From Here to Zero Energy Buildings

Editor’s note: With cold weather in the U.S. affecting even Florida, where frozen iguanas are dropping from trees and strawberry crops are in peril, this is a moment to evaluate the sustainability of current energy needs. Below, Bruce Sullivan talks about building new houses with less energy impact; for more on this subject, watch Dan Nocera present an idea for personalized energy at PopTech 2009, and find out about proposed “cash-for-caulkers” incentives for home weatherization the White House is considering.

In a typical year, millions of houses are built. Each house will last 50 to 100 years. Today each new house encumbers society with a debt of energy required to operate it over its life. The vast majority of houses built today are old-fashioned energy hogs, and each one is a missed opportunity.

Energy visionaries have set their sights on homes that create more than they consume. In ten to twenty years, every new building could be a “zero-energy building,” Or “net zero.” The technology exists today, all we lack is the proper motivation.


Zero Energy Habitat for Humanity home in Wheatridge, CO, a collaboration between Habitat for Humanity and the National Renewable Energy Laboratory (NREL).

A zero-energy building is one that creates more energy than it consumes over the course of a year. In order to achieve this feat, a zero-energy building will be small, efficient and grid-connected. Here are some key attributes:

· Smart design is the key. Homes must be designed for their climates and sited to take maximum advantage of nature’s gifts of sun, wind, water and light. Designs must make the highest and best use of material.

· Small homes use less energy. All modern needs (and many of our desires) can be accommodated in 400 to 500 square feet per person.

· Highly efficient structures that incorporate super-insulation and air-tight shells will not need central heating systems. Insulation uses no energy and never wears out .

· Renewable energy generation, such as photovoltaic (solar electric) panels or wind generators , will be essential. These systems must be connected to the utility grid. They will generate more energy than the building needs on summer days, but will require some energy from external sources at night and during winter.

The challenge is no longer technical. The equipment and know-how exist today. What we need is a commitment to this destination and a clear roadmap showing how to get there.

One big obstacle for designers and builders is that they don’t have a good way to estimate the efficiency of their projects during design. A number of proposals are now under review to establish a building efficiency metric and labeling system. One of these is the Energy Performance Score, which is simply an estimate of how much energy a building would use each year. A typical new home may have an EPS around 120. An “efficient” home might be 50, while a zero-energy home would be, well… 0. You can see that we have a long way to go from our current practice to reach zero energy.

Since on-site renewable energy generation may not be possible for all building sites, ultimately some homes would have to generate excess energy. And despite our yearning for decentralization, we will always need a utility grid with central power generation.

Enterprising young designers from around the world put net zero principles into practice every year for the Solar Decathlon, a competition sponsored by the U.S. Department of Energy. Twenty teams of college and university students compete to design, build, and operate the most attractive, effective, and energy-efficient solar-powered house.

Zero-energy doesn’t have to be expensive. Many Habitat for Humanity chapters around the U.S. build very efficient homes. In Bend, Oregon, where I work, the local Habitat projects use small size, high efficiency and solar energy to achieve EPS ratings as low as 23. With annual energy bills of only a few hundred dollars, this is truly affordable housing. From there, it’s just a small step to true zero energy.

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