Coping with the heat

There’s no plan for a regular home handyman column here, but I notice many people going about heat wave management the wrong way, so here’s what you need to know. First, what you can do quickly, and without air conditioning, which is a lot if you’re smart.

(1) Keep the sun out! Windows facing south to west need shading. Exterior awnings, a wonderful old technology that comes in cheerful striped colors, are the best thing for this; second choice is Venetian blinds, which can stop the sun and allow ventilation; third is a plain white window shade. The awning is best because it interrupts all the radiation outside the house instead of letting it in through the window and then reflecting only some of it back out. (Actually, a tree is best, but the twenty-year installation period puts it in a category by itself.)

These devices need management; if you don’t adjust the shades, you’re living in a greenhouse.

(2) Dump the hot air out of your house in the evening! This is done with a window fan installed in the top (preferably) of a window, in a room where you will mind the noise least, usually a guest room or the kitchen, running to blow out. If you can put it on the second floor, you will exhaust the hottest air in the house and convection helps you. (Don’t use a window facing your prevailing wind, though!) It is much more efficient at moving air through the house set to exhaust, and the incoming air in other rooms won’t stir up all the papers on your desk. We successfully used two of the $20 box fans you can find at the hardware store for my daughter’s LA apartment, mounted in a plywood panel, but you will probably be happier with something more expensive, like 3C614 or 4TM66 from Grainger. I use one 3500 cfm fan in a four bedroom house in Berkeley successfully.

Mounting this fan can require some tools and improvisation; you want it inside the window so the window can be opened and closed without removing it. You can’t just put it on a table pointing vaguely at an open window, but it doesn’t need to seal perfectly around the sides; the outgoing jet will actually induce some additional air flow around the edges by the Venturi effect. Remove the insect screen from this window, it greatly impedes the fan’s performance (the coarse grid that keeps fingers and the cat out is not a problem).

The fan needs to be managed as well. Turn it on in the late afternoon or evening, as soon as the outside temperature is below the inside. Partly open a window in each of the rooms you want to occupy, for example, the living room and bedroom (the total open area of these inlet windows should be about two to three times the area of the fan, . Each of these will generate a jet of nice cool air perpendicular to its opening (you cannot steer this jet by the direction you are sucking from) that’s nice to sit or sleep in front of. In the morning, turn it off, close the windows to keep out as much hot daytime air as possible, check the shades, turn off all the electrical devices you can, especially lighting, and go to work or the beach.

I cannot overemphasize how much cheaper and more environmentally responsible a fan is than air conditioning, nor how much more effective it is than most people realize if used properly. A small air conditioner for one room draws five times as much electricity as a 3500 cfm exhaust fan.

Circulating fans are pretty much useless, though sitting in a warm breeze is nicer than sitting in warm still air, and sometimes you can put a box fan in a doorway to help the air move through the house.

Finally, put in compact fluorescent light bulbs wherever you can use them. These are a license to print money, especially if you are air conditioning, and many are now dimmable (Google “dimmable cfl” for sources like this one). You get two thirds off the top of your electric consumption for each one right away, with a comparable reduction in heating up your house, and the color balance is now entirely comparable to traditional incandescents. A few applications need incandescent bulbs for aesthetic reasons (by the way, a halogen lamp is only a little more green than an ordinary incandescent), but consider this a luxury that entails a hit to the welfare of the planet, and your pocketbook. A few lights that are almost never used, like the bare bulb in your attic, are not worth replacing with cfls, and in contrast, lighting like exterior floodlights that run all night every night are prime candidates, and right away. If your landlord pays for your electricity, he should not only pay for the cfls but buy you a nice bottle of Scotch if you install them. (Tech vocabulary note: in the lighting industry, what most people call a bulb is called a lamp, and the fixture that holds it is a luminaire.)

Maintaining a house full of incandescent bulbs should be regarded as a socially gauche kind of behavior. You wouldn’t light a cigarette in someone else’s house; why would you trash the planet by mismanaging your own?

Longer-term/expensive options include:

an attic-installed whole house fan, sized to replace the air in the house every two-to-five minutes (just calculate the cubic feet of occupied space), drawing hot air from the top of the space so the chimney effect helps;

good double-glazed windows, preferably with differential reflectivity coatings (see your local lumber yard about this very effective option);

good insulation;

a white roof;

and plant that tree now!

