Thermal Conductivity Constants (symbol k) Material BTU . in hr . ft- . FC Air 0.17 Aluminum 1460 Asbestos 4.0 Brass 750 Brick 4.5 Cellulose (blown in) 0.2 Concrete 7.5 Copper 2670 Corkboard 0.30 Fiberglass 0.29 Glass 4.96 Gypsum board 1.17 Hydrogen 1.3 Iron 320 Water 4.15 Wood (Pine across the grain) 0.78