Volume 15, Issue 3 (May 1987)
An Operational Procedure for Guarded Hot Box Testing
An operational procedure for guarded hot box (GHB) testing has been developed in the Thermal Measurements Laboratory (TML) of the Construction Products Division of W. R. Grace and Co. The GHB operational procedures consisting of specimen preparation, “calibration”, testing, data analysis, and reporting are presented in this report. These procedures follow the general guidelines given in ASTM Test for Steady-State Thermal Performance of Building Assemblies by Means of a Guarded Hot Box (C 236). In the specimen preparation procedure, material handling, specimen construction, specimen mounting into the specimen frame, and instrumentation placement and method of attachment are discussed in detail. The “calibration” procedure developed accounts for any variations in the thermal conductance of the metering box walls caused by design or construction. The experimentally determined setting for the thermopile electromotive force is controlled during testing so that the net heat flow through the metering box walls is negligible. The “calibration” procedure does not require knowledge of the thermal conductance of the specimen. A testing procedure is discussed that provides steady-state operation as defined by six steady 4-h periods of temperature and heat flow data within 1% of each other. The test data are analyzed and a GHB test report is generated by a computer software package. Examples of a typical GHB test report and a testing procedure data sheet are presented.