Attention: Performance Marker Ahead

August 11, 2008 · by RK Stewart

Data is beginning to trickle out regarding actual performance as a result of the steps being taken to reduce energy use in buildings. The numbers indicate a need to raise the bar on performance standards.

Data is beginning to trickle out regarding actual performance as a result of the steps being taken to reduce energy use in buildings. The numbers indicate a need to raise the bar on performance standards.

While discussion of sustainable design, energy consumption, and the built environment can be traced to the 1970s, the talk has taken on a new urgency since the 21st century dawned. Climate change and the survival of the planet have jumped to the front of our collective consciousness. While many individuals and organizations can rightly lay claim to a role in advancing these issues in the public’s and the profession’s understanding, there are a few that warrant special recognition because they focus us on solutions.

For my part, issues related to the energy consumption of buildings warrant the greatest attention of the building and real estate industries. In 2006, Ed Mazria gave a significant boost to sustainable design efforts, energy consumption, and climate change when he issued the Architecture 2030 Challenge. Many design professionals are familiar with this program. The short explanation of the Challenge’s goal is an immediate reduction for both new and renovated buildings in the consumption of fossil fuel, greenhouse gas-emitting energy by 50 percent (from the regional average) for a given building type. The baseline to determine regional average consumption is the Commercial Building Energy Consumption Survey compiled by the U.S. Energy Information Administration every four years. It is easy to understand the energy use intensity target for a building thanks to EPA’s Target Finder tool (www.energystar.gov/targetfinder).

The 2030 Challenge does not stop with the initial 50 percent energy reduction goal; rather, it raises the performance goal to a 60 percent reduction beginning in 2010 and an additional 10 percent performance increase each five years thereafter. Meeting the 2030 Challenge will result in all new buildings and renovations being carbon neutral — meaning they require the consumption of no greenhouse gas-emitting energy to operate — by 2030. Many organizations, design firms, and government entities have adopted the goals of the 2030 Challenge to guide their actions and strategic plans.

As we approach the first major 2030 milestone, increasing energy use reductions from 50 percent to 60 percent in 2010, we have to ask ourselves: Are we meeting the challenge?

How Are We Doing?

Thus far, the answer has been hard, if not impossible, to determine. A major data set came forward recently to help us understand what our progress has been in meeting the 2030 Challenge. While not a final analysis given the small sample size, this report is an important document for the design profession and sustainable design standards organizations to begin assessing the impacts on real-world energy consumption performance. As a starting point, it can be used to inform individual project teams as well as to improve the standards.

The Washington state-based New Buildings Institute published its report “Energy Performance of LEED for New Construction Buildings,” in March. Prepared for the U.S. Green Building Council, this report is the most comprehensive study to date of the progress made to improve the energy performance of the nation’s buildings ever released to the public. It analyzes the actual energy performance of 121 LEED new construction buildings completed between 2000 and 2006 that could provide a minimum of one full year of measured post-occupancy energy use for the whole building at the level of monthly energy bill. Buildings were included in the study without restrictions regarding building type, number of energy points received, or other LEED program parameters. The report’s buildings represent 22 percent of all those certified under LEED NC v2.

While no perfect basis for determining energy savings exists today, there is a great advantage to looking at savings from multiple perspectives using documented energy consumption. For the study, actual energy performance was viewed against three recognized energy performance metrics:

• Energy use intensity (EUI) of LEED buildings relative to national average use

• Energy Star performance of LEED certified buildings

• Actual measured energy performance relative to design and baseline performance

Beginning with actual performance viewed against the Commercial Building Energy Consumption Survey (CBECS), which is the national standard baseline referenced by the 2030 Challenge, the NBI study yields interesting results. Quizzing the CBECS 2003 data via the Target Finder tool, we learn that the average EUI is 91 kBtu per square foot for medium energy type buildings. Looking at all 121 LEED buildings in the survey, the median measured EUI was 69 kBtu/sf, which is 24 percent below the national building stock’s average. Refining the view of measured performance reveals that LEED certified buildings average 67 kBTU/sf; LEED Silver buildings average 62 kBtu/sf; and LEED Gold and Platinum buildings average 51 kBtu/sf. (The report’s authors note that Gold and Platinum building data are combined because only two Platinum buildings were included.) These results translate to an energy reduction from the average CBECS building of 26 percent for certified buildings, 32 percent for Silver buildings, and 44 percent for Gold and Platinum buildings.

