Building insulation materials have been subjected to various temperature and humidity conditions and their thermal performance during several weeks of controlled environmental exposure. Several commercially available insulation materials (three aerogel composite blankets, two extruded polystyrene foams (XPS) and one blown polyurethane foam (PUR)) were evaluated. The purpose is to compare performance of newer types (aerogel composites) with established types (foams). Thermal conductivity was measured with a heat flow metering apparatus at one week intervals for five weeks. Insulations were exposed to conditions of 65.6C and 90% RH, 65.6 degrees C and 60% RH, 65.6 degrees C and 30% RH, and 32.2 degrees C and 90% RH. Results indicate that humidity levels play a significant role in PUR performance, but not a significant role in XPS performance. The three aerogel composites have mixed results: one has little relationship between moisture content and thermal performance, one is strongly affected by moisture and the remaining is moderately affected by moisture. Fourier infrared spectrometry was performed on some of the materials to observe chemical stability. Results indicate that factors other than moisture content, such as hygroscopy and volume expansion, significantly contribute to thermal performance. Published by Elsevier B.V.