Alternative methods for building energy preservation
Authors: Grosu Marian-catalin , Hossu Ioan , Visileanu Emilia , Breaban Flori , Gabriela Ene Alexandra , Dondea Felicia 
Published: June 2024

This article deals with aspects of the thermo-physical efficiency of coarse textile fibers arranged in the form of fibrous layers. The study is based on the need to improve the thermal protection of buildings in the context of sustainable development and to reduce the energy weight of buildings by reducing GHG emissions (H2O, CO2, CH4, CFC, N2O, etc.).At this stage, more and more products for construction are certified and analyzed in terms of embodied energy content and potential impact on the environment. In the current research, the tendency is to return to natural materials, with features similar to those of conventional materials in terms of performance.The advantage of exploiting a huge quantity of wool existing in Romania, currently unused, is the excellent wet-thermal and comfort properties of wool, concerning man and nature, 100% natural raw material, ecological and renewable, with a positive impact on man.By applying the technology specific to non-woven products, textile layers with layer density between 13 - 37 kg/m3 were made from wool with a fineness of 45-55 microns and a length of 150-220 mm. Measured characteristics (time-constant and spatially uniform heat flux) of the layers under different thermal conditions, respectively obtained from mathematical modeling and simulation were provided. Thermal measurements were performed with a complex lab device of the Laboratory of Civil and Environmental Engineering (LGCgE) of the University of Artois, IUT Bethune, France. The installation contains thermostatic baths, Huber 240-CC3, XPS thermal insulation on the samples contour, Kapton guard rings of 5 cm on the flux meters contour, Al, isotherm, warm, upper thermal plate, Tmax; upper dissipative flux meter with temperature sensor, Φsup, Tsup, upper warm plate thermal insulation; sample, computer with specialized software, lower cold plate thermal insulation, data acquisition board, lower dissipative fluxmeter with temperature sensor Φinf, Tinf, Pt 100 thermal reference, Al, lower, isotherm, cold, thermal plate, Tmin and a height adjusting samples system.To analyze the simultaneous influence of the independent parameters textile layer thickness (mm) and temperature (0C) on thermal parameters such as thermal resistance R - [m2K/W]; thermal conductivity λ - [W/(mK)] and the amount of heat stored in the sample Q - [J], an experimental design program using the rotating compound central factorial of order 2 was obtained.The designed matrix contains 13 sets of experimental combinations, 8 of which are distinct and 5 of which are the midpoint, and are made to determine the error value during the experiments. The experimental matrix contains the coded and actual values of X1 - textile layer thickness (mm) and X2 - temperature (0C) in 13 sets of experimental combinations in which the sample was measured. The empirical relationship between the independent process parameters and the obtained properties was obtained using the multiple regression technique. The interaction between the values of the independent variables X1 and X2 is presented as a polynomial equation of order 2, where the resulting value of Y depends on the interaction given by the polynomial equation at certain values of X1 and X2.Starting from the experimental data, the solutions provided by this specialized program led us to obtain models and simulations with very high accuracy. Technological limits and potential of the technology were materialized by correction coefficients (repeatable products under the same technological conditions, approximation of a technological, socio-economic optimum).By using this program, it is found that thermal resistance decreases with increasing layer density and hot plate temperature. The highest thermal resistance value of 2.77 m2 K/W was obtained at a density of 13 kg/m3 and a hot plate temperature of 400C. With increasing layer density (keeping the layer mass in g/m2 constant) the layer thickness decreases. Thus, the layer structure becomes more compact (the number of pores decreases, i.e. the amount of air in the structure decreases) causing the thermal resistance to decrease.