Summer cross ventilation in residential buildings

Abstract

In multi-family buildings in Portugal essentially mixed ventilation systems are used. However, this system does not currently have a document that supports its design. The mixed ventilation system envisaged in the prNP 1037-5 considers two situations a) base flowrate given by passive devices which will allow the dwelling to be swept by flow rates due to wind action (e.g. horizontal ducts between compartments located on opposite facades), b) peak flowrate given by mechanical extraction placed in service compartments (kitchen and toilet facilities). In the summer situation, ventilation can be incremented by the permanent opening windows, preferably in cross ventilation mode. In this situation, the type of windows, the size of the apertures and the time extension are essential characteristics to be considered in order to improve the effectiveness of ventilation. The type of windows is an essential feature in cross ventilation. Window specification may be assessed under some criteria, eg: ventilation capacity, impact on comfort, security, protection against the rain and maintenance and cleaning. In climates of Southern Europe, the night ventilation coupled with a strong thermal inertia are also factors that can influence the indoor thermal comfort. This paper aims to support the development of prNP 1037-5, in particular, to characterize the operation of the current mixed ventilation systems in the summer time.