Examining the True Meaning of Statistics
by Jonathan McGaha | December 2, 2012 12:00 am
Statistics are interesting things. People use statistics for all kinds of reasons, usually to support their opinion or to base their own assertion. Another interesting thing is that they can take on a different meaning depending on the context in which they are used. I recently heard three statistics that made me think about our industry. During a lecture hosted by a local USGBC chapter, the speaker said that in the United States, 80 percent of the buildings that we are using today will still be in use 20 years from now. Then, at a webinar hosted by the EPA’s Energy Star program, the speaker asserted that 30 percent of site energy used in buildings is wasted. The third statistic was published in “USA Today” and stated that while 24 percent of the LEED certified buildings in a particular study used less energy than their conventional counterparts, one-third used more energy than conventional buildings. The USGBC itself states that, “Most buildings do not perform as well as designed metrics indicate.” I want to look at how these three statistics impact the green building industry, and how builders and owners should view them.
“Twenty years from now, we here in the United Stat es will still be using 80 percent of the buildings that we are using today.”
The speaker used the first statistic to impress the importance of reusing our existing building stock wisely and to stress the fact that in the near future there will be an increased emphasis on building retrofits rather than on new construction. The point was well taken and the numbers used during the lecture are generally supported with industry indicators. Another way to use this statistic is to say that in 20 years only 20 percent of the buildings we use will be new. The 80 percent could also be used to point out the rising cost of energy. The buildings that were built even five years ago were constructed without much regard to energy conservation. Even the buildings constructed in areas that have an energy conservation section built into the local building codes often had project teams who used those standards as minimums. If 80 percent of our existing building stock will still be used in 20 years, and those buildings are not upgraded to consume less energy, then how will our local utilities keep up with demand? Energy rates charged by a utility are typically comprised of several components: the cost of fuel, equipment used to create the energy, transportation to the consumer, state and federal compliance and maintenance. Indicators suggest that the costs for each of these will continue to rise, so building owners wanting to lower operational costs should focus on improving efficiency of their building.
“Thirty percent of site energy used in buildings is wasted.”
The webinar host used a statistic to demonstrate where energy is used or consumed in a building. If 30 percent of energy consumed in a building is wasted, 70 percent is needed to operate the building as it was designed and constructed. These numbers could also be used to support the argument that if 30 percent of energy consumed in a building is wasted, then it really does not need to be consumed at all. Another way to look at this figure is by considering the fact that building owners could reduce their energy bill by 30 percent if they would stop wasting energy. While the last example is a bit harsh and points the finger at the building owner, it does force ownership of a problem. A person could tie the 30 percent to the first example and assert that if 80 percent of our existing buildings used 30 percent less energy (energy that does not need to be consumed) there would be less demand, reducing the load and adding to the useful life of the equipment used to generate energy from the utility.
“While 24 percent of the LEED certified studied buildings used less energy than their conventional counterparts , one-third used more energy than conventional buildings.”
The “USA Today” statistic is an example of how numbers can easily be used to argue the worth of LEED certification. Opponents would use the statistic to support the argument that using the LEED rating system does not produce better buildings. Supporters would say that no system is perfect and that some of the buildings certified under LEED outperform conventional buildings. The same statistic supports both of these arguments. However, it is important to consider certain questions when breaking down a statistic like this. Were all of the buildings in the study identical? Were these buildings built in the same location? Did the same group of people occupy and operate the buildings? The answer to these questions is most likely no. Interestingly, the USGBC admits that, “most buildings do not perform as well as designed metrics indicate.”
Why would the USGBC, the creator of LEED, make this statement? I am not a spokesperson for the USGBC, so I cannot provide its rational. As a user of LEED, I can say that LEED is a system of prerequisites and voluntary credits. Teams can choose to focus their attention on any number of strategies that, in combination, achieve a point total relative to one of four levels of certification. A LEED certified building does not automatically equal a high-performance building. Another reason why the USGBC may have made the statement is because an energy model that is created to predict a building’s energy use is a tool. It is created using data and assumptions then compared to a baseline standard. Why do buildings not perform as they were modeled? Two reasons: either the building was not modeled the way it should have been for occupancy use or the building is not being used the way it was modeled.
The funny thing about statistics is that the same number can be used to support more than one argument or opinion. It is important that building owners and members of project teams that may be involved in the renovation or construction of a green facility consider what else a statistic might mean. Ask questions and do some research before accepting a statistic as reported. In the end, the result may mean a better, more efficient green building.
Thomas Taylor, a 30-year veteran of the construction industry and noted expert on sustainability, is the general manager of St. Louis-based Vertegy. His recent book, “Guide to LEED 2009: Estimating and Preconstruction Strategies,” provides step-by-step information about the LEED 2009 for New Construction process. To learn more about Vertegy or Taylor’s new book, visit www.vertegyconsultants.com for more information.
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