|This is a note from David describing how roof sprinklers are used on
clay tile roofs in California's Central Valley for cooling.
I live in the Central Valley of California which runs about 500 miles from
Bakersfield to Redding. We have hot dry summers, 3+ months in the 90's with hot
spells to 115 degrees. Many of the early houses built have mission or barrel
tiles which are set in alternating rows. See this photo:
Some of the owners would run a pipe down the peak of the roof and
occasionally turn on the water, letting it soak the tiles. They are unglazed so
they would soak up some water. After the water was shut off the tiles would
slowly dry out, cooling the roof underneath through evaporation. This can be
done day or night due to the low humidity that is common.
We have an evaporative cooler and AC but the humidity is low enough about 25 days a month to stick to the swamp cooler. It uses about 500 watts for a 1300 sq. ft. house. Right now it's 18 percent humidity, 98.5 degrees and the house is at about 77. Evaporative systems work if the humidity is low enough.
Our back porch has a sheet metal roof that radiates heat down about 30+ degrees hotter than the ambient temperature which on a plus 100 degree day is something to experience. I simply built a light framework of PVC and put a silver tarp over it. Now the temperature underneath is about 7-8 degrees above ambient. Our homes soak up so much heat from the sun maybe we should simply shade them from direct sun with some cheap tarps and keep more of the money we spend on energy.
Lots more ideas on passive cooling, active cooling, shading, ...
Gary July 11, 2010