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To be cool, you need the white stuff

Q: Every summer my electricity bill spikes dramatically. What can I do to reduce my electricity bill when it is so hot and I just can’t survive without my air conditioner?

Energy Q&A with ECA

Q: Every summer my electricity bill spikes dramatically. What can I do to reduce my electricity bill when it is so hot and I just can't survive without my air conditioner?

A: You've put your finger on the most problematic aspect of the summer for energy use—air conditioning. Because air conditioners use a compressor to make the air feel colder by removing moisture, they use a lot of electricity. Philadelphia summers can be beastly with their wicked combination of high temperature and high humidity.  To meet the peak demand for summer air conditioning,  PECO has to use additional power plants to meet the demand during peak hours like mid-afternoon on a blistering day in July.  These additional plant are usually the least efficient, which  means that electricity costs more during those peak times. All these factors lead to your high summertime bill.

There are a few things you can do around the house that are free, easy, and will help cool the house naturally. First, shade the south and west facing windows during the day, and keep the windows closed. You want to hold the cooler air inside the house when the air outside is hotter. Then, after the sun goes down open the windows to create a cross breeze and use a fan on the top floor of the house to pull out all the hot air. These methods can do a lot to cool the house without ever turning on the air conditioner. If you feel you need the air conditioner, treat it like your heat during the winter, and turn it off when you are out of the house during the day. If the windows are closed while you are gone, most of the cool air will stay captive inside so you won't return to a hot house.

Q: The Department of Energy Secretary Stephen Chu just mentioned "white roofs" as a great way to save energy at a climate conference in London this week. What are white roofs and why is Chu such a fan?

A: I am so glad that we have readers who follow the celebrities of the energy world! At a climate change symposium on Tuesday, May 26th Dr. Chu mentioned that painting roofs and other surfaces white would reflect a large amount of solar energy and help reduce the cooling load for buildings. I am thrilled that he highlighted white roofs because they have not gotten enough attention.

White roofs reflect solar radiation, typically reducing the air-conditioning load on a building by 22%.  They also protect the roofing materials, thus extending the life of the roof.  White roofs come in many different materials:  metal, tile, membrane, or coatings.  Here in Philly, the home of the flat black tar roof, white roofs are usually accomplished by coating over the existing black roof.    If the roof is in good condition and needs very little repair, then a white roof can cost as little as $1.75/sq foot! If your roof has to be repaired first it can cost a little more.

The benefits are immense. Most people see a reduction of at least 20% in their cooling load, as well as an increased roof life. White roofs last about 10 years before they must be recoated, and if you are handy you can do it yourself.   Our favorite coatings are acrylic, elastomeric white roof coatings.

Dr. Chu also referred to another huge advantage of white roofs:  to slow climate change.  If enough dark roofs were converted to white, reflective roofs, we could slow climate change by increasing the reflectance, or albedo, of the entire earth!  Hey,  Bermuda figured all this out decades ago.  Every roof in Bermuda  is white.

So this summer,  don't sweat in your brick oven.  Coat your roof white, and enjoy a cool, more durable, and more earth-friendly home.

Read more Energy Advice columns from ECA here.