The thermal conductivities of a systematic series of metakaolin-derived Na, NaK, and K geopolymers have been measured under a range of different environmental conditions, including varied relative humidity ( RH) and temperature. The thermal conductivity of geopolymers is closely linked with the specific heat, with little variation in thermal diffusivity observed in different conditions. The thermal transport properties of specimens was found to not change significantly under ambient humidity from 40 to 100 degrees C. The Hashin-Shtrikman model for conductivity in biphasic solids, with an extension developed by Schilling and Parstzsch, has been applied to determine the thermal conductivity of the intrinsic geopolymer binder and a first approximation of the interconnectivity of the gel.