Cool roofs impact on building thermal response: A French case study

The refurbishment of building roofs with cool selective coatings is already defined by some standards. Impacts on urban heat island (UHI) and thermal performance of buildings are well identified. In France, most of the developments on building thermal performances are focused on the building envelope insulation, especially for the winter energy performance, and the cool roof technique as a part of the solution for summer conditions is not well established. This passive technique for cooling the cities and indoor environments has a performance depending on the climatic location and constructions morphology. In this paper, we focus on a case study in Poitiers (France): a cool roof for a low-rise building (public housing), without any cooling active system.The performance of the cool coating is detailed through experimental results, completed by a dynamic simulation work on the studied building. In a first part, the case study is presented; the surface temperatures and the climatic conditions were monitored indoor and outdoor. Then, a dynamic simulation for the summer period is compared to the experimental results. This audit study of the actual case study permits the analysis extension of thermal condition in order to compare the performance of the envelope toward the cool roof. This first case study analysis will help understanding the cool roof potential and limitations in a French context. These results will have to be projected for various construction typologies in order to help its development in the different climatic regions. It will be also a part of different European climate first comparison through the work of the EU cool roof project.

► A residential building in France was refurbished with a cool roof and monitored.
► The proposed building simulation was calibrated with experimental results.
► Both simulation and experimental results show the potential on roof temperatures.
► The impact on indoor temperatures in summer is increased without insulation.