How does wet insulation function as an insulator?

Wet insulation does not function effectively as an insulator because moisture reduces its thermal resistance significantly. Insulation materials are designed to trap air, which provides the barrier against heat transfer. When insulation becomes wet, the trapped air is replaced by water, which conducts heat much more effectively than air. This results in the loss of insulating properties, leading to increased heat loss in winter and heat gain in summer, ultimately compromising energy efficiency in buildings. Therefore, wet insulation is not an effective barrier against temperature changes, which directly supports the selection that it will not work well as an insulator.