An American Passive Home

While studying engineering at MIT in the 1980s, I was given an assignment to calculate the cost of building a 2,000-square-foot home that uses 80% less energy to heat and cool than the average home being built at the time. From that assignment many years ago, the results still apply: The cost to conserve energy by optimizing insulation, proper passive design, improving the home’s thermal envelope, and by using simple but state-of-the-art HVAC systems is one-tenth of the cost to burn energy, when calculated over a 30-year “life” of the home.

If we can keep this lesson in mind, we can address a significant portion of our country’s energy challenges. This lesson completely changed my outlook on home building, and led me on a 30-year quest to find the most affordable way to build comfortable, energy-efficient homes.

The American passive home (APH) is a building philosophy intended to assimilate the positive aspects of the German Passivhaus standard into a new standard for Americans, achieving the energy-performance standards set by the Germans at a cost that compares to a Prius instead of a Mercedes. APH is based on the following goals and principles:

• Cost-optimize the amount and type of insulation for all surfaces.
• Optimize the type, orientation, and surface area of all windows to take advantage of the solar energy.
• Eliminate or minimize the thermal bridging that often occurs at wall, window, and floor junctions.
• Minimize infiltration losses by using airlock entries, tight wall joints, high-performance windows, and well-sealed doors.
• Create a low-cost geothermal system that helps eliminate the need for a conventional HVAC system and provides continuously filtered fresh air.
• Source North American-made components and materials to reduce the home’s overall embodied energy.

Although many of the basic concepts of APH are similar to those used to achieve the German Passivhaus standard, the German standard adheres to an energy-use specification independent of the local climate—and the economics of achieving that standard. For instance, building a home that can be heated with 1 watt of energy per square foot (the approximate Passivhaus standard) in Minnesota is very different than building the same home in Tennessee, since insulating to this specification in Minnesota may be economically impractical. A more affordable strategy would be to use building methods that are commercially available but still achieve a reduction in energy use of between 60% and 80%, or 1 to 2 watts per square foot.

Pure Life

Pura Vida, a common saying in Costa Rica meaning ”pure life,” is the name of a demonstration home that my wife Polly and I built in Oregon, Illinois, in 2007. It was intended to be an affordable, comfortable, and energy-efficient home—and a showcase for my building design company. Although I feel that homes should be smaller, we built Pura Vida large enough (3,200 sq. ft. plus a 1,300 sq. ft. walk-out basement) to host guests and seminars for those interested in affordable and energy-efficient living. In the past five years, more than 3,500 guests have visited.