Building Materials - Radiation Constants

The radiation constant is the product between the Stefan-Boltzmann constant and the emissivity constant for a material. This tool provides radiation constants and emissivity values for typical building materials.

The radiation constant is the product between the Stefan-Boltzmann constant - σ - and the emissivity constant - ε - of a material.

Stefan-Boltzmann Constant (σ): 5.6703×10⁻⁸ W/m²K⁴ = 0.1714×10⁻⁸ Btu/(h ft² °R⁴)

Emissivity Coefficient (ε): The emissivity of the object (ε = 1 for a black body)

Product	Radiation Constant (10⁻⁸ W/m²K⁴)	Emissivity Constant (ε)
Black body	5.7	1
Brass, dull	1.3	0.22
Brick, red	5.3	0.93
Cast iron, rough oxidized	5.1	0.9
Copper, polished	0.28	0.04
Cotton	4.4	0.77
Glass	5.1	0.9
Lampblack paint	5.5	0.96
Oil paint	5.4	0.94
Paper	3.1	0.55
Plaster	5.6	0.98
Sand	5.1	0.9
Silk	4.3	0.75
Silver, polished	0.17	0.03
Tin, unoxidized	0.23	0.04
Water, 0 - 100 °C	5.4	0.95
Wood	5.1	0.9
Wool	4.3	0.75
Wrought iron, dull oxidized	5.4	0.9
Wrought iron, polished	1.6	0.25
Zinc, tarnished	1.4	0.25