Interestingly, looking specifically at the results of increasing points gained for LEED EA Credit 1, there is little difference in energy performance when two to seven EAc1 points are gained. Another finding of the study is that LEED points in related credit areas do not seem to have a significant impact on energy performance. NBI examined the LEED submittals of these buildings to see if a correlation exists between points gained in four credit areas and the resulting energy performance:

• EAc3 (Additional commissioning)

• EAc5 (Measurement and verification)

• EQc8.1 (Daylight)

• EQc8.2 (Views)

While these credits should result in improved energy performance, no clear performance impact was found as a result of gaining points in these credit areas.

Looking at LEED NC building performance relative to the EPA’s Energy Star program, we gain another view of actual building performance. Energy Star rates energy use in relation to the existing national building stock, normalized for variables such as temperature, number of occupants, number of computers, operating schedule, and other factors. The median rating of the nation’s total building stock is 50, meaning 50 percent of buildings perform worse by using more energy while 50 percent perform better by using less energy. The NBI study found the average LEED building would achieve an Energy Star rating of 68, meaning it would perform better than 68 percent of similar buildings nationwide. Further analysis reveals that 47 percent of LEED buildings achieve an Energy Star rating of 75, performing better than 75 percent of similar buildings. Such performance would garner them EPA Energy Star certification. The further analysis also reveals that 25 percent of LEED certified buildings in the survey had Energy Star ratings below 50. At the extremes, 15 percent of LEED buildings in the study have ratings below 30 and 17 percent have ratings above 90.

The NBI report’s last view looks at actual measured LEED building performance relative to design and baseline performance metrics included in submittals for building certification. This view gives us a look at the design intent of a project relative to its actual measured performance. To achieve LEED points, a building’s predicted energy cost savings are compared to the modeled performance relative to building code baseline. Energy modeling tools use occupancy, operational schedule, assumed internal (plug) loads, weather data, and similar data leading to a number of caveats being attached to most such models. The energy models are intended to identify relative energy performance between alternative designs rather than serve as predictors of actual energy use. Despite the intended use of such models and the caveats attached to them, many people view energy models as an estimate of actual energy use in the future. That baseline is the energy cost budget performance requirements generated when using the ASHRAE 90.1 standard.

The 1999 version of ASHRAE 90.1 was used by the majority of the buildings in the NBI report. The actual measured energy consumption of the LEED certified buildings in the report revealed a 28 percent savings compared to the code baseline and approached the 25 percent savings predicted by energy models included in the LEED submittals. While the energy models were good predictors of energy performance for the average building, further analysis of individual projects reveals a wide variance from the average energy consumption even within a single LEED certification level.

The ability of any individual building’s energy model to predict its actual performance is inconsistent. Some buildings perform much better than the energy model predicts. Nearly an equal number of buildings perform much worse than the energy model predicts. These kinds of variations could result from a variety of causes, including operational issues following construction and changes during construction, among others. Such a wide range of accuracy may adversely affect design decisions evaluating energy efficiency strategies or life cycle cost analyses since buildings do not perform as well as predicted by an energy model.

What Do We Do Next?

If our focus on sustainable design and energy performance is to amount to the desired outcomes, then this NBI report represents an important and meaningful step toward understanding. The results of the study suggest that governmental entities should be asking more questions about the results that may be achieved when guidelines are adopted as requirements. For individual design professionals, this study gives us useful data to engage our clients and design team members in driving improved performance.

I urge each of you to visit the NBI Web site to read the report ­(newbuildings.org/research.htm). At only 46 pages, it will not take a lot of time. This article has identified some key findings, but reading the report may lead you to some important insights for your work. In that vein, I take several important points away from reading the NBI report.

