Environmentally-friendly building materials are generally renewable, sustainably produced, or recycled. Other common features shared by many environmentally-friendly building materials include non-toxicity and local production. Many of these materials are organic in nature, such as bamboo and other grasses, cork, sisal, and wood from sustainably managed forests. Other types of environmentally-friendly building materials are also natural, such as stone, clay, and concrete. Many recycled and repurposed materials can also be seen as friendly to the environment, since the continued use of these items in new construction can result in a lower overall level of pollution.
Some of the main factors that are considered when building an eco-friendly structure are the materials that will be used. One major source of environmentally-friendly building materials for these projects are renewable or sustainable resources. Sustainability refers to the fact that the supply of the particular building material can be managed over time so that it will not run out. Some managed forests can be considered sustainable because the trees were all planted for the express purpose of harvesting building materials, and each time one is removed another one takes its place.
In other cases, sustainable materials such as bamboo are preferred. This woody material is actually a grass and can grow quite fast. It is typically better suited to flooring than structural purposes. For structural purposes, many buildings can utilize natural materials such as adobe and rammed earth. Many adobe and rammed earth structures that are hundreds of years old are still standing.
Other natural products, such as stone and concrete, can be useful for structural building. These materials are generally thought to be more environmentally-friendly when they are locally sourced. This is because a piece of stone that is quarried far away can take a great deal of energy to move to a distant job site, resulting in an increased amount of pollution. In most cases, the most environmentally-friendly building materials are sourced locally but produced or manufactured offsite.
A variety of recycled industrial materials may also be used in an environmentally-friendly way. By recycling or repurposing materials such as foundry sand, the products of coal combustion, and debris from demolition, a building project can help the environment. Turning used materials such as these into new building materials can have a net positive effect, since they might otherwise just end up in a landfill. Even though burning coal can release various pollutants into the environment, the resulting ash can be used in an environmentally-friendly way by sequestering it into materials such as concrete instead.