In a study on tropical architecture particularly on

In a study on tropical architecture, particularly on building materials, Lauber (2005) wrote that the most commonly used materials in the tropics include clay, wood, and bamboo. However, these materials are rejected by most new cities, which prefer to use concrete, steel, glass, and shiny metals. Rahman et al. (2013) indicated that affordable houses in Malaysia suffer from a high level of heat build-up, which has to be controlled to overcome the effects of global warming. Most of the cooling 5-fluorocytosine demands in the tropics are directly related to building materials, particularly the roofing area. Vijaykumar et al. (2007) indicated that the roofing system represents 70% of the total heat gain. For example, Allen et al. (2008) investigated roof materials used in Malaysian houses: in semi-detached houses (concrete tiles 20% and clay tiles 2.5%), in terrace apartments (concrete tiles 45% and clay tiles 2.5%), and in bungalows (concrete tiles 17.5%, clay tiles 5%, and metal deck 5%). These materials permit the high transmission of solar radiation that induces a sauna effect, which creates an uncomfortable environment. One of the sustainable approaches to cooling buildings by natural means is the passive cooling strategy (Kamal, 2012). This strategy involves a controller that limits the total effect of the heat gain to provide the interior a temperature lower than that of the natural surroundings (Givoni, 1994). In general, the flow of energy in a passive design is based on natural means, such as radiation, convection, or conduction (Kamal, 2012; Al-Obaidi et al., 2013b, 2014a). Passive cooling systems do not eliminate the use of a fan or a pump, when their application boosts performance (Givoni, 1994). In fact, several studies on the tropics such as Al-Obaidi et al. (2014b, 2014c) enhance passive cooling through the use of hybrid systems. Passive cooling strategies generally consist of all the preventive measures against overheating in the interior of buildings (Asimakopoulos, 1996). Such cooling strategies should cover three levels: The first two approaches reduce the heat gains and air temperature inside the building, whereas the third approach reduces the interior air temperature (Asimakopoulos, 1996). To activate these strategies effectively and to prevent the entry or eliminate the heat entering the building, two factors are required: a heat sink whose temperature is lower than that of the interior air, and an improved mechanism for heat transfer towards the heat sink. These conditions can be achieved through environmental heat sinks, which are divided into four types (Givoni, 1994; Asimakopoulos, 1996; Kamal, 2012): Each of these cooling sources can be utilised in different ways and build various systems. The rejection of heat into these heat sinks can be achieved through the natural methods of heat transfer (natural cooling)—radiation, convection, conduction and evaporation—or through mechanical boosting using small power fans or pumps (hybrid cooling) (Asimakopoulos, 1996). Cavelius et al. (2007) classified the common passive cooling systems into comfort ventilation, nocturnal ventilation cooling, radiant cooling, evaporative cooling, and using the earth as a cooling source. Likewise, Kamal (2012) listed the most important techniques for passive cooling, which include solar shading, insulation, induced ventilation techniques, radiative cooling, evaporative cooling, earth coupling, and desiccant cooling. Moreover, Geetha and Velraj (2012) developed a very clear framework for the strategies of passive cooling, which generally fall into three categories: (i) heat prevention/reduction, (decreasing heat gains), (ii) thermal moderation (modifying heat gains), and (iii) heat dissipation (removing internal heat). The approaches that have been adopted and classified in literature are shown in Figure 3. The present study does not intend to cover all these techniques, but focuses on the roof elements that adopt heat dissipation techniques, which have been discussed by Geetha and Velraj (2012). The study also selects the reflective and radiative approaches of the paint method, as listed in Figure 3. Finally, this study targets the relationship between the fundamental physical principles and building roof design, which are classified as follows: