High-rise buildings are blocking sunlight, affecting human health, green cover: Study

As high-rise buildings fill the city, a first-of-its-kind study by the Environment Policy and Research India (EPRI) analysed how these buildings are blocking sunlight falling on low-rise structures built earlier.

The study looked at one skyscraper in central Mumbai and the building’s impact on the duration of sunlight falling on neighbouring structures and area – four chawls (A, B, C, D), three buildings (A, B, C) construction site, ground, and on the green cover.

The period of time that sunlight fell on the structures and areas ranged from none (zero minute) on the ground to maximum of five hours on the green cover.

Of the four chawls (A, B, C, D), chawl D received sunlight for only one hour followed by chawl A (2.50 hours), chawl B (3.30 hours) and chawl C (4.50 hours). Sunlight on the construction site lasted for 2.30 hours. The sun’s rays fell on buildings B and C for 4.30 hours, and on building A for 5.10 hours.

However, the study did not measure the amount of natural light – New Building Codes mandates at least 150 lux which is a measurement of light intensity during the day – and duration of sunlight inside houses, both of which will be less or even none in case of those closer to the ground, said the researcher.

At present, high-rise category buildings in Mumbai start from 24 metres or 8 floors. Developers have to seek permission from the high-rise committee to construct tall buildings beyond 70 metres (m) or 21 floors. Approvals below that height are sanctioned by the municipal commissioner. At present, of the 700 proposed high-rises, above 70m, construction on 400 has begun.

Studies have shown that the human body needs limited amount of sunlight to produce and use certain vitamins and minerals, plants require four hours to six hours of sunlight in a day for photosynthesis, and a building needs sunlight for preventing algal growth on the walls as well as to power premises if solar panels have been installed.

India does not have mandatory guidelines on the duration of sunlight on neighbouring structures that are dwarfed by construction of a high-rise. In the United Kingdom and South Africa, minimum two hours of direct sunlight is required for any building to survive. Norms in Singapore require that based on the building height and taking a 20 or 40 degree angle, an open space should be created around the building.

Avick Sil, regional director, EPRI, who conducted the study said rampant construction of new tall residential and commercial complexes along with redevelopment of old buildings and rehabilitation of slums into high rises across Mumbai makes it essential to carry out shadow analysis to predict the probable impact of lack of sunlight on human health and the green cover.

With the existing rules permitting a distance of minimum six metres between two redeveloped or rehabilitation buildings, Sil said there is a need for cumulative impact assessment of shadow effect.

“While this is just one case study, the chawls will also eventually be redeveloped into high rises constructed close to each other that is bound to have an impact where the lower floors will get inadequate sunlight. Site planning and urban designing need to factor the movement of the sun and wind,” said Sil.

Based on the findings, EPRI developed a solar rating for neighbourhood structures in and around the high-rise based on the time period when the skyscraper received total sunlight. The solar rating factored in Mumbai’s climate, findings from existing literature, and the height and design of the buildings or structure, and other components present in and around that high rise.

The solar rating identified chawl D and ground as “critically affected” by the shadow due to its height and location placing it in the ‘undesirable’ (sunlight for less than 30 minutes) and ‘very poor’ (between 30 and 90 minutes) category. While Chawl A and construction site were in the ‘poor’ (between 90 and 180 minutes) category, Chawl B was in the ‘average’ (three to four hours) category, and Chawl C green cover, and building A, B, and C fell in the ‘good’ (four to six hours) category.

Pankaj Joshi, who is part of the Supreme Court-appointed high-rise committee, said, “If a proposed high-rise provides sunlight to neighbouring buildings for less than two hours a day, then we ask the project proponent to use reflectors, for instance, that will illuminate neighbouring areas, said Joshi. “The issue is for high-rises below 70m, which requires remedial action.”