Passive Cooling Techniques

I hear so much about ways to keep warm in the winter, but generally all I hear about summer is that the insulation used for the winter will also help in the summer. That's fine, but I live in an extremely hot environment--we are already hitting 100 degree days!! We hold off using our air conditioner as long as we can, but that does not last long, particularly when daytime temps top 115 and night time temps only drop to about 85. What passive cooling solutions are out there? (we do have good insulation and we do have some trees for shading on the south and west). I have heard a little about thermal chimneys but have not heard from people who have used something like that.

I have an idea and would like feedback: What if I took a long, wide pipe, open on one side to the outside air on the north of my house and open on the other end inside the house, with a long middle section buried several feet below ground (running along the north of the house)? To move air through it, what if I then took a black metal pipe and made a chimney that starts at the ceiling? My hope is that the chimney would get hot from the sun and draw cool air up through the ground pipe. Perhaps I could put some sort of swamp-cooler like cooling pad in that ground pipe to cool the air further. If I have the intake on the north of the house and the out chimney on the south side of the house, how effective might this be? (lots of variables to consider, I'm sure--it is a pretty large house, which doesn't help).

What ideas are people using most effectively to deal with extreme summer heat? Thanks for any insights!

There is a word for your idea: qanat -- and yes, it's been done for quite a while.

John Elliott wrote:There is a word for your idea: qanat -- and yes, it's been done for quite a while.

Thanks John. I read the whole entry and gained more respect for ancient Persian civilizations! From there I read about solar chimneys and saw just what I had been thinking about. It sure is tough to come up with a truly original idea! http://en.wikipedia.org/wiki/Solar_chimney#Solar_chimney_and_sustainable_architecture

The only cautionary note I would add as you look into this system would be around the use of metal piping/ductwork buried under ground. You will be introducing hot and moist air into that tube/duct where it will cool rapidly. There is a good chance of condensation on the walls of the metal pipe/duct, and if it stays moist and warm enough, it could be a good spot for mould to grow. And if not dangerous mould, the potential is there for stale, musty air coming into the house.
If you were to use clay pipe (as many of the early civilizations who use this passive cooling would have done), the clay can absorb excess water and is less likely to grow mould.

Chris Magwood wrote:If you were to use clay pipe (as many of the early civilizations who use this passive cooling would have done), the clay can absorb excess water and is less likely to grow mould.

Great idea. I had been thinking of something like these HDPE drainage pipes: http://www.ads-pipe.com/en/ These would be stronger than clay pipes, could be perforated to drain easily, and are probably easier to work with since they are much lighter than clay. Plus, since they are black, I thought I might be able to use them for both intake and the chimney. But I like the idea of clay pipe. I never knew there was a National Clay Pipe Institute, but there is! http://www.ncpi.org/ and they point out that "Vitrified Clay Pipe is, and always has been, the most environmentally friendly and sustainable product available."

More for me to think about!

I would definitely seek out the clay pipe. The black plastic won't have as great a tendency to encourage condensation, but the clay will be much better.

I've used earth tubes made from black ABS plastic before, and I just made sure there was a way to clean them easily. I fed a rope through the pipes as I was assembling them, and now the owner can tie a sponge to the rope and pull it from one end of the pipe to the other a couple times a year. Apparently, there's only been wetness in the pipe at the height of summer heat/humidity.

Chris Magwood wrote:I would definitely seek out the clay pipe. The black plastic won't have as great a tendency to encourage condensation, but the clay will be much better.

When I was looking at clay pipe what I found was the vitrified clay pipe, which is very useful for carrying water or sewage. But wouldn't it be similar to plastic in the tendency to get condensation from the air since it is vitrified (essentially turned into glass) and basically impermeable? Is there more of a terra cotta type of pipe available?

Terra cotta used to be available as septic tile, but not readily available anymore and limited in sizes.

No matter what you do, you will have condensation so you need to deal with it. Drainage slope and sumps, etc.

It sounds like you are looking for a cooling system for your whole home. Another thing to consider is personal cooling methods. Basically it's easier to keep a person cool than a whole house. On hot summer days (though in Michigan we don't have to worry about it quite as much as some other places...) I often will take a damp washcloth and keep it over the back of my neck where it is right near major veins and arteries. Of course this only works if you don't have to be moving around, but there are other methods as well. A damp bandana seems like it could keep you quite cool. Anyway, just some food for thought. In the long run it's probably better to cool your whole home, but if that is too difficult of an option, or it can't be completed right away, maybe this can help you out a little.

Nick Herzing wrote:Another thing to consider is personal cooling methods. Basically it's easier to keep a person cool than a whole house.

Paul has done some great work with this in regards to heating--heat the person, not the air--with heat lamps, heated dog bed for the feet, etc. We use fans, which are nice for feeling cooler, and we combine this with a spray bottle--misting ourselves now and then (and even misting down the bed before going to sleep, then sleeping on top of the sheets). We use a lot less energy than most people here for cooling because we are willing to keep the thermostat at 82 degrees, but cooling costs are still excessive. Some people did live here prior to air conditioning, but it's hard to understand how! There is more we could do to insulate our house, which may still be the biggest help.

An interesting side note is that while in grad school we came down to study lizards each summer then back up to northern Utah to take classes for the winter. It was the opposite migration pattern of all the retired "snow birds" (who double the population of Yuma each winter). After three years of this bake/freeze/bake/freeze cycle I realized that it was getting easier for me to deal with the extreme heat and harder for me to deal with extreme cold. Still, I miss the seasons, the mountains, and the brisk air. . . life is full of tradeoffs!