A structural wall incorporating biosourced earth for summer thermal comfort improvement: Hygrothermal characterization and building simulation using calibrated PMV-PPD model

Abstract

The drive to design modern low-environmental impact buildings with high-energy efficiency has led to an increase in unfired earth masonry studies reflecting the rising trend of earth used in passive buildings. This paper deals with the efficacy of incorporating biosourced earth in the building envelope. Firstly, the development and the hygro-thermo-mechanical characterization of earth blocks biosourced with local agro-aggregates (Alfa fibers and sawdust) were conducted. An aggregate-to-earth replacement ratio of 8 wt% was adopted. Mechanical tests show that earth blocks alone have a compressive strength of about 1.7 MPa. The hygrothermal tests reveal that biosourced blocks exhibit excellent hygrothermal properties, especially specimens with short Alfa fibers. A twofold decrease in the thermal conductivity value and a significant increase of the time lag and sorption capacities were achieved. The moisture buffering tests show that Alfa fibers improve the buffering capacity of earth from 1.9 to 2.3 g/(m2.%RH), leading the blocks to be classified as “Excellent” humidity regulators. Following the laboratory tests, and to overcome the low mechanical strength of earth, a double hollow brick wall integrating biosourced earth was studied. Building-scale benefits during summer were identified using a validated PMV-PPD model, implemented in EnergyPlus, based on real-time monitoring of an existing building. The findings show that the proposed wall increases thermal comfort by regulating indoor temperature and humidity, reducing 24.6% in dissatisfied occupants compared to typical walls. It is concluded that the use of earth presents a sustainable practice for constructing eco-efficient buildings with enhanced occupant satisfaction in hot regions.