Introduction
If you have not yet taken steps to optimize your building’s energy consumption, you may be missing out on a huge opportunity. How huge? Well, as was detailed in this column in February, the Joe Serna Jr. California EPA Headquarters (Cal/EPA) Building in Sacramento, CA annually saves $1.00 per square foot relative typical Class A office space in downtown Sacramento. This annual savings amounts to nearly $1 million for the 950,000 square foot facility which translates to nearly $10 million in increased asset value. Whether your motivation is increased asset value or lower operational costs, a critical first step to optimizing your building’s energy use is first to understand how it is performing.
Often referred to as benchmarking, assessing the energy performance of your building is an effective tool for facility managers and is an excellent first step toward optimizing energy use. Typically, annual energy intensity – annual energy consumption per square foot – is used to assess energy performance. This simple “normalization” of dividing annual energy consumption by the building’s gross floor area can shed light on your building’s performance. Before you go grab your utility bills for the past 12 months though, you need to be aware of the common pitfalls and misconceptions surrounding benchmarking. In taking this first step, it is important to go beyond simple annual energy intensity comparisons and consider the major drivers of energy consumption such as building type and size, business activity, fuel mix, weather, and climate.
Basis of Comparison
There are two commonly used bases of comparison in assessing building performance: to self or to a peer group. Comparing the energy performance of a building to itself over time is useful and limiting at the same time. By tracking building performance over time, if variations in fuel mix and year to year weather conditions are appropriately accounted for, one can effectively trend the performance and should be able to observe the effects of improvements or spikes in energy consumption. While it is certainly worthwhile to track how your building performs on a yearly basis, this type of comparison does not give an indication of the absolute performance of the building, that is, the performance of the building relative to a peer group. Drawing comparisons to a peer group, a facility manager can go beyond a basic understanding of whether their building is simply more efficient and gain deeper knowledge of whether their building is truly energy efficient – as compared to its peers. Since it can serve both as a relative and absolute first measure of energy performance, we’ll focus on peer group comparisons from this point.
Building Type, Size, and Activity
According to the Department of Energy’s Energy Information Administration (EIA), typical office buildings have annual energy intensities twice that of warehouses and over two and a half times less than that of hospitals. EIA data on commercial buildings in the United States also indicates that for buildings greater than 10,000 square feet in size, the average annual energy intensity increases as building size increases. Another issue to consider is business activity. Intuitively, a building which operates longer hours or has more occupants than a similarly sized building will likely have a higher energy intensity. Clearly, in comparing building performance to a peer group, one must be certain they, in fact, are using an appropriate peer group.
Fuel Mix
Virtually all commercial buildings in the United States consume electricity and most consume a secondary energy source such as natural gas or fuel oil. A common mistake in peer group comparisons is to only focus on electricity. While electricity is the most widely used energy source for most commercial building types, limiting comparisons to it can lead to erroneous conclusions. Because electricity can be used to both heat and cool a building comparing the electricity intensity, in kilowatt-hours per square foot, of buildings having electric boilers to those having gas boilers for example will lead one to believe that the latter are more efficient. This may, in fact, be true; however one cannot make that determination if only a single fuel source is considered because the comparison is unbalanced.
Weather and Climate
Weather and climate are just one in same, right? Well, actually, no they are quite different. In making peer group comparisons, be it at a national, state, or regional level it is important to understand the impact and differences of both weather and climate. Weather typically refers to year to year variations from typical – that is, historical – conditions. For example, this past year southern California has experienced cooler, significantly wetter weather than historical norms. This variation from historical norms for southern California has impacted the energy consumption of buildings located in this area. To account for it, clever facility managers find or create ways “weather normalize” their energy consumption; effectively putting their annual energy intensities from one year to the next on equal footing. Climate on the other hand is more related to location. The climate in south Florida can be described as hot and humid whereas the climate in the Pacific Northwest can be described as cool and humid. These descriptions are based on historical averages. All other things being equal, a building in Miami will consume energy differently than a similar building in Seattle. This is largely due to climatic differences. Year to year weather variations are typically within +/- 5 percent in a given location, while energy intensities from one location in the country to another can vary +/- 15 percent or more due to climatic differences.
Closing
As you can see, to effectively assess building energy performance relative to a peer group and track that performance over time, there is a lot to consider. Fortunately, through a program developed and run by the federal government, this task is easy and free. Since 1999, the Environmental Protection Agency (EPA), via the ENERGY STAR© program, has offered an internet-based tool called Portfolio Manager to help building owners objectively assess energy performance in the context of an easy-to-understand 1 to 100 rating scale. To date, over 30,000 buildings have assessed their energy performance using ENERGY STAR’s Portfolio Manager tool. So, whether you are managing a single small office building in Boise, Idaho or hundreds of buildings spread out across the country Portfolio Manager can help you take that first step toward optimizing your energy use. In addition to serving as an objective peer group comparison, the Portfolio Manager tool can be used to obtain recognition via the program. The ENERGY STAR rating system also plays a central role in the U.S. Green Building Council’s Leadership in Energy and Environmental Design for Existing Buildings (LEED-EB) rating system acting as the basis for one prerequisite and up to 10 of a possible 85 credits.
Resources
ENERGY STAR® (Follow: Home > Business Improvement > Assess Building Performance)
ENERGY STAR is a government-backed program helping businesses and individuals protect the environment through superior energy efficiency by providing a variety of tools and resources.
U.S. Green Building Council® (Follow: Home > Rating Systems > LEED-EB)
The U.S. Green Building Council offers up to 10 credits toward achieving their LEED for Existing Buildings certification for buildings demonstrating certain ENERGY STAR ratings.
Energy Information Administration
The Department of Energy’s Energy Information Administration collects and publishes information on commercial building characteristics and energy consumption in a quadrennial publication called the Commercial Buildings Energy Consumption Survey.