If you use an air conditioner, think of it as a very expensive device to carry all the heat that gets in your house out; the less heat you let in, the fewer hours you have to pay it to work. The expensive part is the compressor that cycles on and off; the fan part that just circulates air through it is pretty cheap, so just because it’s making noise doesn’t mean it’s costing a lot. How does heat get in your house? Sun (that window shading is really important), open doors and windows, conduction through windows and uninsulated walls, any electric device, proportional to its wattage and how long it runs (read labels; you may be surprised at what matters and what doesn’t), gas appliances like the oven or range, and people. Before you start it up, use the fan arrangement described above for a half hour; you’ll be pleasantly surprised, and you can probably get through many nights with no AC at all quite comfortably.

Author: Michael O'Hare

Professor of Public Policy at the Goldman School of Public Policy, University of California, Berkeley, Michael O'Hare was raised in New York City and trained at Harvard as an architect and structural engineer. Diverted from an honest career designing buildings by the offer of a job in which he could think about anything he wanted to and spend his time with very smart and curious young people, he fell among economists and such like, and continues to benefit from their generosity with on-the-job social science training. He has followed the process and principles of design into "nonphysical environments" such as production processes in organizations, regulation, and information management and published a variety of research in environmental policy, government policy towards the arts, and management, with special interests in energy, facility siting, information and perceptions in public choice and work environments, and policy design. His current research is focused on transportation biofuels and their effects on global land use, food security, and international trade; regulatory policy in the face of scientific uncertainty; and, after a three-decade hiatus, on NIMBY conflicts afflicting high speed rail right-of-way and nuclear waste disposal sites. He is also a regular writer on pedagogy, especially teaching in professional education, and co-edited the "Curriculum and Case Notes" section of the Journal of Policy Analysis and Management. Between faculty appointments at the MIT Department of Urban Studies and Planning and the John F. Kennedy School of Government at Harvard, he was director of policy analysis at the Massachusetts Executive Office of Environmental Affairs. He has had visiting appointments at Università Bocconi in Milan and the National University of Singapore and teaches regularly in the Goldman School's executive (mid-career) programs. At GSPP, O'Hare has taught a studio course in Program and Policy Design, Arts and Cultural Policy, Public Management, the pedagogy course for graduate student instructors, Quantitative Methods, Environmental Policy, and the introduction to public policy for its undergraduate minor, which he supervises. Generally, he considers himself the school's resident expert in any subject in which there is no such thing as real expertise (a recent project concerned the governance and design of California county fairs), but is secure in the distinction of being the only faculty member with a metal lathe in his basement and a 4×5 Ebony view camera. At the moment, he would rather be making something with his hands than writing this blurb.

21 thoughts on “Coping with the heat”

  1. As a native-born Southerner who grew up without A/C, all this is familiar. Here are a few more tips:
    Cook in the evening–eat a cold breakfast and lunch. This way the house cools down overnight, and you don't re-heat it.
    Put the refrigerator outside, or if that's impossible, put it in a small room that can be closed off from the rest of the house.
    Wear appropriate clothes. There's a reason that seersucker is a classic suit fabric in the South.
    Air circulation matters a lot at high temperatures–once you are sweating slightly, moving air feels several degrees cooler that still air. So get and use a circulating fan.

  2. The tree. I fell in love with the tree, and it was my main reason for buying the house. It is a 50-year-old fruitless mulberry; it provides deep, deep, shade; it stands between us and the afternoon sun. I love my tree.
    BTW, you're right about circulating fans vs exhaust fans. The only time we have used the a/c was at night when the temps refused to fall below 90 degrees and the humidity stayed above 60%.

  3. Nice point about the fridge (and the freezer, if you have one; in Vermont, lots of people kept their freezers outside in the shade all year, though of course you can't do this with the refrigerator in cold climates as all your food will freeze).
    I agree I was too tough on the circulating fan. But it has nothing to do with the more important flushing function of the exhaust fan.
    I can't claim scientific validation for the following (speaking of lunch) but a family tradition holds that the following is an absolutely optimal hot-weather meal:
    Cut up tomatoes, cucumber (opinions vary on whether it has to be peeled), sweet peppers, and chives. Mix these into one to two cups of cottage cheese, a dollop of sour cream, a generous grind of pepper, and salt to taste. Mmmmm….
    Alternate version, could be dessert: substitute peaches, plums, pitted cherries, etc. for the vegetables.

  4. The "shut the windows during the day" advice is indeed important: I know several people who live under the mistaken impression that windows should be kept open during the day, so that breezes would "cool the house down". Unless the house is perspiring, a breeze doesn't cool it: it just speeds up the equilibration between outside and inside. Your body does perspire, so a breeze will indeed cool you down; a reasonable oscillating fan costs about $20-$30 and consumes only ten watts at low speed.

  5. Thank you!
    I grew up in DC in the 50's and some of this I know – but a lot is new to me. It never occurred to me to think about awnings, for example.

