On a warm Sunday morning in Alibaug, I sat on a verandah, surrounded by the still, humid April air. The temperature read 27°C, but it felt like 29°C. There was no breeze, yet the setting felt calm, even pleasant. The next morning, back in my Mumbai office, the same 27°C felt stifling. Almost instinctively, I reached for the AC remote. It made me reflect on thermal comfort and how dramatically our perception of it can shift, even under seemingly similar conditions.
Comfort Begins in the Mind
ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) defines thermal comfort as “that condition of mind which expresses satisfaction with the thermal environment.” In other words, thermal comfort is subjective and contextual, shaped by an individual’s perception and the specific conditions of their surroundings.
And yet, paradoxically, building codes such as ASHRAE itself and India’s ECBC (Energy Conservation Building Code) often reduce thermal comfort to an objective checklist — air temperature, humidity, airflow, and metabolic rate. Even the ‘feels-like’ temperature that we see on our weather forecast apps relies on measurable environmental data, including the ambient air temperature, relative humidity, and wind speed, to determine how weather conditions feel to bare skin.
These metrics, while useful, treat the human body as a passive recipient of environmental conditions, rather than an active interpreter of them. In doing so, they overlook the complex ways in which culture, conditioning, and context shape how we feel heat or cold. To truly design for comfort, we must begin by acknowledging that thermal comfort is not just a matter of numbers, but of perception.
How Perception Alters Comfort
Our perception of comfort is shaped as much by expectations as by actual temperature. At the resort in Alibaug, I was outdoors and mentally prepared for warmth. Surrounded by open spaces and nature, I anticipated a certain level of heat, and my clothing, activities, and mindset were aligned with that. As a result, 27°C in Alibaug felt natural and easy to adapt to. The same 27°C back in my air-conditioned Mumbai office felt unpleasant, simply because my mind expected a cooler, conditioned environment.
Over the years, we’ve grown used to associating thermal comfort with air-conditioning. Since the 1980s, as air-conditioners became more affordable, commercial buildings in India began to mimic the glass towers of the West. As a result, we’ve internalised thermal comfort standards rooted in colder climates, routinely setting our thermostats to 22–24°C regardless of our own context or climate.
The internationally acclaimed architect Charles Correa questioned this shift in his seminal lecture, ‘A Place in the Sun,’ where he critiqued the blind replication of Western models of building. Correa pointed out that this uncritical replication of Western ideals overlooks local realities — including intense sunlight, high humidity, patterns of daily life, and socio-economic factors related to energy use. When buildings are designed without adapting to their context, they often become over-reliant on artificial cooling, disconnected from their surroundings, and less comfortable or accessible to the people who use them. He urged Indian architects to design in dialogue with our specific climate, culture, and ways of living rather than adopting standards rooted in other geographies. While his argument was about form and responsiveness, it applies equally to how we think about comfort. When we ignore local realities, we also risk dulling our ability to perceive and adapt to them.
In doing so, we end up designing spaces where comfort is engineered, not experienced, and where our perception is slowly trained away from the richness of sensory connection to our surroundings.
Heat Resilience is Cultural: Comfort Thresholds Can Shift With Exposure
Heat resilience, the ability to cope with and adapt to rising temperatures and heat waves, is not purely biological. It is also deeply cultural, shaped by habits, lifestyles, and the environments we grow up in. People in tropical regions, where life often unfolds in outdoor or semi-open settings, develop a higher tolerance to heat through repeated exposure.
A 2017 study by Titis Wijayanto et al. compared how students from Malaysia and Japan responded to heat stress. Both groups underwent the same set of activities, including time in a sauna, while researchers tracked their core temperatures. The Malaysian students, more familiar with high-heat environments, showed better tolerance.
This observation naturally led me to the question: Would the Japanese students never acclimatise to heat stress? The answer lies in the human body’s remarkable ability to adapt.
The process of acclimatisation is the body’s way of adjusting to environmental shifts. With time and exposure, comfort thresholds can shift. What first feels unbearable can become tolerable, even preferable.
In fact, we adapt to different climates all the time, often without realising it. We anticipate discomfort when we go trekking in a colder region, like the Himalayas, and we prepare for it. Similarly, in hot regions, we instinctively adjust how we move through the day — by wearing lighter clothes, slowing down during peak heat, or choosing shaded routes. In both cases, we allow our bodies to respond to the climate. This same ability applies to our everyday environments as well.
The Equatorial School in Singapore: A Case Study in Thermal Comfort Adaptation
During a visit to Singapore last November, I came across a compelling example of a building that embodies the principles of acclimatisation: The Equatorial School, part of the NUS Campus, designed by architect Erik L’Heureux. This project is an interesting example of how the human mind can adapt to its environment.
Singapore experiences a relatively stable equatorial climate, marked by uniform temperatures and consistent rainfall throughout the year. Yet, despite the absence of thermal extremes, the country exhibits a strong dependence on mechanical cooling — evident in the widespread air-conditioning of public spaces, including transport systems such as buses, trains, and interchanges.
