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Efficient Wood Use in Residential Construction
The online excerpts of this 1998 NRDC handbook summarize the advantages of several wood-efficient approaches to design, material selection, and construction for residential applications, and describe the extensive practical and resource information for builders, architects, engineers, developers, lenders, and insurers provided in the print version. To order a print copy of the full handbook, see our Publications List. TABLE OF CONTENTS Introduction The Bottom Line On Links Report Credits and Acknowledgments INTRODUCTIONHandbook HighlightsThis handbook describes how wood-efficient home building is a "win-win" opportunity for building industry professionals and the environment. Building industry professionals can save money and time by building more efficiently. The environment wins, too, since saving wood in residential construction conserves forests. Based upon case studies and experiences of builders in the field, we present information on numerous proven "wood-efficient" approaches to design, material selection, and construction. In this handbook, we compare the costs of these approaches with the costs of traditional construction methods. The savings from efficiency measures are significant.
Builders who have combined wood-efficient approaches have profited even more. On one California project, using optimum value engineering, trusses, and certified wood together saved more than $4,800. About the HandbookWhat It's About, Why We Wrote It, and Who It's For
This handbook describes ways to use wood efficiently in residential design and construction. We wrote this handbook because efficiency is a clear winner for the building industry and for the environment. For building industry professionals, wood-efficient practices save dollars by reducing material costs. Many of these methods also reduce the time spent on construction, making it possible to complete more homes each year and increase profits. Efficiency is also good for the environment. Global consumption of wood is expected to double over the next few decades while natural forest cover is expected to decline.1 Natural forests give us clean air, pure water, irreplaceable scenic and recreational resources, and other benefits. The efficient practices and materials that we describe here typically reduce the wood used in building a home by 15 to 30 percent. They can therefore significantly help alleviate the growing pressure on natural forests. As demands on forests have increased in recent decades, the quality of lumber has declined. Framing wood is commonly knot-ridden, warped, and increasingly difficult to work with. As a result, many building professionals are seeking materials that have more consistent quality and are easier to use. In addition, volatility in the price of lumber has increased, leading builders to look for ways to stabilize costs and to seek reliable alternatives to dimensional lumber. We believe that the efficient use of wood can help to alleviate these problems. Besides offering material and time savings, many of these technologies and methods -- such as premanufactured products -- are more reliable and easier to handle. And since most of the approaches we recommend reduce materials costs outright, the effects of lumber price increases are reduced proportionately. The approaches presented in this handbook are:
This handbook contains information useful to builders, architects, engineers, developers, lenders, and insurers. In preparing the handbook, we spoke with several dozen industry professionals and learned that they have an interest in these approaches for philosophical reasons and for their cost benefits. Most had heard of the practices and knew of their qualitative advantages, but lacked practical information and cost comparisons. This handbook provides the practical information needed to carry out these approaches and describes how much money can be saved by adopting these methods. Some of the cost calculations, practical considerations, and available resources that are presented in this handbook are based on information from California. However, the handbook will certainly be useful for professionals nationwide. In California, builders face greater seismic risks, tougher code restrictions, and higher costs compared with much of the rest of the United States. If a practice proves to be cost-effective and practical in California, it is likely to be so in many other parts of the country. We produced this document with technical assistance from the National Association of Home Builders Research Center (NAHBRC) and the University of California Forest Products Laboratory (UCFPL). The UCFPL contributed Chapter 6, Detailing for Durability, in its entirety. The NAHBRC -- which has long been a leading proponent of efficient framing and waste reduction -- contributed significantly to Chapter 3, Optimum Value Engineering, providing results from many years of research. Many other professional organizations and individuals also made significant contributions to this handbook. We hope this handbook will be a reliable and useful document that will improve the efficiency and profitability of your business, as well as benefiting forests. How to Use the HandbookThe handbook will help you answer three questions:
What the Handbook IncludesEach chapter presents a different wood-efficient strategy. Those strategies are:
Each chapter, in turn, includes the following information:
Many of the strategies described in the handbook can be effectively combined. We have highlighted one exemplary project that used a combination of approaches, the Emeryville Resourceful Building Project. That project is featured immediately before Chapter 5 of the print report. What Is Not Included, and WhyThere are a number of promising building materials that save wood that we did not include in this handbook. First are the engineered wood products[2]: I-joists, parallel strand lumber, micro-laminated beams, etc. These products use wood very efficiently and rely less on large-diameter old-growth trees for their production. We did not include them, however, because some significant questions remain unanswered about their full environmental costs. The energy consumed in their manufacture and the use of toxic glues and binders in these products pose unresolved concerns. And, although many of these products are produced from "fast-growing" tree species, these trees are often harvested unsustainably, either from virgin forests or from chemical-intensive plantations established at the expense of natural forests. Also absent from this handbook are concrete and steel. Here too, "the jury is still out" on the environmental tradeoffs. For example, concrete, while requiring high energy inputs for manufacture, has been shown to reduce home heating energy needs by one-half when used in innovative foam-form systems.