An energy auditor inspects the attic of a home in a cold climate and observes dark, dirty-looking patches on the fiberglass batt insulation directly above the interior ceiling joists. What is the most likely cause of this phenomenon?
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A
Radiant heat transfer discoloring the insulation.
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B
Air leakage through ceiling penetrations carrying dust and moisture, which is then filtered by the insulation.
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C
Compression of the insulation, reducing its R-value and causing dust to settle differently.
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D
Natural degradation of the insulation material due to age.