy.
Written by: Jeff X. Wartelle
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