Hygrothermal performance of wood-hemp insulation in timber frame wall panels with and without a vapour barrier

Latif, Eshrar; Ciupala, Mihaela Anca; Tucker, Simon; Wijeyesekera, Devapriya Chitral; Newport, Darryl J.

doi:10.1016/j.buildenv.2015.04.025

Cited by 64 publications

(39 citation statements)

References 17 publications

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“…These components can be separated either by retting including chemical and microbial actions or mechanically, dividing the stem into bark fibres and woody stem (shiv) fractions. These materials have the potential to act as a building material to moderate humidity levels in an indoor environment due to their inherent hygroscopic properties (Latif et al 2015;Laborel-Préneron et al 2016;Hurtado et al 2016;Bourdot et al 2017). The components of fibres and shiv of flax and hemp include cellulose, hemicellulose, lignin, pectin, waxes and water soluble substances.…”

Section: Introductionmentioning

confidence: 99%

Comparative moisture and heat sorption properties of fibre and shiv derived from hemp and flax

et al. 2018

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Unlike many mineral-based insulation materials bio-based lignocellulosic fibre and shiv offer a number of benefits including thermal and hygroscopic properties. The microstructure, porosity and chemical compositions of the plant cell walls play a major role in the moisture exchange process. In this paper, the effects of microstructure, chemical composition, porosity and pore size distribution of both fibre and shiv, from hemp and flax plants, on both moisture and heat sorption were studied for the first time. The physical and chemical characteristics of the fibre and shiv from hemp and flax were studied by using scanning electron microscopy, mercury intrusion porosimetry and Fourier transform infrared spectroscopy. Water moisture sorption and heat of sorption were studied using a dynamic vapour sorption apparatus and a simultaneous thermal analysis system, combined with a humidity generator and using a copper furnace. Results showed that both the fibre and shiv of hemp and flax adsorbed a similar amount of moisture at a given relative humidity, which was dependent on the availability of hydroxyl groups for water in the cell wall. The macroscopic surface area and porosity of the specimen on a large scale had little influence on the availability of hydroxyl groups in the cell wall. The water molecules bound with cell wall molecules through hydrogen bonds over the full range of relative humidities, with a consistent hysteresis difference between the first sorption isotherm and subsequent sequential sorption cycles found in the hemp shiv specimens. For both hemp and flax, the isothermic hysteresis of the shiv was much higher than that of the fibre, which was shown to be dependent on the lignin content. The result of heat sorption indicated that some blocked sorption sites become available to water vapour molecules due to the change in molecular structure of the cell wall during the adsorption process. This study has improved understanding of the hemp and flax sorption behaviour and is important for optimal application of bio-based insulation materials for construction.

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Section: Introductionmentioning

confidence: 99%

Comparative moisture and heat sorption properties of fibre and shiv derived from hemp and flax

et al. 2018

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“…firstly, they are included in relative humidity variation protocols for standard adsorptiondesorption tests such as Nordtest [27] and ISO 24353 [28], secondly, the results can be compared with some of the in situ tests carried out using the same relative humidity variation protocol [11,29]. The time for each step of relative humidity condition was sufficient for the insulation materials to reach equilibrium moisture content.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…When the insulation materials were removed from the framework, water deposits on the lower surface of the framework of the Stone Wool insulation were also noticed, implying that further condensation had occurred in the Stone Wool insulation setup during the experiment. It was not possible to measure the amount of condensate resulting from the experiments but another study by the authors [29] did examine this aspect. Condensation seemed to occur in the acrylic surface of the Hemp-acrylic interface 36 (±1) hours later than it occurred in the Stone Wool-acrylic interface (Fig.…”

Section: Experimental Methodsmentioning

confidence: 99%

Quasi steady state and dynamic hygrothermal performance of fibrous Hemp and Stone Wool insulations: Two innovative laboratory based investigations

Latif

Tucker

Ciupala

et al. 2016

Building and Environment

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Moisture and heat management properties of Hemp and Stone Wool insulations were studied by mounting them between a hot and a cold climate chamber. Both insulations were exposed to identical hygrothermal boundary conditions. Quasi steady state and dynamic tests were carried out at a range of relative humidity exposures. The likelihood of interstitial condensation was assessed and equivalent thermal conductivity values of the insulations were determined. The adsorption-desorption isotherms of the insulations were also determined in a dynamic vapour sorption (DVS) instrument. It was observed that the likelihood of condensation was higher in Stone Wool insulation than in Hemp insulation. Hemp insulation performed better in managing moisture due to its high hygric inertia and water absorption capacity. It was observed that the equivalent thermal conductivity of Stone Wool insulation was dependent on enthalpy flow and phase change of moisture. The equivalent thermal conductivity of Hemp insulation was close to its declared thermal conductivity in dynamic conditions when high relative humidity exposures were transient. In quasi steady state boundary conditions, when the insulation was allowed to reach the equilibrium moisture content at ranges of relative humidity, there was a moisture dependent increase of thermal conductivity in Hemp insulation.

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“…They showed that moisture accumulation was observed in the layer close to the plaster for the wall without Oriented Strand Board (OSB). Latif et al [16] carried out an in situ experiment on a full-scale timber frame test building to study the hygrothermal performance of wood-hemp composite insulation in timber frame wall panels with and without a vapor barrier. They observed a very low impact on the U-value for the stresses studied.…”

Section: Introductionmentioning

confidence: 99%

Study of the Hygrothermal Behavior of Wood Fiber Insulation Subjected to Non-Isothermal Loading

et al. 2019

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Building envelopes are constantly subjected to temperature and moisture gradients. This loading induces a complex response, particularly for highly hygroscopic insulating materials. Latent effects can no longer be neglected for these materials in which heat and moisture transfers are strongly coupled. The purpose of this article is to analyze the behavior of a wood fiber insulation subjected to non-isothermal loading under a vapor concentration gradient. An experimental setup and a mathematical model of hygrothermal transfer were developed to analyze the behavior of the wall. The mathematical model describes the main physical phenomena involved, notably water vapor adsorption and the dependence of thermophysical properties in state variables. The experimental setup developed allows studying a wall under controlled conditions. The temperature and relative humidity profiles within the wall were measured. The evolution of the profiles with time suggests that the adsorption of the water vapor occurs together with the redistribution of liquid water within the envelope. The comparison of the experimental results with the numerical model shows good agreement although the prediction can be improved during the transient phase. The comparisons of these results with a purely diffusive thermal transfer model show the limits of the latter and permit quantifying the latent effects on the total heat transfer.

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Hygrothermal performance of wood-hemp insulation in timber frame wall panels with and without a vapour barrier

Cited by 64 publications

References 17 publications

Comparative moisture and heat sorption properties of fibre and shiv derived from hemp and flax

Comparative moisture and heat sorption properties of fibre and shiv derived from hemp and flax

Quasi steady state and dynamic hygrothermal performance of fibrous Hemp and Stone Wool insulations: Two innovative laboratory based investigations

Study of the Hygrothermal Behavior of Wood Fiber Insulation Subjected to Non-Isothermal Loading

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