Turns out, our reader and myself are not the only ones who find this behaviour perplexing. After some research into the issue, I uncovered a number of seemingly sensible reasons for turning buildings into spaces more suitable as refrigerators. Later this week I will finish off by looking at the problems over-cooling causes and what can be done about it.
First let us look at office buildings mainly because they have a regular, captive audience that can’t escape the commonly imposed icy temperatures. One misconception found in a report by the Globe & Mail, was that employers widely believe that productivity is increased by temperatures slightly below the standard comfort level. They purposefully set the thermostat a few degrees below a comfortable level in order to stop their employees from drifting off to sleep. Unless one’s employees are five years old and accustomed to a blankie and nappy naps throughout the day, this is pretty ridiculous. It is also completely incorrect.
Thanks to a 2004 study cited in the Globe’s report, it was found that when the temperature was dropped from 25 to 20 degrees Celsius, typing mistakes increased by 74% and output fell by 46%. Interestingly, 25 to 20 degrees is the normal range of temperatures widely deemed ‘comfortable’. Many buildings blast their air conditioning to achieve temperatures below that 20 degree mark, so just imagine how useless those occupants become! Conversely, the study found that when the temperature was raised from 20 to 25 degrees, typing errors were reduced by 44% and output increased by 150%. You want more productive employees? Let your office exit the ice age!
Next up, shopping malls, conference buildings, etc. Here, one would think that comfort would be the ultimate goal of the building managers. And one would be right. However, the logic by which so many building managers pursue the comfort of the occupants appears to be really faulty. Here is how the line of thinking commonly goes:
The building manager is expecting a certain number of people in and out of his/her building in a given day. For example, a tradeshow is being held and 5,000 attendees are expected on Friday. The building manager knows that each one of those 5,000 bodies gives of a certain amount of heat, putting added load on the building’s air conditioning system. So, they try to beat that heat to the punch by ‘pre-cooling’ the building. They run the air conditioning before all those bodies even arrive, in order to bring the building temperature well below comfort level. As attendees arrive, they contribute to the heating up process- by the time all 5,000 people are in the building, the temperature has risen to a comfortable level.
There are several flaws with this plan. Most obviously, the first 4,900 people to come into the building are going to be wildly uncomfortable because it is simply too cold for them. Also, what if the building manager’s predictions are off? What if only 4,000 people attend the tradeshow? Well, those 4,000 are going to be popsicles in very short time. Alternatively, over 5,000 people may attend the tradeshow throughout the day but there may not be enough inside the building at any given time to raise the temperature to a comfortable level.
The former president of the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE), weighed in on this issue for USA Today and gave a more scientific reason for over-cooling. Essentially pre-cooling is a method used to make up for a larger problem of under-sized air conditioning. Building managers who have installed an air conditioning system that lacks the capacity to cool the building properly, will pre-cool a space before it is filled with people because they know the air conditioning system needs to get a head start. Once all the added heat from occupants is present, the air conditioning will struggle to keep the temperature in a normal band. Over-cooling is a natural byproduct of a poor decision made over the installed air conditioning.
ASHRAE’s former president also pointed out the role of humidity in the problem of over-cooling. Let’s look at Hong Kong for this point. The BBCnamed Hong Kong as one of the coldest air conditioned territories in the world. Hong Kong is also widely known as being sweltering, hot and humid (outside at least). According to ASHRAE’s analysis, one of the reasons for this discrepancy is because people use air conditioning to not only drop the temperature inside a building but also to reduce humidity. How this should work is with the proper air conditioning system installed and working in conjunction with a dedicated dehumidification system. Both functions will be achieved much more effectively. However, many buildings only have air conditioning in Hong Kong, so the system is forced to achieve coolness and dryness at the same time. In the majority of cases, this results in the temperature being pulled well below the normal comfort level in order to bring the humidity to a manageable level.
So there you have it. This penchant for freezing cold indoors is brought about by a variety of misconceptions or earlier mistakes. I should be clear and state that air conditioning itself is not on trial here- just the over application of it. Later this week I’ll look at the problems over-cooling causes and some possible solutions.