Navigant Research Blog

Zero Energy Buildings Become Reality

Noah Goldstein — April 29, 2014

Every Earth Day, there is a flurry of press releases and announcements in which corporations show how they are doing good for the Earth.  Once the dust settles, and the greenwash dries, it takes time to sort out the green (environmental) signal from the green (dollars) noise.  In the domain of zero net energy (ZNE) buildings, a clear signal can be heard.  ZNE refers to buildings that, over the course of a year, generate as much energy as they use.  Through a combination of efficient design, material choice, and performance, tied in to local renewable power generation, ZNE can be reached with small additional costs.

The signal of good ZNE news came from a recent report by the New Buildings Institute that showed that modifying a new LEED-certified commercial building to reach ZNE would cost an additional 5% to 10% beyond normal construction costs and would achieve a 30% return on investment in just 3 years.  This is a tabletop exercise, demonstrating that ZNE is possible in Washington, D.C., which has the highest per capita square footage of green buildings of any U.S. city.

In the Real World

But how does this concept play out in real buildings?  Two new ZNE buildings are on display this April.  The first is a large commercial building in La Jolla, California, the Tower II at La Jolla Commons.  This 13-story building will use fuel cells to convert biogas to generate electricity.  Through an extensive network of sensors and a grid-integrated building energy management system, Tower II will, at times, send surplus power to the grid.  At 415,000 SF, it is also the largest commercial ZNE building in the United States.

However, Tower II’s ZNE-ness is not without its critics.  A debate originates with where Tower II gets its power, namely from fuel cells powered by waste biogas. There is no formal authority on the many ways to define ZNE, but a good description of the hierarchies of ZNE can be found here.  No matter which way you view it, though, this ZNE looks like …  an ordinary office high-rise, with floor to ceiling windows.  On the inside, the building uses occupancy sensors and daylighting, but there is nothing shocking about the visual design of it.

This seems to be the trend.  A second example of a real ZNE building is the LEED Platinum Research Support Facility (RSF) at the National Renewable Energy Laboratory in Golden, Colorado.  This building is an impressive 360,000 SF in size, with a massive PV array on the roof.  Featuring open floor plans, and a data center, the RSF would look as at home in an office park as it does in a national laboratory.

Retro, Too

While most of the focus has been given to new commercial and residential buildings, there is a growing movement of incorporating ZNE in retrofits, according to Navigant Research’s recent report, Energy Efficiency Retrofits for Commercial and Public Buildings.  The $60 billion retrofit market is going to double in size in the next 20 years due to changes in building codes and the drive to reduce energy costs.  The ZNE concept will contribute to that effort, slowly at first.  As states like California pursue targets like making 50% of all existing commercial buildings retrofit to ZNE by 2030, the occurrence of ZNE-converted buildings will grow.  By 2030, perhaps we’ll be reporting announcements about ZNE cities.

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