JOHN D. WAGNER: What’s Greener: Wood or Plastic Decking?
With all factors considered, both have a very strong green message.
BY: JOHN D. WAGNER
One promising aspect of today’s green building movement is the recognition that the greenness of a product can no longer be determined using bumper-sticker slogans. Today, green products are gauged with a wide range of attributes, from how they are manufactured and the energy consumed to deliver them, to their durability and the lifecycle analysis of the products after they are installed.
Is Wood a Green Product?
Yes. What could be greener than wood? It’s natural, non-toxic, renewable, and it soaks up CO2, while producing oxygen. Wood’s green attributes are many and widely known.
You usually see three wood species in decking: Southern pine, Redwood and Cedar, and each offers strong performance in one of more categories. Southern pine grows fast; there’s plenty of it. But it would fail quickly if not treated with preservatives. Redwood and Cedar, on the other hand, while less plentiful, have natural preservatives built-in, which is why they’re sometimes called “Nature’s Treated Wood.” All three species come from sustainably managed forests. That said, wood does take some dings in a life cycle analysis. Pine has to be treated with chemicals of copper to prevent rotting or insect attack, and during its service life, the wood has to be sealed or treated to be maintained. So the wood is not entirely a neutral impact green product.
Now let’s look at wood in comparison to another product, one that some people even want to ban: PVC. Specifically, let’s look at PVC in deck applications: What’s the greenest deck material, wood or PVC? That question should be considered in a weighted analysis, in light of the entire lifecycle of the two materials, from raw material extraction and manufacture, to delivery, use, preservation, and eventual disposal.
PVC performs far better than wood in dimensional stability, cut-ability, mill-ability, and workability. It also doesn’t rot or splinter, and it’s largely maintenance-free, dramatically lowering its impact by comparison to wood.
Plus, PVC decking has a long service life, potentially an order of magnitude greater than wood, especially pine. Moreover, once PVC is manufactured, it is inert and does not contain toxins that can leach out into the environment… and it’s 100% recyclable.
That said, there are concerns about PVC, because its manufacture creates dioxin. However, the cumulative total of dioxin created across the entire U.S. vinyl industry is 8 to 10 grams per year, which is less than ½ of 1% of all dioxin created in the U.S. annually.
In a lifecycle analysis, is wood greener than PVC? There’s a strong argument to be made that PVC is the greener choice. You may take a environmental “hit” during manufacture, but over its lifecycle, PVC earns back points with its long lifecycle, and the avoidance of the use of preservatives, finishes, sealant (or outright replacement) that wood decking is likely to require.
Let’s face it, every building product has an environmental cost to produce (mill, manufacture), ship, and use (maintain, preserve, replace). The goal of green building is to reduce and contain the negative contributions, mindful of how the product influences the environment during its entire service life, from manufacture to disposal. While we tend to automatically think of wood as being far greener, in a calm, weighted analysis, PVC’s attributes make it a strong contender for greenest decking material.