Dew architectures - Dew annouces the good weather

International audienceDew is a natural phenomenon that occurs under particular weather conditions (clear nocturnal sky, humid air, low wind) and on a surface specially designed for this purpose (high radiative cooling properties, special architectural design). Depending on the weather conditions and the surface characteristics, the water yield can give up to 0.7 litres per square meter and per night. Although the collection of rain water on roof turns out to be relatively simple, dew harvesting needs a more sophisticated architectural design to be efficient. Then this project aims at testing roof designs that improve dew water recovery by modulating two major parameters related to its recovery: (i) surface quality (strong emissivity, wetting character, low heat capacity), (ii) the shape of the roof (slopes, orientations with respect to dominant wind, gravity-induced water flow, etc.). A first step was the exploration of urban structures/sculptures, which was carried out by numerical works and small scale modelling (workshop held on December, 2008). In a second time (April, 2008), three roof prototypes on scale 1:1 of approximately 4 m 2 each are constructed and tested. These prototypes are designed with metals (sets of oriented plane surfaces), resins (modular plays of crooked surfaces) and textile (stretched structures). These multi-disciplinary researches on dew water harvesting aims at a synergy between partners of different disciplines and statutes: physicists, architect-designers, industrialists and teachers. They can apply to all the scales of the habitat, from garden cabins to roofs of building, car parks or supermarkets. It finds its interest in many regions of the world, in arid or semi arid environment and also European countries. (It is worth noting that the surface coating used to improve dew collection also provides natural cooling during the day.). We propose on conclusion of this paper, a pavilion project with on of this system