Neefer Sews, Crochets, Crafts, Swims, and Blathers about Kids

Acorns to Oaktrees

March 3rd, 2015 at 10:55 am

Testing the effect of color on emissivity

in: General

Pulguito’s science project tested the idea that roof color has a profound effect on attic temperature. I suppose I could have pushed him further to calculate the emissivity of each can color, but the point that I was trying to make (thru him? to him? to his little friends who can shape their futures?) was that it is ridiculous to have dark roofs in places where summer temperatures are around 100°F/40°C. When we reroofed our house, white or even a light color was not available in the shingles, and almost no one could understand why I would want a light colored roof. It’s obvious, people. It makes a profound difference in my electric bill in the summer.

For Pulguito’s experiment, we painted empty aluminum cans black, green, red, white, and silver (simulated roof color), filled the cans with water (easier to measure “attic” temperature), allowed temperatures to come to equilibrium over night, and subjected the cans to a head lamp (simulated effect of radiative heating from the sun). There was a large difference between the black (HOT) can and the red and green cans with a similar difference between the red & green cans and the white can. The silver can had the coolest water. We also had an infrared thermometer, so we were able to measure the can surface temperature on the side away from the heat lamp. The results there were similar to the water temperature results.

Maybe we should have shiny, reflective roofs under our solar panels, what?

So, as a good mechanical engineer, I came up with the (experiment) design, procured the materials, and called in my technicians (DH & Pulguito) to do the actual work.

Testing the effect of color on emissivityTesting the effect of color on emissivityTesting the effect of color on emissivityTesting the effect of color on emissivityTesting the effect of color on emissivity

Category: General

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