What happens to the R-value of insulation when moisture is present?

The R-value of insulation is a measure of its thermal resistance, indicating its ability to resist heat flow. When moisture is present, the effectiveness of insulation can be significantly compromised. This happens because water in a porous insulation material can create a conduction path that allows heat to flow more easily through the material, lowering its R-value.

Moisture can fill the spaces intended to provide insulation, leading to decreased air pockets that are crucial for maintaining thermal resistance. Essentially, when insulation gets wet, it tends to conduct heat better than when it is dry, resulting in a reduced R-value. This reduction can lead to increased energy costs and reduced comfort in a space due to insufficient thermal performance.

Proper management of moisture and ensuring insulation materials are kept dry is vital to maintaining their effectiveness over time.