clo
Areal thermal resistanceexact by definition
The clo is exactly 0.155 m²·K/W, defined as the insulation of a typical business suit: enough clothing to keep a resting person comfortable indefinitely at 21 °C in still air. A t-shirt and shorts is about 0.3 clo, a suit 1.0, and heavy winter clothing 3 to 4.
Watch out: The clo describes the whole clothing ensemble, not the fabric. Adding a 0.5 clo sweater to a 1.0 clo suit does not give 1.5, because layers compress and the still-air film between them is what does most of the insulating.
| 1 clo | 0.155 RSI (m²·K/W) |
Introduced by Gagge, Burton and Bazett in 1941 as a unit ordinary people could reason about, and it stuck: ASHRAE Standard 55 and ISO 7730 both specify thermal comfort in clo, and the clo value of the occupants is a required input to any comfort calculation.