Monday, August 29, 2016

Who Needs Air Conditioning?

As I write these words the temperature outside is 91 degrees Fahrenheit, and the August sun has been beating down on my house for several hours, yet the inside temperature is an extremely comfortable 76.

That would hardly be remarkable in this day and age, except that my house has no air conditioning. I don’t even have an evaporative (“swamp”) cooler, which is a great alternative to air conditioning in the arid interior West.

Instead I rely on another benefit of Utah’s low humidity: the nights are almost always quite cool, so I can open windows and run fans to cool off the house at night. Then I shut everything up in the morning as the sun is rising over the mountains, and rely on my house’s thermal inertia to keep it comfortable for most or all of the day.

Of course, this old-fashioned, low-tech way of keeping cool is technically inferior to the modern method of just leaving the thermostat set at your preferred temperature. For one thing, opening and closing windows is hard work! Also, during the course of a typical summer day and night, while the outdoor temperature swings up and down by 30°F, I experience indoor temperature swings of as much as 15°F. Here’s some data (logged by my smart thermostat) from a recent two-week period:


The indoor temperature swings mean that I might need to wear a sweatshirt in the early morning, take it off after a couple of hours, and perhaps sit in front of a small fan on the hottest late afternoons, when it climbs above 85°F. When I go to bed at night I rarely want more than a sheet over me, but after a few hours, as the house continues to cool, I usually reach for the blankets.

Maybe I’m a fanatic for happily enduring these needless, though minor, discomforts. But I can honestly say that a bit of discomfort makes me feel much more alive and connected to the surrounding world—in the same way as riding a bicycle instead of driving a car. As the late, great Tom Magliozzi said, “I mean, before you know it, you're going to spend plenty of time sealed up in a box anyway, right?”

And, of course, using windows and fans for “air conditioning” saves massive amounts of energy, greenhouse gas emissions, and money.

“But wait!,” you ask, “Don’t you have solar panels on your roof?” Indeed I do, but I would need at least twice as many of them to offset the electricity needed by a modest central air conditioning system in regular use. Also, there’s a time lag of several hours between peak solar generation (high noon) and peak air conditioner use (late afternoon), so solar panels by themselves cannot meet all of America’s air conditioning demand. Yes, we could envision massively expensive battery storage systems, but it’s vastly more practical, at least here in Utah, to just forgo the technology and open the windows at night.

Let me say a bit more about fans. Until this summer my arsenal included a basic 12-inch oscillating fan, which I typically placed on a bedroom windowsill at night, and a similarly inexpensive plastic window fan, containing two 7-inch fan units, which I typically placed in the kitchen window. At their highest speeds these fans use 40 and 110 watts, respectively, and they do a pretty good, but not great, job of cooling off the house. The window fan is pretty noisy, so I would usually close a door between it and the bedroom.


In June, however, I invested some money in a major upgrade: an AirScape 2.5e whole house fan.

A whole house fan is mounted in the attic above a hole in the ceiling, so it pulls air upward into the attic from the living space while pushing the hot air out of the attic. You run it only at night, with your windows open, so cool air can come in the windows to replace the air pulled upward by the fan. You can choose which room(s) to cool off most quickly, simply by choosing which window(s) to open.

Some whole house fans can be awfully loud, but AirScape is the Rolls Royce of whole house fan manufacturers, and the model 2.5e is extremely quiet—especially toward the lower range of its five speed settings. The fan itself is suspended from chains a few feet above the attic floor, at the end of a seven-foot flexible duct that provides acoustic isolation. At the other end of the duct, immediately above the opening in the ceiling, is a box containing motorized damper doors. Here are some photos of the installed fan in the attic, the view looking up at the ceiling and the damper doors, and the wall switch (mounted next to my Ecobee thermostat):





The motorized damper doors, in place of a simpler and less expensive back-draft damper, provide good insulation when closed and allow the fan to run at very low speeds, producing only the gentlest breeze. I usually run my fan all night long, choosing the speed based on how hot the house has gotten by evening.

The AirScape 2.5e is also extremely efficient: it draws only 25 watts on the lowest setting, and 200 watts on the highest (which I rarely use). Even on the lowest setting it’s about as effective as my two old inexpensive fans, which together use 150 watts and make much more noise. For comparison, a small central air conditioning system would use about 2500 watts while running.

As if the motorized damper doors aren’t already fancy enough, these AirScape fans can now also be connected to your home network router and then controlled through a smartphone app. This technological sophistication seems a little excessive to me, but the app, unlike the wall switch, tells you the current speed setting and even displays the attic temperature. You can only use it from home—not over the internet—but there would be little point to controlling it remotely unless you also had remote-control windows. Actually I wish AirScape would make a lower-tech damper assembly that you just open and close by hand with a lever, avoiding the complication and expense of all the electronics. This would also eliminate the continuous 8-watt electrical power draw from the electronics, even when the fan is turned off. (To avoid this small energy waste I’ll switch the fan off at the circuit breaker at the end of the summer.)

Of course, Rolls Royces don’t come cheap. With shipping I paid a little over $1500 for my AirScape 2.5e, and then I paid my favorite local HVAC contractor a few hundred dollars more to install it. Even so, it cost less than any central air conditioning system I’ve ever heard of—and you could easily install the fan yourself if you have a helper and the right tools. But I don’t mind spending this money on a long-term improvement to my home, especially when I’m supporting a good company that makes such a useful product. AirScape fans are designed and made in Medford, Oregon.

Not every house is suitable for a whole house fan. It won’t be nearly as effective in a location where summer nights are warm. Your attic must be well ventilated, so the fan can push the air out (see the AirScape web site for detailed ventilation requirements). And for ducted models like the 2.5e, you need a reasonable amount of vertical space in the attic. But if your house meets these criteria and you have the money to invest, then I highly recommend this elegant alternative to air conditioning.

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