TUCSON, Ariz. — The reason why Habitat for Humanity in Tucson has gone green is simple.

"All of the kind of green things that we've done have just started out as an idea," said Habitat for Humanity executive director Michael McDonald. "A lot of them were successful enough for us to do them in all our homes."

Now, the organization has a newly-formed home and community design committee of about eight people to generate more eco-friendly ideas Habitat can implement.

"We are going to do a pilot project for graywater, which is a system that uses wash water for things like watering the plants," McDonald said. "We also want to do solar water heating, too because it's a really great way to use the resource of the sun. It would really lower their energy bill."

Key Words Graywater — All wastewater except for toilet waste, which is called "black water." Rammed earth — Uses compressed blocks of clay, gravel and sand for walls. Solar water heater — Harnesses the power of the sun to provide solar thermal energy for water. Straw bale — A method of building that uses straw bales as structural elements and insulation

The pilot program involves implementing the features into one or two homes.

"If these programs test out well, maybe they can eventually be used in all of our homes," he said. "But we are just always trying to figure out how to cover the cost of adding the product."

The cost that Habitat would endure is more than the purchase price and installation fees.

"We also have to educate our home owners about the use of the products. Both graywater and solar heating involve something beyond just walking into your house," McDonald said. "With the graywater, sometimes it may take turning a knob. But with solar heating, there's higher maintenance that you have to keep up so we would have to teach our families how to do that."

Natural building is something that Habitat may also explore in the future.

Straw-bale construction and rammed earth homes have been built by Habitat without much success, McDonald said. Both were more difficult for volunteers to build efficiently.

"We'll probably do another pilot with the straw bale in a couple years," McDonald said. "We hope to do a better job this time."