[3] Similarly, light-gauge steel studs require considerable energy to manufacture and the thermal performance of steel-framed homes typically has been poor. However, steel has a high recycled content in many parts of the country and insulation techniques are improving. As further research is conducted, we will summarize and provide our recommendations on these technologies in a supplement to this handbook. Also excluded from the handbook are a number of increasingly popular building materials and methods including straw-bale, straw panel, rammed earth, adobe, cob, bamboo, light clay, and heavy timber construction. They offer significant potential to reduce wood use in buildings, but their adoption on a widespread basis still poses significant challenges. The obstacles include unknowns about their performance, questions about material durability, and a shortage of tradespeople skilled in their use. However, because of their high potential for resource conservation, we consider them worthy of exploration and encourage further testing and development to help overcome these barriers. Basics of Resource-Efficient BuildingThe fundamental principles of resource-efficient building should be considered even before evaluating specific wood-saving strategies such as those presented in this handbook. These principles should be adopted by the planning and development team early in the life of a project. They are:
THE BOTTOM LINEComponent SystemsComponent systems include building panels and trusses. A panel is a prefabricated flat building section. A truss is a very strong, efficient structural member made of small individual pieces assembled in triangles. Using components instead of solid lumber for wall, roof, and/or floor framing saves time and materials. Faster job completion means lower carrying costs and the potential to build more units per year. Using components instead of stick framing can save $3,356 per house in materials and labor.[8]
Components also offer numerous other practical advantages, including:
Stressed-Skin Insulating-Core PanelsStressed-skin insulating-core panels ("stressed-skin panels") are manufactured assemblies of rigid insulation sandwiched between skins, usually of structural sheathing, which are used to build walls, floors, and roofs. Stressed-skin panels can be used in both new construction and additions, in walls, floors, and roofs. Panelized homes represent the fastest-growing segment of the home-building market.[17] Using stressed-skin panels can reduce the time to frame the building envelope by more than one-third. This time savings can improve a builder's productivity -- and profitability -- by 16 percent. In addition, the end product is energy- and wood-efficient, generating operating savings for the owner and minimizing negative forest impacts. A builder with ten crews can increase profits by $60,000 using stressed-skin panels.[18] Optimum Value EngineeringOptimum value engineering (OVE) includes a variety of design and construction measures:
One study showed that individual OVE techniques can save hundreds of dollars per house in materials. A second study suggests that a comprehensive, integrated approach, utilizing these techniques as well as others, can reduce framing wood costs from $700 to $3,400 per house or more -- or as much as $1.20 per square foot. Environmentally Certified and Reclaimed WoodEnvironmentally certified and reclaimed wood can be substituted directly for standard dimensional lumber in nearly all residential building. These products are typically of comparable or better quality. Costs vary considerably from place to place and depend on the nature of the substitution. In the best case, using certified hem-fir framing lumber, certified plywood, and reclaimed beams can save up to $1,000 dollars in a single house.103 In California, the best case -- using certified hem-fir framing lumber and plywood and a reclaimed beam -- can save up to $1,000 in a single house. In the worst case, substituting certified Douglas fir #1 for non-certified Douglas fir #2 framing lumber can increase the lumber cost for a house by $2,000 to $3,000. Fortunately, using other wood-saving approaches in tandem can more than offset these costs. Job-Site Waste ReductionReducing waste saves money. Instead of sending all construction-site waste to the landfill, job-site waste reduction features:
Wood waste, the largest contributor to job-site waste, can be reduced dramatically and save builders hundreds of dollars in avoided landfill costs on a single job. In areas where tipping fees top $40 per ton and/or laborer wages are $10 or less per hour, savings for detached single-family house construction can range from $0.14 to more than $1 per square foot, depending on local recycling options and wastes targeted for diversion. Reducing wood waste can save builders between $300 and $800 on a single job. Detailing for DurabilityUsing construction methods and details that increase the life of wood and wood-based materials can have substantial effects on the cost, safety, and longevity of structures. When the service life of materials is shortened because of deterioration, the materials must be replaced prematurely; the cost of disposal must be added to the purchase price of replacement materials and labor costs. The following measures increase the longevity of wood-framed structures:
This section was contributed by the University of California, Berkeley, Forest Products Laboratory. Resource ListComponent systems Stressed-skin insulating-core panels Optimum value engineering Certified and reclaimed wood Job-site waste management Detailing for durability Credits
Additional credits appear in the print report. Acknowledgments
As with all of our work, the publication of this report would not have been possible without the support of NRDC's 400,000 members. Additional acknowledgments appear in the print report. Notes
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![[Graph showing increased profits with stressed-skin panels.]](images/rwoodus1.gif)
![[Graph showing savings from OVE (optimum value engineering) techniques.]](images/rwoodus2.gif)
![[Graph showing savings using certified framing lumber and and reclaimed or certified beam]](images/rwoodus3.gif)
![[Graph showing savings from reducing wood waste]](images/rwoodus4.gif)
