Improving the thermal performance of earthen walls to satisfy current building regulations

Goodhew, Steve; Boutouil, Mohamed; Streiff, François; Guern, Michel Le; Carfrae, Jim; Fox, Merritt B.

doi:10.1016/j.enbuild.2021.110873

Cited by 21 publications

(22 citation statements)

References 19 publications

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“…For this purpose, we investigated the performance of the thermal and mechanical performance of a thermal insulating material based on a GWM-FA-CR mixture incorporating reed fibers (length between 4 and 6 cm). According to the usual method in bibliography [ 33 ], the reed content used was 25%.…”

Section: Resultsmentioning

confidence: 99%

“…Additionally, only residual straws are used in order to prevent ILUC effects and keep their valorization with the largest renewability and CO 2 emission neutrality as possible. The thermal conductivity of cheap wheat straw fibers is between 0.035 and 0.054 W·m −1 ·K −1 [ 33 ].…”

Section: Materials and Techniquesmentioning

confidence: 99%

“…The most popular mud or earth building techniques are rammed earth, daub, compressed earth blocks and cob [ 32 ]. In our region (Normandy, France), the most popular earth building technique is cob (Bauge in French), which uses a mixture of earth and fibers, such as straw [ 33 ].…”

Section: Introductionmentioning

confidence: 99%

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Mud-Based Construction Material: Promising Properties of French Gravel Wash Mud Mixed with Byproducts, Seashells and Fly Ash as a Binder

et al. 2021

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The French gravel industry produces approximatively 6.5 million tons of gravel wash mud each year. This material offers very promising properties which require an in-depth characterization study before its use as a construction material, otherwise it is removed from value cycles by disposal in landfills. We examined the suitability of gravel wash mud and seashells, with fly ash as a binder, as an unfired earth construction material. Thermal and mechanical characterizations of the smart mixture composed of gravel wash mud, Crepidula fornicata shells and fly ash are performed. The new specimens exhibit high compressive strengths compared to usual earth construction materials, which appears as a good opportunity for a reduction in the thickness of walls. The use of fly ash and Crepidula shells in addition to gravel wash mud provides high silica and calcium contents, which both react with clay, leading to the formation of tobermorite and Al-tobermorite as a result of a pozzolanic reaction. Considering the reduction in porosity and improvements in strength, these new materials are good candidates to contribute significantly to the Sustainable Development Goals (SDGs) and reduce carbon emissions.

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Section: Resultsmentioning

confidence: 99%

Section: Materials and Techniquesmentioning

confidence: 99%

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Mud-Based Construction Material: Promising Properties of French Gravel Wash Mud Mixed with Byproducts, Seashells and Fly Ash as a Binder

et al. 2021

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“…The second layer provides a high thermal resistance by using high composition of fibres (25%) in the mixes. The use of a dual layer, respecting structural performance and thermal performance of building, provides a thinner wall (300 mm for insulating cob layer and 400 mm for structural cob layer, as suggested by Goodhew et al [15]) rather than a thick single cob layer using 1400 mm of thickness, as defined by Leguern et al [16].…”

Section: Methodology and Experimental Investigations Of Cob Materialsmentioning

confidence: 99%

“…As most of the studies remain limited to laboratory characterization, rather than considering in situ prototyping to meet the construction regulations, Goodhew et al [15] proposed a combination of two walling layers using earth materials (Cob) to satisfy building regulations. The two layers are comprised of insulation with high fibre content and a load bearing layer with higher density.…”

Section: Introductionmentioning

confidence: 99%

Novel Dual Walling Cob Building: Dynamic Thermal Performance

et al. 2021

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This paper emphasizes the experimental and numerical study of new cob mixes used for insulation and load bearing wall elements. The experimental study provides complete datasets of thermal properties of the new walling materials, using cob with density ranging from 1107 kg/m3 to 1583 kg/m3 for structural walls and less than 700 kg m−3 for insulation walls. Various mixes of French soils and fibres (reed, wheat straw, hemp shiv, hemp straw, and flax straw) with different water contents are studied. The lowest average thermal conductivity is obtained for the structural cob mix prepared of 5% wheat straw and 31% of water content. The insulation mix, prepared with 25% reed and 31% water content, has the lowest thermal conductivity. Investigation of diffusivity, density, and heat capacity shows that, when thermal conductivity is lower than 0.4 W m−1 K−1, the decrease in cob density leads to better insulation values and higher heat capacity. Little variation is noticed regarding the density and heat capacity for cob mixes with thermal conductivity higher than 0.4 W m−1 K−1. Furthermore, the non-uniformity of local thermal conductivity and heat losses through the samples is due mainly to the non-uniform distribution of fibres inside the mixes inducing an increase in heat loss up to 50% for structural walls and 25% for insulation walls. Cob thermal properties are used in a comparative simulation case study of a typical house under French and UK climatic conditions. The energy performance of the conventional building is compared to a dual walled cob building, showing remarkable reduction in energy consumption as the cob walls, whilst maintaining comfortable indoor conditions without additional heating.

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The State of the Art of Cob Construction: A Comprehensive Review of the Optimal Mixtures and Testing Methods

2023

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Earthen construction systems have potential hygrothermal, and environmental benefits over conventional building materials such as concrete. However, such systems are not yet fully optimised to be part of an energy-efficient building. Therefore, to further optimise the material, this review explores peerreviewed research articles that relate to different materials used in cob mixes and the different testing methods used to assess the produced specimen's hygrothermal performance. For data collection, a systematic keyword search was carried out on ScienceDirect, Scopus, Google scholar search engines and relevant books. The filtering of journal articles was based on studying the abstracts followed by analysing their content within the scope of the review. The results show that the soil's constituents and the added fibre ratios critically affect the percentages of clay and water added to the mixture. Fibres' impact on the mix was experimented with by multiple researchers using distinct types of plant aggregates. The percentage of fibre addition ranged between 0.9% and 3% for structural specimens and reached 25% for non-structural specimens with optimised insulation properties. However, there is no consensus and robust collated data available about the ratios of the mixes concerning the hygrothermal performance of the specimens. Therefore, a matrix for mixes and testing methods was developed with the available data to aid the progression of any future optimisation effort.

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Improving the thermal performance of earthen walls to satisfy current building regulations

Cited by 21 publications

References 19 publications

Mud-Based Construction Material: Promising Properties of French Gravel Wash Mud Mixed with Byproducts, Seashells and Fly Ash as a Binder

Mud-Based Construction Material: Promising Properties of French Gravel Wash Mud Mixed with Byproducts, Seashells and Fly Ash as a Binder

Novel Dual Walling Cob Building: Dynamic Thermal Performance

The State of the Art of Cob Construction: A Comprehensive Review of the Optimal Mixtures and Testing Methods

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