TN 61: Natural and Hybrid Ventilation in the Urban Environment

Because of specific urban characteristics, the potential of natural ventilation can be seriously decreased in the urban environment because of reduced wind speeds, high ambient temperatures and increased external pollutant and noise levels. Besides, the performance of hybrid ventilation systems is also affected and they are expected to work most of the times with mechanical ventilation.

This AIVC Technical Note has been performed in the frame of EU RESHYVENT and URBVENT projects and its main purpose is to highlight the most important constraints and limitations of the urban environment on natural and hybrid ventilation. The report mainly focuses on measurements and prediction of natural and hybrid ventilation in the urban environment, mainly as a result of reduced driving forces and the consequences for indoor air quality and fan assistance, while the consequences of external noise and pollutants are treated sporadically.

A state-of-the-art of natural and hybrid ventilation studies has been performed for urban buildings.

Then, detailed information is given concerning the experimental research and computational procedures carried out within RESHYVENT and URBVENT projects in order to investigate the performance of natural and hybrid ventilation systems in urban buildings. The experimental results refer to typical urban canyon configurations with H/W>1.0 for the climatic conditions of Athens.

Furthermore, more general conclusions are discussed through a number of simulations in order to investigate the effect of different urban canyons on the performance of natural and hybrid ventilation systems in different European climates. Finally, a number of recommendations or guidelines are proposed for the use of natural and hybrid ventilation systems in the urban environment.