They may emit unhealthy gases and substances into the air for years after construction. This can be greatly diminished if, during the design process, adjustments and substitutions are made in the materials used. Additionally, HVAC systems can be designed to provide maximum levels of fresh air and minimum levels of mildew and mold build up. By employing proven solar technologies and solar heating methods, thermal massing and insulation systems, energy can potentially be returned to the local power utility during even the hottest or coldest days. Energy use detectors and reflectivity can be used effectively and lighting and electrical fixture selection can dramatically reduce conventional electric use.
Some wood species come from destructive forestry practices.
Some materials require extensive processing and produce toxic waste. Others may be from renewable sources and relatively safe to produce. Building ecologically takes these regional and global factors into consideration. By consistently using low impact materials we will live lighter on the planet. The form of a building can respond to adjacent land form, vegetation and climate patterns.