Building energy consumption accounts for a significant part of the energy use in the world. Therefore it is important to improve the energy efficiency of buildings. In energy efficient buildings such as passive houses, zero energy buildings, and zero emission buildings, high performance thermal insulation, building air-tightness and high performance ventilation systems are regarded as prerequisites [
2]. Also the effective thermal energy storage and release can lead to the peak reduction of building heating and cooling loads. PCMs have been introduced as an innovative way to reduce the cooling and heating demand of buildings by using effective thermal energy storage. PCMs represent a technology that may reduce peak loads and HVAC energy consumption in buildings. They are used by melting with a latent heat of fusion in a unique temperature range. It is generally known that they can store five to fourteen times more heat per unit volume than sensible heat storage materials, such as water, masonry, or rock [
3]. Basically the three different ways to use PCMs for heating and cooling of buildings are: (i) PCMs in building walls; (ii) PCMs in building components other than walls; and (iii) PCMs in heat and cold storage units [
4]. For this purpose, a PCM can be incorporated either in gypsum or in concrete, but in almost all cases, PCMs have to be encapsulated for technical use, as otherwise the liquid phase would be able to flow away from the location where it is applied. There are two different methods for encapsulation of PCM. The first is micro-encapsulation, whereby small, spherical or rod-shaped particles are enclosed in a thin, high molecular weight polymeric film. The second is macro-encapsulation, which comprises the inclusion of PCM in some form of package such as tubes, pouches, spheres, panels or other receptacles. These containers can serve directly as heat exchangers or they can be incorporated in building products. Macro-encapsulation is the most common form of encapsulation. Micro-encapsulation is a recently developed new form of encapsulation for PCM. Several researchers have developed the encapsulation methods of the PCM [
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6]. The PCMs to be used in the thermal storage system should possess desirable thermo-physical, kinetic and chemical properties. Generally the PCMs are categorized as organic, inorganic and eutectic materials from the point of view of basic chemical composition, which have different melting temperature and latent heat of fusion. Among the investigated PCMs, paraffins have been widely used for latent heat storage in building applications because of their large latent heat and appropriate thermal characteristics, such as little or no super cooling, low vapor pressure, good thermal and chemical stability, and self-nucleating behavior. The paraffins are a mixture of pure alkanes which have quite a wide range of phase change temperatures, but these paraffins have low thermal conductivity compared to inorganic materials. Commercial paraffin waxes are cheap with moderate thermal storage densities and a wide range of melting temperatures.