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Massachusetts Green Buildings Used 40 Percent More Energy Than Predicted

Back in 2007, the Energy Engineering Program at the University of Massachusetts Lowell completed a study of the actual energy performance of 19 green buildings across the Bay State. The study was funded by the Massachusetts Renewable Energy Trust and identified 13 schools which were certified under the LEED-based Massachusetts Collaborative for High Performance Schools Criteria, as well as 6 buildings that had earned LEED certification. The study compared energy consumption as predicted during the design phase and actual occupancy post-construction; buildings included in the study provided at least one year of occupancy data. The authors also interviewed individual project teams and energy modelers and conducted occupancy surveys in evaluating the effectiveness of various types of efficiency measures. All of the buildings received design or construction grants from the Massachusetts Technology Collaborative, which provided the prediction data that project teams had submitted in connection with their funding applications.

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.

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8 Responses to Massachusetts Green Buildings Used 40 Percent More Energy Than Predicted

  1. Dirk Faegre October 7, 2009 at 5:03 pm #

    It would be useful, of course, to know more detail about the failure to meet estimates. This, obviously, would help those of us who are doing work now. Of course LEED is a bit bogus in itself esp. as it relates to energy conservation/efficiency. They are good at embedded energy, materials, and the like but energy use is not part of their practice (which is terrible).

  2. Tauran October 7, 2009 at 6:48 pm #

    The LEED process may or may not have included “enhanced commissioning” which should be a requirement for all LEED projects. Also if the construction material was changed during construction phase submittals, then the Energy Model used should have been updated and RESUBMITTED to the green building council before these buildings received LEED certification. It sounds to me like poor planned projects and lack of review by the LEED agency involved?

    It does sounds fair to assume this statement is true and could account for a poor model. I think the models need to be improved:
    “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.”

  3. Mark Stetz October 7, 2009 at 8:39 pm #

    This is consistent with the findings of Frankel & Turner (New Buildings Institute, 2008) that found that buildings don’t perform the way we think they do. LEED-NC places too much emphasis on design intent and not enough on actual performance. LEED-EB requires demonstrating energy reductions using Portfolio Manager, which is a performance-based metric. The good news is that all of the buildings perform better than MA code.

    The gap between intent and reality comes down to our assumptions about how we think a building works vs. how it works in the real world when occupied by real people.

  4. Matt Coglianese October 7, 2009 at 10:06 pm #

    Models, although commonly utilized to make predictive conclusions, are inherently problematic, dependent on assumptions and subject to manipulation. And, they are constantly being revised and improved. So, it doesn’t surprise me that the model did not accurately predict real world performance of the buildings. I would be interested, though, to know how many of the buildings were “value engineered” or subject to design or construction changes, as those regular events in construction may constitute a couple of the most common reasons that promised “green” performance is not achieved.

  5. Timothy R. Hughes October 12, 2009 at 11:15 am #

    Another interesting post Stephen. I bet that we see LEED moving towards more energy performance measures in the future. I am also interested in the comments on modeling v. performance – all these articles and posts certainly seem to point out a predictive weakness there.

    I linked to this post on our recent post at http://www.valanduseconstructionlaw.com that talks about LEED 3.0 and is increased credit shifts towards energy, here is a link if you are interested:

    LEED 3.0: Changes Reflect the Need to Increase Energy Focus http://su.pr/9kfKqt

  6. Thomas December 4, 2009 at 4:41 pm #

    Why can the Germans and some other European Countries build cars that get 65-70 mpg(diesal/bluetec)while carrying 5 passengers and with top speeds of 120 mph or more, build zero energy buildings or even net energy building, plan to have a hydrogen fuel network up and running by 2015 with over 1000 hydrogen fuel stations, huge Soalar and wind developments along with Geothermal, ocean energy,etc. and Germany comsumes 50% less energy per unit of GDP compared to the USA and the Northern European Energy Efficiency continues to improve while here in the states they cannot build Leed Buildings to the same standard as the Germans? If you all cannot get the job done perhaps you should hire some German Consultants to show you how.
    And the average cost of a German Green Building is only about 10-15% more then a non-Green Building construction while the energy savings will eventually pay for the additional costs. But here in the states it may cost double? What is going on with that? Greed? Something else?
    It just is silly sometimes how we pretend that the USA is at the forefront of the Renewable/Sustainable movement while the stats say otherwise. We are one of the most energy wasteful countries and Sustainability is not the top agenda only making a few billionaires richer.
    So what is the plan to match Europe’s Sustainability plans? Should we start consulting them perhaps? Whatever it takes,right?

  7. It is no surprise to me that LEED Certified buildings use more energy than non-certified buildings, assuming that they actually comply with the requirements of ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality, any version. This LEED Prerequisite requires that a prescriptive minimum amount of ventilation be provided to each occupied space under all conditions of occupancy.

    The problem is that most classical HVAC system designs (and designers) try to introduce outdoor air through a “mixed air path.” This is predicated on the erroneous belief that recirculation of air is necessary for energy efficiency. HVAC systems operating on this principal do not have the capability of either efficiently processing or effectively managing ventilation throughout a building.

    Meeting Standard 62.1 ventilation requirements is particularly difficult for variable volume strategies which have become favored in the design community because of their superior energy performance characteristics. This is because these systems actively compromise ventilation to save energy. Correcting the air quality problems these systems create often defeats the objective of energy use reduction. About most of these strategies, one can accurately state, “You can’t get there from here.”

    Can compliance with LEED prerequisites be met efficiently. Absolutely! But it takes creative engineering and “outside-the-box” solutions to accomplish. These are things that many Architects and Engineers are afraid of. In fact, it is far easier, and the facility is much more likely to save energy, if the designers falsely certify compliance with these requirements in a LEED application.

    After all, who is going to catch them?

    If you pump enough outdoor air into a building to meet Standard 62.1 ventilation requirements with a conventional HVAC system, you are going to be lucky if all you see is your energy costs go up 40%. You can have far worse problems than that.

    I’m not knocking “Green” design. It is a good idea whose time has come but the necessary technologies are still very much in their infancy. I am, however, highly critical of the extremely naive USGBC review process. If they do not turn that around and begin to actually enforce their prerequisites, a LEED Certification won’t be worth the scrap price of their plaque and USGBC will not be around much longer.

  8. John E June 22, 2010 at 5:44 pm #

    The article says “all of the buildings were consuming less than a building designed to Massachusetts baseline building codes.”

    It never says that the buildings consumed less energy than a building which was designed without wasting money on LEED.

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