Wardrobes, male to female occupant ratios, and metabolic rate assumptions have changed, but many set-points haven't.
A long time ago, in a galaxy not too far away, Franklin D. Roosevelt was President of the U.S. The last reunion of The Battle of Gettysburg was held. The War of the Worlds was broadcast on the radio, and Winston Churchill beckoned the U.S. and Europe to prepare to fight Hitler. Also, ASHRAE’s Standard 55–specifying the environmental and personal factors that influence thermal comfort conditions in air-conditioned space–was first drafted. And so began, in 1938, the Thermostat Wars.
It’s when summertime rolls around and office occupants breakout the sweaters that the Thermostat Wars really start to heat up. And the conflict is collecting press coverage, too (see recent New York Times articles here, here, and here).
A quick sitrep:
- Many office occupants report that their spaces are overcooled in the summertime.
- In many cases, more women than men report that their space is overcooled during the season.
- ASHRAE Standard 55 (based initially on a document drafted in 1938 and published in 1966) is the guideline referenced for a building’s range of thermal comfort set-points.
- An article in Nature Climate Change (Energy consumption in buildings and female thermal demand) argues that one of the primary variables in Standard 55 is based on an antiquated value of the metabolic rate of an average male–aged 40 and weighing about 150 pounds–and thereby overestimates the female metabolic rate by as much as 35%.
- ASHRAE’s response to the Nature Climate Change article faults the study for sampling only 16 women and for not sampling any men. It also clarifies that Standard 55 takes into account the switch to summer clothing, and reiterates the work ASHRAE has done to continually update Standard 55.
- The author of ASHRAE’s response, Bjarne Olesen (a current ASHRAE board member and former chair of the Standard 55 committee), concedes that field studies show that women prefer higher temperatures than men, and he attributes this difference to differences in clothing. Olesen comments that many men continue wearing a suit and tie while women adapt their wardrobe.
It’s crucial to note that even if ASHRAE standards are met, they are designed to satisfy 80% of occupants… meaning that for an office of 500 people, 100 people will be too hot or too cold. This doesn’t mean you should write-off those hot/cold calls as coming from the 20% unhappy campers and assume your building is operating within its design tolerances.
Strong tenant engagement systems will help keep the people in your building satisfied–even when they get uncomfortable–and you’ll be better equipped to fine-tune startup sequences, pre-cooling, and set-point deadbands. These refinements will help your building lower its lower utility bills.
For example, the building below used Snapmeter to refine its pre-cooling strategies on Sunday and cut its Sunday demand spike by 230kW:
Do your tenant spaces feel as though winter is coming? If so, perhaps your set-points are unintentionally a little sexist. Some offices turn to space heaters, fans, and placebo thermostats while occupants bundle up in their favorite snuggies. It doesn’t have to be this way: with the right data in hand, building teams can fine tune operations and strike a truce between cold calls and cost.
