Abstract—Thermal load calculations have been performed for multi-layered walls that are composed of three different parts; a common (sand and cement) plaster, and two types of locally produced soft and hard bricks. The masonry construction of these layered walls was based on concrete-backed stone masonry made of limestone bricks joined by mortar. These multilayered walls are forming the outer walls of the building envelope of a typical Libyan house. Based on the periodic seasonal weather conditions, within the Libyan cost region during summer and winter, measured thermal conductivity values were used to implement such seasonal variation of heat flow and the temperature variations through the walls. The experimental measured thermal conductivity values were obtained using the Hot Disk technique. The estimation of the thermal resistance of the wall layers ( R-values) is based on measurements and calculations. The numerical calculations were done using a simplified analytical model that considers two different wall constructions which are characteristics of such houses. According to the obtained results, the R-values were quite low and therefore, several suggestions have been proposed to improve the thermal loading performance that will lead to a reasonable human comfort and reduce energy consumption. Keywords—Thermal loading, multilayered walls, Libyan bricks, thermal resistance I. INTRODUCTION HERMAL load calculations of already constructed walls where much of the fine details may not be readily available, are possible only through the use of the very suitable and simplified methods. Using such methods, the calculation procedures are much easier to perform. It is worth to mention that, there are two ways to calculate the R-value, namely the numerical and the simplified methods; however, the numerical methods are based on a detailed computer calculation that needs detailed input data and may include a non-uniform multi-dimensional heat flow [1-6]. In general, they involve detailed variations in heat flow in all three dimensions, however, it is almost always the case that the construction is uniform in one direction, in other words, the 3- dimensional effects do not significantly affect the overall R- value. In this work, a simple R-value calculations formula is used to estimate the R-values for outer multi-layered walls of a typical Libyan house that are based on concrete-backed stone masonry made of limestone bricks joined by mortar. These bricks are excavated from two major places (mines) in the north eastern province of Libya. These bricks were the building blocks of houses built during the seventies (1970’s) with the lack of any technical data on the construction materials such as the thermal properties of the individual components of the wall structure. Thus they were built without performing thermal load calculations or considering any insulation measures. This made the house very unpleasant to occupants during both hot and cold seasons. Bashir M. Suleiman, Applied Physics Department, College of Sciences, University of Sharjah, P. O. Box. 27272, Sharjah, UAE. (phone: 971- 6-5050374; fax: : 971-6-5050352; e-mail: bashir@sharjah.ac.ae). Therefore, technical data such as R-values within the structure of such buildings are essential for the calculations of thermal loads and/or estimating energy consumptions for the purpose of energy savings. Furthermore, such calculations could provide basis for insulation materials manufactures to produce suitable insulation materials that can be used to improve the thermal performance of such houses. II. THE WALLS DESCRIPTION The multi-layered walls are composed of three different parts; a common (sand and cement) plaster, and two types of locally produced soft and hard bricks, see the picture depicted in Fig. 1. The bricks are excavated from two major rock mines used as a supply of solid building bricks. The plaster sample was peeled off the walls then cut into the desired dimensions for thermal conductivity measurements. The values of thermal conductivities of the three parts (samples) were measured using the Hot-disk technique [7-8]. Each sample consists of two different disc-shaped pieces with diameter in the range of 7-10 cm and a thickness in the range of 2-2.5 cm. The samples have an average apparent densities ranging from 1444-1970 kg/m 3 . These values were calculated using the dimensions (volume) and masses of the individual samples. A characterizing parameter such as porosity can also be estimated, using the following formula: r = 1- (ρ ave / ρ cal ). Where, ρ ave is the average apparent density of the sample pieces, and ρ cal is the calculated density based on the atomic weights of the constituting atoms and the dimensions of the unit cell. However, these samples contain micro-voids and composed from large diversity of its individual constitutes (compounds and elements) and it was not possible to estimate the porosities of the samples. To illustrate this large diversity a preliminarily x-ray scan at room temperature of the non- homogeneous plaster sample is depicted by the optical image in Fig. 2. The X-ray was preformed as first run of the recently installed energy dispersion X-ray fluorescence (EDXRF) analyser at the National X-ray Fluorescence Lab in our Department at the University of Sharjah. The analyzers is of The HORIBA XGT-7200 type includes a 1.2 mm x-ray beam , high pure Si detector and a Nai(Tl) scintillator as transmitted X-ray detector. K α lines of Rh target were used for characterization of elements. The X-ray beam was controlled according to the optimal condition of the spectral lines. The automatic computer control of the X- ray generator allows the 50 kV and 1 mA settings to be adjusted automatically. The indexation of the peaks and the mass % of the individual elements were determined using the provided data base through the software Emax, see table I. TABLE I THE BASIC ELEMENTS COMPOSITION OF THE PLASTER SAMPLE Element Mass % Element Mass % Mg 3.96 Ti 0.33 Al 3.99 Cr 0.07 Bashir M. Suleiman Thermal Load Calculations of Multilayered T Walls World Academy of Science, Engineering and Technology International Journal of Physical and Mathematical Sciences Vol:6, No:4, 2012 431 International Scholarly and Scientific Research & Innovation 6(4) 2012 scholar.waset.org/1307-6892/2089 International Science Index, Physical and Mathematical Sciences Vol:6, No:4, 2012 waset.org/Publication/2089