Sagoh
By Green Matters Staff
The relentless hum of air conditioning units is a familiar soundtrack to summer, a symbol of comfort against sweltering temperatures. Yet, behind the cool breeze lies a significant, often overlooked, energy drain. Engineer Jagan Pillai, recognized as the 2026 International Energy Innovator of the Year, argues that the primary culprit behind air conditioning’s colossal energy consumption isn’t the heat itself, but rather the invisible burden of humidity. This groundbreaking perspective challenges conventional wisdom and points towards a more efficient future for cooling our built environments.
The Illusion of Temperature: Why "Feels Like" Matters
On a sticky summer afternoon, a glance at a weather app reveals two crucial figures: the actual temperature and the "feels like" temperature. The disparity between these numbers, particularly pronounced on humid days, is a direct testament to the impact of moisture in the air. Our bodies naturally cool themselves through perspiration. As sweat evaporates from our skin, it carries away excess heat, providing a cooling effect. However, when the atmosphere is already saturated with water vapor, this evaporative process becomes sluggish. The result is a feeling of oppressive heat and stickiness, where a seemingly moderate temperature can feel significantly hotter. This phenomenon, where a 90-degree Fahrenheit day in a humid city can feel well over 100 degrees, highlights the potent influence of humidity on human comfort.
Pillai, a licensed Professional Engineer and a distinguished figure in the energy sector, asserts that this very moisture is the hidden reason why air conditioning systems consume such vast amounts of energy. "Most people think an air conditioner’s job is to make air cold," Pillai explains. "In a humid city, a huge part of its job is making air dry, and the way we do that is surprisingly wasteful." This observation is supported by scientific data, with a 2018 study published in Scientific Reports indicating that moisture removal accounts for approximately 30 percent of the total air-conditioning cooling load, a figure that escalates significantly in tropical and subtropical climates.
The Overcooling Conundrum: A Deeper Dive into Dew Point
The fundamental principle at play is the dew point, the temperature at which air becomes saturated with water vapor and condensation begins to form. Air has a finite capacity to hold moisture, and when it is cooled to or below its dew point, the excess water vapor transforms into liquid. This is why dew forms on grass in the early morning and why a glass of iced water "sweats" on a warm day.
"Nearly every conventional air conditioner, from a window unit to the giant chiller plants that cool office towers, dries air the same way: it chills the air below its dew point so the moisture condenses out and drains away," Pillai states. This method, while effective at reducing humidity, necessitates cooling the air to temperatures far below what is comfortable for occupants. In many large-scale applications, such as office buildings, this overcooled air is then reheated before being circulated, an inherently inefficient process.
The economic implications of this practice are substantial. Research from the Lawrence Berkeley National Laboratory underscores the energy savings associated with raising the chilled-water supply temperature. For centrifugal chillers, a mere one-degree Fahrenheit increase in the chilled-water supply temperature can lead to an operational efficiency improvement of approximately 1 to 2 percent. The study further illustrates that supplying water at 55°F instead of 40°F can boost a chiller’s efficiency by a remarkable 15 to 30 percent, though the exact benefits are contingent on specific operating conditions and the system’s ability to maintain adequate cooling and humidity control. This suggests that by optimizing the chilled-water temperature, significant energy savings can be realized without compromising comfort.
The "Sweater Paradox": A Symptom of Inefficiency
The consequence of this overcooling is not merely an abstract energy inefficiency; it manifests in tangible, often humorous, ways. The ubiquitous sight of office workers donning sweaters in the middle of July is a direct byproduct of HVAC systems designed to prioritize dehumidification over precise temperature control. A 2021 study in Scientific Reports highlighted that indoor temperatures in US offices were found to be lower in summer than in winter, a clear indication of this overcooling phenomenon. This practice not only leads to discomfort but also represents a significant financial drain. An earlier estimate from 2015 suggested that overcooling US commercial buildings resulted in approximately $10 billion in wasted electricity annually.
"That sweater is a symptom," Pillai emphasizes. "In many buildings, the air is cold because the system had to make it cold to dry it. Comfort was never the goal. Humidity control was, and we paid for it twice." This "sweater paradox" serves as a powerful visual representation of the fundamental flaw in traditional air conditioning design, where the dual demands of temperature and humidity control are addressed through a single, inefficient process.
Decoupling the Demand: Pillai’s Innovative Approach
Jagan Pillai, also recognized as a 2025 ACEEE Champion of Energy Efficiency in Industry, has dedicated nearly two decades of his career to deconstructing these intertwined functions. His core argument is simple yet profound: "Temperature and humidity are different problems." By developing technologies and methodologies that address each demand independently, significant improvements in energy efficiency can be achieved.
