How to Ensure that High Performance Designs Result in High Performance Buildings

A Conversation with Architect, Planner and GBI Technical Advisor Jiri Skopek

GBI Insight:  What causes performance slippage? Why aren’t predictions more accurate?

JS:  From the time a building is conceived to its ultimate operation, countless decisions are made which have an impact on performance. Using energy as an example—and performance slippage can occur in any area—the designer predicts what the energy consumption will be, the builder produces the systems that consume the energy, the building operator maintains those systems, and the occupants consume the energy. Given the variables at every stage, it’s no surprise that the performance predicted may be quite different than that of the actual building or that the variance tends to occur in the least desirable direction. People plan for the best case scenario and assume that everything will go smoothly. Unfortunately, it isn’t unusual for actual energy consumption to be as much as three times the predicted value.

GBI Insight:  Is it a case of designers having to lower their expectations or do they need to improve their predictive techniques?

JS:  Bill Bordass, a scientist and building performance expert in the UK, writes extensively on this subject. He says that problems arise not because predictive techniques aren’t accurate, but because they don’t fully account for the realities of an operational structure—and because few designers stay involved with a project long enough to monitor building performance. As a result, they don’t know which strategies work and which don’t. For example, it’s common for control systems to have poor management and user interfaces, which causes equipment to default to the ON position. This is tremendously wasteful and yet it continues to happen time and time again.

GBI Insight:  Can you provide any other specific examples?

JS:  I can provide examples at every stage of the building’s life cycle:

At the design stage, energy estimates may be unrealistically low. Perhaps the designer only accounted for the energy used by building services such as HVAC, lighting and hot water and overlooked functions such as plug load or elevators. Or maybe an incorrect assumption was made that systems would be off at night.

At the design development stage, slippage can easily occur if the designer chooses not to repeat energy modeling (perhaps due to budget) for each design iteration.

During occupation, the building may use more energy than predicted because of poor operation and maintenance, improper fit-ups, changes in occupancy or the occupants’ poor energy habits.

GBI Insight:  You’ve talked about using the Green Globes system, which you helped develop, as a way to help ensure high performance. What do you mean?

JS:  Some slippage at the operational stage is legitimate—when the building is used more intensively than planned, for example, or contains more equipment—so designers can’t be 100% accurate all of the time. But rating systems such as Green Globes, which encourage repeated evaluation from design concept through completion, help to identify and address problems as they arise. An effective rating system tracks the process in a seamless continuum with respect to best practices of integrated design, construction, commissioning, building operations and tenant involvement. Establishing a continual evaluation process makes it possible to assign accountability, diagnose where slippage has occurred and take corrective action.

For more information, Jiri Skopek is scheduled to present a paper titled “Mind the Gap – The Green Globes Approach to Bridging the Gap between Building Design and Performance” at Rethinking Sustainable Construction 2006: Next Generation Green Buildings, September 20, 2006 in Sarasota, FL.