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The building and construction sector is the largest emitter of greenhouse gases, accounting for 37% of global emissions. The production and use of materials such as cement, steel, and aluminum contribute significantly to this carbon footprint. Utilizing valorized agricultural by-products, such as hemp shiv and sunflower pith, in construction can enhance the insulating properties of materials and reduce their environmental impact by capturing CO2. Additionally, during the formulation process, molecules such as polyphenols and sugars are released, depending on process parameters like pH and temperature. In some cases, these releases can cause issues, such as delaying the hardening of agro-based concrete or serving as binding agents in binderless particle boards. This study focuses on the molecules released during the processing of these materials, with particular attention to the effects of pH and temperature, and the modifications to the plant particles resulting from these conditions. Physical, chemical, and morphological analyses were conducted on the treated hemp shiv particles (HS1 and HS2). No physical or morphological differences were observed between the samples. However, chemical differences, particularly in the lignin and soluble compound content, were noted and were linked to the release of plant substances during the process. [ABSTRACT FROM AUTHOR]

In this work, we present an energy efficiency study for a residential building located in the city of Al-Hoceima, Morocco. The aim is to bring the building into compliance with the technical requirements of the Moroccan Thermal Building Regulations (RTCM). To achieve this, several modifications and interventions were carried out, such as the use of hemp concrete for insulation and the integration of passive strategies to minimize energy loads. Similarly, this energy study is carried out as a simulation using TRNSYS software, so that the building is modeled as a multizone entity with an occupancy schedule. The simulation results show that the technical requirements of the RTCM are achieved using a construction containing hemp concrete with an optimum thickness of around 10cm, this thickness can be reduced to 4cm using double glazing, or to 1cm using controlled natural ventilation in summer and winter. [ABSTRACT FROM AUTHOR]

The search for environmentally friendly and low-carbon-footprint construction materials continues progressively. Researchers are now interested in innovative materials that connect with the principles of sustainable construction, and materials such as hemp concrete prove to be promising. This article presents the results of a study that aimed to evaluate the hygrothermal performance of hemp concrete integrated into the building envelope using the hygrothermal tool WUFI Pro 6.2. The simulation model was compared and verified with existing models before its utilization for this study. The results of this verification were in good agreement, which gave us more confidence in its application for further parametric studies of building envelopes in hot climate zones. Three wall systems were simulated: (i) a wall system with hemp concrete, (ii) a compressed earth block wall, and (iii) a cement block wall. The most important variables used in the simulations were the hygrothermal properties of the materials or wall components and the incident solar radiation. The simulation results showed that hemp concrete has good thermal performance and temperature and humidity regulation capabilities of the building envelope. The interior surface temperatures of the hemp concrete walls were between 22.1 °C and 24.6 °C compared to the compressed earth block and cement block walls, where the surface temperatures were between 22.0 °C and 27 °C and between 21.2 °C and 28.7 °C, respectively, and between 23 °C and 45 °C for the exterior temperatures. These values remain the same with the increase in exterior temperatures for hemp concrete walls. In conclusion, hemp concrete could be a great alternative material for use in construction for hot climate zones. [ABSTRACT FROM AUTHOR]

The building and construction sector is the largest emitter of greenhouse gases, accounting for 37% of global emissions. The production and use of materials such as cement, steel, and aluminum contribute significantly to this carbon footprint. Utilizing valorized agricultural by-products, such as hemp shiv and sunflower pith, in construction can enhance the insulating properties of materials and reduce their environmental impact by capturing CO2. Additionally, during the formulation process, molecules such as polyphenols and sugars are released, depending on process parameters like pH and temperature. In some cases, these releases can cause issues, such as delaying the hardening of agro-based concrete or serving as binding agents in binderless particle boards. This study focuses on the molecules released during the processing of these materials, with particular attention to the effects of pH and temperature, and the modifications to the plant particles resulting from these conditions. Physical, chemical, and morphological analyses were conducted on the treated hemp shiv particles (HS1 and HS2). No physical or morphological differences were observed between the samples. However, chemical differences, particularly in the lignin and soluble compound content, were noted and were linked to the release of plant substances during the process.

This paper presents a numerical study of the lateral load-carrying capacity of hemp concrete as infill material in timber frame walls. The parameters that significantly affect the lateral resistance of hemp walls were investigated. For this purpose, vertical stud timber frame walls measuring 2.5 m in height and 1.2 m in length were used as the benchmark to validate earlier experimental work. A numerical study of three timber walls filled with hemp concrete was conducted to assess the effect of wall length on the lateral load-carrying capacity of hemp concrete. Three vertical stud timber frame walls with a standard height 2.5 m and different lengths (1.2 m, 1.6 m and 2.4 m) were investigated using Abaqus software. This study confirms, firstly, that the length of a timber wall plays a significant role in the lateral load-carrying capacity of hemp concrete. Secondly, the contact and bonding between the hemp concrete and timber wall have a significant effect on the lateral load-carrying capacity of hemp concrete as infill material in timber frame walls. It was clear, from the numerical results, that increasing the length of the wall significantly increases the contribution of hemp concrete to lateral resistance. Good contact and bonding between the hemp concrete and the timber elements also increase the lateral strength of the hemp wall. [ABSTRACT FROM AUTHOR]

