The differences between composite and natural building materials

by Sally Bouorm | December 1, 2013 11:41 am

By Joel Seibert

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Over the past 20 years, composite and plastic composite decking products have increased their share of the Canadian decking market versus traditional building materials (i.e. wood), and for good reason. With warranties against colour fade, and manufacturer defects often exceeding 20 years, claims of extreme durability, splinter-free finishes, hidden fastener systems, and essentially a maintenance-free deck upon completion, why would one choose any other product for their deck other than composite?

Perhaps the biggest contributing factor to composite decking’s increased popularity is its heavily advertised ‘green’ aspects. However, one must keep in mind there are many different interpretations of ‘green’ building products. Composite companies make various claims that their products use recycled components or low toxicity binding agents, and/or are shipped on trains to reduce the amount of fuel burned in getting product to distributors, while at the same time using shipping containers that use more recycled product than any other. All products, when viewed in the right light, will show some aspect of environmental compassion. That said, this article will outline the industry definition of green building products, as well as provide a brief overview of the Leadership in Energy and Environmental Design (LEED) program.

It will also detail the makeup of composite/plastic composite decking, outline some of the key manufacturing processes of composite and wood decking, which contribute to their ‘green’ aspects, and provide some pros and cons with respect to composite versus natural wood building materials to provide readers with some direction to draw their own conclusions on ‘green’ decking products.

What is green building?

Green building[2] (also known as green construction or sustainable building) refers to a structure and using process that is environmentally responsible and resource efficient throughout a building’s lifecycle—from design, construction, operation, maintenance, and renovation to demolition.

A little about LEED

Leadership in Energy and Environmental Design (LEED®) is intended to provide building owners and operators a concise framework for identifying and implementing practical and measureable green building design, construction, operations, and maintenance practices.

Developed by the United States Green Building Council (USGBC), LEED comprises a suite of rating systems for the design, construction, and operation of high performance green buildings, homes, and neighbourhoods. Its certification system deals with the environmental performance of a building based on the overall characteristics of the project. Credits are not awarded based on the use of particular products, but rather upon meeting the standards in their rating systems.

LEED is an international mark of excellence, which lets the end user know the manufacturer/producer/builder of said product(s), has met certain predefined environmental and sustainability benchmarks. The program does not certify, endorse, or promote any products, services, or companies. Rating systems generally have 100 base points plus six ‘Innovation in Design’ points and four ‘Regional Priority’ points, for a total of 110 (LEED for homes is based on a 125-point scale, plus 11 ‘Innovation in Design’ points). Each credit is allocated points based on the environmental impacts and human benefits of the building-related impacts it addresses.

End users of green building products with LEED[3] certification can expect lower operating costs of their projects, the products have been produced efficiently, and/or contribute to the efficient operation of the overall project, and many will qualify for money-saving incentives such as tax rebates and zoning allowances.

Wood composite decking

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Wood composite decking products are often synonymous with green building. They gain LEED points through their manufacturing processes and recycled content. Traditional wood composite decking are typically made from high-density polyethylene (HDPE) and comprise 50 per cent less reclaimed wood byproducts, and 50 per cent recycled plastics, e.g. trash bags, plastic milk jugs, and shampoo/laundry detergent bottles.

These plastics have a higher tensile strength and are chosen to contribute to the density, structure, and durability of the composite deck boards. The wood component incorporated into composite decking is often referred to as wood flour, which can come from many different sources ranging from lumber mill byproducts, recycled/reclaimed door and window trim, recycled wood framing material, cabinets, or any other natural wood product. These accumulated wood products are then ground into a powder, similar in consistency to ‘flour,’ then combined with the plastic mix and a urea-formaldehyde free binding agent, before being formed into deck boards. The plastic then encapsulates the wood flour to provide a barrier resistant to harsh weather, splintering, mould, and decay. The majority of composites are then wrapped with a vinyl coat, which gives the surface of the product its durability, as well as the colour of each deck board.

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In addition to using recycled and reclaimed materials in the construction of the boards, wood composite decking companies pride themselves in their efficient, waste-free manufacturing processes. For example, after the boards are compressed and formed, water is used to cool them. As the water washes over the boards, it comes in contact with the multiple chemicals used during the manufacturing process. This water is contained in a closed loop system, which is recycled and used over and over again. The system does not release any water back into the environment.

Nearly all composite companies pull their recycled content from areas immediately surrounding their manufacturing plants, thus relieving their local landfill sites of thousands of tons of recyclable waste annually. Due to the recycled content, and environmentally responsible manufacturing process, the majority of composite decking products are even recyclable after they have reached their use.

Plastic composite

Plastic composite decking products, specifically cellular polyvinyl chloride (PVC) decking, differ greatly from traditional wood-flour composite deck materials. Primarily, plastic composites do not use recycled materials during the manufacturing process, and there is no wood or wood flour incorporated into the construction of the board.

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The PVC resin component of these boards is derived from abundant, naturally occurring salt, and combined with natural gas. Colour is added to the resin mixture; the boards are then moulded and embossed with the chosen texture or grain pattern.

