NZEBs: The next chapter in the saga of green building

March 14, 2011 |
Rob Cassidy

I have a confession to make: Two years ago, when we first considered the topic of our eighth White Paper on Green Buildings, I was less than enthusiastic about devoting 40,000 words and months of staff time to “Zero and Net-Zero Energy Buildings + Homes.” I just didn’t believe in “ZEBs” or “NZEBs.”

Rather than trying to get to zero energy use in a few select new buildings, I felt that we should be putting scarce resources—money, time, and effort—into making tens of thousands of existing buildings incrementally (maybe 30-35%) more efficient. I didn’t think the cost of adding renewables—PVs, wind, etc.—to get buildings to zero energy use (or net-zero: even defining “zero energy buildings” gets sticky, as you’ll see in the White Paper) was worth the payoff.

Having investigated the topic more fully (with the help of our dedicated White Paper contributors), I’ve come to the conclusion that there are good reasons for Building Teams and property owners to pursue net-zero energy buildings.

First, maximizing energy conservation and achieving net-zero energy use are not incompatible; in fact, energy conservation is a prerequisite for NZEB projects to succeed. Everyone we consulted for the White Paper agreed on this point: You must start with the basics—correct building orientation, a tight envelope, insulation, proper window-to-wall ratio, optimized daylighting, high-efficiency mechanical systems—before getting into the more pricey renewables—solar, geothermal, wind, or biomass.

Second, we have considerably more theoretical data on the feasibility of NZEBs today than when we started our research nearly two years ago. Last month, we published an analysis by Kirksey EcoServices on the feasibility of achieving net-zero energy use in six different building types in hot and humid Houston ( In this month’s White Paper, we have a study by HOK and The Weidt Group on the feasibility of achieving net-zero carbon emissions (which tracks closely to net-zero energy use) in a four-story office building in St. Louis.

What these studies show is that getting to net-zero may be the end game, but first, certain steps must be taken: 1) a fully integrated Building Team must be assembled, with the mutually agreed goal of achieving net-zero; 2) the owner must allow extra time and thought to go into the design process before anything is finalized; 3) extensive energy modeling must be done; and
4) only when the building’s energy efficiency has been maximized, preferably to at least 65-70% compared to a standard building, only then do you add PVs and other renewables.

Finally, we now have a number of completed NZEB projects to put under the microscope. Most of the early examples were small special-interest buildings. But with the successful completion of the Research Support Facility at the National Renewable Energy Laboratory, in Golden, Colo., we have a major building (220,000 sf) that makes a strong case for NZEBs.

Add to this numerous NZEBs being undertaken by the General Services Administration, and it is clear (as we note in the White Paper) that owner-occupied net-zero buildings can be cost-effective for a broad range of clients—federal, state, and local governments, school districts, colleges and universities, healthcare systems, and environmentally aware corporations seeking to enhance their sustainability branding.

I encourage you to check out the White Paper, then send me your thoughts on NZEBs: Let’s get the dialogue going.

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Rob Cassidy |

Robert Cassidy is Executive Editor of Building Design+Construction. A city planner, he is the author of several books, including “Livable Cities,” and was a co-founder of the Friends of the Chicago River.

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