Concrete Urban Buildings, Neighbourhoods Can Heat Up Climate in Cities

During hot months, urban regions with concentrated concrete buildings, pavements and surfaces can experience extreme temperatures. Much of it is due to the heat island effect that gets aggravated due to the modern urban designs and techniques. These buildings trap and retain heat, and later emit them, causing neighbourhoods to reach extremely high temperatures as compared to city outskirts. Recently, a research team has developed a method of modelling urban building energy that takes into consideration heat waves and how human-caused parameters aggravate it. It studies the heating pattern of urban cities during city-wide heat waves. The research is based on a case study conducted in Los Angeles, California, during a five-day heatwave event in September 2009.

During the research, these parameters of the buildings were kept in mind — building type, urban microclimate, and large-scale climate conditions. Researchers have studied the magnitude and distribution of these heating effects and noticed that heat emitted from buildings to the urban environment increases by 20 percent during a heatwave. Most of this emitted heat is waste from air conditioning. AC discharges contribute to almost 86.5 percent of the total waste heat being dissipated in the surrounding urban environment.

To simulate the energy flows in an urban setting, researchers mapped urban environmental data from the mesoscale Weather Research and Forecasting (WRF) model and the Urban Canopy Model (UCM).

Meanwhile, the rise in microclimate temperatures requires more heating and cooling energy inside the buildings. The microclimate depends on several factors like heat exchange between neighbouring buildings, heat transfer by wind flow, the temperature of city infrastructure, local weather, the heat from direct and reflected sunlight, ground temperature, and other urban heat island effects. Researchers are trying to design neighbourhoods by keeping in mind the changing weather patterns of a region, which can help lower energy demands.

Researchers studied local and regional meteorology within a two-way-coupled mesoscale weather model. This study evaluates potential changes to building energy demands using global climate projections, combining the effects of population shifts and urbanisation. The data can be used for energy-efficient urban development and planning.