A number of different insulation materials have a hygrosopic behaviour. Their physical, temperature dependent adsorption properties can be investigated by thermo-gravimetry. A less sophistic, but more application-oriented method was used for the described investigations. A model-collector (45x45x10 cm) equipped with an absorber was exposed with an inclination of 45° to a fast change of the ambient humidity from 30% to 80% in a climatic cabinet at 25°C. The absorber was kept at 40°C by a temperature-controlled heat-transfer fluid. The insulation material (thickness 5cm) behind the absorber could be varied. Two diagonally placed openings in the back-plane of 7mm diameter, which were not covered by insulation materials, allowed ventilation. The humidity inside was measured in the air-gap (5cm width) between absorber and glazing with a capacitive humidity sensor.

The response function shows a big variation for the different materials (figure 6). Different types of mineral-wool (or rock-wool) behave differently and even poly-urethane foam and melamine foam buffer humidity, but with a clearly longer time-constant (figure 7), which was defined as the period when 63% of the asymptotic maximum was reached. This kind of definition is not completely suitable, since the shape of the response curve of some materials indicates differences of the mechanisms or the presence of various processes with different time constants. High temperature loads cause a degradation of the rock-wool. Polymeric grease, which is used during the manufacturing processes is decomposed. One result is a change in the water absorption behaviour (figure 8). The increase of the time-constant means an increase of the water adsorption ability, that was proven by thermo-gravimetry.

SHAPE * MERGEFORMAT