Smarter Business: Green Building
Efficient Wood Use in Residential Construction
A Practical Guide to Saving Wood, Money, and Forests
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
This 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.
- Trusses and panels ("components") can save 250 hours on the job site and save more than $3,300 per house. They use 26 percent less wood than traditional framing techniques. They offer numerous other practical advantages, including longer floor and roof spans, lighter weight, consistent material quality, and vendor-supplied engineering.
- Stressed-skin panels can reduce the time to construct the building "envelope" by more than one-third. This time savings can improve a builder's productivity -- and profitability -- by 16 percent. A builder with one crew, building four houses per year, can increase annual profits by $5,900. Stressed-skin panels can save between 25 and 50 percent of the framing lumber used in a typical house.
- Optimum value engineering can reduce framing wood costs by $700 to $3,400 per house or as much as $1.20 per square foot. Builders who have used these practices have reduced the amount of wood used for framing by 11 to 19 percent.
- Reducing wood waste can save builders hundreds of dollars. Approximately one-sixth of the wood delivered to a construction site ends up in the landfill. Builders who have adopted construction site waste reduction programs have saved $300 to $800 on a single job.
- Environmentally certified and reclaimed wood can be substituted directly for standard dimensional lumber in nearly all residential building. Using environmentally certified and reclaimed lumber can, in some cases, save hundreds of dollars and also offers a "green" marketing advantage. Using certified hem-fir framing lumber, certified plywood, and reclaimed beams can save as much as $1,000 dollars in a single house.
- Building more durable homes can reduce long-term costs and improve safety. Deterioration of wood shortens the life of buildings, creating added costs for replacement materials, disposal, and labor. Building to prevent deterioration can help to avoid these costs.
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 Handbook
What 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:
- Using component systems (trusses and manufactured panels)
- Using stressed-skin insulating-core panels
- Designing and framing in ways that use wood more efficiently
("optimum value engineering")
- Reusing wood and using wood that comes from environmentally "certified" sources
- Reducing wood waste on the job site
- Building more durable, longer-lasting homes
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 Handbook
The handbook will help you answer three questions:
- What are wood-efficient approaches to building?
- Are these approaches feasible and cost-effective?
- What resources are available to help begin using these methods?
What the Handbook Includes
Each chapter presents a different wood-efficient strategy. Those strategies are:
- Chapter 1: Component Systems
- Chapter 2: Stressed-Skin Insulating-Core Panels
- Chapter 3: Optimum Value Engineering
- Chapter 4: Certified and Reclaimed Wood
- Chapter 5: Job-Site Waste Reduction
- Chapter 6: Detailing for Durability
Each chapter, in turn, includes the following information:
(Only The Bottom Line section of each chapter is included in the online version of the handbook.)
- The Bottom Line -- a brief overview of the strategy and its dollar savings potential based on data provided in the body of the chapter.
- Practical Considerations -- information about the feasibility and cost-effectiveness of the strategy, organized as follows:
- Description -- a technical description of the technique or material, its applications, design and construction implications, product availability, building code issues, scheduling, etc.
- Costs & Savings -- typical and specific costs in comparison to conventional stick framing, based on California data as well as case studies from other U.S. cities, and potential savings in materials and/or construction time.
- Other Benefits -- other advantages to using the material (e.g., lighter weight, ease of construction, services provided by suppliers).
- Limitations -- practical issues that affect design and/or construction, or other attributes of the material/method.
- Description -- a technical description of the technique or material, its applications, design and construction implications, product availability, building code issues, scheduling, etc.
- Resources -- training opportunities, suppliers, specifications, reference books, trade magazines, videos, Internet sites, and other practical information from industry trade groups, homebuilders' associations, and governmental agencies.
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 Why
There are a number of promising building materials that save wood that we did not include in this handbook. First are the engineered wood products: 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. 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 Building
The 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:
- Build small. Too often, building size is dictated by image and not by function. In the last three decades, the average American house size has increased while household size has decreased; the average floor area per person rose from 427 to 756 square feet, or 77 percent.
- Pick a resource-efficient location. Possibly the greatest construction-related harm to the natural environment and the greatest costs to governments, businesses, and individuals result from building on previously undeveloped land. Seek out sites in already-developed areas; consider rehabilitating or remodeling an existing structure.
- Design simply and elegantly. A great deal of wood and money is wasted on excess, such as unnecessarily complex roofs and applique decoration, instead of being invested in the design of timeless structures whose appeal relies on beautiful proportions and fine craftsmanship.
- Design for flexibility. A house that can accommodate a variety of household types, lifestyles, and functions is less likely to require remodeling than one that is designed for a narrowly defined market. "Open" building methods such as post-and-beam framing lend themselves most easily to adaptation.
