Last summer, I wrote about staying cool with fans. This summer, I’m sharing lessons from Hap Haven, our region’s long-time energy efficiency specialist. This essay was originally published in the June 2016 Shuttle, a monthly publication of Weavers Way Co-op.
The “dog days” of summer will be here soon; high temperatures and high humidity. This phrase was created by the Greeks and related to the time of year when the Sirius constellation 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. First, electric companies have collected hundreds of millions of dollars from their air conditioning customers. Second, many people have forgotten how to stay cool without air conditioning. Fortunately for us, there are still many non-AC strategies available. Here are just a few:
SHADE: Staying cool is easier in the shade. This is true for your home, as well as 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 sized 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 the humidity level near them. Higher humidity means lower comfort so give yourself plenty of room between your patio and plants like vines on trellises.
REFLECTION: If you cannot shade a home, the next step is to reflect the sun as best as possible. If you need to purchase new windows, choose ones that can reflect part of the sun’s heat. Go to the manufacturer’s web site 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 reflective mini-blinds inside the window. Assuming that 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 retro-fitted with reflective film to cut down on 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 USA and most still have black colored roofs. The black color turns the top floor into an oven during the summer, but this can be changed. A new trend in flat roof rehab is the white roof. The elastomeric white roof coat has a lot of limitations in terms of when and how it is applied, but once applied, it is far superior to silver or black (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 a ceiling fan over the dining room table or in the bedroom, are designed for local cooling. Fans cool you by evaporating your 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 to cool you as well, but the fan is designed to remove the heat built-up in your house during the day. Whole house fans and window fans should not be used unless the outside temperature is cooler than the inside temperature, otherwise you are just going to heat up the inside.
SEAL THE SHELL: You wouldn’t walk outside with holes in your rain coat, but your home has thousands of little, and not so little, holes. These holes allow your nice conditioned 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 just a start. 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 get to control how and when your home interacts with the outside weather.
LIFE STYLE: Philadelphians have historically closed up shop and vacationed in the Poconos, “down” the shore or to any body of water that could provide a cool dip. One all-time Philadelphia favorite is the fire hydrant sprinkler. Staying cool before air conditioning demanded a slower life style 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 after the outside temperature is lower than the inside temperature. Use personal or ceiling fans during the day. Shade the house where ever 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.
And to lighten the message, here’s a humorous reflection on seasonal clothing for the office: Frigid Offices, Freezing Women, Oblivious Men. Please re-assure me that Mt Airy men are different, that we heart summertime under the fans and under the trees.
If you found any of Hap’s material useful, or are considering a home energy audit, I know Hap would love to hear from you. He is reachable at firstname.lastname@example.org.