Saving 70 Percent or More of Energy Use in Your Home—Berkeley Lab Scientists Study the Deep Energy Retrofit
Cutting your home's energy use by more than two-thirds of what it presently uses is increasingly a topic of discussion, and a goal, in the home energy performance industry. While everyone from contractors to building researchers have been attempting and studying the so-called "deep energy retrofit" since the 1970s, right now the building industry is searching harder than ever for the right combination of strategies, technologies, and approaches to achieving deep energy cuts at a reasonable cost.
Currently, weatherization programs save 10 to 15 percent of a home's energy use, and some utility programs can save 20 to 25 percent. But to make a dent in the greenhouse gas emissions of the residential sector and make housing more sustainable requires much larger reductions.
"A problem we need to solve," says Iain Walker, leader of a Lawrence Berkeley National Laboratory (Berkeley Lab) research team that evaluated a group of deep energy retrofits in northern California, "is determining how we measure the success of these projects. Do we measure energy, carbon, or cost savings? Do we consider percent savings per house, per person, or per square foot? Do we use site energy or source energy in these comparisons? Is performance based upon a reduction in energy use, a comparison to a reference design, or an absolute post-retrofit energy target?" Walker is a scientist in Berkeley Lab's Environmental Energy Technologies Division.
The complexity of these projects, and the variety of energy performance measures that a homeowner can take to reach these goals, is such that a reduction in energy use at the home in question does not necessarily translate to a similarly deep reduction in energy use at the source of energy generation, or to a deep reduction in greenhouse gas emissions. "There isn't even a consensus definition on what constitutes a deep energy retrofit," says Walker. "They can range from 50 to 90 percent."
Another problem is that deep energy retrofits are relatively untried and expensive. Only a few homeowners today commit to such a large home renovation project focused solely on energy bill savings, particularly given the risks they perceive with doing anything out of the ordinary with their homes. Are there particular energy-efficiency measures or packages of measures that do a better job of improving a home's energy performance at lowest possible cost?
Today there are about 20 million home remodels a year—usually to expand the home's size, to replace worn-out interiors and poorly functioning heating and cooling equipment, or to meet aesthetic goals. Homeowners spend more than $150 billion per year on these remodels, and every year more than a million homeowners spend more than $100,000 on their homes. The majority of remodeling is not done to achieve high energy performance. The home performance industry's challenge is to figure out how to motivate homeowners to spend some of this investment on energy and comfort upgrades.
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