Both Wood and Plastic Have a Strong Green Message.
The sign of a really even argument is that it continues to rage, and one side never seems to put distance between itself and their opponent’s point of view.
That is surely true in the debate of wood versus PVC for such applications as deck and trim.
If you ask anyone if wood is a green product, they would surely answer "Yes." What could be greener than wood? Is wood greener than plastic, in the form of PVC trim and decking? Here too, the average person would answer "Yes"…however, the greenness of a product can no longer be determined by campaign 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.
As for wood, it’s natural, non-toxic, renewable, and it soaks up CO2, while producing oxygen. Wood’s green attributes are many and widely known, and it’s commonly seen in three species, especially for decking: Southern Yellow Pine, Redwood, and Cedar. (For cabinets, it’s Ash, Cherry, and Maple.) Redwood and Cedar have natural preservatives, but they are less plentiful than Southern Yellow Pine, which grows rapidly. But it would fail quickly if not treated with preservatives…preservatives that do not always have the greenest attributes. That’s because pine has to be treated with chemicals or copper to prevent rotting or insect attack; and during its service life, the wood has to be sealed or treated to be maintained. So, wood is not entirely a neutral 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 in comparison to wood. PVC decking also has a long service life, potentially orders 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 percent 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 an 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.