Made in the shade- Passive cooling

We just survived another major heat wave here. People and plants were positively melting. The sidewalks were veritable solar cookers. I’m sure I could have fried an egg on the sidewalk outside my house.

I prefer not to crank the air conditioning, so I have been thinking a lot lately about simple ways to cool ourselves and the spaces we inhabit.
Air conditioning is the main mechanical means by which we cool buildings these days. However, there are several ways that we can cool buildings without plugging in so much as a fan. These technologies are referred to as passive. They don’t require any kind of motor or electricity, just a some good planning and design.
If one were designing a building from the ground up there are myriad features that can help that building use a minimum of mechanical heating or cooling mechanisms. There is no one size fits all design. Passively heated and cooled buildings are adapted to local climate conditions. Current construction practices tend to favor the same type of ramshackle 2×4 and drywall buildings from California to Long Island, and all the climate zones in between. Just stick an air conditioner on top, put in a heating unit, and you’re done. Sadly, most buildings are an energy efficiency disaster. Poor design is so prevalent, it is shocking once you know what to look for. Have you ever leaned up against a stucco or brick wall on a hot day? Ouch! You can literally burn your skin off.
However, a passive building in the humid South, might feature carefully placed windows to maximize air flow. In the desert Southwest, where temperatures can be scorching in the summer and freezing in the winter, thick, heavy walls of adobe, strawbales or rammed earth provide protection from extreme weather conditions.
Here in the Homegrown neighborhood, most of us live in old houses that are not designed with passive solar features. The Homegrown Evolution house is practically a greenhouse. My house is about 20 degrees hotter at night than it is outside. All of the hot air gets trapped and has no where to go. The windows are poorly placed allowing for little cross ventilation. Hot air rises so we need windows up high. Do you hear me architects?
Yet there are simple things those of us with old houses can do. I already mentioned window placement. Vents up high could also work. Insulation is of course a must. I had my attic insulated a few years ago and now I don’t need to run the heater nearly as much in the winter. I’m not sure what effect it has on the summer heat, because it still feels pretty darn sweltering in here.
Shade is an easy way to keep things cool. Shade can be utilized inside and out. An outdoor seating area begs for shade. This can be achieved with trees and shrubs or vines trained over a trellis. A roof structure of some sort can also provide shade for outdoor areas. If you have pets that spend time outside, make sure to provide them with a cool, shady spot for hot summer days.
Trees can also provide valuable shade for your house. Leafy trees will protect your house from the direct rays of the sun. Shade prevents solar heat gain. Pure and simple. Deciduous trees that lose their leaves in the Winter can allow sunlight to enter your house in the cool season, making them ideally suited to passive heating and cooling.
You can also shade your windows. Solar shades project out over a window, thus blocking the highest angle of the sun. When the angle of the sun is lower and the heat and sun less extreme, in Winter and during sunset and sunrise in summer, sunlight can still get in the windows. A roof that projects past the walls of the house serves the same purpose by also blocking the highest angles of the sun.
I chose to employ this technology and give myself more growing space by building an arbor on the back of my house.
This shades the back of my house and makes it look much nicer at the same time. I have planted hardy kiwi on it. The kiwi will help to provide shade, give me tasty fruit, and because it is deciduous, it will die back in the Winter to allow in a little more light. Brilliant.
This of course is just a few of the things you can do to use less energy to heat and cool your home. But I hope it provides a little inspiration and gets some of you out there to reach for a shovel instead of a thermostat.

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  1. Almost 3 years ago, I left my job as an indoor tech and started letter carrying. I have been surprised how adaptable my body has been to climate changes. Doing most of ones living outside, using shade in the heat and wind and rain shelter (or clothing) when needed…. drink lots of water when hot, move lots when cool… keep your wrists and ankles warm when it’s really cold and snuggle up close to your mate. Let the temp in your house swing outside the “comfort zone”… our body can take it, really, it can. Dress and eat/drink for the weather. Choose the time of day you work the hardest.

  2. A friend of mine in the solar panel and cooling industry once told me the best ways to keep a house cool are:

    -double pane windows
    -bushes & trees strategically placed around the house

    I just insulated the south side of my house during a recent renovation and notice a big difference already. Changing my windows in next. Bushes planted close to the house act as natural insulation and big trees planted in such a way they block after sun is another natural option. I also put in a whole house attic fan and in a few minutes the house is cool. We dont have air conditioning here in Southern Calif and our electric bills are normally $15-$20 a month.