In this article, the functional properties of hemp concrete are studied. Hemp concrete stands to reduce the carbon impact and improve the energy consumption of houses. Hence, numerous properties are measured: mass and dimension (volume) variations are found, as is the variability in hygrothermal properties (density, thermal conductivity, heat capacity, moisture buffer value, and water vapor permeability). This entry proposes three different characterization campaigns. The first is a short introduction to the spatial variability in thermal conductivity; the second is dedicated to the study of univariate variations in the mass, volume, and hygrothermal properties of hemp concrete samples. The last one tackles the aging evolution of the properties characterized during the second campaign, in which the samples follow several aging protocols, including exposure to outdoor conditions, the application of immersion-drying cycles, and the application of freeze–thaw cycles. A set of samples is kept under control conditions to allow for comparison. As the main result, spatial variability was found in the material. This is related to the random manufacturing variability or the spatial position regarding the height of the manufactured element. A high univariate variability is found across hemp concrete samples. Moreover, the storage of samples under stable reference conditions implies very little change in the studied materials' properties, whereas all accelerated aging protocols implied major changes of properties. In particular, we observed an evolution of the thermal conductivity of the samples kept under control conditions for 4 months, with the thermal conductivity ranging from −2.7% to +6.3% with a mean evolution of +1.22%. We observed an increase in the same property, ranging from +2.7% to +18.3%, with a mean of +9.0% for samples kept for 4 months under natural outdoor conditions, an increase ranging from +7.3% to +23.6% with a mean of +15.2% for samples that had undergone 20 cycles of immersion-drying, and an evolution of this property ranging from −5.6% to +12.3% for samples that had undergone 20 freeze–thaw cycles. [ABSTRACT FROM AUTHOR]

The search for environmentally friendly and low-carbon-footprint construction materials continues progressively. Researchers are now interested in innovative materials that connect with the principles of sustainable construction, and materials such as hemp concrete prove to be promising. This article presents the results of a study that aimed to evaluate the hygrothermal performance of hemp concrete integrated into the building envelope using the hygrothermal tool WUFI Pro 6.2. The simulation model was compared and verified with existing models before its utilization for this study. The results of this verification were in good agreement, which gave us more confidence in its application for further parametric studies of building envelopes in hot climate zones. Three wall systems were simulated: (i) a wall system with hemp concrete, (ii) a compressed earth block wall, and (iii) a cement block wall. The most important variables used in the simulations were the hygrothermal properties of the materials or wall components and the incident solar radiation. The simulation results showed that hemp concrete has good thermal performance and temperature and humidity regulation capabilities of the building envelope. The interior surface temperatures of the hemp concrete walls were between 22.1 °C and 24.6 °C compared to the compressed earth block and cement block walls, where the surface temperatures were between 22.0 °C and 27 °C and between 21.2 °C and 28.7 °C, respectively, and between 23 °C and 45 °C for the exterior temperatures. These values remain the same with the increase in exterior temperatures for hemp concrete walls. In conclusion, hemp concrete could be a great alternative material for use in construction for hot climate zones.

The paper presents the results of testing the performance of lightweight structural concrete containing hemp shives as an aggregate. It has been analysed how the higher binder content and use of the Portland cement affect the thermal and microbiological properties of the lightweight concrete. The aggregates of the plant origin and cement are incompatible because the plant chemical compounds, dissolved in water or an alkaline environment, inhibit cement hydration. To avoid this, mineralisation of the aggregates of plant origin is necessary. The most often used binder in hemp concrete is hydrated lime, a mineraliser. An addition of hydrated lime and sodium trisilicate was used for hemp shiv mineralisation in the tested materials with a cement binder. Concrete containing hemp shiv and cement binder, of which volume share in the concrete was at most 15%, was prepared as a reference concrete. In the remaining three concretes, the total content of the binder in relation to hemp shiv (by mass) was increased 2.5 times. It was shown that lime-binder hemp concrete offers a promising antimicrobial strategy, as it can inhibit bacterial and fungal growth on their surface with superior efficacy. The best results were obtained for tested concretes with the cement–lime binder regarding compressive strength; the average compressive strength was 9.56 MPa. [ABSTRACT FROM AUTHOR]

In this paper, the authors begin their scientific approach by briefly defining the most representative types of ecological houses currently in existence, together with their particularities. Also, a series of energy-efficient houses are presented, with the aim of identifying their efficiency elements. Also in the introductory part, the authors have made a tabular comparison between the properties of ecological construction materials and those of usual materials/traditional ones with the aim of showing that ecological materials can substitute the usual ones, having similar characteristics and properties and many times, even superior to them. The modeling stage assumed, in a first phase, the identification of the most efficient type of house and material, then used to fulfill the proposed purpose. In addition, the installations and systems suitable for the site area and the designed house model were chosen, ensuring its operation in an ecological way. The final culminated with the design of the actual conceptual model and its validation. [ABSTRACT FROM AUTHOR]

