Tube skylights: Two reflective pipes channel light into a windowless bath and a closet, reducing the need for artificial light, which typically accounts for 15 percent of household energy.
Tankless gas water heater: About 15 percent of a home's energy costs go toward heating water. Their on-demand system can cut costs up to 30 percent.
Dual-flush toilets: Toilets typically account for 30 percent of indoor water use. The Manns' dual-flush models should save about 18,000 gallons a year.
Gray-water recycling: The Manns' system filters and stores bath-sink and shower wastewater, then pumps it into toilet tanks. Filter maintenance has been a problem, so they're not sure they'd do it again. And with their ultra-efficient toilets, there's a gray-water surplus—they'd like to find a way to use it outdoors.
Shown: The master bath has its original pine floor, a vintage-table vanity, and pendants fitted for LED blulbs.