*In 1992, Steve Loken built a home for his family that is a model of environmentally friendly construction.
As head of the Center for Resourceful Building Technology in Missoula, Mont., Mr. Loken wanted to show how homes can be tasteful, comfortable, and economical, and still be resource-efficient.
His house includes a rooftop light well that acts as a ''passive cooling system,'' sucking out hot summer air as well as bringing in daylight. Numerous recycled materials include an old cast-iron bathtub.
Meanwhile, as Loken's organization has built several more demonstration houses from Minneapolis to Martha's Vineyard, Mass., other groups have been focusing on similar issues:
*The American Institute of Architects has an active environmental committee. The institute oriented its 1993 annual meeting around the topic.
*Last November, the University of Florida's Center for Construction and Environment hosted an international conference on sustainable building practices.
*The Northwest EcoBuilding Guild, a Seattle-based regional group founded two years ago, has grown so much that it has monthly meetings in five cities.
*Resource guides are springing up, including the Harris Directory, a twice-yearly publication on computer disk covering sources for 700 building materials. It is produced in Seattle by B. J. Harris of Stafford Harris Inc.
*Wise resource use has precedents going back long before Earth Day. According to a recent report by Worldwatch in Washington, D.C., St. Albans Abbey in England, built 900 years ago, includes bricks from Roman ruins. Facing a shortage of fuel wood, ancient Greeks learned to capture solar heat with south-facing openings.