Balancing Energy Conservation and Occupant Comfort

Sept. 11, 2013
Lately, there has been a lot of talk concerning the adverse effect of energy conservation on occupant comfort, blogger Larry Clark says, admitting that although he makes his living helping clients reduce energy consumption, it is a real issue.

My wife’s favorite HPAC Engineering blog post is not, I’m sorry to say, one of mine. It’s Senior Editor Ron Rajecki’s April 18 “Rambling,” “Dreaming of a Pashmina-Free World." Like me, she didn’t even know what a pashmina was before she read it, but the topic resonated with her. We live in South Florida, where folks (visitors and resident alike) complain it’s too hot and humid in the summer. Yet, if there’s any air conditioning at all, my wife, like Ron’s, will be cold, whether it’s in her office (she is a human-resources [HR] manager at a university), in a movie theater, or at the airport (she actually bought a pashmina in the terminal last July while we were waiting for a flight).

Of course, it’s not just our wives who are uncomfortable in air-conditioned buildings. One of the first things I look for when I do an energy audit in a commercial office building is the number of sweaters on the backs of chairs and the number of space heaters under desks. And, no, it isn’t just about being cold—usually, there are some fans on desks, too.

Lately, there’s been a lot of talk concerning the adverse effect of energy conservation on occupant comfort, and although I make my living helping clients reduce energy consumption, I have to agree it’s a real issue. Often, the solution that saves energy doesn’t improve (or maybe even worsens) occupant comfort. For example, suppose we have a building with an ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality-compliant ventilation system, and we’re adjusting the outside-air (OA) rate to be controlled by the building-management system. Within the range of ventilation rates possible—staying above the minimum threshold, of course—the owner (who’s paying the electricity bill) wants the minimum permissible OA, while the HR/health-and-safety folks want the maximum OA to minimize indoor-air-quality-related complaints and sick days. So when building scientists blame energy auditors like me at least in part for the problem, they may be justified. In some cases, we’ve become so focused on reducing energy consumption that we often forget the end game: the comfort and safety of the building’s occupants and visitors.

Although green-building rating systems may give credit for occupant comfort, energy is by far their major focus. In both Green Globes Continual Improvement of Existing Buildings and LEED for Existing Buildings 2009, for example, energy accounts for roughly a third of the total possible points. Perhaps we can make rating systems more subjective for issues like occupant comfort by incorporating an occupant survey. But how do we balance actual energy consumption—the basis for our utility bills and various financial incentives—with what should be our goal of providing comfortable indoor climates for occupants? Today, we have amazing technology available to condition and control indoor environments, and we’re constantly reducing the overall energy-use intensity of our buildings. Yet, more often than we like to admit, we still seem unable to keep our occupants comfortable.

It is hoped that simple mindfulness will make us more sensitive to comfort considerations as we go about our business of designing, constructing, assessing, and operating buildings. But in the meantime, don’t throw away those sweaters … or pashminas.

About the Author

Larry Clark

A member of HPAC Engineering’s Editorial Advisory Board, Lawrence (Larry) Clark, QCxP, GGP, LEED AP+, is principal of Sustainable Performance Solutions LLC, a South Florida-based engineering firm focused on energy and sustainability consulting. He has more than two dozen published articles on HVAC- and energy-related topics to his credit and frequently lectures on green-building best practices, central-energy-plant optimization, and demand-controlled ventilation.