Thermal resistance values of natural fiber-based insulation panels and the impact of their thickness on the thermal transmittance values of an external wall structure

Abstract

The purpose of this paper is to experimentally study the thermal resistance values (R-value) of insulation panels made mainly from natural fibers. Another investigation is to study the impact of the panel’s thickness on the values of thermal transmittance (U-value) of a multilayered installation for external wall systems to determine the optimal thickness of insulation panels used for building envelopes. Natural fibrous materials or renewable resources and their reinforcement composites are currently being used in building and construction as a potential solution to significantly reduce thermal load and energy consumption. In this study, the thermal resistance values of several samples made from rice straw, energy reed, and coir fiber are calculated from the thermal conductivity which was measured at room temperature (20 °C) using the mean of heat plate method. The lowest R-value was recorded from the polymeric composites reinforced by coir fiber and rice straw fiber (0.11 to 0.19 m2·K/W). Although these samples showed the least heat insulation capacity, however, they can be used as an additional layer in multi-layered wall structures because of their low thermal conductivity coefficient. Besides, the R-value per mm was also scored to highlight a strong dependence of thermal resistant performance on the thickness of the samples. On the other hand, the simulated data showed that increased thickness resulted in decreased U-value and the optimal thickness can be determined when the thickness is larger than 120 mm according to the standard of low energy house. Overall, the calculated R-values is a valuable parameter to evaluate the thermal resistant effectiveness of a multi-layered installation, which allows us to investigate the effect of additional layers from different insulating materials used in building envelopes.