This work analyzes and discusses analytically a method of controling the insulating properties of an assembly. It establishes the feasibility of utilizing gas layers within the insulating assembly separated by flexible soft seals. The volumetric thermal expansion of the main gas layers within the insulating assembly are determined taking into consideration the variation in the gas pressure due to the elastic behavior of the supporting flexible soft seals. It was found that the volumetric thermal expansion of the main gas approaches its isobaric condition value as the main gas layer thickness decreases. Also, it is found that insulating properties are enhanced when the main gas has a minimum thermal conductivity and when relatively high temperatures are experienced. However, insulating properties deteriorate at large temperatures when the main gas has a relatively large thermal conductivity. Finally, advanced insulating assemblies with maximized insulating properties are proposed. (C) 2003 Elsevier Ltd. All rights reserved.