  6. Another bit of advice is to put your computer to sleep if you're not using it. For modern computers a short press of the power button will do this (save your work first just in case). The computer emits almost as much heat (and consumes almost as much power, about 300 watts) running your screen saver as when you're actually doing work.
    Also consider buying a flat-panel monitor if you're still using a CRT. Not only do they use a lot less power, they also "warm up" instantly, so having your computer sleep more often isn't nearly as annoying.

  7. Very little. It depends on how much air it moves. A typical range hood is only about 200 cfm; it's good to get this hot air out directly, but it won't have much impact on the rest of the house. A serious range hood with a 10" exhaust duct can be rigged up to a fan that really moves air, but the maximum here will still only help the whole-house fan, not substitute for it. 2000 cfm through a 10" pipe will sound like a jet warming up. Anyway, you wouldn't want to be throwing away all that heated air in the winter.

  8. Don't forget–if you live in one of those old houses with a nice, stone, full or 3/4 basement, spend as much time down there as you can. We move our family room set up down there in May, and keep it there through September. Our basement will be a good 8-10 degrees cooler than the top two floors.
    It's funny, when the temp is about 72 degrees, we can actually get a situation where the basement is cold enough to require long sleeves or a blanket, the first floor is just right, and the top floor is warm enough to require the ceiling fans or a brief AC cool down.

  9. Alternately, you could move into GSPP 105, crank up the AC, and bring a cooler of Budweiser.

  10. Don't run a screensaver at all. In circumstances where you don't want to put your whole computer to sleep at least set up your computer power management to put the monitor to sleep when the screensaver would have run. Screensavers served a purpose before monitors had that capability but for the last decade or so they've been a monumental waste of electricity.

  11. If convincing slum lords that such things as "radiation" and "watts" even exist were so easy I might not be sitting in an 89 degree Utah living room at 9:52 p.m.
    However, the exhaust fan trick has already helped me. I was trying to blow cool air in and, as a result, only cooled one room that is rarely occupied. Thanks for the tips.

  12. If you can handle the color of the light and plan to stay in your current abode for a long time (say at least 5 years), LED lights save even more money, energy, and waste heat than cfs. There are now LED replacements for can light bulbs, which I find a particularly good use.

  13. This is all great adivce until the dew point hits 70. Then all the fans in the world won't help due to humidity.

  14. This only works if you're building a new house or replacing a bad HVAC system, but geothermal cuts your heating/cooling costs by a lot.
    The main disadvantage is the extra $6,000 over the price of a regular system it takes to drill the wells and install it. The system pays itself back, but not everyone will think 5-7 years out.

  15. There are three-way fluorescent lamps (bulbs) to replace your incandescent ones, which produce 85% of their output as infrared energy: heat. Hope that helps.

  16. I unfortunately have to disagree with your bit about dimmable cfls. I just went out this weekend and tried to replace all our bulbs- most of it went well, and there were coupons sponsored by the energy companies for discounts on the standard bulbs. However, we have two rooms with dimmable fixtures (11 bulbs total) and four two-setting floor lamps. I tried 3-way bulbs in the floor lamps, but on the low setting the bulbs didn't work, so they were effectively one setting bulbs- we use both settings, so I returned them and put the incandecents back in. For the other fixtures, a chandelier had no equivalent wattage dimmable bulb- I got the only wattage available (5x3W), but it's too dark now- and the other set didn't have dimmable bulbs in the right base size. I think the market for cfls is still a bit immature since some matching replacement products are not available anywhere.

  17. A dimmable cfl is not the same as a three-way. Your two-level luminaire probably requires the former. A fair number of incandescent lamp styles have no practical cfl replacement, especially including those that are physically small and bright, like 60w candelabra base. And dimmable cfls are only provided in a few basic shapes. Replace what you can and await the march of technology; fortunately, the payoff is proportional and not all-or-nothing.

  18. Blowing the hot air out of the house and bringing cool air in with an attic fan worked great over 20+ years for most summer nights in the San Fernando Valley of SoCal.
    But in the last 5-6 years, summer nights have very very noticeably NOT COOLED OFF enough to make that approach worthwhile anymore.
    We used to have 95-degree summer days, but temps would normally go down into the mid-60s
    by 10-11 PM.
    Not any more.
    We still get the 95-degree days (or hotter), but it never seems to get below the low 70s anymore at night, even by 4 AM!
    We finally surrendered to the change and are having refrigerated AC being put in as I speak.
    Once again, the big difference in recent years is not so much in the DAYTIME temps, but much *warmer nights*.
    And the change has been consistent now
    for a few years.
    I can't apeak for Global Warming, but I sure as hell CAN speak for Southern California warming in recent years.
    That's for damn sure.

Comments are closed.