Forget cooling: Let’s talk about thermal comfort

Amidst the pressing climate change concerns, it is time that the building industry re-imagines cooling and prioritise thermal comfort. Ashish Rakheja, Managing Partner, AEON Consultants, shares how the foundation set by the India’s green building movement and out of the box sustainable practices can drive positive change.

When we think of energy conservation, the spotlight naturally falls on air conditioning systems, considering they account for the largest portion of electricity consumption; a staggering 50% of the total energy bill. To pave the way for a de-carbonized world and a sustainable future, we must re-imagine our cooling approach. Most part of India enjoys multiple seasons and the requirement of cooling solutions can be limited to periods of hot, warm, and humid seasons. A mindset change to thoughts of thermal comfort (and finally adaptive thermal comfort) rather than cooling presents a new prospect for de-carbonizing our country. 

The Green Building movement

For the past two decades, India has witnessed a robust green building movement, which began in 2001 with a modest beginning. Today, the country boasts of an impressive 13 billion square feet of green footprint, encompassing under-construction and completed structures. This remarkable achievement positions India as the world’s second-largest green building footprint. While this may be a source of pride, the reality is more nuanced. The Green movement’s impact has been profound, offering valuable training to the design and construction industries. Through codes like NBC, ECBC, Eco Niwas Sanhita and ASHRAE Standards, as well as effective rating systems from multiple agencies, the country has cultivated a deep understanding and appreciation for equipment efficiency and energy conservation.

As a result, India today enjoys a host of world-class third party certified products manufactured locally and also exported in the world. The cooling technologies employed in buildings have gone through technological generation advancements ranging from VRFs, high COP chillers, VFD on equipment and now magnetic bearing chillers.Similarly, the low-side cooling systems have seen a rising demand for innovative products like radiant cooling, radiant panels, VAV systems, Displacement ventilation under-floor air distribution etc. Despite these impressive advancements in energy-efficient technologies, the question remains: are these measures sufficient to meet our needs for a sustainable future?

The current crisis of climate change tells us a different story.Inspiteof a strong green building movement, advanced technologies& products and a good understanding of building science, the last two decades at best have managed to extend the deadline for doomsday but in no way arrested the risk which changing weather patterns pose to us. Last year unprecedented floods in Pakistan, this year monsoon impact in northIndian states, changing weather patterns, heat waves, wild fires, etc. are a universal phenomenon, As the third-largest CO2 emitter globally, India faces persistent challenges with high carbon emissions. The construction boom in coming decadesdriven by rapid urbanization offers no respite, hinting at a continued uphill battle in tackling climate change.

Prime Minister Narendra Modi has emphasized the significance of the next three decades, declaring it to be the India’s era. With a young population base and a rapid pace of construction, the country is focused on improving the quality of life for its people. It’s been reported that India is possibly constructing at a rate equivalent to building one Chicago every year. Considering India’s current standing as the third-largest carbon emitter globally, the question arises – where will this path lead us in terms of carbon emissions?

According to a Times of India article, India will face a significant challenge in dealing with global warming, with the rising demand for air conditioners expected to reach one sold every 15 seconds by 2037. The rapid pace of urbanization adds to this concern. In the recent CoP26, our Prime Minister pledged the goal of making India carbon-neutral by 2070. However, achieving carbon neutrality is a complex task due to the challenges of managing both embodied carbon and operational carbon, which are not yet well-known to all of us. The surge in construction activities leads to a substantial addition to embodied carbon footprint, while the new stock of buildings will contribute to a significant operational carbon impact. Balancing both these aspects becomes crucial for securing a sustainable future.

The pressure is mounting on developers and building owners as regulatory authorities and the government impose stricter guidelines. The requirement of ESG reporting for the top 1000 companies has already been enforced, and similar measures are expected to intensify. Concepts like carbon tax and GHG accounting are becoming increasingly prevalent. As a result, the industry is compelled to shift towards sustainability and embrace net-zero practices. The rapid shift towardsgreen power and adoption of net-zero energy building practices in recent years indicate a growing focus on sustainable operations within the construction sector, reflecting the industry’s response to these pressures. However, it is important to note that both green building movement and renewable energy adoption is largely limited to big Corporate and a large part of the population remains untouched and possibly unconcerned. There is a need for one big idea that can help cut down building carbon emissions significantly and involves the masses to help to contribute for a de-carbonized India.

