DOI: 10.7569/JRM.2017.634135
M.Cˇ ekon et al.: Cardboard-Based Packaging Materials as Renewable Thermal Insulation of Buildings
its own measurements, weight and overall thickness have to be measured separately. The sample is placed between plates with upper and lower surface covered by contact mat with a thickness of 3 mm. The plastic foil with thermocouple batteries is installed between the contact mat and surface of sample. The higher plate is slowly lowered until the pressure on the sample reaches a predefined level. Considering 10 K temperature difference of both sample sides, testing may have several point measurements, which means various temperatures in the middle of the sample. The measurement process starts by cooling and/or warm- ing plates at a predefined temperature in the measure- ment point. The top Peltier plate monitors voltage and electric current, whose values are used for determina- tion of overall heating power. Finally, as demonstrated above, the thermal resistance of tested sample is cal- culated according to Equation 1. The time varying power is managed by microprocessor control system according to the surface temperatures of sample. It has mainly decreasing behavior until it reaches steady state corresponding to Fourier’s law. Measurement is completed if the time is over or stability criteria are reached. At the end the equivalent thermal conduc- tivity coefficient λ ekv is calculated based on material thickness. 3.2 Thermal Measurement Results and Discussion The testing of each sample included repeated meas- urements at different mean temperature levels: 10 °C, 20 °C and 30 °C respectively. The load force of 200 N was applied on the samples through the top plate dur- ing the measurements. The temperature dependency between thermal resistance and mean temperature of sample was recorded. Thermal resistance approxi- mated by linear function indicates a similar tendency of the slope; the higher the temperature difference, the lower the thermal resistance of all tested samples. Thermal conductivity of all materials described in Section 2 was measured. Thermal conductivity param- eters at three different measurement points are pre- sented in Figure 4. The PIR has the lowest thermal conductivity. It is undoubtedly the best performing of all tested materi- als. Next, and relatively close to each other, are MW and EPS. Their thermal conductivity is approximately two times higher than the PIRs. The CBM samples reached various results. In gen- eral, it can be said that (logically) samples with more layers had better thermal conductivity. Supposedly the division of the air cavities eliminates the prevail- ing effect of convection. Samples with undivided air cavities reach worse results as the height of the
0,16 0,14 0,12 0,10 0,08 0,06 0,04 0,02 0,00
5
10 20 Mean temperature point measurement (°C) 25 30 15
35
M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
Figure 4 Thermal conductivity at mean temperature.
cavities increases. It is therefore logical to further develop materials with smaller and more numerous air cavities.
4 LIFE-CYCLE ASSESSMENT An inseparable part of the research presented in this article is a life-cycle assessment (LCA) that evaluates and compares the environmental impacts of the indi- vidual materials. LCA is an analytical method for eval- uation of the environmental impacts of products from the extraction of necessary raw materials for waste management. The method originated in the 1960s [13]. Currently the LCA framework is well established thanks to international standards like ISO 14040 [14]. This standard describes the general principles and gives the users a general framework for the evalua- tion. Specifics of the building industry have led to the creation of European standards, like EN 15804 [15] or EN 15978 [16], that address evaluation of building elements, materials or even whole buildings. Product category rules (PCR) [17] for Environmental Product Declarations are also considered in the presented evaluation. This PCR further specifies the evaluation methodology for thermal insulations; for example, it defines recommended boundary conditions and impact categories. 4.1 Goal and Scope of the LCA The goal of the presented LCA is to estimate the envi- ronmental impacts of the CBM samples and compare them with the environmental impacts of more com- mon insulation materials. The application of the card- board in building structures is not yet fully addressed. Thus only the product stage defined in EN 15804 [15] is considered in the assessment. This approach is also known as cradle-to-gate LCA in the literature, e.g. [18]. It means that only the environmental impacts
J. Renew. Mater. Supplement June 2017
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