What effect does wet insulation have on its R-value in crawl spaces?

Wet insulation significantly loses its R-value in crawl spaces due to the physics of heat transfer and moisture absorption. R-value is a measure of insulation’s ability to resist heat flow; the higher the R-value, the better the insulation performs.

When insulation material becomes wet, several factors come into play. The most critical is that moisture-filled insulation cannot trap air as effectively as dry insulation. Air is a poor conductor of heat, and it is this trapped air that gives insulation its effectiveness. When moisture takes its place, the insulation's ability to slow down heat transfer is reduced. In many cases, when insulation becomes saturated, its effective R-value can drop dramatically, sometimes losing as much as 50% of its effectiveness.

In crawl spaces, where condensation and moisture problems are common, maintaining dry, properly ventilated insulation is crucial to ensure optimal thermal performance and energy efficiency. This is why it is essential to address any water intrusion issues and ensure that insulation is adequately protected from moisture to preserve its insulating properties.