Experimental monitoring of hygrothermal transfers and condensation in an insulated rammed earth wall

Abstract

Rammed earth (RE) regulates heat and water vapor according to daily and seasonal cycles, but its high thermal conductivity remains a handicap. To make it a regulatory panel, it is necessary to insulate it. The insulation must guarantee the water balance of the RE to keep its integrity. The use of bio-geo-sourced insulation is relevant especially when contributed to the carbon neutrality of the complex. At the same time, the hygroscopic and capillary properties of these insulations must influence the condensation phenomena and the transfers of water and vapor at the interfaces. To verify this, several conventional and bio-sourced insulations (glass wool, wood fiber, lightweight earth), having the same thermal resistance but distinct hygroscopic and capillary characteristics, associated with a RE wall element are tested. A climatic chamber regulating temperature and humidity on one side of the complex is specifically built while the other side is subjected to stable climatic conditions. A measuring chain monitors the relative humidity, water content, temperature and heat flow through the complex. Different scenarios are applied in order to study hygrothermal transfers and evaluate the conditions for the appearance of condensation at the interfaces. The results of this study should make it possible to establish regulations for the insulation of RE.