Thermal Comfort

The air conditioning industry can play a crucial role in de-carbonizing our built environment through a shift from thetraditional practice of promoting cooling as a solution (where the focus is merely on temperature control) to a broader concept of thermal comfort and finally adaptive thermal comfort. The human body is a remarkable machine, capable of withstanding a wide range of temperatures, from extreme cold to scorching heat. The idea is to design buildings wherein priority is thermal comfort over conventional heating or cooling approaches.

Thermal comfort is a psychological state of contentment with our environmental conditions. When considering its fundamentals, six key factors come into play: the right temperature, relative humidity, air velocity, metabolic rate, clothing, and mean radiant temperature. It’s not solely about achieving a specific temperature, like 22 degrees centigrade, but rather the interplay of these factors. For instance, at a room temperature of 27 deg C and by increasing air velocity,one can experience thermal comfort equivalent of 22 deg C thereby saving significant energy. 

Various standards, including ASHRAE Standard 55, offer valuable insights into the subject which can help redefine building concepts. Most modern buildings are designed to be insulated from nature and thus our indoor environment has to be conditionedusing expensive energy even in cities with pleasant climates. Focusing on cooling rather than thermal comfort creates this big gap and is leading to a behavioral shift in the future generations which is detrimental to the climate. By embracing a more open approach in building design and allowing the nature to infiltrate indoor spaces, use of mechanical cooling systems can be easily minimized and possibly shut-down for nearly six months every year in most Indian cities. The adaptive thermal comfort and revert to conventional technologies like fans in indoor spaces and evaporative cooling are a viable solutions and they are once again gaining traction.

Case Study: AEON Consultants Corporate Office in Noida

At AEON Consultants, a remarkable experiment was carried out in their 30,000 square feet office space, primarily focusing on achieving adaptive thermal comfort and not just cooling. The key to success lies in meticulous planning, despite limited flexibility in plot allocation from the Government. The AEON team pushed the boundaries of design by strategically blocking out the sun, maximizing natural light, and implementing a facade design that offered optimal daylighting options. The result was an impressive day-lighting of 98 percent indoor spaces thereby providing a pleasant and non-intrusive ambience despite the intense heat often experienced in the region.

The key to achieving optimal energy efficiency is careful planning of building passive features like glazing, insulation, glare control, minimize heat islands and thereafter deploy technological interventions like mini chillers, lighting fixtures, heat recovery wheel etc. The key to an efficient design was validating the performance by preparing a digital twin at the initial stages of the project. The finished building enjoys a day-lit & glare free interiors, minimal artificial lighting with Lighting Power density of merely 0.35 W/sft and a good indoor air quality without compromising energy efficiency. The building’s efficiency is further enhanced through use of HVLS ceiling fans with BLDC motors which help generate thermal comfort for its occupants. The use of mechanical cooling is limited to just 6 months in a year. Entire building operation is monitored through state of the art wireless IoT system and a dashboard to educate its users and provide them appreciation of their contribution towards environment preservation. 

AEON commitment to sustainability is evident in efforts to benchmark and monitor their CO2 emissions. They started by mapping their own Scope 1, Scope 2 & Scope 3 emissions and thereafter registered with SBTi (Science-based target initiative) to commit restricting their emissions to ensure they do not rise to permit earth temperature rise beyond 1.5 deg C. The building has received Platinum rating from Indian Green Building Council (IGBC) and the energy consumption is merely 89.5 kWH/sqm-year. The onsite solar power generation is also raised from earlier 10 kW to now 23.5 kW in order to offset the operational carbon. 

AEON office is a fine example of de-carbonization efforts led by a MSME through an affordable means which makes business sense. It sets the foundation for a bottom-up green movement which can help India achieve its de-carbonization target. The other features in the building include water conservation & metering, condensate recovery, rain water harvesting, organic waste management and human centric lighting solution.

The building industry’s future hinges on performance-based practices, especially in pursuing net-zero goals for energy, water, and waste. Emphasizing actual operational outcomes rather than design alone is the key to achieving net zero status. The construction industry is undergoing a mindset shift, focusing on design, installation, and efficient operation. New rating systems worldwide prioritize operational data and incorporate IoT, data logging, and AI to reduce operational energy consumption. The evolution of codes and standards, like the under revision ECSBC (Energy Conservation & Sustainable Building Code), is likely to includeadditional chapters on new aspects like water & waste management, sustainable materials, indoor environmental quality, building commissioning and IoT etc. By prioritizing thermal comfort over mere cooling and leveraging human adaptability, true sustainability can be achieved by effectively reducing embodied and operational carbon.