Everyone talks about climate change, increasing energy efficiency, and the impact of buildings. What have been the results?
Here we are. A new decade has dawned, and the first half of 2010 has already drawn to a close. The first decade of the 21st century saw an unprecedented discussion of the impacts humans are having on the planet’s climate. There are an equal number of people raising their voices disputing the reality of climate change as those who believe the scientific data. There are lines of thinking about climate change that raise economic issues as a growing concern. Costs of all forms of energy are increasing. Reducing energy consumption in buildings to control operating expenses is becoming smart business. Some people argue, as Thomas Friedman does in his book Flat, Hot and Crowded, that reducing energy consumption will have a direct influence on national security.
Whichever set of arguments you ascribe to, there are plenty of reasons to design, renovate, and operate buildings in the 21st century to use less energy than they did in previous centuries.
As these discussions have transpired, the design professions and sustainable design advocates have come together around a few ideas. In founding Architecture 2030, Ed Mazria captured the imagination of many with his call to action. Thanks to Mazria’s ability to articulate the contribution buildings make to the nation’s energy consumption, we have come to understand the opportunity for change we can effect through the buildings we design. The 2030 Challenge took the next step, defining a process to get to net zero energy buildings by 2030. Way back in 2005, Mazria called for us to use our design talents to reduce energy consumption by 50 percent immediately. In each subsequent five-year period, the need to reduce energy consumption an additional 10 percent was designated to reach the 2030 goal.
Now that we are in 2010, the bar has been raised a notch: The buildings we design should be consuming 60 percent less energy to remain on the path defined by the 2030 Challenge. I point to the the 2030 Challenge because it still offers the most clearly defined targets for us to use in design.
Where’s the Assessment?
But most of you know that part of the story about transforming the design and operation of buildings for the purpose of using less energy.
What has been missing is an assessment of what we have actually achieved. Has all the talk lead to any real improvements in the outcomes of the work of architects, engineers, builders, and owners? Do we know more about how we really use energy in buildings?
The best answer is a resounding “Maybe.” To understand if we have made progress, we need to understand the baseline we are measuring progress against. In 2006, Architecture 2030, the American Institute of Architects, the U.S. Green Building Council, and the American Society of Heating, Refrigerating, and Air-Conditioning Engineers agreed on a baseline to determine energy consumption reductions in accordance with the 2030 Challenge. Following a lively debate, the baseline agreed upon by all was energy intensity levels documented in the Department of Energy’s Commercial Buildings Energy Consumption Survey (CBECS) — specifically the 2003 CBECS database.
CBECS has posted this rich database of audited energy consumption records from buildings in operation on its Web site (www.eia.doe.gov/emeu/cbecs). The data can be sliced and diced by building type and region. While far from perfect, CBECS is a good place to develop an understanding of the baseline. Unlike energy consumption determined through the design process, CBECS numbers record real-world experience.
Several studies, such as the New Buildings Institute’s 2008 report “Energy Performance of LEED for New Construction Buildings,” have identified the differences that exist between energy consumption anticipated by the design process and actual consumption following construction. To focus attention on an individual building, it was agreed that site energy rather than source energy would be the measure of performance. Site energy measures the energy used by the building regardless of where the energy comes from. Source energy considers how it is produced and transmitted to the building. While source energy yields a better understanding of CO2 emissions, it is nearly impossible to control through our design work because each utility has a different mix of generation capabilities.
You may have heard a lot about portfolio requirements for generation, but that’s a discussion for a different day. Today, let’s concentrate on what we can control as designers, focusing our attention on the site energy used as result of the design we create.
Understanding Energy Consumption
CBECS dates back to 1992, the first year of the survey. It was updated in 1995, 1999, and 2003. Some changes in methodology have evolved in those intervening years, making direct comparisons to derive overall trends something of a challenge. An update of the 2003 data has been underway since 2008, when building interviews were conducted in February and September. Energy supplier data was collected between February and May 2009 to complete the data collection effort. The Department of Energy has not determined a release date for this update, to be titled the 2007 CBECS Survey. Once we have access to the 2007 Survey, it may be possible to determine what progress we have made in the energy consumption of buildings.
