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In Terms of Indoor Air Conditioning, How Cool is Too Cool?

by August 30, 2011

An article in Sunday’s New York Times by Elisabeth Rosenthal (Oh, to Be Warm in Summer’s Heat) reinforced the notion that some not-so-painful behavioral changes might lead to significant energy (and cost) savings. Yet, we may not be empowered with good information to help us connect the dots. Rosenthal zeros in on our exuberance to crank up the air conditioning in stores and other public spaces like airports. It does seem rather silly that we often need to grab a sweatshirt before heading out, knowing that we’re libel to run into chilly indoor environments.

I’m reminded of an NPR story from yesterday (Summer Sounds: Air Conditioning). It is a story by Teller (of the stage duo Penn & Teller) recounting his solution to the noisy air conditioning unit in his room. His parents had bestowed the unit to him because they knew that his upstairs room would be hotter than their downstairs bedroom. Even though his parents’ sleep was fitful, he solved the on-and-off noise of the A/C unit by turning on the “constant cool” feature, meaning that his room turned into the Arctic, and he needed to bundle up like on a winter’s night…

Back to Rosenthal’s story. She highlights an experience many have no doubt had: the rush of cool air that pours out the open front doors of many retailers. I often joke that they’re fighting a losing battle if their goal is to cool off outside. Of course, their goal is to lure us into the cool indoors, where we’ll want to stay and buy their merchandise.

I wonder if retailers have the information they need to weigh the benefit (extra business) against the cost (inefficient cooling system). Maybe they’d get a boost in consumer traffic if they kept the doors closed and used a marketing campaign advertising their responsible energy plan. Perhaps they could add some low-energy cooling fans near doorways to give pedestrians a sample of the coolness that awaits just inside the (closed) doors. This is clearly a ripe issue for attention, as a quick online search reveals considerable space devoted to this “open door policy” of retailers (here’s a Washington Post article about how the energy-conscious are upset by open doors, and another NY Times post about an informal survey of open doors after NY City banned the policy, albeit with plenty of loop holes for cool air to pour through!).

As discussed in a previous post, we do not do very well estimating the relative energy use of different appliances, such as window versus central A/C units. Similarly, we do not do a good job at predicting the energy savings from various behavioral changes, like adjusting our home thermostat to make it a bit cooler during the winter and a bit warmer during the summer. This blurb and accompanying graph of the typical energy usage in a home from the Energy Star website sums up why we should all pay attention in this time of ever-increasing energy costs:

As much as half of the energy used in your home goes to heating and cooling. So making smart decisions about your home’s heating, ventilating, and air conditioning (HVAC) system can have a big effect on your utility bills – and your comfort.

  energy_star_graph_1

A final note has to do with a statistic that Rosenthal cited in her article:

Many energy experts recommend setting thermostats at 78 degrees in summer, to conserve energy and to combat rising greenhouse gas emissions. The exact energy savings depends on numerous factors, including the type of air-conditioning and the temperature outside. But turning up the programmable thermostat of a central air-conditioning system 1 degree can yield a 6 percent savings in energy used for cooling, according to the United States Energy Star program.

We’ll need to get to the bottom of the potential savings, which undoubtedly vary regionally and across different types of home construction. The 6-percent-savings is higher than I’ve seen elsewhere, and it seems like a lot for adjusting the thermostat by only a single degree.


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