When you hear about the life and habits of energy conservationist David Hrivnak, you might begin to think that the world's energy shortage could be resolved if everyone could just plug in to him. In his time away from his day job as an industrial engineer at Eastman Chemical Co. in Kingsport, Tenn., he has designed and built two passive solar homes and created an electric-assist system for his heretofore-gas-guzzling truck that he hopes to make available to the masses. Apparently his spare time isn't so spare.

Hrivnak, who rides his bike to work at least half the year, says he's always been passionate about energy conservation, and this enthusiasm manifested itself in a big way 25 years ago when he designed and built his first solar home using a technique called earth berming. The home, which was featured in Solar Today magazine, was mostly underground.

"It was a self-facing lot overlooking the city, so you almost had to dig into the hillside to put a house. ...The southern wall was almost all glass taking in a nice view of the city, but on the north side there was 14 feet of dirt," he explains.

In 2000, Hrivnak and his family were ready for new digs, so the second solar home was erected. Both homes were built as passive solar homes, meaning that the house is "one big solar collector," absorbing the sun's energy based on its orientation and not on any moving parts.

"The house is designed so that in the wintertime, in December, we get sun in the house from sunrise to sunset; but in the summer, the house is completely in the shade. ...The only thing you really have to do in our house (and I still have challenges with my kids on this) is in the morning you raise the shades and at night you close the shades."

Hrivnak may have felt more comfortable than most people embarking on these projects because of his IE background.

"It amazes me how few people even understand basic geometry and to be able to draw out and measure sun angles and calculate overhangs of the house so you can maximize your solar gain - those are engineering calculations."

He also gained building experience as a former president of the local chapter of Habitat for Humanity, going on builds in six countries, including a village in El Salvador a year before a devastating earthquake hit in 1996.

"We were told that out of 550 structures in town, there were only 40 left standing. And all 13 of the 13 Habitat homes were among those 40 left standing," Hrivnak recalls.

Clearly he knows his way around a basic construction site, which explains why he was anxious to be his own contractor for his homes. He employed insulated concrete forms for the walls and structural insulated panels for the roof.