Chandra Sekhar, Ph.D.
(Accepting In-Person & Virtual Presentation Requests)
National University of Singapore
Department of the Built Environment
4 Architecture Drive
Singapore 117566
(65) 65163479
Region: XIII
Honorarium: None

Chandra Sekhar is currently a tenured Professor and Programme Director (M.Sc – Building Performance and Sustainability) in the Department of the Built Environment at the National University of Singapore (NUS). He is also a Founding Director of Enhanced Air Quality Pte Ltd., a former NUS Spin-off Company incorporated in June 2004, arising out of his research in the fields of IAQ and Energy. He holds BE (Mechanical Engineering) from the University of Rajasthan (Malaviya National Institute of Technology), India; and PhD (Mechanical Engineering) from the University of Adelaide, Australia, in the area of energy efficient cooling and dehumidification systems. He has been a faculty at NUS since 1992, where he teaches at all levels and conducts research in the areas of thermal comfort, ventilation and indoor air quality, bedroom IEQ and sleep quality, airborne infection control, resilient and energy efficient HVAC systems, building energy analysis/management and integrated building design/operation and has published more than 300 papers in these areas in several international journals and conferences.

Dr. Sekhar is an Associate Editor of ASHRAE Science and Technology for the Built Environment (STBE) journal, Regional Editor (South East Asia) Indoor and Built Environment and an editorial board member of Energy and Buildings, Building and Environment, and International Journal of Sustainable Built Environment. He is a co-inventor and holds 3 US and other patents in the area of energy efficient air-conditioning system with zonal ventilation control for enhanced IAQ. He is an International Scientific Committee member of several IAQ and energy conferences. He was the Steering Committee Chair for ASHRAE IAQ2010 conference in Kuala Lumpur in 2010 and continued to be on the steering committee of subsequent ASHRAE IAQ conferences (Vancouver, 2013; Alexandria, USA, 2016; Athens, 2021/2022).

Dr. Sekhar is a Fellow of ASHRAE, International Society of Indoor Air Quality and Climate (Academy Fellow of ISIAQ) and Engineers Australia (FIEAust). He has been an ASHRAE Distinguished Lecturer since 2006 and is regularly invited as a DL speaker around the world (more than 100 DL presentations). He has been recognized through several awards, including: E.K. Campbell Award of Merit, Environmental Health Award, Exceptional Service Award and Distinguished Service Award from ASHRAE; Uichi Inouyi Memorial Asian International Award from SHASE, Japan; SPRING Singapore Merit Award, ASEAN Energy Award and The Enterprise Challenge (TEC) Award of the Prime Minister’s Office in Singapore. He is currently ASHRAE Vice President and Board Member (2023-2025), a member of SPC241P (Control of Infectious Aerosols) and TC2.1; and a consultant of Planning Committee and SSPC62.1. He is a past DAL (2018-2021) and past Chair of Environmental Health Committee (2012-2013). He was also a Vice Chair (2022-2023) and member (2021-2023) of Residential Buildings Committee, Position Document Committees (such as Infectious Aerosols, Indoor Carbon Dioxide, Resiliency in the Built Environment), IEQ-Global Alliance Ad Hoc Committee (2013-2017), EHC (2006-2012 & 2016-2018) and TC4.3. He has served the ASHRAE Singapore Chapter in various capacities, including as its President during 2010-2011 and as a BOG member, and is also actively involved in local standardization activities in Singapore.

During the COVID-19 pandemic, Dr. Sekhar has been an active member of two teams (Residential and Applications) of the ASHRAE Epidemic Task force. He is also a member of the WHO Environment and Engineering Control Expert Advisory Panel (ECAP) for COVID-19 that published the “Roadmap to improve and ensure good indoor ventilation in the context of COVID-19” in March 2021.

Oversized air-conditioning systems and overcooled buildings in hot and humid climates

Why are air-conditioned buildings in hot and humid climates so cold that one gets reminded of carrying a jacket when going to office?  Would raising the set point temperatures in these buildings do the trick?  What are the engineering challenges that necessitate a relook at the way air-conditioned buildings in such climates are designed?  This talk will review some of the fundamental issues of cooling and dehumidification facing the HVAC designer and the inevitable and inherent design of an oversized system and its undesirable consequences in terms of an overcooled indoor environment.  It will provide an understanding of the psychrometric challenges involved in cooling and dehumidification at peak and part loads in hot and humid climates. Possible solutions to creating a more thermally comfortable and healthy indoor environment that can also save energy will be discussed.