Bio-based materials help reduce the consumption of non-renewable resources, contributing to the development of sustainable construction. Industrial Hemp Concrete (IHC), which uses hemp stalk (HS) as an aggregate and a lime-based binder, is a bio-based material with various applications. This research developed a new hybrid composite in order to improve the mechanical strength and durability of hemp concrete, with the incorporation of sugarcane bagasse (SCB) as an aggregate, a resource of a renewable origin that is abundant in several countries. Different formulations were used, which were molded and pressed manually, evaluating their cohesion and compactness. The performance of the developed hybrid composite was measured considering mechanical, thermal, and durability properties. The compression test results showed an increase of 19–24% for composites with 75% hemp and 25% SCB. Thermal conductivity and thermal resistance coefficients were also improved, reaching 0.098 (W/m °C) and 0.489 (m2 °C/W), respectively. This aggregate combination also showed the lowest water absorption coefficient (reducing by 35%) and the best performance in durability tests compared to IHC. The resistance to freeze–thaw is highlighted, increasing 400%. The main reason is the influence of the SCB addition because the short and thin fiber form helps to maintain the physical integrity of the composite by filling the spaces between the hemp aggregates. [ABSTRACT FROM AUTHOR]

To address the need to reduce consumption and pollution in the industrial sector, composite materials were created using a new type of raw materials—organic lake sediments (sapropel) as a binder; sphagnum moss, flax fiber, and vermiculite as a filler. The main application of these composite materials is for sound absorption and moisture buffering, but since they contain bio-based binders and fillers, they also work as carbon storage. Within the framework of this work, a total of 100 samples of composite materials were created. Fungicides—a biocide quaternary ammonium compound and its natural substitute montmorillonite mineral material were also added to the materials to improve microbiological stability. The mechanical sound absorption and microbiological properties of materials were investigated and compared to similar environmentally friendly materials, such as hemp-lime concrete (FHL), hemp magnesium oxychloride composite (MOC), and hemp magnesium phosphate cement (MPC). The results showed that sound absorption and mechanical and microbial properties of the created composite materials are sufficient for their intended use, with flax fiber and vermiculite composites showing more stable mechanical, sound absorbing, and microbiological stability properties than materials containing flax fiber and moss. [ABSTRACT FROM AUTHOR]

Geleneksel betonun çevresel etkisini düşürmek için kullanılan yöntemlerden bir tanesi bitki-bazlı agregaların kullanılmasıdır. Kenevir betonu mineral bağlayıcıların kenevir sapı parçaları ile birleştirilmesi ile elde edilmektedir. Bu çalışmada, Türkiye’de yetiştirilen atık endüstriyel kenevir saplarının kenevir betonu üretiminde değerlendirilmesi amaçlanmıştır. Çalışmada, üç farklı bağlayıcı (çimento, hidrolik kireç ve kireç) ile yedi farklı bağlayıcı kombinasyonu oluşturulmuştur. Kütlece bir kısım kenevir, iki kısım bağlayıcı ve iki onda bir kısım su içeren kenevir betonlarının birim hacim ağırlığı, basınç dayanımı, kapiler su emme gibi fiziksel ve mekanik özellikleri araştırılmıştır. Üretilen numunelere laboratuvar sıcaklığında açık kür uygulanmıştır. 28 günlük kür sonrasında birim hacim ağırlığı 401-455 kg/m3, basınç dayanımları 0,08-0,28 MPa ve kapiler su emme katsayıları 2,45-4,47 kg/m2⋅s1/2 aralığında değişen kenevir betonları üretilmiştir. Karışımlarda hidrolik bağlayıcı miktarının azalması ile basınç dayanımının ve birim hacim ağırlıklarının azaldığı tespit edilmiştir.

Thermal insulation is the most widely used solution to reduce the energy consumption of buildings. In order to minimize the cost and time needed to build an insulated wall as well as to decrease greenhouse gas emissions, this manuscript proposes to incorporate a bio-based insulation material into the air cavities of hollow bricks constituting the external walls of buildings. Therefore, the aim of this paper deals with the assessment of the thermal performance of Moroccan external building envelope constituted of double hollow brick walls filled with hemp concrete and separated by a 5 cm air layer thickness. Three configurations composed of three types of hollow bricks were studied (8-, 12- and 16-holed bricks). Firstly, using numerical simulations based on a two-dimensional Computational Fluid Dynamics (CFD) method, a parametric study was conducted in order to determine which of the three configurations meet with the requirements imposed by the Moroccan thermal building regulation. In terms of thermal resistance R and thermal transmission coefficient U, results have shown that double brick walls with 12 and 16 hemp concrete filled holes were the only configurations meeting the requirements of Moroccan Thermal Regulation. Afterwards, the study was revolved at a whole building scale and a dynamic thermal simulation considering various internal parameters was performed using TRNSYS software. Furthermore, an economic and environmental analysis was conducted and a comparison with Moroccan thermal regulation shows that our results perfectly meet the requirements of this regulation and are more efficient from thermal, economic and environmental perspectives. Finally, the insulation technique used in this investigation can be widely applied around the World and similar thermal performances can be achieved for the case of different regions characterized by the same Mediterranean warm climate considered in this paper.

