Passive Housing Design Strategies

**11**

**Chapter 2**

City

**Abstract**

*Jideofor Anselm Akubue*

ventilation is paramount.

**1. Introduction**

natural ventilation, canyon effect

Effects of Street Geometry on

Ventilation in Three Different

Street Configurations in Enugu

Efficient natural ventilation is dependent on the micro climate conditions of an urban environment. This is affected by ambient wind flow, radiation and air temperatures. The airflow within the urban street can be cultivated into two regions. The first is a recirculation region, which forms in the near wake of each building. The Second is a ventilated region downstream of the recirculation region, formed when the street is sufficiently wide. The development of the flow into these two regions depends on geometry. This chapter looks at the impacts of street geometry on these regions of airflow cultivation in three different street configurations in high density residential settlements in Enugu city. It utilized schematic analysis of airflow regimes to identify the behaviors of flow in these street configurations relative to the height and width ratios of the street canyon. This schematic analysis can be utilized in preliminary design studies by city and building designers for justifying street dimensions and configurations in tropical regions where natural

**Keywords:** urban street canyon, street geometry, street ventilation,

Achieving natural ventilation is subject to the micro climate conditions of an urban environment. This is dependent on the ambient wind flow, radiation and air temperatures of the location. At the micro level, the urban space geometry is the most relevant parameter responsible for the microclimate variation [1]. Recent studies on urban air flow conditions identified the structure of wind field as characterized through the creation of vertical structure which occurs in two layers. When the air coming from the rural environments flows to the urban areas, it naturally adopts the new boundary conditions created by the city structure, thus resulting in the formation of the obstructed urban canopy sub layer, which is extended from the ground surface up to the buildings height, while the urban boundary free surface layer extends over the roof-tops. This urban canopy sub layer possesses specific

Airflow Regimes for Natural

## **Chapter 2**
