Investigation of the thermal insulation performance of fibrous aerogel samples under various hygrothermal environment: Laboratory tests completed with calculations and theory
Ákos Lakatos
Abstract
Insulation materials are mainly porous or fibrous materials. Therefore, the presence of moisture can easily cause problems inside the materials, and in the whole building structure. For correct calculations of heat and moisture transfer problems in building applications, practitioners need design values. Design thermal values are deduced and calculated from declared values which are reached from laboratory measurements. This is the case for both insulation and building materials. If the design environments are different from those where the declared values should be used, the data have to be changed to the relevant conditions. There are standards giving suggestions on how to calculate the design values of thermal insulation materials, however, their database and tables are insufficient regarding the values of the super insulation materials. In this paper, a calculation method will be presented so as to specify the design thermal conductivities of a glass fiber-reinforced aerogel. The calculation method is based on measurement results, where the lambda values were measured treating the samples in a humid environment. As a result, the moisture conversion coefficient for the thermal conductivities is obtained after measuring the humid thermal conductivities of materials. Moreover, a new calculation method will also be presented to estimate the vapor absorption coefficient from humidity measurements. Furthermore, the effects of ice and freeze on the thermal conductivities of the aerogel samples are characterized, too. The thermal conductivities were measured in a Holometrix type heat flow meter, while for the wetting a Venticell 111 type drying apparatus and a Climacell 11 climatic chamber were applied. Moreover, the cooling treatment was executed in a freezing room. In addition, new theory for the thermal conductivity was given, for moist/frost insulation materials.