Fiber cement siding?s primary benefit from a green standpoint is its durability. With 30- to 50-year warranties, manufacturers have placed a lot of confidence in their products? ability to perform for the long haul. Made from cement, sand, wood pulp and water, it requires little maintenance, won?t warp or rot, doesn?t off-gas, and stands up well to extreme weather events. It also comes in a number of styles (plank and shingle with numerous surface patterns) and can be ordered either pre-finished or sealed and ready to paint.
The primary drawback to most cement products is the embodied energy involved in manufacturing cement. Some alternatives to Portland cement, such as magnesium-based cement, have significantly lower embodied energy but also have different technical characteristics and have been used mainly for specialty applications. Some product manufacturers are substituting fly ash, a waste product from coal-fired power plants, for a portion of the Portland cement in their products to their and the planet?s benefit. It is a reused waste product, it reduces the embodied energy of the end product and, in the right quantities, it strengthens the end product.
When using cement fiber siding, make sure to follow the installation instructions. Key points include painting (or staining, in some cases) the siding with an acrylic paint within the time period allotted (unless it is pre-painted) to avoid moisture issues, sealing joints with caulk, and proper cutting. Try to avoid using a circular saw or anything that is going to create dust. If you have to do it, make sure to do it outside and use a mask or respirator. The cement (like all cement and many other products) contains crystalline silica, which causes respiratory issues when it is churned up in dust form.
Cement fiber siding manufacturers have been working on reducing the amount of water it takes to manufacture their product, primarily by recycling their process water. It would be nice to see manufacturers also look into some of the soy-based concrete stains and sealers and soy polymer paints that are on the market as potential green improvements, either in their pre-finished products or as a recommended coating for applying on-site. Incorporating wood pulp from a Forest Stewardship Council-certified lumber mill would also provide additional green benefits, as would a recycling or take-back program. The road to sustainability provides many opportunities for creativity.
Good luck with your home project!