Assessment of pre-heating air through a double window system on different building location and weather condition

Double windows are a currently adopted construction system in Portuguese dwellings. Simple changes enable this construction system to pre-heat the ventilation air. The air coming from the outside circulates goes upward through the channel between windows where it is pre-heated before entering the building. Heat that escapes from inside through the inner window and solar radiation, heats up the air between the two windows. This paper presents the performance of such passive system and focuses on the design aspects of this system and its building integration in function of weather conditions. One type of building is used where the window is located on different facades, thus, different orientations. Four different weather conditions are chosen, from mild to cold winters. The methodology used is based on previous validated parametric studies. Results indicate that the ventilated double window system offers an alternative to cold natural ventilation in any cold region and any facade orientation. The colder the location, the higher the pre-heating of the incoming air. This study expects to help designers to conceive ventilated double windows duly adapted to local climate where natural ventilation is an important design consideration and where energy consumption must be reduced.