Dynamic thermal performance of three types of unfired earth bricks

Fgaier, Fayçal El; Lafhaj, Zoubeir; Antczak, Emmanuel; Chapiseau, Christophe

doi:10.1016/j.applthermaleng.2015.09.009

Cited by 51 publications

(24 citation statements)

References 14 publications

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“…Cagnon et al [17] assess extruded earth bricks heat capacity both by calorimeter and Desprotherm, finding values from 900 to 960 J kg −1 K −1 for the first one and from 950 to 1030 J kg −1 K −1 for the second one. El Fgaier et al [32] measure heat capacity by the indirect method, finding values lower than the reference literature ones: from 545 to 662 J kg −1 K −1 . Allam et al [21] present different specific heat capacity for dry earth brick samples (750 J kg −1 K −1 ) and wet ones (1200 J kg −1 K −1 ).…”

Section: Specific Heat Capacitymentioning

confidence: 86%

“…In this case the specimens must have the same dimensions of the heating resistor. Finally, heat capacity can be also determined with an indirect method, using a guarded hot plate apparatus, imposing different thermal stresses, enabling the sample to store an amount of internal energy Q, and calculating the integral of the difference of flows from the initial temperature state, to the final one [32]. For effusivity assessment, samples must be thick enough because heat flow does not have to pass through it, as the measure is done in front of the sample under the hypothesis of semi-infiniteness of the material.…”

Section: Hygrothermal Properties Of Earth−based Materials and Methodomentioning

confidence: 99%

“…Laborel-Préneron et al [40] compares dry thermal conductivity of raw earth with its 6% barley straw-stabilized version, finding out a decrease from 0.57 W m −1− K −1 to 0.14 W m −1− K −1 caused by the addition of natural fibers, and consequent decrease in dry density (from 1075 to 1995 kg m −3 ). El Fgaier et al [32] work on three extruded raw earth bricks, produced by brickworks in France and composed by fine aggregates: they measure homogeneous λ-values around 0.9 W m −1− K −1 . Gomaa et al [41] present an interesting work on 3d-printed cob elements with 2% straw and cohesive soil, realized as solid elements, with two cavities and with one single straw-filled cavity: these specimens are tested in a heat flow meter and conductivities ranging from 0.32 W m −1− K −1 to 0.48 W m −1− K −1 are found, corresponding to dry densities from 1283.7 kg m −3 to 1780.3 kg m −3 .…”

Section: Thermal Conductivitymentioning

confidence: 99%

“…Cagnon et al [17] measure high thermal effusivity for all the five extruded earth bricks, all approximately equal to 900-1100 J m −2 K −1 s −1/2 . Thermal effusivity can be found also by the theoretical way, knowing c, λ and material thickness: F. El Fgaier et al [32] find values ranging from 936.49 J m −2 K −1 s −1/2 to 1176.95 J m −2 K −1 s −1/2 , correspondent diffusivity values range from 5.72 × 10 −7 m 2 s −1 to 9.23 × 10 −7 m 2 s −1 . As known, thermal effusivity can be used to represent thermal inertia of a material [50] and can be estimated through an admittance procedure implemented by a finite element analysis: in this way, using thermal conductivities provided by two standards, Stone and Katunsky find thermal effusivities lower then experimentally measured ones, from 529.2 J m −2 K −1 s −1/2 to 833.9 J m −2 K −1 s −1/2 , and diffusivity values from 4.6 × 10 −7 m 2 s −1 to 7.3 × 10 −7 m 2 s −1 .…”

Section: Thermal Effusivity and Diffusivitymentioning

confidence: 99%

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Hygrothermal Properties of Raw Earth Materials: A Literature Review

2019

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Raw earth historic and contemporary architectures are renowned for their good environmental properties of recyclability and low embodied energy along the production process. Earth massive walls are universally known to be able to regulate indoor thermal and hygroscopic conditions containing energy consumptions, creating comfortable interior spaces with a low carbon footprint. Therefore, earth buildings are de facto green buildings. As a result of this, some earthen technologies have been rediscovered and implemented to be adapted to the contemporary building production sector. Nevertheless, the diffusion of contemporary earthen architecture is decelerated by the lack of broadly accepted standards on its anti-seismic and thermal performance. Indeed, the former issue has been solved using high-tensile materials inside the walls or surface reinforcements on their sides to improve their flexural strength. The latter issue is related to the penalization of earth walls thermal behavior in current regulations, which tent to evaluate only the steady-state performance of building components, neglecting the benefit of heat storage and hygrothermal buffering effect provided by massive and porous envelopes as raw earth ones. In this paper, we show the results of a paper review concerning the hygrothermal performance of earthen materials for contemporary housing: great attention is given to the base materials which are used (inorganic soils, natural fibers, and mineral or recycled aggregates, chemical stabilizers), manufacturing procedures (when described), performed tests and final performances. Different earth techniques (adobe, cob, extruded bricks, rammed earth, compressed earth blocks, light earth) have been considered in order to highlight that earth material can act both as a conductive and insulating meterial depending on how it is implemented, adapting to several climate contests. The paper aims to summarize current progress in the improvement of thermal performance of raw earth traditional mixes, discuss the suitability of existing measurement protocols for hygroscopic and natural materials and provide guidance for further researches.

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Section: Specific Heat Capacitymentioning

confidence: 86%

Section: Hygrothermal Properties Of Earth−based Materials and Methodomentioning

confidence: 99%

Section: Thermal Conductivitymentioning

confidence: 99%

Section: Thermal Effusivity and Diffusivitymentioning

confidence: 99%

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Hygrothermal Properties of Raw Earth Materials: A Literature Review

2019

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“…Nowadays crude earth is still the most widespread building material in the world because it has advantages in energy and climate fields: it is available in large quantities, cheap and easy to work, it is a totally recyclable resource and it requires a very low amount of energy to the manufacture as well to the transport [2].…”

Section: Introductionmentioning

confidence: 99%

Clay and fibers: Energy efficiency in buildings between tradition and innovation

Cardinale¹,

Sposato²,

Feo³

et al. 2018

MMEP

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Building construction technology using clay soil in various forms, already known since ancient times, presents a great potential to regulate indoor humidity, to reduce the indirect impact of construction sector on the environment and on energy consumption. Extensive studies have also been done on the effects of natural fibers on the mechanical and physical behaviour of composite materials in terms of strength, energy efficiency and impact resistance. This work is focused on some natural fiber composites made from different mixtures containing clay soil with different percentages of jute, straw and basalt fibers, in order to determine the ideal mixture between clay and fibers providing the optimum values of thermal inertia, mechanical performance and shrinkage able to improve the energy efficiency of buildings. The mechanical, physical and thermal properties of some specimens have been investigated. The obtained results show an improved mechanical strength and a better thermal conductivity of the clay composite material.

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