The share of bio-based materials in modern construction needs to grow more rapidly due to increasingly stringent environmental requirements as a direct result of the climate emergency. This research aims to expand the use of hemp concrete in construction by replacing traditional lime binder with magnesium oxychloride cement, which provides a faster setting and higher strength, opening the door for industrial production. However, the negative feature of this binder is its low water resistance. In this work, the water resistance of magnesium cement was studied, and the possibilities of improving it by adding fly ash, various acids and nano-silica were considered. Nano-silica and citric acid showed the most significant impact, increasing the binder water resistance up to four times, reaching softening coefficient of 0.80 while reducing the compressive strength of the magnesium cement in a dry state by only 2–10%. On the downside, citric and phosphoric acid significantly extended the setting of the binder, delaying it 2–4 times. Regarding board production, prototype samples of hemp magnesium biocomposite demonstrated compressive strength of more than 3.8 MPa in the dry state but only 1.1–1.6 MPa in the wet state. These results did not correlate with binder tests, as the additives did not increase the strength in the wet state. [ABSTRACT FROM AUTHOR]

In this article, the functional properties of hemp concrete are studied. Hemp concrete stands to reduce the carbon impact and improve the energy consumption of houses. Hence, numerous properties are measured: mass and dimension (volume) variations are found, as is the variability in hygrothermal properties (density, thermal conductivity, heat capacity, moisture buffer value, and water vapor permeability). This entry proposes three different characterization campaigns. The first is a short introduction to the spatial variability in thermal conductivity; the second is dedicated to the study of univariate variations in the mass, volume, and hygrothermal properties of hemp concrete samples. The last one tackles the aging evolution of the properties characterized during the second campaign, in which the samples follow several aging protocols, including exposure to outdoor conditions, the application of immersion-drying cycles, and the application of freeze–thaw cycles. A set of samples is kept under control conditions to allow for comparison. As the main result, spatial variability was found in the material. This is related to the random manufacturing variability or the spatial position regarding the height of the manufactured element. A high univariate variability is found across hemp concrete samples. Moreover, the storage of samples under stable reference conditions implies very little change in the studied materials’ properties, whereas all accelerated aging protocols implied major changes of properties. In particular, we observed an evolution of the thermal conductivity of the samples kept under control conditions for 4 months, with the thermal conductivity ranging from −2.7% to +6.3% with a mean evolution of +1.22%. We observed an increase in the same property, ranging from +2.7% to +18.3%, with a mean of +9.0% for samples kept for 4 months under natural outdoor conditions, an increase ranging from +7.3% to +23.6% with a mean of +15.2% for samples that had undergone 20 cycles of immersion-drying, and an evolution of this property ranging from −5.6% to +12.3% for samples that had undergone 20 freeze–thaw cycles.

The paper presents the results of testing the performance of lightweight structural concrete containing hemp shives as an aggregate. It has been analysed how the higher binder content and use of the Portland cement affect the thermal and microbiological properties of the lightweight concrete. The aggregates of the plant origin and cement are incompatible because the plant chemical compounds, dissolved in water or an alkaline environment, inhibit cement hydration. To avoid this, mineralisation of the aggregates of plant origin is necessary. The most often used binder in hemp concrete is hydrated lime, a mineraliser. An addition of hydrated lime and sodium trisilicate was used for hemp shiv mineralisation in the tested materials with a cement binder. Concrete containing hemp shiv and cement binder, of which volume share in the concrete was at most 15%, was prepared as a reference concrete. In the remaining three concretes, the total content of the binder in relation to hemp shiv (by mass) was increased 2.5 times. It was shown that lime-binder hemp concrete offers a promising antimicrobial strategy, as it can inhibit bacterial and fungal growth on their surface with superior efficacy. The best results were obtained for tested concretes with the cement–lime binder regarding compressive strength; the average compressive strength was 9.56 MPa.

Bio-based materials help reduce the consumption of non-renewable resources, contributing to the development of sustainable construction. Industrial Hemp Concrete (IHC), which uses hemp stalk (HS) as an aggregate and a lime-based binder, is a bio-based material with various applications. This research developed a new hybrid composite in order to improve the mechanical strength and durability of hemp concrete, with the incorporation of sugarcane bagasse (SCB) as an aggregate, a resource of a renewable origin that is abundant in several countries. Different formulations were used, which were molded and pressed manually, evaluating their cohesion and compactness. The performance of the developed hybrid composite was measured considering mechanical, thermal, and durability properties. The compression test results showed an increase of 19–24% for composites with 75% hemp and 25% SCB. Thermal conductivity and thermal resistance coefficients were also improved, reaching 0.098 (W/m °C) and 0.489 (m2 °C/W), respectively. This aggregate combination also showed the lowest water absorption coefficient (reducing by 35%) and the best performance in durability tests compared to IHC. The resistance to freeze–thaw is highlighted, increasing 400%. The main reason is the influence of the SCB addition because the short and thin fiber form helps to maintain the physical integrity of the composite by filling the spaces between the hemp aggregates.