© Finbarr Fallon; Courtesy of Erik L’Heureux, FAIA; Campus Design Innovations Group, National University of Singapore; and DP Green | Source: AIA NY
Within the context of Singapore’s heavy reliance on mechanical cooling, the Equatorial School offers a deliberate counterpoint — a three-zone thermal comfort strategy that foregrounds adaptability and perception. More than 65 per cent of the building is hybrid-cooled or naturally ventilated. Spaces that require strict environmental control remain fully air-conditioned. In the zones where air-conditioning is optional, baseline AC temperatures are raised to 24–26 degrees Celsius — a subtle but significant shift from the default 22 degrees — helping occupants recalibrate their sense of comfort.
Meanwhile, circulation spaces such as corridors and stairways are left entirely naturally ventilated, transforming them into socially active zones that engage directly with the tropical climate. Additionally, the extended west façade is designed as an envelope that engages with the tropical climate, screening the building from heat gain by creating a deep veil. This approach shows how architecture can be utilised as an instrument of thermal adaptation.
© Finbarr Fallon; Courtesy of Erik L’Heureux, FAIA; Campus Design Innovations Group, National University of Singapore; and DP Green | Source: AIA NY
When I spoke to the architect about the reception of the building, he mentioned initial resistance. Singaporeans are so used to air-conditioned environments that the transition to naturally ventilated spaces was met with discomfort. However, over the course of 6 to 8 months, as students adjusted to the new thermal conditions, the heat gradually became something they expected, and their perception of comfort shifted. The naturally ventilated corridors became a space that students began to enjoy, showing how adaptable human beings are when exposed to new, though initially uncomfortable, environments.
The Adaptive Comfort Theory
Most conventional models of thermal comfort, such as the widely used PMV-PPD model developed by Danish engineer P.O. Fanger, are based on climate-controlled environments. They assume comfort can be achieved by maintaining a fixed range of temperature and humidity, typically through air-conditioning. These models treat comfort as a universal physiological response, calculated using parameters like air temperature, humidity, metabolic rate, and clothing insulation, regardless of geography or lifestyle.
But as we have already discussed, comfort is not one-size-fits-all. In a country like India, with five distinct climatic zones and diverse ways of living, fixed thresholds fail to reflect how people actually experience temperature in daily life.
The Adaptive Comfort Theory, introduced by Prof. Michael Humphreys and Prof. J. Fergus Nicol in the 1970s, addresses this complexity. It recognises that people adapt to their environment—physiologically, behaviourally, and psychologically—and that comfort can be achieved across a wider, more responsive temperature range.
Rather than prescribing a universal temperature, this theory accounts for everyday adjustments: opening windows, changing clothing, drawing curtains, or modifying routines. It expands the definition of comfort to include expectation, context, and lived experience. In doing so, it aligns more closely with both how people actually feel and how sustainable buildings must function.
Yet despite its relevance, this theory remains underutilised in mainstream practice. Most large-scale developments still follow conventional models that prioritise uniform, air-conditioned environments, often ignoring regional variation and occupant adaptability.
This gap between research and reality highlights the need to rethink how we define and design for comfort, especially in a climate-diverse country like India.
The Silent Heatwave
We have become so used to air-conditioning that we forget — air-conditioning doesn’t just cool the inside of buildings. It also heats up the world outside. The mechanism is simple; it takes heat from indoors and releases it outside. But in already warm urban environments, that extra heat adds up. In cities, this has been shown to raise night-time temperatures by as much as 2°C, creating a feedback loop where people crank up their ACs even more.
This cycle is especially dangerous in dense built-up areas where green cover is minimal. The more we rely on artificial cooling, the hotter our cities become and the more energy we use. It’s an invisible damage that worsens over time.
Of course, air-conditioning is sometimes essential. It helps manage thermal comfort during extreme heat. But our relationship with it needs a shift. Not just in how much we use it, but in how we think about comfort, resilience and design.
A Shift in the Mindset
If comfort is shaped by what we expect to feel, then maybe the first step is to question those expectations.
As architects, calibrating our own expectations as well as clients’ expectations about thermal comfort is necessary. If we keep chasing the idea of 22°C indoors, air-conditioning will always seem like the only answer. But if we adjust our thinking, accepting that in a tropical climate, comfort can exist between 24–28°C, new solutions begin to emerge.
Integrating passive design strategies and revisiting traditional methods of cooling like water coolers or khus coolers, or adopting mixed-mode ventilation, where mechanical cooling is supplemented by ceiling fans or natural ventilation through openable windows, for lowering indoor temperatures as much as possible. The good-old ceiling fans must become fashionable again! Many new companies are already doing a good job at it; now it’s time to align our aspirations.
Mixed-mode ventilation gives users the flexibility and agency to respond to their needs—opening a window in winter, switching on a fan in summer—rather than relying on systems to decide comfort for them. We don’t have to rely entirely on machines to feel okay. With a little more awareness and a little more trust in our bodies and our environment, we can begin to redefine comfort on our own terms.
And in doing so, we move closer to a mindset where thermal comfort is rightly understood as subjective and circumstantial rather than a fixed, universal standard, which is arguably the most important mindset shift we need to make.
