Proof that you can build a “green” house with only modest cost increases is one lesson from a recently completed house by Carl and Jeanine Santilo. Their 6000 square foot traditional Virginia house is mainly an exercise in installing energy efficient heating and cooling components like geo-thermal, triple-paned windows, structural insulated panels, and solar panels in the future to end up with an energy-wise house that sheds the $1000 a month Alexandria summertime electric bills.

To reach this level of savings the homeowners say they didn’t have to spend as much up front as most people are led to believe is required. The conundrum though is how a mansion like the Santilo’s that averages a much smaller $100 a month electric bill won’t be certified by any of the major green building labels.

The answer seems to be that when it comes to green houses, size matters. Typically, a plan to build a house this large is frowned upon by green building standards, and in the case of LEED, is penalized before the first shovel hits the dirt. The simple rationale is that larger houses require a lot more materials than the average-sized house.

In apparent disagreement with the LEED point system homeowner Jeanine Santilo said, “we felt that it just emphasized feel-good green, and not really making-the-planet-a-better-place green.” Similar critiques in different contexts have been hurled at LEED before by a number of outspoken architects, builders, and developers. But the LEED side of the argument may come back to how a house handles energy use, or how much it saves. And the LEED category with the most available points is in fact about using less energy – so energy savings is indeed an important part of obtaining a LEED certification.

In the end the Santilo’s have an energy-efficient mansion that will use less energy resources this year than many American houses half the size.

Still, as the “green” housing trend engrosses the industry, houses like this will likely ignite future debate over what it means to build “green.” Will it be enough to build a house that saves energy after being built, or should the selected building materials and construction methods be equal requisites to building the “green” house of the future?