A study was made to devise a method for grouping walls and roofs with similar transient heat transfer characteristics. Analytical and correlational methods were investigated. None of the analytical methods successfully predicted the transient heat characteristics of all multi-layer walls and roofs. The correlational methods utilized thermophysical properties and geometric similarities in grouping walls and roofs with equivalent heat transfer characteristics. A grouping method similar to that employed in an earlier ASHRAE project was finally investigated and achieved the desired results.

The grouping method employs a combination of four thermophysical and geometric parameters to place a wall or roof assembly into a group whose transient heat transfer characteristics are within a limited range. It was finally resolved that all common wall assemblies could be accurately represented by 41 distinct wall groups and all common roof assemblies could be described by 42 roof groups.

Units: I-P