How does poor ventilation trap heat in Delhi homes?

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Poor Ventilation Traps Heat in Delhi Homes Through Material Properties and Architectural Design

In Delhi's densely populated and lower-income neighbourhoods, homes are particularly susceptible to trapping excessive heat due to a combination of their construction materials and architectural features. These structures, often built with concrete walls and low roofs, possess characteristics that significantly hinder airflow, leading to elevated indoor temperatures that persist long after outdoor heat dissipates. This phenomenon is exacerbated by the urban environment itself, creating conditions where residents have limited respite from the sweltering conditions, even during the night.
Architectural Features Limit Airflow and Heat Dissipation

Many homes in areas like Sundar Nagri are characterised by one-room structures, a common design in densely packed urban settings. These dwellings frequently feature concrete walls, which possess high thermal mass, meaning they absorb and store significant amounts of heat during the day. Coupled with low roofs, these architectural elements restrict natural ventilation pathways. Consequently, the heat absorbed by the walls and roof during daylight hours is not effectively released, leading to a sustained high temperature within the living space throughout the night. For instance, Durga Devi's one-room home has been recorded radiating trapped heat, reaching temperatures as high as 45 degrees Celsius at night.
Material Properties Contribute to Heat Retention

The use of materials like concrete in the construction of these homes is a primary factor in heat entrapment. Concrete has a high capacity to absorb and store thermal energy. During the day, solar radiation and ambient temperatures cause the concrete walls and roofs to heat up considerably. Unlike materials with better thermal conductivity or reflective properties, concrete retains this stored heat for extended periods. This stored heat is then slowly released into the interior of the home, preventing indoor temperatures from dropping to comfortable levels even when the external environment cools down after sunset.
Urban Density Amplifies the Heat Island Effect

The dense nature of settlements like Sundar Nagri in Delhi contributes to the urban heat island effect, further intensifying the problem of trapped heat. In such environments, buildings are closely packed, with limited green spaces or open areas to act as natural cooling mechanisms. The prevalence of heat-absorbing surfaces, such as concrete roads and buildings, means that the overall ambient temperature in these areas is higher than in surrounding rural regions. When combined with poor indoor ventilation, this amplified external heat creates a challenging environment where homes become inefficient at dissipating heat, leading to a continuous cycle of heat accumulation.
Health Implications of Sustained High Indoor Temperatures

The prolonged exposure to high indoor temperatures, a direct consequence of poor ventilation and heat entrapment, poses significant health risks to residents. Official meteorological stations may not always capture the extreme conditions experienced indoors. For example, while outdoor temperatures can be high, the internal temperature of homes like Durga Devi's can reach 45 degrees Celsius at night. This sustained heat can lead to heat exhaustion, dehydration, and exacerbate pre-existing health conditions, particularly for vulnerable populations. Campaigners are actively documenting these conditions, including temperature readings using thermal cameras, to highlight the urgent need for policy interventions that address housing quality and improve thermal comfort for low-income communities.

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How does poor ventilation trap heat in Delhi homes?

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