Acoustic and thermal properties of panels made of fruit stones waste with coconut fibre

Abstract

Using natural porous and fibrous materials for acoustic and thermal conditioning in the construction sector is a solution to achieve a comfort level in buildings. The novelty of this research work lies in employing agricultural and agro-industry waste to solve noise and thermal insulation problems. This study was conducted to investigate a multilayered panel made of fruit stones and coconut fibre from agro-industry waste. Acoustic absorption, and acoustic and thermal transmission, tests were run on four different fruit stone types, olive, cherry, apricot and peach, plus a coconut fibre layer. Although they are not structural elements, bending tests were run to ensure panels’ structural integrity. Acoustic tests complied with the recommendations of Standards ISO 10534–2 and ASTM E 2611–09, based on the standing wave tube to obtain the acoustic absorption coefficient and sound transmission loss, respectively. Standard EN 12667 was considered for the thermal test to determine the thermal conductivity coefficient based on the hot plate method. The results show an average sound absorption coefficient above 0.5 and sound insulation over 25 dB within certain frequency ranges. The cherry panels had absorption values of around 0.7 and apricots had sound insulation values of up to 30 dB. Samples’ thermal transmittance coefficient values were between 3.0 and 3.4 (W/m2K), which indicate panels’ ability to provide thermal insulation. The cherry and olive panels obtained the lowest thermal conductivity (around 0.14 W/mK). The backing effect of the coconut fibre layer improves all the panels’ acoustic absorption and thermal properties.