Thermal Conductivity

Hi: I am looking for information about thermal conductivity of metal roofs, independently of its radiative properties (e.g short wave radiation absorptivity). Most roof products I have explored have a base of steel but there is a variety of coatings (aluzinc, galvalume, zincalume, etc). I have been searching for technical information of diverse coatings and brands and none of them provide data on thermal conductivity. In some basic studies or calculations is assumed that these roofs would have the thermal conductivity of steel (50 W/mK). However, I do not trust this criteria. I suppose that the material used in roof products is not pure steel and that the coatings may also have an influence in the conductivity. The conductivity of the metal layer is usually not significant when there is a layer of thermal insulation (polystyrene, polyurethane, etc), but is not the same for cases with no insulation. I require this information for thermal performance simulations of buildings without insulation in their roofs, which is the case of many public buildings and houses in third world countries. I will appreciate your guidance to find information like this. Thank you Claudio Diaz

Claudio, The reflectivity and emissivity rates are going to be coating and material specific. That information is usually readily available in the manufacturers specifications. Did you have general questions about that or were you asking about a specific manufacturer.