Experimental evaluation of different natural cold sinks integrated into a concrete façade

Abstract The new demands, the climate change and challenges set by society intend to generate major reductions in the heating and cooling demands of buildings. However, conventional measures to improve the performance of the building envelope can easily reduce the heating demand and, in many cases, worsen the cooling behaviour of the building. Therefore, we need innovative solutions that provide high heating performance and use natural heat sinks to cool the building's thermal mass when in cooling mode. This work describes and tests a solution consisting of a facade built as a precast concrete element with high thermal inertia. This solution integrates different natural cooling techniques as a natural sink. For that, it has different modes of operation when in cooling mode, which allow it to adapt to the needs of the building and the natural resources available to guarantee high performance. To evaluate the impact of the three operating modes of the proposed solution, an experimental prototype has been built and tested over two summers. This experimentation, combined with an inverse thermal characterisation model, has made it possible to estimate the real impact of three passive cooling measures (nocturnal storage of cold in the thermal mass of the facade element, nocturnal ventilation of the building itself through the facade element and pre-cooling of the air before entering the chamber by using the evaporative system). All these measures are presented as different possible modes of operation of the described solution, with hardly any extra cost on the base solution, but with a considerable energy impact.