Which condition is indicated when insulation is unable to provide its full rated R-value?

When insulation is unable to provide its full rated R-value, compression is a significant factor. R-value measures the resistance to heat flow, and insulation needs to maintain its thickness for optimal performance. When insulation is compressed, it loses air pockets that are essential for its insulative properties. This reduction in thickness directly impacts its ability to resist heat conduction, making it less effective at insulating.

Other conditions like moisture, soil, or damage can also influence insulation performance, but they don't specifically pertain to its physical state of thickness and air retention in the same way compression does. Moisture can lead to reduced effectiveness due to water saturation, but it doesn't directly imply that the insulation has been physically compressed. Similarly, soiling could hinder performance but does not affect the structural integrity of the insulation itself. Damage refers to physical impairment but also does not specifically indicate a failure in the insulation's thickness. Thus, compression is the most accurate answer regarding the loss of R-value.