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Modification of walls’ radiative properties with cool paints is a traditionally well-known passive cooling solution. Radiative properties of conventional cool selective materials allow limiting heat gains from solar radiation with a high albedo and to re-emit heat with a high thermal emissivity. Standardization of these materials is reflected in different building design standards and recommendations for the limitation of urban heat islands. Numerous innovations on radiative properties are being developed with the prospect of developing new categories of thermochromic products., Le traitement radiatif des parois par des produits sélectifs froids est utilisé de façon traditionnelle comme solution de rafraîchissement passif. Un matériau sélectif froid classique a des propriétés radiatives lui permettant de limiter les apports de chaleur par rayonnement solaire avec un albédo élevé, et de réémettre la chaleur avec une émissivité thermique élevée. La standardisation de ces matériaux se retrouve dans différentes normes de conception du bâtiment et préconisations pour la limitation des ilots de chaleur urbain. De nombreuses innovations sur les propriétés radiatives sont développées, avec en perspective la mise au point de nouvelles catégories de produits thermochromes.

This paper presents a multicriteria analysis of ventilation during summertime in Europe. Multicriteria analysis theories are used to determine the most suitable ventilation strategy on a university building, that is to say to ensure the best possible indoor air quality, thermal comfort of the occupants and the lower energy consumption in case of accelerated diurnal or nocturnal ventilation and/or air conditioning. After defining the possible actions, the criteria of quality regarding thermal comfort, indoor air quality and energy consumption are defined. The possible actions are then assessed relative to each of these three criteria and ranked from the best to the worst ones using two different multicriteria analysis methods.

A simplified approach to thermal building behaviour using natural cooling techniques has been proposed within the frame of the Pascool/Joule II European project. This provides useful information relating to the feasibility of integration of natural cooling techniques into a given building, taking into account only the climatic potential of the site, the indoor comfort criteria and the building cooling requirements. This approach is useful for architects and building designers, offering them helpful tools for the selection stage of the cooling system types. However, it is insufficient for the building design stage, where more accurate results, dealing with thermal behaviour and energy consumption of the building, are required. In order to solve this, we propose a thermal evaluation approach to building using direct and indirect evaporative cooling systems. This work has been realized using the integration of the passive cooling system models developed by our team in Passport+, a thermal building software, developed in the European projects Pascool/Joulell and Altener/Sink. This approach has been applied to a typical office building in La Rochelle (France). This procedure offers useful informations relating to the building behaviour (thermal and comfort behaviour), defines the cooling installation by sizing the passive and/or conventional cooling systems and shows the building energy saving by both the direct and indirect evaporative cooling system.

This study is a contribution to European projects Pascool/Joule II and Altener/Sink that deals with feasibility of passive cooling systems in Europe. The first aim of this work was to define a design methodology to evaluate natural cooling potential according to the climatic quantification criteria of the site, the cooling system performance, and comfort criteria defined by the couple of temperature and relative humidity set points. A simplified approach, based on climatic potential criteria as theoretical cooling potential index, the available potential index, the cooling need index, and the natural cooling normalized capacity, was developed. It was applied to 105 European sites for different types of evaporative cooling systems (direct and indirect), and for various temperature and relative humidity set points. During the second stage, a refined approach taking into account building characteristics and the cooling system performance, was developed. This method is based on the integration of numerical models of passive cooling systems in a thermal building software in order to consider interaction phenomena between cooling system and building. Application of this approach to one building has been done in order to assess energy consumption gain achieved by using passive cooling systems. These two complementary approaches provide helpful information dealing with the feasibility of a passive cooling technique based on comfort and energy saving criteria. They could be used by architects and building designers as helpful decision making tools during the different stages of building design.

The use of water droplet evaporation in shower towers and passive downdraft evaporative cooling needs the estimation of the time needed to completely evaporate the drops. To solve this problem, a cellular approach is proposed in which the spray is considered as a pile of rigid spheres of equal size; each sphere has multiple layers and contains a drop in its center. The evaporation takes place gradually from the superficial layer towards the internal layers. Parametric studies show the influence of each variable on the evaporation time of the droplets. The model may be used for sizing passive evaporative cooling systems and towers for buildings using the passive evaporative down draught effect. A building equipped with a shower tower has been tested in the framework of the European project PDEC/JOULE in Catania (Italy). The spraying system was successfully sized by using the model proposed in this paper.