Identifying America's oldest green home is not exactly a cut-and-dried process. The definition of "green home" varies, and there are many homes -- some historic -- that boast earth-friendly design features. Plantations dating from before the Civil War may feature cutting-edge green landscape design [source: Monticello]. Mid-century modern architecture may make use of passive solar features and underground construction [source: The Glass House]. And even ancient Americans designed homes to make the most of the natural resources around them, although one can suspect their motives had little to do with carbon footprint and much to do with security and safety [source: National Park Service].

To determine the nation's oldest green home, it helps to pick a standard of measurement to define "green." One popular standard is the measure of how much energy a home uses. And in this regard, there is a clear winner in the oldest green home contest: a 110-year-old house in Ann Arbor, MI, that actually produces more energy than it consumes.

When homeowners Kelly and Matt Grocoff purchased their home, it had many of the features of any Victorian-era fixer-upper: little to no insulation, leaky windows and old building materials like lead paint and asbestos siding. These called for many standard renovations, such as refinishing the hardwood floors and removing the hazardous materials. The Grocoffs easily could have produced a pretty, livable rehabbed home, but they chose to go many steps further by making the home so efficient that it's net zero: It produces more energy than it consumes.

Some of the steps that went into making the home green were fairly basic. By thoroughly insulating the attic and walls, restoring the windows and adding high-efficiency storm windows, the Grocoffs sealed the hundreds of tiny air leaks that often make old houses drafty and frightfully expensive to heat. Likewise, the couple replaced all of the home's incandescent lightbulbs with compact fluorescent ones, which use much less energy [source: GreenovationTV]. These are all steps that nearly any environmentally (and cost-) conscious home restorer in America could apply to make an old home more efficient and cheaper to heat, cool and light.

But what else makes this new-old home so eco-friendly? Read on to find out.