How to Interpret Clo Ratings

PrimaLoft provides relevant Clo testing data for all applicable products. Clo ratings can be found on our product tech sheets. Outlined here are definitions that will help navigate the information found on these documents.

Total Clo is the thermal resistance of an insulation at a given weight. The higher the weight of a given insulation, the more insulating it will be, resulting in higher total Clo values.

Wet Clo is the thermal resistance of a wet insulation at a given weight. PrimaLoft® fibers are treated with a proprietary PFC-free finish that makes them highly effective at retaining warmth when wet.

Clo ratings per oz/yd 2 or g/m 2 allow you to compare the relative thermal performance of one insulation versus another. A higher clo/ oz/yd 2 represents a higher warmth to weight.