Heat transfer is the measure of the heat flow from the test plate (heated to a skin surface temperature of 35°C) through the material into the test environment (21°C, 65%RH), and is determined in watts/m²°C for dry skin and wet skin conditions. Comfort parameters, calculated from heat transfer values, include:

a. Clo is a unit of thermal resistance that indicates the insulating ability of the test material. Materials having higher clo values provide wearers with more thermal protection. A clo value of 1 represents a typical man's business suit and is expected to maintain thermal comfort for a person in a normal indoor environment.

b. The i_m value, or permeability index, indicates moisture-heat permeability through the material on a scale of 0 (totally impermeable) to 1 (totally permeable). This comfort parameter indicates the effect of skin moisture on heat loss as in the case of a sweating skin condition.

c. Comfort limits are the predicted metabolic activity levels that wearers may sustain and maintain body thermal comfort in the test environment. Three comfort limits are reported with the first: min being associated with maintaining a dry skin surface; the second: comf is associated with having 20% of the skin surface wet with sweat and is considered to be the key comfort limit which more accurately represents typical activity levels of people; and the max level is for a 100% wet skin condition indicating a person is in a highly stressed state.