Tall buildings and shadows in the city – 03/29/2024 – Claudio Bernardes

Growing housing demands, the need to rationalize travel and promote social inclusion, enabling the use of quality infrastructure by more people, resulted in the need for greater density in cities. As a result of this need, the existence of taller buildings becomes imperative.

However, one of the biggest controversies in the real estate world is the construction of tall buildings. It seems that when a new venture is announced, there is an instant and knee-jerk reaction against it.

Critics come up with a long list of reasons why they seek to argue that they are not good for the city. However, one item that predominates is the shadows they are likely to cause.

But are these shadows significant? How harmful would they be to the city and its inhabitants? The construction of tall buildings is often, perhaps due to misinformation, a cause for alarm among some members of the community. But to what extent is the height of buildings really a problem?

The answer to these questions must be assessed carefully, avoiding hasty conclusions that lead to the adoption of policies that mistakenly aim to limit the operation of the real estate industry and housing production.

Shadows may be a tangible and fair concern, but the height of buildings may have less of an impact on shading than one might think.

To better study the phenomenon of shadows produced by buildings, researchers in New York evaluated these effects in the Manhattan region, where there is a significant concentration of tall buildings.

According to researchers, the shadows of buildings in a city play an important role in determining the environmental quality of public spaces.

They can be both beneficial, for pedestrians during the summer, and harmful, by impacting vegetation, blocking direct solar radiation for long periods. Therefore, determining the effects of shadows requires not only an instantaneous view of the phenomenon, but the determination of the accumulation of shadows over time, at different periods of the year.

To do this, they sought to measure, during an established interval, the total time that a given location is in shadow, and the maximum time that a given region is continuously in shadow.

Alternative scenarios were tested, comparing tall buildings with shorter buildings, but which have a larger occupancy area on the land.

This simulation of two different typologies resulted in comparable shadows in summer, however, it was observed that the magnitude of the impact (increase in gross shadow) is greater for lower buildings, being much wider in the immediate surroundings, especially closer to its base.

Shadows are generally associated with tall buildings; however, a tall building is limited in its floor plan, and will cast less shadow nearby than a mid-rise building. Additionally, tall buildings, generally with a thinner frame than wider, mid-rise buildings, will cast a narrower shadow, which moves more quickly throughout the day.

Therefore, choosing the best height for a building in relation to the impact that its shadow can cause is essentially the search for balance between distribution and concentration.

In other words, for buildings of similar population density, a taller building distributes its shadow over greater distances, with less impact on the neighborhood, while medium-height buildings concentrate their impact more broadly, in a closer area.

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