- Build for disassembly. Too often, the only way to get a building apart is with a wrecking ball, reducing valuable materials to rubble. Use screws and bolts, instead of glue and nails, whenever possible; avoid unrecyclable composites, especially those that are short-lived.
- Build a durable structure. Repair and replacement of deteriorating wood accounts for a significant percentage of the total demand for new wood. A well-detailed, solidly built house will outlive its shoddy counterpart by many years.
- Plan to minimize waste. Wasted materials are paid for twice: once to buy them, and again to dispose of them. Estimate carefully so you buy no more than you need; use materials to their fullest potential.
- Collaborate with the rest of your team. Opportunities for material efficiencies and time savings often can be found when the developer, architect, engineer, and builder combine resources. Set a meeting as early as possible in the project to discuss this goal.
THE BOTTOM LINE
Component 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.
STICK FRAMING $21,373 COMPONENTS $18,017 SAVINGS $3,356
Components also offer numerous other practical advantages, including:
- Longer floor and roof spans
- Lighter weight
- Consistent material quality
- Vendor-supplied engineering
- 26 percent less wood use.
Stressed-Skin Insulating-Core Panels
Stressed-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.
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.
Optimum Value Engineering
Optimum value engineering (OVE) includes a variety of design and construction measures:
- Design and engineer for materials efficiency
- Frame at 24 inches on center
- Align framing and use a single top plate
- Design headers for loading conditions
- Choose a slab floor
- Align openings with stud spacing
- Eliminate unnecessary framing at intersections.
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 Wood
Environmentally 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 Reduction
Reducing waste saves money. Instead of sending all construction-site waste to the landfill, job-site waste reduction features:
- Materials sorting
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 Durability
Using 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:
- Use a roof overhang
- Use properly installed flashing
- Avoid exposing large beams and columns to the elements
- Protect band boards and underlying sheathing and siding
- Provide adequate gaps between deck boards and between ledgers and walls
- Provide drainage and avoid creating spaces where water can collect
- Provide ventilation where appropriate
- Select wood that will last.
This section was contributed by the University of California, Berkeley, Forest Products Laboratory.
Optimum value engineering
Building America Program
Building Science Corporation
Center for Resourceful Building Technology
Energy & Environmental Building Association
Energy Efficient Mortgage Service
National Association of Home Builders
National Association of Home Builders Research Center
Job-site waste management
California Integrated Waste Management Board
ReSource 2000 Program
Alameda County Waste Management Authority
Triangle J Council of Governments
Whole House Building Supply
Additional credits appear in the print report.
|NRDC gratefully acknowledges the following donors for their support of our Forest Initiative:|
The Educational Foundation of America
The James Irvine Foundation
W. Alton Jones Foundation
|The Moriah Fund|
Rockefeller Brothers Fund
Turner Foundation, Inc.
United States Environmental Protection Agency
Wallace Global Fund
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.
Only notes to text appearing in online version of handbook appear here.
1. World Resources Institute, The Last Frontier Forests, 1997, p. 16. "Natural forests" refers to forests that have not been cut and do not include plantations or second-growth forests.
2. Stressed-skin insulating-core panels, some of which use oriented strand board, are a recommended approach in this handbook. In our judgment, the combined energy and wood savings creates a resource-efficient system that holds distinct advantages over traditional framing. We have not yet drawn this same conclusion for other engineered products, largely because they lack the superior energy performance qualities of stressed-skin insulating-core panels.
3. Home Energy, "Foam Forms Bring Concrete Results." June 1998. 510-525-5405
8. "Framing the American Dream II: Continuing a Successful Tradition," WoodWords, Vol. 7. May 1997. Wood Truss Council of America, "What We Learned by Framing the American Dream" (brochure), 1997. This was a demonstration project for display at the NAHB Builders' Show in Houston, Texas, in January 1997. Members of the Wood Truss Council of America built two houses in the convention center parking lot, side by side, using identical floor plans, each 2,631 square feet.
17. G.Z. Brown, et al., Industrialized Housing Trends in the U.S., p.10. Energy Studies in Buildings Laboratory, Center for Housing Innovation, University of Oregon, 1996.
18. Profit is estimated based on data shown in table, page 23 of print version of this handbook, multiplied by ten to reflect ten crews. Also see footnote 25 of print version.
Efficient Wood Use in Residential Construction : A Practical Guide to Saving Wood, Money, and Forests. By Ann Edminster, Sami Yassa. October 1998. Photocopy only, $10.00. Order print copies .
last revised 10/1/1998