Principle: The sustainable residential site should be a nurturing and safe

environment for all life.

The underlying notion of all sustainable principles is to create an environment that not only is enjoyable and visually fulfilling, but also is wholesome to live in. All of the previously discussed sustainable principles and strategies contribute to such an envi­ronment. Nevertheless, there are additional tactics that can be employed to ensure that the residential landscape is indeed a healthy place. These primarily involve the use of materials and maintenance practices that are pollutant and toxin free.

Use Toxin-Free Materials

Much has already been said about appropriate materials for a sustainable residential site. In general, safe materials are toxin and pollutant free with relatively little em­bodied energy. Healthy materials are safe to produce, harmless to install, and benign to live with over an extended period of years. They are ideally made without poison­ous chemicals, heavy metals, or oil. Although many materials fulfill these criteria to different degrees, some materials should ideally be avoided because they do not. Pressure-treated lumber manufactured with chromated copper arsenate (CCA) be­fore 2003 is one such material and has already been discussed (see “Discard Toxic Materials” in “Site Restoration” in this chapter). Even new pressure-treated wood manufactured with amine copper quat (ACQ) or copper azone (CA) remains con­troversial because of the associated history with chromated copper arsenate. Again, the best procedure for working with pressure-treated wood is to handle it with gloves and apply a penetrating stain as a finish to seal in the chemical preservatives. Other wood, such as railroad ties or old utility poles, that contains creosote or pen – tachlorophenol is not recommended either because these chemicals are potentially harmful to touch or breathe.

Another material that has questionable use on a sustainable residential site is polyvinyl chloride (PVC), frequently found in plastic pipes and tubing. Although this is a popular and commonly used material in the landscape, the chlorine is a poten­tially harmful chemical when it leaches into ground water or outgases into the air. PVC plastic is also toxic if it burns. Other forms of plastic, clay, or metal pipes should be considered as alternatives to PVC pipes.

Two other commonly used materials that ideally should not be used in the sus­tainable landscape are asphalt and oil-based paint. Asphalt produces fumes when hot


Figure 3-52

A compost area should collect and recycle vegetative material from the house and site.

that can be a problem for individuals who have chemical sensitivities. Further, asphalt is an oil-based material that relies on a dwindling resource that is ever increasing in fiscal and political costs. Asphalt also needs regular recoating to maintain its seal and structural integrity. There are numerous substitutes for asphalt, especially on a resi­dential site where it is frequently limited to driveways. Oil-based paints are similar in that they produce toxic fumes when wet. Water-based paints are recommended re­placements and often have similar durability over time.

Other landscape construction materials have varied degrees of toxicity. Background research should be conducted on each material by carefully reading man­ufacturers’ specifications and product labels before it is adopted for use in a sustain­able landscape. Another source is “The Hazards and Impacts of Landscape Materials,” an appendix section in Sustainable Landscape Construction, by J. William Thompson and Kim Sorvig.