This work is devoted to developing an energy-efficient solution for the external wall and evaluating its environmental impact. Several types of innovative single-layer and sandwich-type wall solutions were analysed and compared. Different constructive and thermal insulation materials were used, including traditional wall materials such as AAC (autoclaved aerated concrete) and normal concrete. Advanced materials, such as high-performance foamed concrete (HPFC) and natural biofibre composites, have been evaluated as an alternative solution. Ultra-light foam concrete was applied as an alternative for polymer-based insulation. The next development was sandwich three-layer wall constructions consisting of foam concrete and natural biofibre composites. A prototype of a wall panel was elaborated with outer layers of high-density bio-composite and a middle layer of high porosity hemp composite. Basic properties of sandwich blocks, such as density and thermal conductivity, were evaluated and compared. The environmental impact of the studied wall systems was analysed using a life-cycle assessment (LCA) to assess carbon dioxide emissions during the production phase of the material. The results show that replacing traditional insulation with bio-based materials has greatly reduced the negative environmental impact of the wall elements. A combination of natural fibre bio-composite and mineral insulating foam makes it possible to obtain an eco-friendly and sustainable sandwich-type wall system.

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The share of bio-based materials in modern construction needs to grow more rapidly due to increasingly stringent environmental requirements as a direct result of the climate emergency. This research aims to expand the use of hemp concrete in construction by replacing traditional lime binder with magnesium oxychloride cement, which provides a faster setting and higher strength, opening the door for industrial production. However, the negative feature of this binder is its low water resistance. In this work, the water resistance of magnesium cement was studied, and the possibilities of improving it by adding fly ash, various acids and nano-silica were considered. Nano-silica and citric acid showed the most significant impact, increasing the binder water resistance up to four times, reaching softening coefficient of 0.80 while reducing the compressive strength of the magnesium cement in a dry state by only 2–10%. On the downside, citric and phosphoric acid significantly extended the setting of the binder, delaying it 2–4 times. Regarding board production, prototype samples of hemp magnesium biocomposite demonstrated compressive strength of more than 3.8 MPa in the dry state but only 1.1–1.6 MPa in the wet state. These results did not correlate with binder tests, as the additives did not increase the strength in the wet state.

This study proposes a method for fast estimation of the hydric properties, including liquid and vapor diffusivities, of three distinct materials: a conventional biosourced insulating material (hemp concrete) and two innovative hybrid composites (hemp concrete with capric acid and hemp concrete with lauric acid). To estimate these parameters, an approach based on an inverse method has been developed. It involves minimizing the quadratic difference between numerical and experimental values of relative humidity, using the Nelder-Mead algorithm by assuming an exponential evolution of the liquid and vapor diffusivities. An unsteady-state experiment has been conducted in a climatic chamber during 18 days to provide experimental data for parameters' estimation. The obtained maximum root mean square error (RMSE) for all the samples is 4.4% that is a satisfactory approximation given the model assumptions and the experimental uncertainties (±2%). The estimated parameters allow calculating all investigated materials' liquid and vapor diffusivities. The validation of the approach is achieved by comparing its results with those from the existing literature. • Development of an inverse method to estimate the liquid water and vapor diffusivity. • Three materials are tested comprising capric, lauric acid and reference hemp concrete. • Experimental investigation under unsteady state conditions in a climatic chamber. • Maximum root mean square error for all the samples of about 4.4%. • Estimated liquid and vapor diffusivity showed good agreement with the literature. [ABSTRACT FROM AUTHOR]

The determination of the energy consumption of a building requires the computation of the coupled heat and mass transfers inside the wall. The existing models require the determination of the hygrothermal properties of the materials, and of the boundary and initial conditions, prior to computing numerically the temperature and vapour fluxes and the energy and mass balance of the building. However, the experimental measurements do not give accurate values, yielding a wrong estimation of the energy consumption. In order to determine the influence of the uncertainties on the values of the input parameters of the Kunzel model, we carried out a local sensitivity analysis (LSA) by varying by 5% the hygrothermal properties of the materials, the surface transfer coefficients and the initial conditions. The results of the LSA are treated by means of quartile boxes in order to identifiy the most influent parameters. The LSA is applied to two walls made of highly porous and hygroscopic materials: limestone and hemp concrete. The results show that the surface transfer coefficients and the adsorption isotherm are the most influential parameters. However, the conclusions are slightly different between the two materials, because of differences in the relative importance of transfer phenomena. [ABSTRACT FROM AUTHOR]

