Unrealistic Energy Models Cause Rub

Posted on February 10, 2012


Energy modeling is a tool growing in use to assist in both building design and operations—especially in buildings where energy costs are high, such as a hospital.  Green Source had an article a couple months ago noting the importance of occupant behavior in energy modeling. In particular, it noted how occupant behavior is often not accurately accounted for, which leads to inaccurate models. In blogging about the NREL net-zero project, one thing that stuck out to me was the importance of occupants in reducing variable energy usage like plug loads.

The issue causing the rub between designers and building owners is inaccuracy in the energy model, and occupants appear to be the scapegoat because their behavior is hard to predict. Green Source notes that the burden is on the design community to “more effectively communicate the role of operations and occupants in building performance”. This should be obvious to both designer and owner.

I think any reasonable owner cannot expect high energy performance without compliance on the user side since energy use is integral to everyday building use, and people inside a building affect energy use.  People give off heat; they consume water; they require light, heating and cooling for comfort; people use equipment and machinery to do their jobs, and that equipment requires electricity and puts off heat. Building users also open windows, fiddle with thermostats, bring in space heaters, and waste water and electricity from time to time.

Likewise, I think any reasonable designer cannot expect building users to act in an ideal way. In modeling energy use, designers must ask a lot of questions about expected building use and anticipated user behavior.  Designers must input realistic numbers based on industry benchmarks for building type, size, occupants, historical data from the client, or base input on defensible assumptions. Builders do this all the time when they produce estimates. Any builder knows it is easier to put in a place-holder value with a reasonable explanation than to come back later and say they didn’t know, excluded it, or blame the owner:  ‘they didn’t give me such-and-such information’. Much like formulating a personal budget, an individual cannot allocate money based on what they wish or hope will happen, or conditions in an ideal situation, and hope to succeed, but how money actually gets spent each month. The same is true for energy:  model on reality. Improvements can come at a later time, not in a model.

Given the recent advent of lawsuits by owners against designers and builders for not meeting LEED energy design targets, it seems important for owners and the design team to do two things throughout the project, and especially in regard to the energy model:  communicate and align expectations. LEED is addressing this issue by auditing buildings to verify they perform as designed, especially in regard to energy.

On a project basis, it simply makes the most sense to include all hospital parties with a stake in, or passion about, the energy performance, including Plant Operations, Facilities, IT, Planning, Clinical Services, Design & Construction, COO, CFO, even CEO, along with the Architect, Engineers, Construction team and relevant consultants like Commissioning Agents and even Food Service Design. With hundreds of thousands of dollars in energy costs a month for many hospitals, and well into seven figures for large facilities, this coordination is a huge step for a high-performing hospital—and on a smaller scale may simply ensure the doors stay open.