The number of options available in composite decking can be dizzying (just see this chart ), but the lumber industry wants to simplify that by suggesting a single best option for deck-building: wood.

A recently published life-cycle assessment (LCA) comparing pressure-treated wood (PTW) to wood-plastic composites (WPCs) anchors the wood industry’s current agenda. Commissioned by the Treated Wood Council but performed by third-party firm AquAeTer in strict adherence to ISO standards, the LCA results may come as a surprise. While composite decking may be low-maintenance, it’s not necessarily low-impact.

“The results of the life cycle assessment were actually quite surprising, even to those of us within the pressure-treated wood industry,” said Steve Michael, president and CEO of Spartanburg Forest Products. “We felt our product was environmentally sound, but we were pleased to discover that pressure-treated wood decking outperformed wood-plastic composites in each impact category.”

During the course of the LCA, AquAeTer studied seven impact indicators as they apply to WPCs and PTW through the materials’ production, use, and disposal stages of life. In terms of materials, researchers looked at 1,000 board feet (approximately 320 square feet) of 5/4-by-6-inch, radius-edged material designed for above-ground use. For the composite material, an industry-average blend of 50% recycled wood flour, 25% recycled HDPE (high-density polyethylene), and 25% virgin HDPE was used.

In studying greenhouse gases, fossil fuel use, water use, acid rain, smog, eutrophication, and ecological impact, researchers found that wood outperformed WPCs in six of the seven categories. The steepest difference was in fossil fuel use, in which WPC decking was found to be 14 times more potent than wood.

“We hope that builders, architects and consumers will consider the results of this LCA as they make their design and purchasing decisions,” Michael says.

—­Lauren Hunter, associate editor, REMODELING.

This is a longer version of an article that appeared in the April 2011 issue of REMODELING.