In the context of global warming associated with the excess of energy consumption, energy saving and environmental sustainability in buildings have become significant issues at both national and European levels. Therefore, the adoption of energy-efficiency measures in new and renovated dwellings will increase the demand for thermal insulation, which is crucial to improve the housing comfort by reducing the heat loss through the building envelope. Over the past two decades, several bio-based materials have been used in building thermal insulation, such as hemp concrete. Promoting the use of hemp concrete in new constructions and restoration of existing buildings first requires a validation of its hygrothermal behavior at both wall and building scales. For this, several models dealing with various physical aspects of hemp concrete were developed to understand their impact on the prediction of changes in temperature and relative humidity. These physical phenomena include hemp concrete hygroscopic hysteresis and thermal dependency of sorption curves. The preliminary results show that hysteresis has a significant influence on the numerical prediction in the short-term, while temperature dependency has less influence at the wall scale. The next part of this article is devoted to the study of these phenomena at the room scale by monitoring the internal conditions and energy consumption of a virtual hemp concrete office. The results highlight the fact that hysteresis and thermal dependency have low impact on indoor conditions, which could probably be related to the other parameters at the room scale. [ABSTRACT FROM AUTHOR]

• The effects of hysteresis were highlighted at several scales. • A new hysteresis implementation method was proposed and validated using a bi-climatic chamber. • Considering the hysteresis phenomenon improved the accuracy of prediction of the developed numerical model. • Significant deviations in relative humidity and heat flux were observed in the habitable ambience between simulation cases. Experimental measurements of sorption isotherms show a difference between the water contents in the adsorption phase and the desorption one. This is mainly due to the hysteresis phenomenon. Not considering this phenomenon in hygrothermal behaviour models impacts the reliability of the latter. In this paper, we have studied the effects of hysteresis on the hygrothermal behaviour at the building scale. For this purpose, a new implementation method of a hysteresis model was proposed and validated at the material and wall scales using a bi-climatic chamber which controlled the indoor and outdoor climate conditions. Then, the effect of the hysteresis phenomenon at the building scale was evaluated following a COMSOL/TRNSYS co-simulation approach to consider the gains and losses in the hydric fluxes going through walls. The results showed significant differences in terms of the relative humidity of the living environment. However, no difference was noticed in the temperature variations. On the other hand, the total heat fluxes were also affected by the hysteresis phenomenon due to latent heat parts, that were driven by variations in relative humidity. The maximum gain and loss discrepancies (with and without hysteresis) in total heat fluxes of 1121 kJ/h and 1086 kJ/h, respectively, were obtained during the first week of February (winter period). The results also revealed that these discrepancies are sensitive to the number of persons in the living environment. [ABSTRACT FROM AUTHOR]

An in situ estimation of the thermal properties of bio-sourced building wall insulation components is of critical importance in improving both the energy efficiency of buildings and the development of construction materials with a smaller environmental footprint. Depending on weather conditions, passive methods are not always feasible; they require time to conduct lengthy testing and may lead to significant uncertainties. This article presents an active method based on power dissipation via flat electrical resistance. The method can be implemented regardless of outdoor weather conditions and is suitable for walls with high overall thermal resistance for which the small average component of the through flow is difficult to estimate. Measurements are conducted of both wall input flows and temperatures. An inverse method, derived from a finite difference model of 1D transfers along with a multi-objective approach, enables the characteristics of a two-material assembly to be identified. A multi-objective method was chosen to solve the problems of high correlation between the thermal parameters of the model. However, the method requires the use of two temperature sensors integrated inside the wall. Following a laboratory validation phase on a PVC/plasterboard assembly, the method is implemented on an actual wall. A coating/hemp concrete assembly is also characterized as part of this work program. The thermal conductivity of the hemp concrete block was estimated at 0.12 W m−1 K−1 and is consistent with values found in the literature.

In this article, both numerical and experimental investigations were carried out on the durability of hemp concrete. For this, an accelerated aging process was performed using cycles of immersion, freezing and drying. Then, an experimental campaign was enabled to determine heat and mass transfer properties, as well as the microstructure for both aged and reference materials. Observations using a digital microscope showed the appearance of cracks at the interfaces and an increase of the porosity of about 6%. These microstructural modifications imply a non-negligible evolution of heat and mass transfer properties. Thus, a numerical model for the prediction of heat and mass transfer was developed. The prediction of physical phenomena was computed using both aged and reference material properties. It highlights the aging effects on the behaviour of the hemp concrete. The numerical simulation results showed significant discrepancies between the predicted relative humidity values for the two configurations (aged and reference) of about 18% and a maximum phase shift of 40 min, due to the amplification of the mass transfer kinetics after aging. Nevertheless, few deviations in temperature values were found. Thus, after aging, sensible heat fluxes were overestimated compared to the reference case, unlike latent heat fluxes, where an underestimation was shown.

