This past month was the coldest February on record in Connecticut, but inside Mike Trolle's Passive House in Danbury, the indoor temperature never dipped below 68 degrees. He says, "When it got to -12 degrees the house stayed toasty with all systems working as they should."

He and his brother have run BPC Green Builders, in Wilton, Conn., since 2000. They've worked on many energy-efficient houses and received numerous commendations, including a DOE Challenge Home Award.  They have also built three LEED Platinum houses.

But Mike's own house was their first Passive House. 

The 1,650-square-foot home started life as a summer cottage and is technically a remodel, but all that's left of the original structure is the CMU foundation and the first-floor joist system. "If I were to do it over," says Mike, "it would have been easier to start from a bare lot."

The house's energy use has been monitored by Steven Winter Associates, in Norwalk, Conn. Since Mike, his wife, and daughter moved in, the one-year cost of electricity for heating and cooling has been $337.  Overall annual energy costs have been $1,285 for electricity and $103 for propane for a tankless Navien water heater.

To find out more about the house, you can read Mike's 10-part series that he wrote for his local newspaper.