Thermal Conductivity Measurements By Means of a New 'Small Hot-Box' Apparatus: Manufacturing, Calibration and Preliminary Experimental Tests on Different Materials

The evaluation of the thermal performance building components requires a high level of accuracy. Windows, doors and thermal bridges are not homogeneous, and their thermal transmittance can be evaluated by means of Hot-Box, used for full-scale elements. For homogeneous materials and one-dimensional heat flux, the thermal conductivity can be easily measured through other experimental apparatuses, such as the guarded hot plate and the heat flow meters. This study presents a new experimental apparatus named Small Hot-Box, built at the University of Perugia. No European standards are available for this innovative facility, but it takes into account some prescriptions of EN ISO 8990 and EN ISO 12567; it was built for the evaluation of the thermal properties of small specimens. The apparatus was designed, built, and calibrated by means of preliminary measurements. It is composed of a hot and a cold side, and the external walls are made of thick insulation. The thermal conductivity can be calculated by two different methodologies: the Hot-Box and the thermal flux meter method. Preliminary calibrations were carried out and different materials with known thermal transmittance were tested. The aim is the development of a new experimental apparatus; guidance documents could be defined for the measurements methodology requirements.