It is interesting to note how little attention we pay to actual energy consumption. The building codes that currently regulate our work focus solely on design values for energy consumption. Once a building is complete, building departments do not require any documentation that the designed energy consumption is being achieved. This lack of follow up is a gap in code enforcement that does not currently receive much attention. As noted earlier, the New Buildings Institute’s report and other studies indicate that variances between design values and actual consumption can be large. Changes that occur during the construction process and changes to equipment or control systems can lead to differences in actual consumption figures during operation of the building. The delicate interaction between building systems can be undone by such changes, potentially furthering the distance between design and actual consumption numbers. The occupants of the building then play their part: plug loads, over-riding automated controls, or similar interventions will impact actual energy consumption. In addition, building operations and maintenance staff’s actions will influence actual consumption. Using actual energy consumption to inform design assumptions and models will incorporate more of these variables than current design practices.
The real, untapped potential of CBECS as a design tool is the energy target setting called for by the 2030 Challenge. Using the CBECS data as a benchmark, we can establish an energy budget for a project we are designing by understanding its energy use intensity. Even if you are not concerned with climate change, the 2030 Challenge, or any of those issues, it is time you understand the energy consumption that results from your design work.
The Energy Budget
Everyone seems to know the dollar budget for their projects, but few know the energy budget. We regularly talk about project budgets in dollars per square foot, using that as a metric to compare projects. There are many data services that regularly report those economic values on a regional basis as well as by building type. That data bears a striking resemblance to the CEBECS data. Rare is the project team that knows the kBTU/square foot/year of the project they are designing. This value is the basis for understanding an energy budget and how we allocate energy use in buildings. Without that understanding, it’s impossible to tell if we are improving the performance of buildings as individual practitioners, as firms, as a profession, or as a nation.
Developing an energy budget is not especially difficult. It is a something your mechanical engineer is doing already, particularly if an energy model is being developed for use in the design process. The energy budget must include all inputs to the building, heating, cooling, fans, hot water, lighting, equipment, pumps, elevators, process loads, and of course the occupant-controlled plug loads. Add all those loads together, normalize them to kBTU/square foot/year, and there you have it: an energy use intensity (EUI) budget for your building.
As a first step to improving our understanding of energy consumption, we simply need to ask the question and hear the answer. Your design team may not understand what you are getting at the first time you ask. Keep after it. Be persistent and you will be surprised at how they react. Start asking for the EUI early in the design process. Each time you make a design revision, have the EUI/energy budget updated to see if it lowers the energy consumption or drives it higher. Every time you discuss the project budget, discuss the energy budget as well. Link these elements in the minds of the entire design team, including the construction and owner team.
Report the EUI/energy budgets for all projects in your office. Different building types have different energy profiles; getting your staff to understand the range for various building is a great learning opportunity. By reporting the EUI/energy budget, over time you will see teams beginning to find ways to lower the consumption on each successive project.
If you want to be more rigorous in using EUI/energy budgets as a design tool consistent with the 2030 Challenge, the Department of Energy offers a tool. TargetFinder is a quick calculator to determine a percentage reduction from the 2003 CBECS database used as the 2030 baseline described earlier. Set if for 60 percent if you want to achieve the current target. Push it to 70 percent or more if you want to be a bit bolder and put your work on the leading edge of energy consumption reductions. These are the kinds of clear targets we can aim to achieve with each and every project we design.
Understanding a project’s design EUI is a vital first step in regularly improving the performance of our buildings. Being able to discuss a project’s energy budget, we can begin to make meaningful decisions about how to allocate energy to individual building systems. Knowing what the energy budget is for lighting systems may lead to a greater reliance on daylighting to balance the budget, for example. The selection of HVAC systems and their controls can be better informed when we understand how they interact with other systems to achieve total energy consumption. Some design teams are using these tools, but they are the exception rather than standard practice.
As we begin a new decade, the challenge of improving the energy performance of buildings will not diminish. We can expect regulations to become increasingly rigorous in their expectations of performance, as evidenced by the International Code Council’s recently published draft of the International Green Construction Code. Public policy makers are paying increasing attention to the impact of buildings on national energy policy, holding regular Congressional High-Performance Building Caucus meetings on Capitol Hill. Other nations are implementing regulations for continual improvement of building performance: Japan requires existing buildings to improve their performance by 1 percent annually.
One simple way for the design and construction community to understand our progress is to understand energy use intensity and energy budget data for each of our projects. Tomorrow when you get to the office, ask your project teams what their EUI is. I’d love to hear what they answer.
R.K. Stewart is an associate principal with Perkins + Will in San Francisco, where he focuses on building performance and sustainable design. Stewart is a former president of the American Institute of Architects, current vice chair of the National Institute of Building Sciences, a fellow of the American Institute of Architects, and a senior fellow of the Design Futures Council.
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