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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]

Hemp-concrete is a green material which has become nowadays highly recommended in the construction field. It finds applications as internal or external thermal insulator in wooden frame walls. At wall scale, studies proved that using Hemp-concrete in building envelope can improve indoor hygrothermal comfort. However, at building scale, hemp-concrete is scarcely studied. In that context, a French building in Grand-Est region, Champagne-Ardennes, employing hemp-concrete as external insulator is selected and studied. An apartment is monitored for several months. Indoor temperatures, relative humidities, thermal heat flux as well as external weather conditions are measured using sensors installed inside the apartment and a weather station at the building roof. Measurements underline the hemp-concrete ability to dampen external weather conditions by showing good results for both indoor temperature and relative humidity. Experimental approach is then coupled with a numerical validation at the wall and room scales using SPARK simulation tool. Investigations are conducted on thermal heat flux through the wall, indoor office air temperature, and relative humidity. Results show a good agreement between numerical values and experimental measurements. [ABSTRACT FROM AUTHOR]

Energy efficiency and the reduction of greenhouse gas emissions are actual key issues in all the economic sectors and, in particular, in buildings which is acknowledged worldwide as one of the most energy-consuming. In this context, it would be desirable to duly address those issues by searching for and assessing proper solutions and strategies: the usage of eco-friendly construction materials can be considered as one of those. This paper reports upon the performance of three façades containing sustainable products that are manufactured using natural resources and, alternatively, post-consumer waste based materials; those are: hemp-concrete; and Recycled PolyEthylene Terephthalate (R-PET), respectively. The energy performance of each façade was assessed in terms of cooling and heating demands, electrical consumptions and indoor thermal comfort including indoor temperature and relative humidity. Additionally, a Carbon Footprint (CF) assessment was carried out considering both the estimated energy demands and the life-cycle emission factors associated with the energy mix of the countries where the façades were located, i.e. France and Italy. Based upon the findings of the study, the R-PET façade represented the most performing solution between the three façades in all the scenarios considered and, moreover, the humidity-sensitive flow rate ventilation system came out as a solution able to reduce the electricity consumptions. Finally, considering the Carbon Footprint results, the energy country mix emerged as a key issue, making the Italian case study the worst one, though the total electrical energy consumption were comparable with those of the other case studies. [ABSTRACT FROM AUTHOR]

This article describes the results of a research project carried out at the University of Reims Champagne-Ardenne. The aim of this article is to develop a new insulating material produced by bonding hemp shives with wheat starch as a binder and to characterize its physical properties such as sorption isotherm, water vapour permeability, thermal conductivity, heat capacity and porosity. The equations of coupled heat and moisture transfer within the panels are introduced. These governing equations are applied on the room level in order to assess the hygrothermal behaviour of the panels and its impact on energy consumption and indoor comfort. Simulations are performed for Nancy (France) winter conditions with the simulation environment Simulation Problem Analysis and Research Kernel (SPARK) suited for complex problems. [ABSTRACT FROM AUTHOR]

Following the environnement grenelle, reaching 10% of bio-resourced materials in building sector except wood is one of goals until 2020. Among these agro-materials, one can distinguish the hemp concrete. Based on hemp hurds and mineral binders including lime or polymer as starch, the hemp composites are appreciated for their hydrothermal and acoustic properties. In this study, a vegetal binder based on starch and extracted from wheat is used with treated and non-treated hemp hurds to form an ecological composite. The studied hemp-starch is prepared with a ratio (H/S = 3,3). Hygrothermal properties such as moisture buffering value, sorption isotherm, water vapor permeability, thermal conductivity, and heat capacity are experimentally studied. The pore size distribution is performed using mercury porosimetry. Results reveal that the hemp-starch composite may be a promising solution in the insulation field due to its relatively low thermal conductivity and capacity to regulate the indoor relative humidity. [ABSTRACT FROM AUTHOR]

This paper presents the results of a laboratory investigation into the hygric properties and moisture buffering performance of hemp-starch composite panels designed for building applications. Composite panels were produced by bonding hemp shiv with wheat starch as a binder. Two types of hemp shiv were tested: chemically processed shiv with enhanced adhesion between fibers and starch matrix, and non-treated shiv. The panels were then characterised in terms of their hygroscopic properties (sorption curve and vapour diffusion resistance factor) and their moisture buffering performance (moisture buffering value, MBV). The determination of theoretical MBV was based on the effusivity of the material, which is obtained from its basic hygroscopic characterisation. The results show that both panels are excellent hydric regulators that can be used to improve indoor hygrothermal comfort by buffering indoor relative humidity variations. [ABSTRACT FROM AUTHOR]

Construction is considered as one of the most relevant sectors in terms of environmental impacts, due to the significant use of raw materials, fossil energy consumption and the consequent Greenhouse Gases emissions. The use of unconventional and environmentally-friendly materials and technologies is worldwide recognised as a key factor to enable the decrease of material and energy consumption in buildings. Between natural/sustainable materials, those using hemp products and by-products (fibres and hurds) have rapidly widened their field of application in the building industry, mainly because of their good hygrothermal and acoustic insulation properties. Moreover, the usage of these materials allows high carbon storage due to the CO 2 sequestration during the agricultural phase. This study represents an energy and environmental assessment of hemp crop cultivation in France, carried out through a Life Cycle Assessment approach, showing positive and negative contribution related to the different life cycle phases. The total CF evaluated through the IPCC, 2013 GWP 100 method (IPCC, 2013) is equal to 0.975 kgCO 2 eq, in view of a CO 2 uptake of −1.29 kgCO 2 eq. So, it is understood that the total CF results therefore lower than the CO2 uptake due to the biogenic carbon captured and stored during hemp growth. The total Energy Footprint, instead, was calculated in 17.945 MJ. The Upstream phase came out as the main contributor to the impacts. A sensitivity analysis was performed to explore changes in results related to main inputs assumptions and, in particular, the environmental benefits associated with the replacement of conventional fertilisers (ammonium sulphate) with organic matter were highlighted. • A Life Cycle Assessment (LCA) of hemp-hurd production was carried out in this study. • The LCA was focused upon carbon emissions and primary-energy consumption. • Primary and secondary data were inventoried for the study development. • Major environmental impacts were found in fertiliser and pesticide production. • A sensitivity analysis was focussed upon different compost application rates. [ABSTRACT FROM AUTHOR]

Hemp shives is a lightweight material known for its insulating properties. Associating these bio-fibers with plant-based matrix instead of a mineral binder in insulation applications is of ecological interest. This article describes the study of a low environmental impact 100% plant-based material made solely from wheat starch and hemp shives. The hemp/starch ratio (H/S) influence and hemp shive size are studied. Samples are evaluated in terms of physical properties, mechanical behaviour and hygrothermal properties through an experimental approach. Results show that increasing 0–5 mm hemp shive proportion from 15% to 30% leads to a significant enhancement of the mechanical and hygric characteristics due to the load transfer and porosity. However, when the H/S ratio increases, mechanical and hygrothermal characteristics decrease slightly. Finally, the hemp-starch agro-material with H/S equal to 8 and 30% of 0–5 mm hemp shive seems to be the optimal composition between the studied samples. [ABSTRACT FROM AUTHOR]