PATH - A Public Private Partnership for Advancing Housing Technology
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Less is More: Demand a House with Less Framing, Less Waste, and Better Performance
Over the years, builders have developed several framing practices that lower material and labor costs, and result in improved thermal performance of the building. Despite the win/win proposition these technologies offer the builder and homebuyer, they have been slow to displace traditional framing practices. But they are slowly gaining acceptance as framers learn the techniques and as builders and remodelers of all sizes see that these principles of advanced framing enhance the quality in their projects.
Collectively known as optimum value engineering (OVE), advanced framing techniques help builders reduce the amount of lumber used to build a home while maintaining the structural integrity of the building. They allow insulation to be more easily installed, and installed correctly more easily. Also, by reducing extraneous framing, OVE maximizes the cavity space available for insulation. Through-the-wall wood is thus minimized, as is the resulting "thermal bridging" of heat flow directly through the studs. And delivering a more efficient home for the same or less cost is an effective way for builders to differentiate themselves on quality.
The following innovations are generally included in the family of advanced framing techniques:
Unlike other innovative building techniques, advanced framing is not an all-or-nothing proposition. Builders can take on as many-or as few-of these techniques as they choose. Even very modest applications can deliver considerable benefits when the framing is exploited to enhance energy efficiency. For instance, various OVE framing principles are being or have been applied in the gut rehab of a rowhouse in Philadelphia; a new home for a low-income family in Brownsville, Texas; and a new high-end, energy-efficient home in Manassas, Virginia.
OVE and Gut Rehab
Thanks to careful planning and the trained and well-supervised crew, the technical advisors with Philadelphia's Habitat for Humanity felt confident that a fairly comprehensive collection of advanced framing techniques could be successfully employed in the gut rehab of a 1200 square foot rowhouse dating from the early 1900s. These included 24" OC framing, single top plate on non-bearing walls, right-sized headers, no headers in non-bearing partitions, ladders at T-intersections , and open corner framing . Taking a whole-house approach to the rehab effort, the team exploited the framing to increase exterior wall insulation while cutting framing costs by 30 percent. The home received the U.S. Environmental Protection Agency's ENERGY STAR certificate for its superior energy performance.
Other techniques, such as modular layout and in-line framing that allows the use of a single top plate on load-bearing walls , were rejected as too difficult to use in rehab; they are more applicable when the plans for a new building are prepared with these innovations in mind.
The rowhouse is expected to serve as a prototype for Habitat for Humanity affiliates and other affordable housing developers involved in rehabilitation projects.
High Winds, Low Income
The technical advisors to the Brownsville PATH Demonstration Site rejected many advanced framing techniques as incompatible with the high wind design loading criteria of the area; a three-second gust of 110 miles/hour. But with careful consideration of the specific site requirements, the designers specified economical yet structurally sound framing that allowed the builder to produce a remarkably well-insulated low-income prototype home that cost only $30,000.
The architect employed one innovative technique, not normally considered part of the OVE family, by steepening the roof pitch on the short sides of the hipped roof so that half of the roof was framed like a simple gable roof. This gave the house a more imposing appearance without raising the roofline, but, more importantly for the building process, gave the house a 12' ridge line, rather than 5'. This adjustment allowed a more efficient layout of roof sheathing that minimized waste, and allowed a modular layout throughout most of the framing, with 24" OC rafters and ceiling joists, and 24" OC interior studs aligned with the joists. Lumber-saving ladders at T-intersections were used where interior partitions joined each other and where they joined outside walls. Due to the high wind loading, the exterior wall framing was maintained at 16" OC.
High End, High Efficiency
In suburban Washington, DC, the Department of Energy's Building America program sponsored a 5,000 square foot pilot home as a prototype for energy-efficient, high quality residences. The Integrated Building and Construction Solutions (IBACOS) Consortium provided the designs, which included many energy-efficient innovations; the home was awarded an Energy Star certificate for superior energy performance.
The builder, Washington Homes, builds over 1,000 homes per year using a high level of mass production. Since the home's structure had already been engineered and approved, any framing techniques that would affect the structural integrity were not considered. For these reasons the designer concentrated on the advanced framing techniques that are easier for production framers to adopt, and that would not require a structural re-review. Open corner framing and ladders at T-intersections were used wherever possible throughout, both as a cost-cutting measure and to allow exterior insulation to be more effectively installed.
Large production builders stand to reap the largest savings from OVE framing, as mass production allows the costs of any necessary additional analysis and prototyping, as well as the re-training of framers, to be spread out over more units. But even small builders can realize substantial savings by replacing over-framing habits with carefully planned OVE techniques.
Other advanced framing techniques that can save a builder time and materials, and reduce the cost of a home, are drywall clips and stops, engineered wood wall framing, trim-able open web floor trusses, shear wall panels, and flexible framing tracks.
Content updated on 9/13/2005
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