The “dog days” of summer will be here soon. This phrase was created by the Greeks and related to the time of year when the constellation Sirius rose with the sun. It’s a time when seas “boil” and people go mad. While I’m not certain about the seas boiling, we all understand the physical and emotional problems we experience with hot, humid weather. 

Skip forward to 1902 and we find Willis Carrier inventing modern air conditioning. Since then, two things have happened. Electric companies have collected hundreds of millions of dollars from their air-conditioning customers, and many people have forgotten how to stay cool without air conditioning. Fortunately for us, there are still many non-AC strategies available:

Shade: Staying cool is easier in the shade. This is as true for your home as it is for you. It helps if you have large trees that cast long shadows, but not everyone has older trees around their homes. To those people I say, “Plant one for the next generation.” In the meantime buy an umbrella, install an awning or build a trellis. Nothing has to be fancy. A king sheet tied between poles will work just fine to block the sun’s radiation. You might be surprised that the temperature difference between sun and shade can be 30 degrees.

One cautionary note about plants; they block sunlight, but they can also raise humidity near them. Higher humidity means lower comfort, so give yourself plenty of room between the patio and plants like vines on trellises. 

Reflection: If you cannot shade a home, the next best thing is to reflect the sun. If you need to purchase new windows, choose ones that can reflect part of the sun’s heat. Go to the manufacturer’s website to see how much reflection you should have. You need more reflectivity in hotter climates. Some new windows even allow you to “dial in” the shade and reflectivity you need. These windows have built-in reflective mini-blinds. 

If your windows don’t need to be replaced, window film is a good second choice. Thousands of homes and commercial buildings in the Delaware Valley have been retrofitted with reflective film to cut down summer heat gain. Typically, you put the film on west-facing windows or windows that get direct sun for more than a few hours every day. 

Philadelphia has more row homes than any other city in the America, and most still have black-colored roofs. The dark color turns the top floor into an oven during the summer, but this can be changed. White is the new trend in flat-roof rehab. An elastomeric white roof coat has a lot of limitations in terms of when and how it is applied, but once in place, it is far superior to black or silver oil-based roof coatings. 

Moving air: Fans come in every shape and size and continue to be an important way to stay cool. Most fans, such as a desk fan or even ceiling fans, are designed for local cooling. Fans cool you by evaporating sweat. Changing liquid water into vapor (evaporation) removes energy and, in turn, cools your skin. (Remember to drink water to replenish the water evaporated from your skin!) 

There is another type of fan that is very effective, but not for cooling people directly. It’s called a whole-house fan. Some older homes have them, but they are rarely used properly. The whole house fan’s job is to cool the house. Yes, the moving air will help cool you as well, but the fan is designed to remove the heat built up in your house during the day and replace it with cooler evening air. Whole-house fans and window fans are useless unless the outside temperature is cooler than the inside temperature.

Seal the shell: You wouldn’t walk outside with holes in your raincoat; your home has thousands of little, and not so little, holes. These holes allow your nice cool air to escape and hot humid air to come indoors. Sealing your home used to mean caulking your windows and weather-stripping your doors. That’s a good start. But modern air-sealing contractors use computers and powerful fans to find out how leaky your home is, where those leaks are and which ones are cost-effective to seal. Sealing the shell means you control how and when your home interacts with the outside weather.

Lifestyle: Philadelphians have historically closed up shop and fled to the Poconos, the shore or any body of water that could provide a cool dip. Another all-time Philadelphia favorite is the fire hydrant sprinkler. 

Before air conditioning, staying cool  demanded a slower lifestyle in the summer, maybe something we should consider again. 

So to wrap up, the easiest way to keep your home cool is to open up your windows at night, then close them during the hot day. Keeping cool is a dance between you and the sun. Use whole-house or window fans at night once the outside temperature is lower than the inside temperature. Use personal or ceiling fans during the day. Shade the house where possible. If you do all these things, you will only need your AC when there is a heat wave or to knock down humidity levels. Either way, if you do all these recommendations, you shouldn’t need to run your AC more than about an hour a day.