Factors that the study identified as responsible for the increase included:

• The building averages 450,000 visitors per year, not the 300,000 anticipated by the model;

• Its two theaters operate for 7 hours daily, not the 2 hours anticipated by the model; and

• Office space is used 7 days a week, not 5.

According to a spokesperson quoted in the Observer article, the library did not track its energy consumption “due to the cost.” Rather, it was “a reflection of [the library's] faith in the LEED certification process that [it] did not go back and second-guess the efficiency of the equipment.” As the Observer notes, the building’s increased energy requirements are, in some sense, due to its own success. However, as ASHRAE Fellow and Distinguished Lecturer Larry Spielvogel, P.E. pointed out in a letter to the New York Times which we reproduced here at GRELJ last summer, “[b]uildings alone do not use energy. The occupants, operators, and systems do.” The factors driving ImaginOn’s performance gap are another example of why the type of predictive energy modeling on which LEED relies is so imprecise and why project teams need to remain careful about the types of representations they make to their clients about the performance-related results of potential LEED certification.

I also think it is also useful here to emphasize again that, under LEED 2009, this type of performance gap would not be the basis for a LEED 2009 decertification proceeding. Rather, the decertification discussion which was so heated last summer related to LEED 2009 projects which fail to commit to sharing performance data or to satisfy any of the other new Minimum Program Requirements- not if projects simply use more energy than anticipated.

• ImaginOn’s Energy Use Grows With Popularity (Charlotte Observer)

Although the study concluded that these 19 green buildings were consuming (on average) 40 percent more energy than predicted, all of the buildings were consuming less than a building designed to Massachusetts baseline building codes. The disparity in predicted versus actual energy consumption is probably not surprising, but the study did identify a number of issues common across the buildings which resonate with many of the technical and operational provisions of documents like the Model Green Lease. I think it is therefore worthwhile to review the study both from a green leasing perspective, but also in terms of LEED, particularly because the Lowell study has not been referenced in many of the recent articles discussing the ongoing LEED performance gap.

Among other factors, the study identified the following as accounting for the disparity in predicted versus actual performance:

• The predictive energy models used during the design phase were created based on the incremental amounts of projected energy savings from each of the proposed systems and efficiency measures which, according to the energy modelers interviewed for the study, did not account for the building’s performance in its entirety once those systems were installed and operational;

• By nature, predictive energy modeling does not account for the behavior of building operators and occupants with respect to their use of plug loads, occupancy levels, and operating hours (but note the importance of green leasing practices in this context);

• Design and materials changes during the construction phase on account of budget constraints (which emphasizes the need for ongoing construction counsel); and

• Some of the buildings suffered from increased energy consumption during the initial months of occupancy due to incompletely installed or commissioned systems, which the study concluded stemmed from contractors who incorrectly set the systems initially, as well as occupants who did not understand how to use the systems.

In addition to suggesting that these specific design and construction factors may impact green building performance, I think it is also important to note that the authors identified a “frustration” in stakeholders over the observed energy performance gulf. The study suggests that the gap be bridged through “communicating uncertainties in design predictions” and “better training in the use of the technologies in the buildings;” the former is a marketing and construction contracts issue which we’ve frequently discussed in the context of LEED, while the latter can be addressed through the use of various types of green lease provisions.

Although the study itself is somewhat dated, I do think that it emphasizes two important points. First, LEED building performance has been a question mark for quite some time, and will likely remain a critical issue for the foreseeable future, particularly while industry stakeholders continue to grapple with addressing the foregoing building performance factors through risk management strategies, construction contracts, and green lease provisions. Second, it confirms the unpredictable nature of energy modeling and importance for project teams to manage their clients’ expectations when discussing the opportunities presented by green building and other sustainable construction practices.

• Barrientos, J., U. Bhattacharjee, T. Martinez, and J. Duffy, 2007, “Green Buildings in Massachusetts: Comparison between Actual and Predicted Energy Performance,” Proceedings Annual Meeting American Solar Energy Society

Specifically, while the new Stadium was projected to more or less play the same as the old one across the street, a number of factors that the Yankees and their design team may not have considered, underestimated, or were outside of their control all along have resulted in a drastically different performance than the club anticipated. For example, the new Stadium stands sixty feet taller and concourses on each level of seating are exposed to the building’s exterior, which may be creating a wind tunnel effect that is blowing baseballs out towards the fences. Interestingly, the Yankees and their engineers are not entirely certain about what will happen to these wind patterns once the old Stadium is razed as demolition has yet to start in earnest.

The analogy here, of course, is where policymakers, owners, or other stakeholders make legislative or project-related choices that are based on projections which do not accurately reflect actual performance once a structure is brought online; these dangers are even more acute where contract documents obligate a project team to achieve a certain level of performance or fixed reduction in operating expenses that are based on a predictive model. The reasons why a building’s performance could diverge may be complex and entirely unanticipated by stakeholders; building science is complicated and buildings themselves are complex systems for which modeling does not always reflect reality. The experience at New Yankee Stadium to date may be a rather simplistic example, but I do think it helps make the point that predicting performance and evaluating performance based on actual data are two very different ballgames.