Ashrae Journal - November 2008 - (Page 30)

Does ‘Green’ Save Energy Over Traditional Buildings The U.S. Green Building Council (USGBC) wanted to see how well Leadership in Energy and Environmental Design® (LEED) buildings were doing on energy compared to regular buildings. The New Buildings Institute (NBI) did the looking for the USGBC. Information on regular buildings came from the Commercial Building Energy Consumption Survey (CBECS). The findings were presented in a March 4, 2008 report “Energy Performance of LEED for New Construction Buildings.” Check out Figure 1. NBI–LEED data that does not include high-use data centers buildings is plotted against CBECS 2000–2003 data that does not include vacant buildings and nonrefrigerated warehouses. The two distributions look pretty much the same, don’t they? These LEED buildings have a mean that is 15% better than the CBECS mean, which is good. But they are not statistically different by t-test. In other words, the LEED buildings did not conclusively save energy compared to typical buildings built at the same time. This is not good. Think about what is happening behind all of the numbers. The building codes use ANSI/ASHRAE/IESNA Standard 90.1 to establish a “floor” or minimum for energy performance. Few buildings, if any, are built to go beyond the building code minimums so the CBECS plot is really a plot of Standard 90.1. LEED uses Standard 90.1 to establish a target. Guess what? The target appears to have been met. The “target” resembles the “floor.” There should be no surprise that the two data sets are pretty much the same. So how to fix this? Many folks, including the ones who helped me with this Figure 1: Which One is Which? The two populations of buildings look pretty much the same. There do not appear to be any conclusive energy savings with LEED buildings compared to traditionally constructed new bu ildings. USGBC needs to ἀx this—and fast. This does no one any good. column, feel that the problem is only partially LEED. They feel the real problem is Standard 90.1. I am not completely there yet. However, the folks at Standard 90.1 are getting pretty hard to defend when they say that airtight building enclosures do not save energy, and airtightness standards have no place in Standard 90.1. Fixing LEED might best happen while also fixing Standard 90.1. Note: The plot was created from data provided to Bill Rose by Cathy Turner of NBI with the permission of the USGBC. The statistical analysis was done by Paul Francisco. course, not too many clients actually want to pay the engineer for houses in the 1970s.† It seems that bad ideas keep coming the design. And, if the money is spent, it is often wasted because back every other generation—typically after the generation of the enclosure is bad. You can’t make a building green by having adults that dealt with the bad idea the first time around retires the mechanical engineer try to compensate for a poor building (Photos 1 and 2). enclosure design. Here is the generWhat’s “green” about al premise behind the underfloor supply pledouble façade. The outer nums? How do they save façade creates a buffer any energy? They sure as space between it and the heck don’t contribute to inner façade, tempering indoor air quality. They the environment the inner may make it worse. Do façade sees. So we have to you want to breathe air build two walls, not one— delivered in a ductless an outer wall and an inner Photo 1 (left): The ἀrst double façade building in the U.S. was built in the 1970s. void under the floor that wall with a bunch of space It turned out to be a bad idea, but the folks who knew it was bad retired, and their cannot be cleaned? Even in between. Seems to me, knowledge was lost. Photo 2 (right): Mind the Gap. Double façade detail shown. if you can clean them, if you built the inner wall they are filled with services, so they are filthy. And, they are correctly, you don’t need the outer wall and vice versa. Then, you expensive. The building must be taller, which burns up resources don’t get to use the space between them because there is no space and money. But, it’s green. Says who? between them—it is all inside. We call that rentable floor area Double façades? Green? What’s with that? I thought we killed where I’m from. Double façades are a low energy way to provide that idea after the nonsense associated with “double envelope” an all-glass enclosure, but they always use more energy than a 30 ASHRAE Journal ashrae.org November 2008 http://www.ashrae.org

Table of Contents Feed for the Digital Edition of Ashrae Journal - November 2008

Ashrae Journal - November 2008 Contents Commentary Industry News Meetings and Shows Feature Articles Reducing Data Center Energy Consumption Building Sciences Feature Articles Sustainable Nature Center Emerging Technologies Special Products Washington Report Special Supplement: BACnet® Today BACnet® Goes Green Seeing the Light with BACnet® BACnet® on Campus BACnet® for Net Zero Analyzing BACnet® BACnet® at Xerox Campus BACnet® in Europe BACnet® for Green Library BACnet® at the University of Minnesota: Flexibility, Interoperability InfoCenter Product Showplace Classified Advertising Advertising Index

Ashrae Journal - November 2008

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