  3. An attic fan, while not totally passive, is a low-energy way to increase circulation in your house and counter the greenhouse phenomenon.

  4. Before building our home about 20 years ago, my husband would drive me crazy going to the land and watching the path of the sun during each season. When it came to building the home, we positioned the house at a slight angle to the road. I asked him why he was doing that. He said, he was positioning our large area of windows to be facing south, so that during the winter, the sun would heat the rooms. Well, it worked! Not only do we have low heating costs in the summer, we do not need to use any lighting during the day…even on a very cloudy day. We live in Massachusetts, so the low heating costs help alot. In the summer, because the sun rays are high they do not heat up our home. I don’t have air conditioning for the summer and I keep my heat on 62 in the winter. My heat barely goes on in the winter on a sunny day.

  5. Today I had some termite damage repaired which resulted in, for the time being, a missing window. The window used to house an ugly AC unit. The window is one of the few that I have that faces the southeast. The house is cooler from the increased ventilation than it was with the AC blasting and I’m thinking of leaving it out.

  6. I have a solar powered attic fan from Home Depot. I purchased one extra solar panel (for a total of two) and installed the fan inside a gable vent. I live in an old Spanish stucco and the blown in attic insulation along with the attic fan makes a huge difference. I no longer feel heat radiating through the ceiling in the summer. Only downside is that by the end of our dirty, gritty L.A. summers, I usually need to go up on the roof and wipe off the solar panels.

    One other thing I noticed… When my home was repiped some of the copper pipe was run through the attic. In the summer, the cold water no longer comes out of the tap scorching hot.

  7. I have been spending that last couple months installing a radiant barrier in my attic. It would probably take a weekend for any insulation company, but I’m doing it by myself. Whenever I can manage to get up early on the weekend, I’ll install 3-5 rows of insulation… before my attic turns into an oven. It’s not fun, but I’m about 80% done and it’s been a lot cooler this summer. I had dual pane windows installed a couple years ago so that helps too. My next project is also the solar attic fan. You can get them at your local costco.

  8. I am an architect in Los Angeles (advice only applicable there as climate issues are regional)and building efficiency is a very complicated issue. With regards to attics, most attics that I see don’t have enough eave venting or the eave venting is blocked by insulation. Basically, you have to have enough venting to passively move hot air out and suck cool air in. If the temperature is hotter in there than outside, you need more venting. The radiant barriers help considerably, but you also have to remember that it helps with conduction and you also have to worry about air leaks.
    With regards to the window replacement, I would caution people to be wary of all the cheerleading about new windows. If your house is very leaky you should fix that first before getting new windows. Those little cracks add up quickly. Also, there have been independent tests that show old wood windows in good condition to have similar R and U values to cheap aluminum and vinyl replacement windows. The nice pricey ones work great though. If they aren’t installed correctly you can cause all new problems. FWIW, I would shade my windows on the outside before I swapped them out.

  9. Just a note on your solar shades idea. My wife and I redid our master bedrooom and we were going to use the basic and lifeless mini-blinds. Well, we did ma little research and discovered the solar shades and solar blinds. We decided to do our ever expanding eco lifestyle and spend the extra dollars for the solar shades. They definately work and we use them on ever window in our bedroom. Found this website that listed the pros and cons of solar shades: I was able to install my self and our room is defintely cooler in the summer and warmed in winter. Not too many choices yet, but I guess they are new and may take some time for manufacturers to mass produce them.

  10. In the book The Urban Homestead, you guys reference Ancient Greece in regards to city planning and passive solar. The ideas were so captivating to me, I wondered if there is a book you could recommend about that? I’d love to read more.

  11. Hey Joss,

    I wish I could remember where I read about that. It was probably some 1970s era appropriate technology tome. I have a book called 6,000 Years of Housing by Norbert Schoenauer which mentions, in passing, the heating and cooling strategies of many different kinds of buildings around the world.

  12. Great article, for what is worth, hot homes is one of the root causes of people dying from malaria. The homes in sub-sahara Africa are so poorly designed, so hot, with steel roofs, it is just amazing how badly they are designed. What happens? The locals just open the windows, doors, and refuse to even sleep under a mosquito net because they are cooking inside the house. Malaria mosquitoes enter, and kiil the babies. Generally, home construction worldwide is denigrated to lowest levels in history. 200 years ago, a person looked a the sun, and made a decision if they wanted it in the morning, or night. Thanks for this well written explanation.

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