The Fire Resistance and Heat Conductivity of Natural Construction Material Based on Straw and Numerical Simulation of Building Energy Demand

Abstract

The motivation for research to help address climate change is a continuous process of searching for eco-friendly materials in the building industry, which will allow minimizing the negative impact of this sector on the environment. The main objective of the paper is to assess the properties of a natural resource such as straw as an eco-friendly material in various variants for use in low-energy demand construction. The research results will fill the knowledge gap in the field of numerical analyses of the energy demand of straw material buildings based on the results of the conducted laboratory tests. A test of a heat transfer coefficient was conducted with different orientation of straw stalks. Then, samples were subject to a fire resistance test to determine material behavior at 1000 °C. During the fire resistance test, the clay-based plaster was ‘burnt out’, which hardened its structure, effectively preventing flames from reaching the insulation layers in the form of straw stalks. As a result of shrinkage (no plaster mesh), the plaster cracked and turned brick-red in color. The insulation layer of straw under the plaster was charred to a depth of 3.0 mm due to the high temperature. However, when the torch was turned off, no fire spread was observed in any layer of the sample. The 3D models of the buildings were created for different eco-friendly materials applied to make external walls. The results of numerical simulation allowed determining the amount of final energy needed to heat the designed building at the level of 26.38 (kWh/m2·year). Conclusions of the above-mentioned tests indicate very good thermal insulating properties determined using the lambda coefficient of 0.069 (W/m·K) and the possible application of straw bales as an alternative for conventional construction. Research has proven that it is possible to construct a building with low energy requirements using natural, easily available waste and completely biodegradable material.

Characterization of a Thermal Insulating Material Based on a Wheat Straw and Recycled Paper Cellulose to Be Applied in Buildings by Blowing Method

“…However, other authors report a variability of the thermal conductivity of materials; for example, humidity is an essential factor, and its increase is directly proportional to the thermal conductivity. Yapin Zhou et al, reported results between 0.03-0.1 (W/mK), while other authors have reported results for lignocellulosic materials of 0.033 and 0.065 and 0.07 and 0.08 (W/mK) at different densities, achieving in some cases values over 400 (kg/m 3 ) [1,16,20,21,26,57]. It is important to note that the research mentioned above generates materials in a rigid or panel format, unlike the proposal, which uses a much less commonly used method: the blowing method.…”

“…Furthermore, it is observed that the thermal conductivity of the mixture increases as the density increases, similar to other lignocellulosic fiber materials but different to other conventional materials that decrease their thermal conductivity as they have a higher density. Figure 8 shows the results of the measurement at different density levels, wh can be observed that the mixture has a thermal conductivity lower than 0.041 (W which demonstrates its potential as a thermal insulating material, since this value is parable with conventional insulating materials in the current market [1,11,16,20,26] thermore, it is observed that the thermal conductivity of the mixture increases as the sity increases, similar to other lignocellulosic fiber materials but different to other con tional materials that decrease their thermal conductivity as they have a higher dens According to these results, and considering that cellulose is usually blown into tical elements at densities between 50-90 (kg/m 3 ) [48], it was decided to restrict the de variable between 60-90 (kg/m 3 ) and to work with mechanically processed wheat stra the second stage of tests, thus obtaining the thermal conductivities shown in Figure According to these results, and considering that cellulose is usually blown into vertical elements at densities between 50-90 (kg/m 3 ) [48], it was decided to restrict the density variable between 60-90 (kg/m 3 ) and to work with mechanically processed wheat straw for the second stage of tests, thus obtaining the thermal conductivities shown in Figure 9.…”

“…In these samples, thermal conductivity was also measured, which shows negligible variations with respect to the material in the test cylinders. Figure 8 shows the results of the measurement at different den can be observed that the mixture has a thermal conductivity lower which demonstrates its potential as a thermal insulating material, sinc parable with conventional insulating materials in the current market thermore, it is observed that the thermal conductivity of the mixture i sity increases, similar to other lignocellulosic fiber materials but differe tional materials that decrease their thermal conductivity as they have According to these results, and considering that cellulose is usua tical elements at densities between 50-90 (kg/m 3 ) [48], it was decided to variable between 60-90 (kg/m 3 ) and to work with mechanically proces Figure 8 shows the results of the measurement at different density levels, where it can be observed that the mixture has a thermal conductivity lower than 0.041 (W/mK), which demonstrates its potential as a thermal insulating material, since this value is comparable with conventional insulating materials in the current market [1,11,16,20,26]. Furthermore, it is observed that the thermal conductivity of the mixture increases as the density increases, similar to other lignocellulosic fiber materials but different to other conventional materials that decrease their thermal conductivity as they have a higher density.…”

“…Other precedents indicate that developments from lignocellulosic fibers are around 0.096 (W/mK) at a density close to 440 (kg/m 3 ), values that are directly proportional [17]. Other authors have reported thermal conductivity values between 0.03-0.1 (W/mK) and that its variability can be attributed to density, heat flow orientation, relative humidity, among others [1,16,26].…”

“…In this scenario, local wastes and residues from food industries have a high potential for the development of thermal insulation materials or for housing construction as they have good thermal insulation properties. This allows reducing environmental impacts, as it gives a second life to waste and in parallel minimizes energy consumption associated with the production of materials and the use of housing [15,16].…”