Diurnal Radiative Cooling of Spaces in Mediterranean Climate Isabel Crespo, Helena Coch, Antoni Isalgué and Aleix Borrell, All from Architecture & Energy Group. School of Architecture of Barcelona. UPC. - Av. Diagonal, 649, 7th floor; 08028 Barcelona (Spain). ABSTRACT The absence of solar radiation at night gives good opportunities for passive cooling of buildings in hot climates with frequently clear sky. However the possibility of also taking advantage of a clear sky cooling potential during the day is seldom considered. Thermal radiation to sky can be used to cool. A body surface emits thermal radiation (far IR) and if direct solar radiation (visible and near IR) and thermal radiation coming from other surfaces do not reach it, there would be a net heat flux out. A previous prototype was done with a simple element. That experiment confirmed that was possible to reduce around two degrees the interior temperature of the test unit exposed to sun light in July. In this work a new design based on the first one is developed to adapt it to architectonical needs in order to reduce interior spaces temperature in hot climates. The aim of this design is focused to so an architectonical adaptation is needed. Modular and replicable units could be a solution that permits to fulfill large flat surfaces as roofs or other architectonic elements. In this occasion, measurements were taken from a modular model with a geometrical design that avoided de direct solar incidence. These measurements were taken by a pyrgeometer during two weeks of August and results were similar to the previous experiment. INTRODUCTION A body surface emits thermal radiation (far InfraRed, IR), and if it can be made that direct solar radiation (visible and near IR), and thermal radiation from other bodies (far IR) do not reach the body surface, there would be a net heat flux out of the body, cooling it (Head 1962). The cooling can be obtained by selective surfaces, that reflect visible and near infrared solar radiation (near IR), avoiding direct solar gains, while they are emitters for far infrared radiation, if they are appropriately exposed, and allowing radiation going to sky. Cooling can also be achieved with the help of reflective surfaces and geometry (Trombe 1967 and Hull 1986). A polished surface with high reflectance to infrared radiation is able to reflect the image of the sky and maintain the radiation characteristics (Granqvist 1982). An emitting surface “seeing” the reflected image of sky, will loss energy to the reflected part of cold sky (Craig et al. 2008). The previous prototype tested in Barcelone was done with a single element (Serra et al. 2010). In that occasion, the analysis let us know that it is possible to reduce the inside temperature of a chamber, in about two degrees, during the sunny hours if an emitting surface can see nothing but the cold sky zone and its emitted radiation is thrown far away without reflection that take it back. That prototype checked 30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad 1