Aggressive Passiveness

When spring returned, with its first hot, sunny days, we started using our air conditioning again. As always, I closed all the doors and windows to keep the cool air in. Around nine o’clock one night, with the air conditioning still going off and on, I took the dog out for a walk and made a shocking discovery: the temperature outside was cooler than inside. Why was I running an air conditioner when there was plenty of electricity-free cold air available right outside my house?

I came back inside, turned off the AC, opened some sliding doors and windows, and then went for a walk. When I returned, the house was still warmer than outside, but definitely cooler than it was when I left. And thus I became a passive cooler.

Within days, I was obsessive about using all the free cold air I could. I opened doors and windows all night to let in the cold. As the sun came up and started heating the air, I closed my doors, windows and shades, and enjoyed most, if not all, of the day in cool comfort.

That was still not enough. Where we live, there is little wind, often not so much as a breeze. Even with windows open to get cross ventilation, there was sometimes almost no air flow to cool the indoors. One time when I was at Lowe’s, I saw a large, semi-industrial fan that I knew would be just the ticket. It was rated at 360 cfm. (The cfm is cubic-feet-per-minute, the rate at which the fan moves air.) That is a lot of air.

With the fan placed at the foot of the stairs to the basement and the basement slider open, I could feel the breeze of warm air leaving my house near any open window or door upstairs. Now I could lower the temperature inside the house in minutes, regardless of whether there was any breeze. Yes, I know, the fan uses electricity. But it uses far less than my air conditioner, and with cool air outside, is much more effective at cooling.

As the days went by, I found an additional source of cool air: my basement. Three of the basement (foundation) walls are fully or mostly underground. With only cinder blocks between the inside of the house and the cool earth outside, I had a small source of geothermal cooling. Even with warm air outside, I could delay the need for AC by judiciously running the fan to push cool air from downstairs up during the day.

I was able to use at least a little passive cooling on all but the hottest days (and nights) of summer. With the coming of fall, I am back to my obsessive ways.

For a few months of winter, I also get some passive heating in my house. The long eaves that hang over two sides of my house, along with several mature deciduous trees, keep direct sun away from almost all of my windows most of the year. However, once the trees lose their leaves and the sun makes a lower arc through the sky, several windows do get direct sun. I raise the shades on those windows, which raises the temperature in those rooms a degree or more above the rest of the house on sunny days.