The need to determine the thermal performance of thick, light-density fibrous insulating materials at full manufactured thickness has necessitated the design and construction of new, large test equipment. The technical challenges imposed by thicker, high R-value insulation test samples and longer system time constants have increased the stability and precision measurement requirements of all system parameters.

This paper describes the Owens-Corning Fiberglas approach to the design and construction of a 1.22 by 1.22 m (48 by 48 in.) guarded hot plate (GHP) apparatus for testing insulation at full thicknesses up to 460 mm (18 in.).

This GHP utilizes a unique heater design to provide uniform power density, a floating mount cold plate support system to eliminate expansion and contraction problems, and a multitank cascaded fluid temperature control system to provide cold plate temperature stability of ±0.01°C (±0.02°F).

The apparatus has demonstrated excellent long-term stability of measured parameters and compatibility with automatic data acquisition equipment. A variety of features were incorporated for improved system flexibility, versatility, and ease of maintenance.