In the global will of reducing fossil energy consumption and greenhouse gas emission in the building sector, the use of bio-based insulating materials is gaining interest thanks to their profitable properties and their suitability for the renovation of ancient buildings made out of unconventional materials. However, such materials are still lacking of characterization, and more precisely of on-site evaluation, as no complete measurement protocol is available. The starting point to fill this gap would be to set-up a protocol for whole building instrumentation, and this paper is investigating questions arisen in that goal, and more precisely regarding the impact of sensor locations on the assessment of key parameters. For that purpose, instrumented polystyrene and hemp concrete wallets of dimensions 0.9 × 0.9 × 0.1 m3 with well-known thermal and hydric characteristics are tested within a double climatic chamber. The impact of temperature sensor locations and implementations are tested through indirect estimation of the thermal conductivities of the materials composing the wallets. The effect of the hygrothermal processes on the measurement of thermal performance is also investigated through the analysis of the wall global transmittance. These results finally allow to provide some recommendations concerning the on-site instrumentation of hemp concrete walls.

The use of bio-based materials such as hemp concrete in the field of construction allows limiting environmental impacts and improving the energy performances of buildings. The aim of this paper is to understand the influence of adsorption and desorption of moisture in hemp concrete on its internal morphology and its dimensional variations. That’s why, the high porosity and the adsorption capacity of hemp concrete were discussed. Then, an experimental cell was developed to follow the geometric evolution over time of hemp concrete microstructure under hydric solicitations: humidification and drying. The digital image correlation was used to determine the strains fields on the surface of the material. This technique showed the behavior of this hygroscopic material subjected to different hygrometries. Indeed, the hemp shiv undergoes larger strains than the binder, thus affecting the morphology of hemp concrete. The results obtained highlighted the influence of the hydric state of hemp concrete on its very heterogeneous microstructure. It has also been revealed that the durability of the material can be affected by the dimensional variations caused by the relative humidity variations.

• Thermal diffusivity measurement of hemplime concrete. • Thermal testing of approx. 1 m by 1 m wall panels. • Direct measurement of conductivity, diffusivity and heat capacity from a single test. • A diffusivity of 1.56 × 10−7 m2 s−1 was measured. • A conductivity of 0.129 0.7 W m−1 K−1 was measured. Hemplime concrete is a material that has a different combination of properties to other, more traditional, building materials, and as such it exhibits potential advantages. Its thermal mass characteristics are often viewed as favourable to reducing the energy used to heat or cool indoor buildings. As a dynamic property, the effects of thermal mass on thermal behaviour depend not only on the conductivity but also on the heat capacity of the materials; the combination of conductivity and heat capacity being the diffusivity. The thermal diffusivity of hemplime concrete is comparatively under-researched, particularly given that most measurement techniques are designed for small samples of homogeneous material and may not give accurate results for inhomogeneous, anisotropic materials such as hemplime. This paper uses a technique recently developed for testing the diffusivity of whole wall panels, to measure the diffusivity of a section of hemplime wall, establishing the diffusivity as 1.56 × 10 - 7 ± 3.8 × 10 - 8 m2 s−1. This method may offer more accurate results. This paper compares the results of diffusivity measurements using this new technique, to diffusivity values calculated through measurements of the thermal conductivity and heat capacity via separate tests. The new technique is found to give results in agreement with previous techniques. The property space filled by hemplime is contrasted with timber, hard aggregate concretes, and insulating materials. [ABSTRACT FROM AUTHOR]

The classic models describing the hygric mass transfers inside porous materials seem unsuitable in the case of bio-based materials. They are based on the assumption of instantaneous local equilibrium between relative humidity and water content (Künzel in Simultaneous heat and moisture transport in building components—one- and two-dimensional calculation using simple parameters, Fraunhofer IRB Verlag, Stuttgart, 1995). These two parameters evolve according to the diffusive fluxes following the sorption isotherms. This study shows that it leads to predicting much shorter times of stabilization than those experimentally obtained. A new approach is presented here; it is free from the local instantaneous equilibrium introducing a local kinetics to describe the transformation of water from vapor state to liquid state and vice versa. The local kinetics of sorption is coupled with the well-known hysteresis phenomenon. It is adjusted from bibliographic data (Collet et al. in Energy Build 62:294–303, 2013) giving mass evolution of three hemp concretes under adsorption/desorption conditions. 1D cylindrical simulations allow an excellent fitting on the experiments. Finally, a semiempirical model is proposed, allowing to determine the kinetics parameters more easily. [ABSTRACT FROM AUTHOR]

