Subtle issues in the measurement of the thermal conductivity of vacuum insulation panels

Vacuum insulation panels have values of thermal conductivity that are extremely low (similar to 4 mW/m(.)K) compared to the thermal conductivity of most common insulations. Typical ASTM test methods are not designed for testing these very low thermal conductivity materials. An apparatus has been built and tested that uses a thin foil heater and vacuum chamber to test vacuum insulation panels. Several different measurement configurations are studied to determine the effects of the parasitic heat losses. The differences between the ASTM standards and this technique arc described and the rationale explained. A new ASTM technique,for vacuum panels appears to be needed.