Experimental Analysis of Thermal Conductivity for Building Materials Depending on Moisture Content

The presence of moisture in building envelopes can have many causes and may lead to deterioration of useful thermophysical characteristics of the materials, to weakening of the building structure, and to facilitating growth of mold. The International Standard ISO 13788 establishes a calculation procedure for the determination of hygrometric characteristics of building components and materials, assuming that the influence of moisture content on the thermal field across walls, ceilings, and roofs may be neglected. However, condensed water increases the effective thermal conductivity of building materials, thus modifying the temperature profiles across the building envelope. This effect is analogous to the one due to the material aging. In this paper, the authors show the results of effective thermal-conductivity measurements in some commonly adopted building materials as a function of moisture content, in order to assess the potential significance of interstitial condensation on thermal losses and to verify if the maximum allowed moisture content reported is useful to prevent the decay of the thermal properties of building materials.