%0 Journal Article %T Ventilated Double Window for the Preheating of the Ventilation Air Comparison of Its Performance in a Northern and a Southern European Climate %A Jorge S. Carlos %A Helena Corvacho %J Journal of Renewable Energy %D 2013 %I Hindawi Publishing Corporation %R 10.1155/2013/290865 %X Keeping the indoor air quality within the reference levels requires that the polluted indoor air be replaced by fresh air coming from the outside. This paper presents a sensitivity analysis and a series of simulations where the performance of this passive system is studied. The influence of each relevant factor, like the wind, the solar radiation, and the outdoor air temperature, is assessed. Two different local sets of climatic data were chosen, a mild and a cold winter. 1. Introduction Buildings envelope has been optimized over the last decades assuring a better insulation between the indoors and the outdoors, thus reducing heat transfer through the construction elements. Part of the thermal losses of a building takes place through the necessary renewal of the indoor air to maintain a good air quality for the inhabitants. Increasing thermal resistance of buildings envelope leads to an increasing relative importance of heat losses through ventilation. Those losses may come to represent an important percentage in the overall thermal losses. Energy Research Group [1] points to 20% to 40% of heat loss by the renewal of air in homes in central Europe, with an increase to 70% in buildings well thermally insulated. Various technologies and building systems have been developed to reduce the impact of climate, thus reducing the energy consumption of buildings. A survey of studies on buildings facades is listed by Quesada et al. [2, 3] where active and passive solar facade solutions, either opaque or nonopaque, are presented. Sadineni et al. [4] made a review of building envelope components and respective improvements from an energy efficiency perspective. Preheating of the ventilation air in winter has also been studied in the last decades. A study was done and a model was proposed by Woods et al. [5] to reduce energy consumption due to ventilation by heating the air through an atrium of large public buildings. In fact, several possible ways of preheating the ventilation air are available. ¡°For a high insulated house or low energy house, the minimum heating requirement should be supplied by heating the supply air in the ventilation system¡ªa system which is necessary in any case,¡± as it was referred by Persson et al. [6]. The unglazed transpired solar collectors [7], the solar air collector mounted on sun-facing walls [8] or on the roof, the ventilated photovoltaic facade [9] with an air channel between the photovoltaic panel and the facade, the ventilated double glazed facade [10], the window air collector [11], the supply air window [12], and the ventilated %U http://www.hindawi.com/journals/jre/2013/290865/