Tubes

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.