Indoor CO2 buffering potential of clay-based building materials

Abstract

To mitigate the anthropogenic greenhouse gas emissions from the operational energy consumption in buildings, increasingly high-performance envelopes are developed. A reduction in indoor air renewal is observed that leads to a higher pollutant concentration in the built environment. Particular attention was given to CO2, an anthropogenic gas that has consequences on the Indoor Air Quality (IAQ) and the health of occupants. Developing a passive regulation system appears to be a promising solution for improving IAQ and reducing the energy consumption of ventilation systems. For that purpose, earth-based materials present interesting characteristics through the presence of clay minerals and their microstructure. In this context, this paper aims at presenting a novel experimental method to assess the CO2 retention potential of natural earth plasters. The method uses a thermogravimetric device (TGA/DSC) associated with a gas mixer and humid air generator. The mass variation resulting from the interaction of the increasing CO2 content could thereby be measured and analysed. Results show the important role of reversibility in the phenomenon: the majority of the captured CO2 being released when the CO2 concentration drops. It also highlights the role of the relative humidity on the retention capacity. As the retention of CO2 is lower when the material is wet, the water molecules may occupy part of the adsorption sites and react themselves with the CO2. This experiment provides the first values and thus evidence of the CO2 retention capacity and passive regulation potential of this material.