Phone: 612-624-5551
24-hr number: 612-293-0831

Advanced Search

This is an archived story; this page is not actively maintained. Some or all of the links within or related to this story may no longer work.

For the latest University of Minnesota news, visit Discover.


A row of half opened windows.

When the temperature inside your house becomes too hot for comfort, open up your windows and use strategic ventilation where you are spending your time to help your body's natural cooling ability.

Hot days: keeping cool and saving money

Published on July 29, 2005; updated August 3, 2005

August 2 marked the 20th day this year that the Twin Cities hit 90 degrees--although, even in the shade, it easily felt like the mercury topped 100. According to the National Weather Service, we'll have more sun in the coming week, but highs are likely to only reach 87. Nevertheless, it doesn't hurt to prepare for more mercury-popping days.

Here are a few tips from Patrick Huelman, an associate professor of bio-based products and extension educator at the University of Minnesota, to keep you and your home cool when it's steaming hot outside.

Reduce heat production in the home. Limit the use of items that produce a lot of heat, such as lights and appliances. Use fluorescent bulbs where possible because they generate 1/5 to 1/4 the heat of incandescent bulbs. Use a microwave instead of the oven or range, or better yet cook outdoors. Set the dishwasher to air dry. Make sure your clothes dryer is properly vented to the outdoors and that your refrigerator has clean coils (this will keep it efficient).

If you are trying to stay cool without air conditioning

* Ventilate to remove heat. When outdoor temperatures are lower than inside (usually nighttime) ventilate aggressively with outside air-by using a fan and opening the windows or patio doors. Then close up the house before temperatures rise again.

* Circulate the air for comfort. When outdoor temperatures are higher than indoor temperatures it is generally wise not to ventilate heavily with outside air, because you'll just heat up your home further. Use internal (ceiling or floor) fans instead. However, when the indoor temperature becomes too hot for comfort, open up your windows and patio doors, and use strategic ventilation where you are spending your time to help your body's natural cooling ability.

Did you know?

* On July 17, the Twin Cities faced its ninth consecutive 90-degree-mercury-topping day. The longest stretch of 90-plus-degree days in the Twin Cities was 14, from July 5 to 18 in 1936. And the mercury cracked the 100 mark in 5 of those days in a row.

* Heat-related deaths outpace fatalities in other severe-weather categories, according to the National Oceanic and Atmospheric Administration Weather Service. For example, between 1992-2001, excessive heat claimed 219 lives each year in the United States. By contrast, floods killed 88 people; tornadoes, 57; lightning, 52; and hurricanes, 15.

* According to two University climatologists, there are some emerging weather patterns. Read "A Change in the air" on UMNnews to learn more.

If you use air conditioning

* Keep your air conditioner in tip-top shape and try to place the outdoor unit in a cool place. However, make sure the unit is free from leaves, vines, and other debris. Studies have shown that shading the air conditioner can save energy as long as it does not interfere with airflow around the unit. Replace the indoor filter regularly. Have a service technician check that the system is properly charged and that the inside coils are clean.

* Be aware that intermittent air-conditioning can cost more. During hot weather it is common to leave the windows open until it gets too hot and then turn the air conditioner on. This means you have to remove excess heat from the house. In other words, your air conditioner has to work harder. Using the air conditioner only when it is very hot causes peak load problems for our utilities. (They end up having to build more power plants, and you'll end up having to pay for those new facilities all year long.) *Reduce heat gain into your home.

Shade windows from direct sun-leafy trees or awnings are most effective, but drapes and shades inside the home will help too. Insulate your home with energy efficient windows.