Experimental analysis of moisture-dependent thermal conductivity, and hygric properties of novel hemp–shive insulations with numerical assessment of their in-built hygrothermal and energy performance

Latif, Eshrar ORCID: https://orcid.org/0000-0003-3982-6929 2024. Experimental analysis of moisture-dependent thermal conductivity, and hygric properties of novel hemp–shive insulations with numerical assessment of their in-built hygrothermal and energy performance. Materials 17 (2) , 486. 10.3390/ma17020486

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Abstract

The use of lime as a binder in hemp–lime considerably increases the drying time of hemp– lime after casting. Furthermore, lime is a non-renewable mineral resource. As such, this paper explores the effectiveness of using an alternative non-mineral binder instead of lime to formulate a novel hemp–shive insulation. The moisture-dependent thermal conductivity, adsorption isotherm, vapour diffusion resistance factor, and in-built hygrothermal performance of four variants of a novel bio-based insulation were investigated. The hygrothermal performance of the novel hemp–shive insulation was compared with that of a previously developed novel hemp–lime insulation. No significant variation in thermal conductivity of hemp–shive insulations between the equilibrium moisture contents (EMC) at 0% and 50% relative humidity (RH) was observed, but there was a substantial increase in thermal conductivity hemp–shive insulations when the material reached the EMC at 98% RH. The average dry thermal conductivity values of hemp–shive and hemp–lime insulations were also similar. The adsorption isotherms of hemp–shive insulations were determined at 0%, 20%, 50%, 70%, 90%, and 98% relative humidity steps. At 98% RH, the moisture adsorption capacity of hemp– shive insulations was 4-to-5-times higher than that of hemp–lime insulation. Hemp–shive insulations’ vapour diffusion resistance factor (μ value) was about double the μ value of hemp–lime insulation. Hemp–shive insulations exhibited 4-to-5-times higher water absorption resistance than that of hemp–lime insulation. Numerically determined porosity values of hemp–shive agree with the values of wood-based insulation materials of similar density. Finally, using all experimentally acquired data as inputs, dynamic whole-building hygrothermal simulations were carried out and the results show that novel hemp–shive insulation materials perform at a similar level to the hemp–lime insulation in terms of heating and cooling energy demand but require 45% less energy for humidification. However, the relative humidity inside the hemp–shive wall remains higher than 70%, which can potentially induce mould growth.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Architecture Engineering
Publisher:	MDPI
ISSN:	1996-1944
Date of First Compliant Deposit:	19 January 2024
Date of Acceptance:	16 January 2024
Last Modified:	26 Jan 2024 11:15
URI:	https://orca.cardiff.ac.uk/id/eprint/165683

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