But is it really "ultrasustainable" to demolish a serviceable old house to build a more energy-efficient design? Consider the issue of embodied energyâ€”that is how much energy does it take to build the house and manufacture and ship the materials used to build it? Here's a widely cited City of Philadelphia web page stating:
"The materials in an average home contain 892 million Btu's of embodied energy, an amount of energy equal to 7,826 gallons of gasoline, or enough to drive an SUV 5 Â½ times around the earth."
The average home consumes about 101 million Btu's a year, according to the U.S. Department of Energy. So even if a new ultrasustainable house uses zero Btu a year, it could still take it about nine years to break even with the old house.
The well-meaning Portland brothers appear to have considered the issue, recycling a lot of the wood in the old house and using other materials in the new house with low embodied energy. But not everything can be reused or recycled and the question remains, how sustainable is it to tear down an old house to build a new, greener house?
There's also a broader question here. What about the embodied energy of solar panels? A Prius? According to some reports, it would take about 20,000 miles of driving a Prius to recoup the embodied energy in the car's manufacture. It can take about three to seven years to recoup the embodied energy of a solar panel.
These are important questions to consider. The ethanol and bottled water once favored by some greens haven't turned out so green. Maybe the green revolution isn't about building or buying something new. Maybe the most sustainable home is a renovated little old house, or an old high-rise apartment. Maybe the greenest vehicle won't be a high-tech car that runs on hydrogen, but an old-bike that runs on donuts.