The total surface area of an adult is about 2 m2, and the mid- and far-infrared emissivity of skin and most clothing is near unity, as it is for most nonmetallic surfaces.[33][34] Skin temperature is about 33 °C,[35] but clothing reduces the surface temperature to about 28 °C when the ambient temperature is 20 °C.[36] Hence, the net radiative heat loss is about