Cool in the summer

Heat Wave

Photo courtesy Steve Johnson, some rights reserved.

The blog is woefully out of date, but after having gone through one heat wave and about to enter another (with higher humidity) it seems time to add some information about keeping cool in an Arlington summer in an energy efficient manner.

You’re likely familiar with the somewhat annoying adage “It’s not the heat, it’s the humidity.” It’s annoying but true, and an important part of how to keep cool in this weather. (Its also the subject of the next post.)

Keep the heat out, let the cool in.

This seems obvious but home comfort sometimes works in mysterious ways. When cooler weather is predicted at night and early morning open the windows. Before you leave for work, or before the sun burns off the haze, close the windows – all of them. You want to trap that cooler air inside the house. Open windows may provide a breeze but they’ll also let in the hot, sticky air. Keep them closed until it starts to cool down at night. (Nights will be cooler but frequently humidity will rise. That’s generally okay, it’ll still be more comfortable.)

When you close the windows, close the shades.

Shades help stop ‘solar gain,’ or the heat that comes through the windows in the form of solar radiation. If you question how much heat comes in this way try an experiment. On a hot day close halfway a shade that gets midday or afternoon sun. After the sun has been coming through for an hour or two put your hand on a shaded portion of the floor or wall, then put your hand where the sun has been beating down. It is usually a very significant difference.

If you have thin shades that let too much light in, or don’t want to spend money on a new set of shades, try this: I went to my local fabric store (Fabric Corner) and purchased “light blocking” shade material for $9 per square yard. For another $3 I purchased some thumb tacks. I took the material home, cut it to size and tacked them in place. Pull any existing shades down over these and the tacked-on shade becomes almost invisible. When the heat wave goes away, so do the light blocking shades (stored for later use). This has made a huge difference in the temperature and comfort of those rooms.

Stop the sun outside if possible.

Of course, if you can stop the sun on the outside, rather than inside with a shade, that’s even better. We’re all familiar with the idea that a deciduous tree is a great idea as it blocks the sun in the summer, but leaves fall and let light (and heat) through in the winter.

There are also, however, shades (and awnings) that can go outside to block the sun. I haven’t seen these locally but if you search online for exterior shades or outdoor shades you’ll find many options.

In my house I have a domed skylight which due to spacing issues wouldn’t allow a shade to be placed on the inside. Even before the first heat wave hit, a thermometer just under the skylight measured more than 120 degrees! So I went online and purchased some exterior-grade solar blocking material and attached it on the outside. Since then it hasn’t gone above 90. (This was more expensive, about $30 for a 4’x5′ piece, more on this in a later post.)

Keep the air moving on people, not things.

As you probably know, ceiling and other fans are great at cooling people off. As I type this I’m sitting, quite comfortably, under one while the temperature is 82 degrees, humidity is 67% and according to the online sites it “feels like” 86 degrees.

Fans, however, are often wasted electricity because people leave them running while nobody is in the room. Fans make you feel comfortable by moving your own heat away from you and by evaporating perspiration. They do NOT cool a room – they cool you. That means that if you’re leaving the room, turn off the fan.

Air conditioning.

Of course, there are times where air conditioning really is going to be wanted. If you’re someone who needs cooler temperatures then the above will help, but perhaps not completely, eliminate the need for AC. If you do turn it on remember to use it wisely. If you’ve got window units, put them in shaded windows if possible (but not where air cannot flow well.) Set the temperature to warmer settings to save energy – try edging the temperature down, over a few hours, to see the warmest temperature you feel comfortable.

These are just a few quick hints. If you’ve got others that work well please add them in the comments below.


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