The answer to the previous question is A. A blower door attaches to a home's outside door. The fan blows air outside, exaggerating the air leaks in a home, which is one way to find places to plug when trying to make a building more air-tight.
Next question: These evacuated tubes are used for:
A. solar hot water systems.
B. ground-source heat pumps.
Answer and new question on next page.
March 16, 2009 4:00 AM PDT
Photo by: Martin LaMonica/CNET
| Caption by: Martin LaMonica
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