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Subject and purpose of work: The raw materials which are the purpose of the current hemp cultivation (

Hemp-lime composite is a thermal insulating material used as a filling in timber frame construction walls. It is a material based on the wooden part of industrial hemp stalk (hemp shives) and lime binder. In practice, different wall thicknesses, composites with different thermal properties and various configurations of timber structure are used. These factors affect the temperature distribution in the wall. In the thermally weaker areas of walls, there is a greater risk of condensation and mould growth. This issue is important while designing walls based on organic materials. The paper presents the two-dimensional (2D) heat-transfer analysis based on the finite-element method, using THERM software. Several variants of external walls were adopted for the analysis. Thermal parameters of hemp-lime composites used in the analysis were obtained from our own research. The results of the analysis were presented as the values of the thermal transmittance coefficient and linear thermal transmittance equivalent to timber construction. The temperature distribution for an exemplary wall was also shown graphically in the form of isotherms and colour-flooded isotherms.

The paper presents experimental measurements and numerical simulation of thermal environment in naturally ventilated room by a fresh air valve. For the aim of Computer Fluid Dynamics (CFD) simulations, a model room was created. The fresh air valve is located in an occupied space, at the external wall. It has a major effect on mixing indoor and outdoor air, temperature profiles, thermal condition and indoor air quality of the rooms during the heating period. To determine the thermal condition of a naturally ventilated building, PN-EN 15251:2012 standard was used. According to the standard, using PMV/PPD is suitable for evaluating the thermal environment. In the naturally ventilated buildings, the following criteria are very important for local thermal discomfort: draught, radiant temperature asymmetry and vertical air temperature differences. To compare the simulation results, real air temperatures were measured by the thermocouples in a day room having the same geometry. A series of simulations has been carried out to determine the profiles of temperature and velocity of indoor air. Obtained results prove correlation with calculations of profiles of indoor air temperature, estimated using the thermocouples.

Hydrated lime, due to its life cycle (return to the natural form as a result of binding and hardening) shows a positive ecological aspect. The binder is often used in building materials based on plant components due to the high alkaline reaction and low diffusion resistance, as well as in mortars and plasters. However, it is an air binder with low strength parameters and the process of its binding and hardening is long-lasting. One of the ways to accelerate the binding processes and also to increase the strength of the binder is the use of additives in the form of pozzolanic materials which react with calcium hydroxide and form compounds with hydraulic properties. These are natural materials or industrial waste, so they do not affect the environmental impact of lime binder. The article presents the influence of the addition of pozzolan (three types) in various weight amounts, on the strength properties of mortars, their absorbability and capillary rise (presented as water absorption coefficient). The influence of pozzolan presence on workability of fresh mortars - their consistency was also checked.

One of the objectives of sustainable development in construction is the use of low-processed materials. They have a positive impact on the ecological balance of the building throughout the entire life cycle. Examples of such materials are materials of plant origin - straw, shives, cellulose fibers. They are used as thermal insulation or wall material. In recent years, hemp shives are increasingly used as a component of a lime-based composite, which performs the function of wall filling in timber frame constructions. The shives, due to the high porosity, determine the high thermal insulation properties of the composite. The physico-mechanical properties of the composite can be modified depending on various factors, including the ratio of hemp shives to the binder. The lime binder, in turn, can be modified by hydraulic and pozzolan additives. The paper presents mechanical properties (compressive and flexural strength) as well as physical properties (density, porosity, thermal conductivity coefficient, absorbability) of composites with various proportions of hemp shives of the Bialobrzeskie variety to the lime binder modified with Portland cement and metakaolinite.

The paper presents the results of studies concerning raw flax shives obtained from Polish crop of flax as a loose-fill thermal insulation material. The study focusses mainly on measurements of the thermal conductivity and water vapor permeability of material, but on water absorption and capillary rise as well. The shives showed satisfactory lambda values, comparable to traditional thermal insulation materials. They also showed high mass absorptivity and the ability to uptake large amounts of water by capillary action in a short time. The paper presents also an example of the use of the tested material as thermal insulation of the flat roof. The analysis of the heat flow through the flat roof with different thicknesses of flax shives insulation was carried out. [ABSTRACT FROM AUTHOR]

The paper presents the results of research concerning three fiber materials – hemp fiber, cellulose fiber and mineral wool as a loose-fill thermal insulation materials. It focused on the study of moisture properties and wettability of these materials. The analysis involved evaluation of moisture sorption in different relative humidity conditions and evaluation of wettability of fibers by contact angle measurement. The study showed that the sorption equilibrium has been achieved at different times, which proves the various nature and properties of the materials. Hemp fibers were less wet than cellulose fiber, but the time needed to stabilize was shorter. The largest contact angles, indicating the strongly hydrophobic properties, were shown by mineral wool. Some samples of hemp and cellulose fibers were characterized by similar contact angles providing high wetting properties. [ABSTRACT FROM AUTHOR]