"If you can remove moisture another way, you don’t have to overcool anything," Pillai explains. "You cool the air just enough to be comfortable." One of the key innovations Pillai champions involves the use of desiccants. These materials possess an innate ability to absorb moisture directly from the air, much like the silica gel packets found in new shoe boxes. In a desiccant-based system, the air is first dried, allowing the subsequent cooling equipment to operate at warmer, more efficient temperatures.
However, a practical challenge arises: once a desiccant becomes saturated with moisture, it requires regeneration through heat before it can effectively absorb more. Pillai’s ingenious solution involves harnessing waste heat that buildings are already generating and expelling. This closed-loop approach minimizes the need for additional energy input for desiccant regeneration, further enhancing efficiency.
A Holistic Performance Metric: Beyond the "Design Day"
A significant hurdle for desiccant systems has historically been their evaluation against conventional metrics. Often, these systems are judged against a single, extreme "design day"—the hottest and most humid day of the year. This approach fails to capture the dynamic nature of building performance throughout the year. During his tenure as Practice Leader for Energy and Analytics at the sustainability design firm Atelier Ten, Pillai developed a novel methodology. This approach analyzes a building’s performance hour by hour across the entire year, allowing for a more nuanced and adaptive dehumidification strategy tailored to the building’s actual needs at any given moment.
This innovative methodology has been instrumental in the design of several highly sustainable buildings. At New York University’s Center for Urban Science and Progress at 370 Jay Street in Brooklyn, Pillai’s analysis informed a design that integrated desiccant dehumidification, heat recovery, on-site power generation, and thermal energy storage. This comprehensive approach successfully reduced peak demand, contributing to LEED Platinum Core and Shell and LEED Gold Commercial Interiors certification and an estimated 50 percent reduction in energy costs, according to Atelier Ten.
Similarly, at NYU’s John A. Paulson Center at 181 Mercer Street in Manhattan, a LEED Gold-certified building, the desiccant system is regenerated using waste heat from the university’s campus cogeneration plant. Combined with other advanced strategies such as displacement ventilation, decoupled systems, and enthalpy recovery, this integrated design achieved a remarkable 46 percent reduction in energy costs, as reported by Atelier Ten. These case studies demonstrate the tangible benefits of Pillai’s holistic approach to building design and energy management.
The Urgency of Now: Climate Change and Grid Resilience
The relevance of Pillai’s work is amplified by the intensifying reality of climate change. Heat waves are not only becoming more frequent but also more humid, placing unprecedented strain on existing power grids. "Efficiency used to be about the utility bill," Pillai observes. "Now it’s about whether the grid can keep up on the worst afternoon of the summer. Every kilowatt we don’t need at that moment matters." This shift in focus underscores the critical need for innovations that can reduce peak demand and enhance grid resilience in the face of escalating climatic challenges.
Emerging Technologies: The Promise of Metal-Organic Frameworks (MOFs)
Looking towards the future, emerging materials like metal-organic frameworks (MOFs) offer promising avenues for more efficient moisture capture. MOFs are highly porous crystalline materials with an exceptional capacity for absorbing water vapor. Experimental systems have demonstrated their potential in coating heat exchangers, enabling moisture removal without the need for excessive cooling. By utilizing residual condenser heat for regeneration, these MOF-enhanced systems present a potential pathway towards more efficient cooling and drying, with scalability for larger applications. While further development and real-world testing are necessary to validate performance across diverse building environments, the underlying principles align with Pillai’s vision of decoupling temperature and humidity control.
A Personal Perspective: Reimagining Home Comfort
The principles of efficient humidity control extend beyond large commercial buildings to our own homes. An oversized air conditioner, a common issue in many residential settings, can cool a room rapidly but shut off before adequately removing moisture. This results in a space that feels cool but clammy, prompting occupants to lower the thermostat further in a futile attempt to achieve comfort, thereby consuming more energy without tangible improvement.
"Comfort isn’t just a number on the thermostat," Pillai asserts. "Get the humidity right, and you can run warmer, use less energy, and actually feel better." As cooling demands continue to rise globally, Pillai’s emphasis on humidity as the central element in the energy efficiency conversation is crucial. By separating the critical functions of moisture removal and temperature regulation, his approach offers a pragmatic and effective strategy for reducing unnecessary cooling loads while simultaneously enhancing occupant comfort. The ultimate goal is a built environment that is not only more energy-efficient but also a healthier and more pleasant space for everyone within it.
Nana Wu
Asro
