Thermal comfort in the workplace
Ever thought that your work building was too cold? Or too hot? Too drafty? Or to stuffy?
Believe it or not, your building manager is not trying to freeze you out or make it uncomfortable to work.
Chances are, the temperature in your office came from a recommendation from the American Society of Heating, Refrigerating and Air-Conditioning Engineers via their building code Ashrae 55.
This code helps determine the ideal temperature for large buildings.
And it’s based on Fanger’s Comfort Equation; a prediction of thermal comfort. It takes into account the worker’s level of activity, type of clothing and environmental variables like air speed and humidity.
This equation has been used around the world, and for decades — it was developed in the 1960s — to help determine a comfortable atmosphere for a very specific worker: a man in a three-piece suit.
While that may have made sense in 1967, the workplace population, and the workplace attire, have changed.
Engineers have updated Ashrae 55 over the years, but it’s still hard to make everyone comfortable.
In talking with the building manager at the paper, I learned our building is set for 70 to 73 degrees, year-round. The HVAC system is split into about 20 zones which keep there sensors happy and communicate with the other zones.
The system is intuitive and democratic, said Tom Norton, vice president of operations at the York Newspaper Company, and the keeper of the thermostat.
That means, each zone gets a vote. If 15 zones think it’s warm enough, the other five zones will not adjust their temperatures even if they’re off from normal.
It also means if the outside temperature is different today than yesterday, the system remembers and can adjust accordingly. If the outside temperature change is drastic, it might take longer to make the inside temperature “comfortable.”
Norton can see the temperatures throughout the building on his computer. If all is going well, green boxes will glow back at him.
Sometimes yellow or blue zones might pop up. Those areas are warmer or colder than the average, but as the minority, they aren’t likely to change.
Norton tries to make the office a reasonable temperature, but there are some circumstances out of his control: the height of ceilings, the lack of walls in the interior of the building, what people choose to wear.
And the temperature at the paper is probably higher than Fanger’s algorithm would suggest.
In case you were interested, the algorithm looks like this:
f(M,Icl,v,tr,ta,Pw)=0
where M=metabolic rate
Icl=cloth index
v=air velocity
tr=mean radiant temperature
ta=ambient air temperature
Pw=vapor pressure of water in ambient air