What is a passive design home, the subject of this week’s My Green Mind Best of The Green News story? It’s a virtually air-tight, well-insulated home that’s heated primarily by passive solar (sun exposure) along with heat gains from body-heat, electrical equipment and even the tea kettle whistling on the stove. In a passive design home, any needed remaining heat is supplied by an extremely small source. A traditional furnace isn’t needed. (Learn more at the Passive Home Institute).
The popularity of passive design homes is established in Europe, but they are just gaining interest in the US. A combination of design advances create a comfortable home with the most minimal traditional heat requirements. That combination includes:
- super thick insulation that creates a virtually air tight envelope
- orientation of the home with window and facade exposure toward the southern sun
- architecture based on algorithmic calculations from software that insures an air-tight design
- a mechanical ventilation system that removes stale air and doubles as a heat transfer system to minimize heat loss.
- triple paned windows that let thermal energy from the sun in yet prevent it from radiating back out
A New York Times video offers an example of passive design home construction, a 2000 square foot home in Vermont. The walls have about 18” of fiberglass batting compared to the average US home now with 6”. And the Times article notes that “America’s drafty building methods account for as much as 40 percent of its primary energy use, 70 percent of its electricity consumption and nearly 40 percent of its carbon-dioxide emissions.”
Owners of new passive homes built today in the US will pay a premium of an estimated 15 to 20% more for their homes, in part because needed materials are less available in the US. In Europe, where passive homes are more common, the premium for a passive design home shrinks to from 2 to 5%. Based on current costs in the US, owners of a certified passive design home can recapture their investment in ten years, varying by home size and location.
In the new Vermont home, electric radiant heating occasionally supplements the sun’s natural heating, for examples if the owners are away from the home for extended time periods. Solar roof panels provide the energy for hot water. With the addition of photovoltaic solar panels , wind turbines or other energy collectors, passive homes can become energy-neutral homes and even positive energy producers.
A temporary downside to passive home construction in the US is that the technology is so new that Congress has yet to offer special tax incentives for the new green design homes. That’s expected to change soon, because the issue is heating up…or maybe because it’s about not heating up.
Find a passive design consultant in your state.