My project is to build a eco-friendly house using natural materials. What constitutes environmentally friendly materials? Generally, green builders utilize components that are recycled or have been salvaged from other houses or buildings that were torn down. Sometimes, it's a matter of getting materials locally instead of shipping them from across the country or world. Houses constructed from those materials may be in short supply, but according to Masiello, at least in his part of the country, it is becoming more common to see green add-ons to homes like wind turbines and solar panels.