Only sustainable virgin materials are used during the manufacturing process of cellular PVC decking products[7]. That said, these decking materials achieve their ‘green’ designation via product packaging, transportation, product longevity, and no maintenance.

These companies use recycled packaging containers to protect their product during transportation. Whether the packaging is plastic wrap, cardboard, or wood crates, all of these protective barriers can be made from recycled product. Also, protective packaging shields the product from damage, making more of the product useable, and reducing the amount of damaged product entering landfill sites. Lessening the amount of non-biodegradable waste products entering landfill sites is always better for the environment.

PVC decking is significantly lighter than its wood composite cousin. Being a lighter product means more of it can fit on trucks, trains, or any other mode of transport, which results in fewer vehicles needed to move this material to its retail destinations and, therefore, reducing the carbon footprint generated during transportation from the manufacturer.

One significant advantage to PVC/plastic composite decking is its extreme durability. These deck boards are scratch and dent resistant, and they do not chip, cup, or warp. The durability of PVC decking contributes to the product’s lifespan, which is typically 25 years. The durability and longevity of PVC decking, combined with its minimal maintenance requirements, means a deck that looks great for many years without having to sand, stain, or paint, thus minimizing the use of products containing harmful volatile organic compounds (VOCs).

Traditional wood decking

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Wood decking does not contain recycled products, it is not formed in a factory, it does not need colour added or grains embossed into it, nor does the manufacturing process require numerous hazardous chemicals. Yet, to the majority of the general public, when it comes to green or environmentally friendly decking, traditional wood decking is often thought to be far worse for the environment than its composite counterparts.

There are many different options for wood decks; however, for the sake of comparison, a common cedar deck board will be used for the remainder of this section. Cedar decking is selectively harvested from sustainable growth forests. Many of the cedar deck boards used today are harvested from second growth forests. These are areas that have already been replanted once prior, and it is these smaller trees, which are being used as an alternative to larger, majestic, old growth trees.

After an area has been harvested, it is the harvester’s responsibility to replant and maintain the saplings in their block cutting (i.e. a forestry/logging practice in which most or all trees in an area are uniformly cut down) until the trees have reached a height the provincial forestry division deems good enough for the trees to grow on their own. Once the saplings have reached their ‘free to grow’ maturity, and access to these block cuttings are no longer needed, the haul roads are reclaimed and returned to their natural state as close as humanly possible.

Much of the actual tree felling is still performed by hand with chain saws in the steeper more treacherous areas in the alpine. This minimizes soil erosion and site degradation. A yarder is situated atop the block cutting and the felled trees are strung to a yarder line and hauled up the mountainside to the landing area. On gentler block cuttings, skidders are used to gather and bunch the felled logs and move them to the landing areas.

Once the raw materials have reached the landing areas, a processor cuts the logs to the longest lengths that fit on the haul trucks before they are shipped to the mill. Once at the mill the logs go through a number of selection processes to determine which are best suited for each product. Then, the log is processed and cut in order to minimize waste, and the raw boards are sent off for finishing. During the milling process, nearly 100 per cent of the waste product is repurposed. For example, waste wood chips are sent to paper mills[9], some products are turned into finger jointed siding or trim, bark chips and some wood chips are repurposed as animal bedding or bark mulch, and saw dust is collected and incinerated to generate power (e.g. steam power for heat) in local areas.

Cedar trees have naturally occurring chemicals, which deter rot, mould, and insects, and when left to the elements, turns a silvery patina colour. Because of these naturally occurring chemicals, end users can put as much or as little maintenance into their cedar deck as they deem necessary. When the cedar product has reached the end of its life cycle, natural untreated cedar is completely biodegradable, and can be recycled, repurposed, or reused.

[10]Cedar is considered a soft wood, along with spruce, pine, and fir. Softwoods are not as durable as wood/plastic composite decking products; however, mahogany decking is extremely hard, durable, and more versatile than a composite deck board.

Overall performance   

Green building products are evaluated on their performance during all phases of their lifecycle—from design, construction, and operation to maintenance, renovation, and demolition. How these products react and interact with other products they interface with, and how they contribute to the overall performance of the project they are a part of, all contribute to how ‘green’ a building product is.

All decking material has its ‘green’ attributes. It is up to the end user to determine, which attributes they value more, and pursue the decking product, which mirrors their values best. With the advent of organizations such as LEED and built green, consumer awareness has been heightened with respect to green building products, which has created transparency between the manufacturer and consumer. Those builders who are interested in a particular product are urged to contact their supplier or even the manufacturer with any questions. Building ‘green’ and being environmentally aware is everyone’s responsibility. Builders who conduct their own research and choose the right products for the right applications are doing their part for the environment.

Joel Seibert, is the operations manager at Mountain View Building Materials in Calgary, Alta. They specialize in the design/build of decks, fences, and high-end residential exteriors. Seibert previously owned-and-operated a landscape construction company and is the third generation of the family to enter the lumber industry. He can be reached via e-mail at joels@mountainviewbm.ca[11].

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