Biobased materials are increasingly being used for building insulation. Hemp concrete is an efficient thermal insulation material containing renewable resources, providing living comfort thanks to its acoustical and hygrothermal properties. In this study, two hemp concrete 'wall' formulations are manufactured with the same type of hemp shiv and two commercial binders: natural cement and a lime-based formulated binder. Ninety days of curing (65% RH – 20 °C) ensure the hardening of the materials. Mortars are made up simultaneously to control the behaviour of the binders. The influence of binders on functional properties of hemp concretes and the relation with their microstructure are investigated in this article. The two materials exhibit similar thermal conductivity, acoustic performances and hydric properties, linked to their similarities considering density, open porosity, air resistivity, specific surface area and pore size. However, several other parameters describing the microstructure of the concretes are different depending on the binder, such as interparticle porosity, intra-porosity and tortuosity. Both formulations have low compressive strength compared with hemp concretes analysed in other studies. In our case, hydration of binders does not appear to occur. This could be due to an impact of the shiv extractible compounds on the hydration of the mineral binders. [ABSTRACT FROM AUTHOR]

Highlights • Hemp concrete rigidity is assessed using different methods: floating, cyclic, etc. • Three types of modulus – apparent, elastic and hardening modulus – are determined. • Tendency of floating method to overestimate the modulus values has been highlighted. • It is highlighted that cyclic method tends to underestimate modulus with low values. • Thanks to its low dispersion, the floating method is better suited for such material. Abstract Parameters influencing the variability of Young's modulus for hemp concrete include, among others, the method by which it is calculated. At present, a range of methods are available in the literature, but as yet, little is known about how they might affect the obtained results, given that hemp concrete is a highly sensitive material. For the in-depth study of this issue presented herein, the Young's modulus properties of two formulations of hemp concrete are analysed. Three main types of modulus – apparent, elastic and hardening modulus – are determined, using different calculation methods: floating, tangential, cyclic and hardening with 5 strategies. Therefore, for a stress–strain curve with 3 loading/reloading cycles, a total of 38 modulus values are calculated. Using the aforementioned methods, a comparative study of the results at 60, 90 and 180 days on 5 specimens for each formulation and each age reveals that the cyclic modulus method gives low values and the tangential modulus method gives medium values, while the floating modulus method gives higher values. In this latter case, low dispersion is observed, making this method more suitable to calculate hemp concrete's modulus. [ABSTRACT FROM AUTHOR]

In this paper, the coupled heat and mass transfer within porous media has been studies. First, the studied materials have been characterized experimentally and than evaluated their thermal properties, namely thermal conductivity and specific heat in different states (dry-wet). The hygroscopic properties, namely water vapour permeability, water vapour sorption. At second time, we present and validate the mathematical model describing heat and mass transfer within bio-based materials, by the confrontation with the experimental results. The materials properties obtained from the characterisation part are used as model's input parameters. Moreover, a test facility is mounted in the laboratory in order to compare the numerical and experimental data. The founded results show a good concordance between the simulated and measured data. According to this results the mathematical model of Philip and de Vries gives a good prediction of hygrothermal behaviour of biobased material. This model will allow us to save money and time of the experimental part in the future. [ABSTRACT FROM AUTHOR]

Abstract This article develops a novel mathematical model using multi-scale homogenization approach to model the effective thermal conductivity tensors of a hemp shiv particle and lime hemp concrete (LHC). This bio-based material is an environmentally-friendly material that is used more and more in building construction. The thermal conductivity of lime hemp concrete which is generally either cast or sprayed, cannot be expressed as a scalar due to its anisotropic microstructure. The paper develops a novel model to predicting effective thermal conductivity tensor of lime-hemp concrete that takes into account the anisotropy and the size of hemp shiv, the preferred spatial distributions due to fabrication process and the imperfect particle-binding interfaces. Two probability density functions are used for modeling the particle size distributions of hemp shiv and the preferred alignment distribution of hemp particles. A good agreement is obtained between the model and experimental data provided in the literature. The presented analytical solutions offer a suitable tool for a fast optimization of the thermal conductivity of hemp concrete. Such promising future is very useful for the building design, in particular in three-dimensional (3D) simulation models. [ABSTRACT FROM AUTHOR]

• Incorporation of organic phase change materials (PCM) into hemp concrete composition. • Improvement of hemp concrete thermal performance with PCMs. • Addition of PCM has no significant impact on hygroscopic properties. • Degradation of hemp concrete mechanical strength with PCMs. Among the promising solutions to reduce the ecological impact of construction materials is the promotion and development of local natural materials, such as the valorization of agricultural by-products. These bio-based materials offer interesting thermal and acoustic characteristics while significantly reducing the consumption of fossil energy (grey energy) and greenhouse gas emissions associated with their manufacturing process. Moreover, due to their permeable nature, these materials ensure stable hygrothermal exchanges with the surrounding environment. This work aims to develop a new bio-based composite thermally reinforced by incorporating organic and non-paraffinic phase change materials (PCMs) into hemp concrete. Different PCM contents, namely 5%, 10% and 15% of the binder mass, are considered. In this study, an extensive hygrothermal and mechanical experimental analysis was carried out on hempcrete-PCM composites. The incorporation of PCMs in hemp concrete resulted in a degradation of the mechanical strength, an enhancement of the thermal storage capacity, and no significant impact on the hygroscopic performance. [ABSTRACT FROM AUTHOR]