I readily admit to a strong personal bias that the professions become much more aggressive in rapidly reducing the energy used by buildings and achieving the goals of the 2030 Challenge. NBI’s analysis indicates that we are not achieving the 50 percent reduction marker of the 2030 Challenge using the LEED guidelines or ASHRAE 90.1. It was both surprising and troubling to learn that the most common building code baseline, ASHRAE 90.1, is resulting in buildings that perform at or near (within 5 percent) the national average building energy use. Granted, the buildings in the NBI report conformed to the 1999 version of ASHRAE 90.1 and ASHRAE continues to evolve the standard. The 2001 and 2004 version is applied to most current projects; the 2007 version will soon to come into regular use. However, most people, particularly government officials and the public, assume that building code requirements define preferred performance. Those of us working in the industry — architects, engineers, building officials, and sustainable design advocates — know that building codes merely define the minimum legally acceptable level of performance, not what we seek as a society to meet a stretch goal such as the 2030 Challenge.

To improve energy performance significantly and achieve the 2030 Challenge goals, we should all advocate for higher levels of performance in the code requirements embodied by ASHRAE 90.1. While there is a general assumption that these standards are delivering higher performance levels, the NBI study illustrates that the performance of new buildings approximates the average of the national building stock.

We should advocate that each of the sustainable design standard and guideline organizations — EPA, U.S. Green Building Council, Green Building Initiative, and all the rest — make significantly higher energy reduction performance a requirement to achieve certification under their programs. While each of these organizations encourages increased performance by the points they award, the significant energy reductions of the 2030 Challenge targets are not specifically rewarded by any of them. Such robust requirements within the standards and the building code would more closely align the promise of sustainable design with the expectations of the public and policy makers.

We need to understand better what the energy reduction targets are for each project we undertake. Almost everyone associated with a project can tell what its economic budget is and how many dollars per square foot the project is expected to cost. Far too few people can tell you about the energy budget and how many kBtu per square foot a project is projected to consume. Nor can people typically tell you what the CBECS baseline average is for the building type. It should no longer be acceptable to talk dollars and cents budgets without also knowing the kBTUs being consumed.

We also need a lot better data on what we are actually achieving. I want to applaud USGBC and NBI for undertaking this study. The importance of this first step cannot be overstated. At the same time it points out several steps we all need to take, and soon. The database that feeds the CBECS needs to be improved. A lot of room exists to increase the number of project types, the number of individual buildings supplying data, and the regional diversity of buildings included in the data set. Design professionals should encourage clients to join the discussion and participate in the EPA’s Energy Star Portfolio Manager program to enhance the database.

To reduce energy use, we all need to understand how we use energy in our buildings and the interaction between various building systems. There are a number of important benchmarking discussions going on that we could reference in our work. A good place to begin is the Lawrence Berkeley National Laboratory Web site (energybenchmarking.lbl.gov). As some other sites do, it points to tools, concepts, and strategies we can employ today to help us understand energy use in buildings.

We all need to follow through and benchmark our design work. We need to look back, as the NBI study has done, to see if the energy reductions intended during the design process are being achieved. Actual measured performance experiences will tell us how to achieve ever more stringent energy performance levels. Once your own building performance is documented, sharing it with others in the profession in the form of case studies will serve to advance the cause of sustainable design.

We have come a long way in recent years in understanding the impact that buildings have on the nation’s energy consumption profile. The impact buildings have on climate change continues to grow. As policy makers and the public better understand the role our work plays in this critical issue, one thing will become increasing certain: The architecture profession and the building industry will be called upon to deliver real, meaningful results to reduce energy use by improving, drastically improving, the performance of our buildings.

The NBI report is an important beginning to assess the impact we are having. While some progress has been made, the trends detailed in the report tell us we have much, much more to do if we are to avoid disaster. Knowing the creativity and innovative skills of the design professions, I remain confident that we will respond to secure the future for future generations.

RK Stewart is an associate principal with Perkins + Will in San Francisco. There, he focuses on commercial and civic projects with an emphasis on sustainable design. Stewart is a past president of the American Institute of Architects and a Senior Fellow of the Design Futures Council.

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