Comparison And Validation Of Modelling Methods For Non-Homogenous Walls Incorporating Vacuum Insulation Panels

This paper compares the effective thermal resistance of 5 wall assemblies incorporating vacuum insulation panels (VIP) encased in extruded polystyrene (XPS), known as composite panels, through three different evaluation methods. The methods consisted of using steady-state and in-situ experimental testing as well as computer simulation. The computer modelling of the wall assemblies used simplifications, such as symmetry, and involves creating a thermal model for each unique 2D profile within the wall assembly independently. The results of the modelling method were compared to an experimentally calculated thermal resistance based on measured heat flux through a representative assembly under steady-state conditions in a guarded hot box and the measured heat fluxes under in-situ conditions at the Natural Resources Canada CanmetENERGY seasonal test facility. The feasibility of using a composite panels to address concerns of VIP constructability was determined to be successful with a strong dependence on the ratio of the VIP dimensions to the overall performance of the wall assembly design. An effective thermal resistance range of 8.44 m2K/W to 9.07 m2K/W was found during steady-state testing in the guarded hot box, and an agreement within 0.1% to 7.9% was found between steady-state and computer model results. In addition to the initial modelling, a 4.5% agreement was achieved with a new method using simplifications that are based on the coverage area of the unique cross section. The approach utilizes the current simplifications used for homogenous walls, and further develops the methodology to prove they are applicable to non-homogenous wall assemblies as well.