The overall objective of this work was to measure transient moisture content and temperature distributions in a 6 to 12 in. (15.2 to 30.4 cm) thick slab of fibreglass batt insulation. The data were needed to verify a model of heat and mass transfer in fibreglass with diurnal varying temperature and humidity boundary conditions. The experimental setup was designed as two primary subsystems - (1) a humidity/temperature control system to maintain the desired diurnal variation at the boundary of the slab and (2) a gamma-ray attenuation system to measure the moisture content distribution within the fibreglass slab. The humidity/temperature control system uses a chiller to dry the air and stream or water to humidify to the desired level. Electric resistance heaters control the temperature. The system can produce sinusoidal or any chosen diurnal variation ranging from 5 deg C to 50 deg C and 20% to 80% RH. The moisture content measurement system uses a collimated Am-241 gamma beam. A second source, Cs-137, was available for use in a dual-source mode but was not needed. Approximately two minutes are needed for each moisture content measurement, and moisture contents as low as .01 g/g, corresponding to a relative humidity of 10%, can be measured. The system measures moisture content at eight points within the slab.

KEYWORDS: transient, heat flow, moisture, glass fibre, thermal insulation, measuring, temperature distribution, calculating, relative humidity, equipment