## 1 Introduction  
The effect of reflective thermal insulation was discovered in the middle of the 19 th century by [PERSON] [1]. He experimentally observed that a multilayer structure of thin metal foil facing airspaces presents good insulation properties. Nevertheless, the commercial development of this technology started in the early 1900s with the patents that were published by [PERSON] [2] and [PERSON] [3]. Thermal radiation is emitted by all the surfaces at T \(>\) 0 K, the radiative power is reciprocally exchanged between bodies at different temperatures. \"The term 'thermal' includes all of the electromagnetic waves with a wavelength between \(10^{-2}\) and \(10^{3}\)\(\upmu\)m: ultraviolet (UV), light (L) and infrared (IR), wavelength\" [4]. However, in opaque building components not exposed to solar radiation, the radiative heat transfer discussed in this paper only includes the IR-radiation (wavelength between 0.76 and \(10^{3}\)\(\upmu\)m). The radiative energy is transported by electromagnetic waves that do not need a medium to be transferred (in contrast with conduction and convection heat transfer). \"The radiation that is emitted by a surface, and the rate at which energy is released per unit area (W/m\({}^{2}\)) is termed the surface emissive power \(E\). In grey bodies (real surface) it is calculated by Equation (1). Where: \(\varepsilon\) is a radiative property of the surface termed the global emissivity. This property provides a measure of how efficiently a surface emits energy relative to a blackbody. It strongly depends on the surface material and finishing\" [5]. \[E=\varepsilon\cdot\sigma\cdot T_{s} \tag{1}\]  
The term \(\sigma\) and \(T_{s}\) are, respectively, the Stefan-Boltzmann's constant = \(5.67\times 10^{-8}\) W/(m\({}^{2}\) K\({}^{4}\)), and the surface temperature (K). The basic principle of Low-E materials is to reduce the emissive IR-radiation power (Low emittance) or reflect most of it in the case of received IR radiative power (high reflectance). Most of the typical building materials show high IR-emissivity \(>\) 0.8 and low IR-reflectivity \(<\) 0.2, on the contrary, \"Aluminum foil and metallized surface has a very low emittance, which explains its use in reflective insulation and radiant barriers\" [6]. In reflective paints identified as Radiation Control Coatings RCC [6], the emissivity can be dramatically reduced from 0.9 to below 0.25. This is possible due to the dispersion of aluminium flakes as pigment inside the base paint coat [6]. Despite the emissivity values of conventional paints being between 0.85 and 0.9, it is possible to find on the market Low-E paints with emissivity that range between 0.15-0.49 [7] (higher if compared to aluminium foil). This solution can have an advantage, since it could be applied in a faster way (spray paint, brush paint) and can be suitable for a large set of applications in the construction sector by painting: \"the inside of a boiler room to reduce the heat losses, the external roof surface to repel summer heat and lower radiation losses in the winter\" [6]. Some other examples are provided by [8], in which low emittance paints were applied in the wall behind heaters/radiators to reduce the wall heat losses or by covering the void surfaces in hollow bricks (also analysed in [9; 10; 11]). [PERSON] et al. (2011) studied an interesting application on the exterior surface of ETICS to reducing the Risk of Microbial Growth [12]. Despite the growing interest in this paint technology, nowadays it mainly found its application in reducing the overheating in title space in cooling dominant climates (Figure 1), as investigated in [13]. Figure 1: Application of an interior radiation control coatings (IRCC) in roof attic. Nevertheless, only a limited number of studies, some of them only theoretical, were focused on analysing the possible application of Low-E paints as interior radiation control coatings system (IRCCS) to reduce the building energy consumption for heating and cooling. An experimental study by [PERSON] et al.