Know Your "Clo"

Ever wonder why women often seem colder in the same room that a man finds comfortable?  It’s not just because men are from Mars and women from Venus, is it also the "Clo."

The Clo?  What is that?  Leave it to engineers to figure out not only the insulation in buildings but the insulation in clothes.

A clo is the amount of insulation provided from a standard set of clothing.  A typical business suit has a clo of one; typical women’s clothes – skirt, thin soled shoes, light blouse with long sleeves is less than 0.5 clo.  Adding a thin sweater brings this up to just over 0.5 clo.  The more clo you have, the warmer you are.

If you are wearing one clo and sitting still, you should be comfortable at 74°F.  If you are wearing 0.5 clo, you need it to be 79° to be comfortable sitting still.  So if a man in a business suit and a woman in a skirt and blouse are in the same room, one thing they definitely can’t agree on (and there may be other things as well) is the temperature.

The September 2011 issues of Fast Company magazine had a story about the heating and cooling value of changing your wardrobe habits with the seasons.   In winter, wearing a sweater has the “warming power” of 3.4°F.  In summer, ditching the suit jacket has cooling power of 4°F.  The article pointed out that the Empire State Building is undergoing a $20 million energy retrofit to reduce costs by $4.4 million.  If workers wore sweaters and therefore reduced the temperature by 3.4°, they could meet 10% of their goal at no cost!

Adding a sweater, or dropping the sport coat, are easy changes within the parameters of normal business attire.  Other changes challenge conventional standards of fashion, both for women (shoes with socks, for instance, instead of stylish heels in winter), and for men (imagine sandals and Capri pants at the office in summer).    It is doubtful we will see changes like this just for energy reasons so we may continue to disagree on temperature setpoints.  One thing we can agree on was said by the wise Mark Twain - "Clothes make the man. Naked people have little or no influence in society," he said.  But not only that, naked people have a clo of zero!

By Wayne Robertson