Comfort Zones

Thermostats are usually set to trigger heating when the air temperature falls below a certain point; similarly, cooling is triggered when the air temperature gets above a pre-set point.

The range between those two points is called the “dead band” … neither heating or cooling is activated.

The term “dead band” is not widely known outside the HVAC industry, but it’s useful in understanding the challenges (and opportunities) involved in keeping a space comfortable.

If the two points are too close together, the HVAC system may cycle often between heating and cooling, particularly on a day of moderate temperatures.  Instead, if we set the “dead band” as wide as possible, it reduces energy use … the HVAC systems stay off more of the time.

“Dead band” is a terrible term; our proposal is that we rename it the “comfort zone” and  encourage users (and system designers) to set it as wide as possible,  and narrow it only reluctantly if users complain too often.  A “comfort zone” of 6 degrees (from 68 to 74 F, for example) is perfectly reasonable.  If we can widen the zone to 10 degrees (e.g. 66 to 76 F), that would be even more efficient and affordable.

This is an example of where culture can help.  In Japan, “CoolBiz” and “WarmBiz” are corporate programs that ask building residents to wear warmer clothes inside in winter, and lighter, cooler clothes in summer.

Companies relaxed the expectation that employees would wear suits, jackets, ties etc.  This represented a change in culture that effectively allowed systems to be set for a wider comfort zone.

Establishing this expectation within an organization can help “socialize” the need to save energy.