Extreme heat waves, drought, and water stress are a few of the challenges that will affect India more intensely than many countries, based on the impacts caused by extreme weather events on India’s poorest population. For example, this year, India encountered 200 days of heatwaves, compared with 36 days in 2021—a considerable increase. One would naturally ponder how a society—which is expected to become the world’s most populous nation in 2023—can persist in the wake of dangerously high temperatures occurring more than half the year.
Unsurprisingly, those who can afford it increasingly rely on air conditioning to endure the relentless heat. This dependency results in a negative feedback loop in which more AC use increases climate-related emissions and the urban heat island effect, encouraging even more AC use, and so on. Access to air conditioning also enlarges an already vast socioeconomic divide, causing disproportionate suffering among the lower class.
India’s dire circumstances represent a near future for the rest of us: climate extremes testing the resilience of populations living in increasingly urbanized areas built with petroleum-dependent infrastructure. But, on the positive side, India also offers model solutions for a climate-adaptive built environment with the potential for broad applicability. These approaches are evident in the county’s wealth of centuries-old Indo-Islamic architecture—monuments that rank among the world’s most historically significant and invite renewed analysis in light of today’s climate calamity.
During a recent trip to northern India, I was struck by how these strategies make a palpable difference in comfort and livability. Many forts, palaces, and tombs in Delhi and surrounding areas are built with generous quantities of stone and thus benefit from thermal mass. Temperatures in this region range between 46 and 103 degrees Fahrenheit annually, with an average diurnal change of approximately 20 degrees. Thermal mass, a property of heat storage that effectively flattens out temperature swings, is most advantageous in climates with large daily fluctuations. However, the strategy can still be effective in this range.
Red sandstone, Makrana marble, and red brick were some of the most common materials the Mughal empires used to build notable structures like the Taj Mahal and Agra Fort. Obviously, many thermal mass alternatives exist today, the most common being concrete, although such materials almost always carry a high embodied energy. One can limit excessive material by 'tuning' thermal mass elements to suit the climate: Overly thick walls, for example, require too much time to absorb and release heat. The performance-based tailoring of thermal poche thus represents an opportunity to align form and environmental function.
One of the most distinctive features of India’s architectural heritage is the jali, a perforated screen made of cut stone. These devices are characterized by intricate ornamental patterns, which require significant labor to fabricate. A jali’s porosity enables the passage of filtered light and air while its materiality gives it a small amount of thermal mass. The historical function of the jali was to provide a view portal for occupants who could remain hidden from the outside. These screens offer an additional benefit by enhancing the circulation of cool air within a building. Remarkably, jalis not only permit airflow but increase and cool it. Depth plays an important role, as the thickness of the screen is often equivalent to the length of a perforation, and the section usually varies in profile. Once air enters through the screen, the small chambers cause it to increase in velocity and drop in pressure, which in turn cools the ambient temperature—a phenomenon known as the Venturi effect.
A study in the International Research Journal of Engineering and Technology investigated the flow of air through two types of jali in the Hawa Mahal, an 18th-century construction in Jaipur. On a 93-degree day, the researchers recorded a temperature drop of 5 to 6 degrees behind the screens. The jalis also permitted 58 to 65% outdoor wind to penetrate and achieved a daylight factor indoors of 0.98 and 1.48 (depending on the screen type). Striking in their design and performance, jalis offer benefits that are missing in glass, such as passive cooling and glare mitigation, and therefore welcome a second look in today’s building envelopes.
Adequate tree cover and greenscape also mitigate climate extremes. Trees and gardens are appreciated for their aesthetic benefits, but their environmental functions often remain undervalued. Natural vegetation reduces air and surface temperatures through shade and evapotranspiration. According to the EPA, shade can cool materials between 20 and 45 degrees below the temperatures of exposed surfaces, and evapotranspiration can diminish peak temperatures by 2 to 9 degrees.
The architects of monuments such as Delhi’s Isa Khan Tomb or Jaipur’s Amber Fort understood this tempering function of greenscape, which is often further enhanced with cooling water features. For example, Humayun’s Tomb in Delhi is considered the first garden-tomb of the Indian subcontinent. Constructed in 1570, the structure is centered within a four-quadrant charbagh landscape representative of the description of paradise in the Quran. The original planting plan likely included neem, mango, and other fruit trees, a hibiscus grove, a pomegranate orchard, and other vegetation providing shade and food. A system of cooling fountains and water channels completed this depiction of heaven.
Taking architectural lessons from these centuries-old works requires interpretation, as these remain some of the most rarified and expensive constructions of this or any region. The goal is not to specify Makrana marble or mimic the Hawa Mahal facade but to recognize how simple, passive strategies can make a measurable difference in confronting a warming climate—in Delhi and beyond. If adopted in contemporary fashion, such approaches might even blunt the negative spiral of AC dependency.
Although many would agree conceptually with this logic, it is most meaningful to experience the difference firsthand. For me, a visit to Humayun’s Tomb delivered the most compelling argument. The transition from Delhi’s oppressive, exposed streets to the shaded, paradisaical garden represented an abrupt and welcome change. Once inside the main building, enveloped by cool stone and a steady breeze passing through the jali, I was amazed to realize that, on a 96-degree day, no air conditioning was necessary. I had discovered the optimal indoor climate.
The views and conclusions from this author are not necessarily those of ARCHITECT magazine or of The American Institute of Architects.
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