Hey Mr. Green,
Our house needs new siding. We know that vinyl is bad, aluminum isn't great for the environment, and steel siding is coated with PVC for the color, so we were considering cement board. But we’re concerned that cement board might be made with fly ash (as part of the cement) and may pose an environmental/health risk. What can you tell us about siding?
–-Richard, in Lees Summit, Missouri
First, don’t count out plain old wood. After all, wood is manufactured primarily by solar energy, meaning that its energy demands are lower than for other products, plus it is a renewable resource. If you can get wood siding that is certified by the Forestry Stewardship Council (FSC) www.fsc.org/ it’s a very reasonable option. And with the new, far less toxic paints, preserving wood is nowhere near as hazardous as back in the day when lead-tainted paint exhaled pollutants, aka Volatile Organic Compounds (VOCs).
Because all the materials you mention have such different and complicated impacts from cradle to grave, it is extremely difficult to say with certainty that any one is vastly superior to any other. Yeah, I know, it sounds like a copout, but ranking such products has boggled far keener scientific minds than Mr. Green’s. Consider the U.S. Green Building Council’s (USGBC) comparison of vinyl products with other building materials and you’ll see what I mean. In trying to arrive at a rating of vinyl versus other building products, their expert panel reviewed over 2,500 documents and 890 stakeholder submissions. The conclusion? “No single material shows up as the best across all the human health and environmental impact categories, nor as the worst.” (Italics theirs.)
But considering data from this and other studies, it appears that wood and cement board are better choices than vinyl and aluminum. As for steel, although it may be coated with PCV, it requires less PCV than vinyl, and steel requires far less energy to process than aluminum. Besides, over 80% of steel is recycled, compared to about 53 percent of the aluminum, and less than 10 percent of the plastic.
As to your reservations about fly ash, it is produced by burning coal. Since this ash is captured instead of spewing out of smokestacks, it is better to recycle it in cement products than simply to dump it. (Of course it’s not safe to breathe dust from any cement product, so the manufacturer’s safety precautions should be scrupulously obeyed when installing it.)
Finally, there’s the intangible aesthetic dimension. In the end, you should choose a material that harmonizes with the basic design of your house. We are generally happier, and less restless, irritable, and discontent if the built environment is pleasant. I have no empirical proof of this, but then neither did Sierra Club founder John Muir when he claimed that an untrammeled, healthy natural environment was good for the soul. I experienced this aesthetic revelation during a delightful orgy of destruction when we ripped the snot-green aluminum siding off a friend’s house and uncovered the beautiful, old Spanish-style stucco-covered structure underneath this miserable clanking, dented armor. Not only do my friend and his neighbors seem more content, but he got $67 for the recycled aluminum siding, which defrayed the cost of the food and drink that fueled this stunning architectural restoration.