For outdoor structures and fittings, wood is good, since it always blends into a garden setting, enhances outside living areas and is a sustainable material if properly sourced. Plastic composite decking has been hailed as a green alternatives to wood for decks, and ideal for people doing green remodeling. But it has also been the subject of some controversy.

Wood plastic composite (WPC) decks hit the market in the 1990s. They are a mixture of wood particles and thermoplastic resins. PVC is perhaps the best known of the thermoplastic materials used. Various claims have been made for the eco-friendliness of WPC decking, and its suitability for green building projects. The big issue is whether they hold up to scrutiny or are just ‘greenwashing’.

Can an artificial wood, the production of which depends on the use of toxic chemicals and high tech manufacturing processes really be green? The main claim for green status is that WPC can make extensive use of recycled plastic – as much as 80%. The wood components make use of waste from the wood industry. Subsidiary claims include the fair point that, unlike wood, WPC decking doesn’t need to be painted or treated with toxic preservatives or insect pest repellents. Also, because it is more durable, a WPC deck won’t need to be replaced as quickly.

In fact WPC decks and their green status have had a checkered history. Some have not lived up to the durability claims, and have faded, weakened and developed problems with mildew, because of the use of cellulose in the composite. The cellulose may itself be treated with chemical preservatives. This is where the problems lie. Some manufacturers may use primarily recycled plastics and little or no cellulose. Their decks may well live up to the claims. Others do not.

Another issue that has emerged has been the eco-friendliness of the plastics. Weathered PVC and other plastics may emit POPs (persistent organic pollutants) and phthalates – banned in most countries for use in baby bottles because of the hazards they pose to health. The increased fire risk has also been raised as a concern with WPC decks, since the plastic is more flammable than wood. The potential for recycling WPC decks is yet another problem. They can be recycled, but not very easily. Critics point out that this probably means that most of it will end up in landfill sites, where it could last a very long time indeed.

The bottom line with WPC decking is that the best quality products can compete with wood as an eco-friendly alternative, but even then there are some disadvantages. Attempts to improve the quality of the product have included a PVC cap to protect against stains and scratches, but that’s hardly an improvement in ecofriendliness. WPC may have its place but if you’re doing green remodeling of your home it’s a toss up, even if you do source your WPC decking from one of the better quality manufacturers.