A Dynamic Test Protocol for Thermal Property Measurements Using the Heat Flow Meter Apparatus

Abstract

While most buildings experience fluctuating exterior temperatures, the predominant mode of evaluating thermal performance of building enclosures has involved testing based on steady-state methods. Thus, data that is needed to analyze building performance under non-steady temperature conditions is scarce, and difficult to generate. Of the many approaches developed for rapid thermal measurements using transient heating schemes, few of them are able to satisfy this need, since they generally require small, homogeneous specimens and are typically less successful testing low density, low conductivity materials. Recent work has been done to adapt the heat flow meter apparatus (HFMA), a device commonly used for steady-state measurements (ASTM C518, ISO 8301) on building materials, to this task, and a test protocol for operating this device in a dynamic mode has been developed. The heat flow meter apparatus was selected as the starting point for this effort because it can accommodate large, insulative, and often quite non-homogeneous specimens of building materials; its standard features include instrumentation for making precise measurements of temperature and heat flux, and for highly stable temperature control; it also offers the advantages of relatively short test times and simple specimen preparation. Major objectives of the study included techniques for measuring specific heat, latent heat of fusion, and other properties of building enclosure components, with a particular focus on comprehensive characterization of containing phase change materials (PCM). The new protocol is also intended to support future studies of materials containing moisture, and the nature of their response to changing boundary temperature conditions. Descriptions of the test protocol are presented, along with a discussion of samples tested, problems encountered, and results obtained. Tests were performed on extruded polystyrene foam insulation, loose-fill cellulose insulation (conventional and PCM-enhanced), PCM-wallboard composites, and a PCM product mounted on flexible sheet.