Western Red Cedar: Life-Cycle Sustainability, Indoors & Out

For holistic green building approaches, timber structures and finishes reveal natural benefits
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Sponsored by Western Red Cedar Lumber Association
C.C. Sullivan
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Finding the Footprint:
Western Red Cedar and the Environment

Western Red Cedar is a sustainable resource with a low carbon footprint. Created by sun, rain, and naturally occurring nutrients, the trees emit oxygen (O2) and absorb and store carbon (C) when living. This naturally made product is lightweight yet highly stable and strong, so it performs well while requiring much less energy to transport and handle, as compared to other materials.

“The renewable material comes almost exclusively from sustainably and responsibly managed forests in British Columbia, Northern Oregon, Washington, Montana, and Idaho,” says WRCLA’s Mackie, reinforcing the North American provenance of the materials. “Those who manage the various forests are responsible stewards,” he adds, noting that more than 85 percent of timberland in British Columbia is certified by internationally recognized, independent, third-party forest certification agencies that protect biodiversity, soil, and water quality. These not-for-profit agencies include Sustainable Forestry Initiative (SFI), the Canadian Standards Association (CSA), and the Forest Stewardship Council (FSC). British Columbia‘s forest managers must meet or exceed government standards and meet this kind of third-party certification. Forests are assessed according to measurable scientific criteria.

When it comes to forest certification, North America leads the world in scale and expertise. In Canada more than 150 million hectares of forestlands are certified; in the United States, add another 40 million hectares for a total of 200 million hectares (500 million acres) certified in North America. On all these lands, forests are replanted immediately and in-kind. A recent FSC report concluded that more forest companies are certified in North America (39 percent) than South America (less than 7 percent), Africa (about 3 percent) and Asia (just more than 5 percent).

In addition, for many North American building projects, the source of Western Red Cedar is relatively close geographically, and due to its light weight it can be less costly to transport than, for example, plastic composites or fiber cement panels, as shown in the comparison of shipping Western Red Cedar versus fiber cement panels. So with lightweight materials like Western Red Cedar, less fossil fuel is used.

In short, Western Red Cedar not only symbolizes a connection to nature, it also represents responsible and sustainable forest management. In addition, as shown by many new building projects including schools and retail facilities, Western Red Cedar can be used both indoors and outdoors. In recent decades, architects have used the material for interior doors, ceilings, floors, and other custom millwork, and then extended the same wood finishes outdoors with cladding and railings, terraces, decks, gazebos, and the like. For exterior structures, Western Red Cedar can be specified and installed without pre-drilling, which is typically needed for other wood types. Western Red Cedar is less prone to cracking over time because of its malleable composition.

Sustainably harvested softwoods such as Western Red Cedar have been cited as a highly green choice for other reasons. The Minnesota Sustainable Housing Initiative (MSHI), for example, has advocated using Western Red Cedar because it “is energy efficient to produce, and very little waste is produced in its manufacture.” Waste wood can be used for other wood products and even balms. The product is also environmentally efficient for envelope construction because it contributes to low U-values and high R-values. Under a microscope, one can see millions of air-filled cells per cubic inch, which provide effective thermal insulation. Finally, MSHI notes that Western Red Cedar can be applied without need for toxic chemical treatments to provide requisite durability and stability.

In this way, Western Red Cedar is suitable for children’s rooms, playgrounds and school buildings, whether for claddings, railings, decks or seating. Playground equipment of Western Red Cedar is often preferred by school districts as opposed to other materials or finishes.

Western Red Cedar: Stable, High Performance

Western Red Cedar can be found on high-rise buildings, mountaintop villas, waterfront estates, decks, boardwalks and even ships. Because Western Red Cedar is exceptionally stable, it is resistant to warping and rot and also highly weather resistant— performing as required regardless of exposure to sun, wind, and wave, says WRCLA’s Mackie. No matter the grade, Western Red Cedar seems ready to meet the challenges of innovative uses, as it is the most stable softwood according to measures such as elastic modulus, shrinkage percentage, and modulus of rupture given in The Wood Database.

In addition to these raw measures, the full life-cycle attributes of various woods and comparable materials have been studied by groups other than WRCLA. The University of Minnesota’s MSHI, for example, has compared the use of composites, concrete, steel, brick, and metal to wood siding materials, and concluded that wood has the lowest environmental impact, especially if sustainably harvested and maintained. Because Western Red Cedar is harvested to standards audited by third-party inspection agencies, forest management plans control harvest levels and require reforestation to enhance growth stocks, biodiversity, and forest vitality. In British Columbia the forestry practices are guided by ISO 14001, as part of the CSA Z809 Canadian national standard.

These assurances, along with Western Red Cedar’s ability to naturally resist weathering, rot, and insect infiltration, offer architects and their clients reasonable confidence that their buildings are environmentally benign as well as durable and resilient.

Considerations for life-cycle durability also tend to favor Western Red Cedar, which is a softwood even though the word seems to be a misnomer. In fact, Western Red Cedar has twice the stability of commonly available softwoods. Its dimensional stability values are also high for a softwood. It resists warping, twisting, and checking. Low density and specific gravity are actually essential to its stability. WRCLA adds that its heartwood, the face of any cladding, contains Thujaplicins and water-soluble phenols that make it highly resistant to rot and decay. For best performance, savvy architects specify noncorrosive fasteners, such as aluminum, hot-dipped galvanized or stainless steel. Whether clear or knotty grade, paints, stains, oils, or charring are recommended for a longer service life.

The wood species also surpasses steel and concrete in energy efficiency through its qualities of thermal performance, heat conductivity, and insulation, according to WRCLA. Because of its low density—21 pounds per cubic foot and specific gravity of 0.32—Western Red Cedar offers good R-values (and is also easy to transport). Wood siding outperforms metal and glass claddings on R-value because of its high proportion of cell cavities, a natural thermal insulator. “With its low density and high proportion of air spaces, Western Red Cedar is the best thermal insulator among the commonly available softwood species” as compared to brick, concrete, and steel, according to a WRCLA report: Its coefficient of thermal conductivity (k value) is 12 percent mc of 0.74 BTU inch/ft2h degrees F; the R value (the reciprocal of k) for Western Red Cedar is 1.35 R per 1.0 inch (34mm) of thickness.

Other considerations for wood specification include ratings for flame spread and smoke development. For most building types in the United States, the maximum flame-spread rating for interior wall and ceiling finishes is set at 200. Western Red Cedar is tested at a spread rating of 45, which is Class II, based on new testing conducted for the American Wood Council. The flame spread rating for generic lumber, regardless of species, is given as 150 by the Canadian Wood Council (CWC). The criteria for smoke development for most buildings in the United States provides for a maximum smoke-developed classification for interior wall and ceiling finishes of 450; in this case, Western Red Cedar provides a rating of 125, according to CWC. The group notes that flame-spread rating decreases with increasing thickness for wood products up to about 1 inch (25 mm). [Sources: http://cwc.ca/design-with-wood/fire-safety/flame-spread/ ].

A major consideration for certain building types, such as schools or office spaces, is acoustical damping, or the deadening of sound transfer. For this measure, wood also performs well; its cellular network of minute interlocking pores “converts sound energy into heat by frictional and viscoelastic resistance,” according to Mackie, “and because of this high internal friction, wood has more sound damping capacity than most structural materials.”


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Originally published in Architectural Record.