Indoor Air Quality Audit in Buildings – System Zone Concept
An IAQ audit methodology is useful in evaluating the existing status of IAQ and enhancing it in a building. In this context, the importance of being able to associate the HVAC system performance and the ensuing contaminant concentration levels in the breathing zones, will be highlighted. This can be accomplished by adopting a system-zone concept, in which the determination of the ventilation characteristics of the HVAC system along with the measurements of the contaminant concentration levels in an in-situ building will provide an understanding of the air distribution profiles in the occupied zones and an insight into the status-quo IAQ. This IAQ signature can then be used in developing short-, medium- and long-term strategies to enhance the IAQ in the building.
Sustainability and Resiliency - A paradigm shift in HVAC system design and operation during a pandemic and beyond
Resilience, in every phase of human life, has been an important realization from the recent pandemic. When it comes to the built environment, the role of the HVAC system during a pandemic goes beyond the fundamental principles of thermal comfort, IAQ and energy efficiency. Occupant health is of paramount importance and the micro-environmental quality around every individual in a building becomes the primary consideration. This talk will cover some of the energy efficient HVAC systems and advanced room air distribution strategies, enabled by the concept of decoupling “ventilation air” from “supply air” that play an important role in the mitigation of the spread of infectious aerosols. Filtration and disinfection are other strategies that would complement ventilation in the overall quest for occupant protection against airborne transmission in indoor environments. The attributes of enhanced ventilation, filtration and disinfection, coupled with energy conservation, could be seen as salient features of resiliency of the HVAC system. Going beyond a pandemic, it is the ability of the HVAC system to adapt and operate between NORMAL and RESILIENT modes that will determine how buildings can effectively cope with future challenges of the outdoor and indoor environments in ensuring the comfort, health and well-being of occupants in a rapidly and dynamically changing world. The fundamental requirement of such systems to operate efficiently and effectively over a multitude of operating conditions never imagined before is now seen as a paradigm shift towards resiliency.
Bedroom Ventilation – What do we know and what are the current standards telling us?
On an average, we spend roughly a third of our life either sleeping or attempting to do so. Although we may realize that sleep is important for our health and wellbeing, we often do not pay much attention to the adequacy and quality of sleep. This is strongly influenced by the bedroom environmental factors, most important of which would be the bedroom ventilation and bedroom air quality. This lecture is a review of field studies involving ventilation and CO2 measurements conducted in bedrooms in residential dwellings across different climates. It will also include an overview of what some of the international standards are stipulating in terms of bedroom ventilation and CO2 requirements. With a focus on enhancing sleep quality, the lecture will conclude with suggestions to improve ventilation and air quality in sleeping environments.
International Ventilation and IAQ Standards

Whilst research on ventilation and indoor air quality (IAQ) is ongoing and a better understanding of the impact of ventilation and IAQ on human comfort, health, and productivity is continuously evolving, it may be argued that it is difficult to agree upon one international standard that is universally accepted. Most existing Standards/Guidelines stipulate criteria or requirements that are given as ventilation rates. However, some of these standards also include more than one procedure to address the issue of acceptable IAQ.

All current and proposed Standards aim to deal with both HEALTH and COMFORT issues. This talk is an attempt to review some of the current international efforts in the development and review of ventilation and IAQ standards, such as ASHRAE, ISO and CEN standards.

Advanced room air distribution strategies for effective airborne infection control

In the context of airborne infection control, it is critical that the ventilation system is able to extract the contaminated exhaled air within the shortest possible time.  In order to minimise the spread of contaminated air exhaled by occupants efficiently, a novel Personalized Ventilation (PV) - Personalized Exhaust (PE) system has been developed, which aims to exhaust the exhaled air as much as possible from around the infected person.  The PV-PE system was studied experimentally for a particular healthcare setting based on a typical consultation room geometry and four different medical consultation positions of an infected person and a healthy person.  The findings are encouraging and the PV-PE system is envisaged to help in the ventilation design of consultation rooms in healthcare centres and hospitals. The advantage of PE for infection control can also be applied in any open area with the presence of an infected person to obtain better infection control as well as better inhaled air quality.

Emerging HVAC technologies for energy efficient healthy buildings in hot and humid climates
AIA Approved| 1LU |Sekhar05
GBCI Approved | 1 CE Hour | 0920017418

In recent times, clear associations are being established between ventilation rates, Indoor Air Quality (IAQ) and the productivity of workforce in various types of buildings, most significant of which is the commercial and office building sector. It is also an established fact that HVAC systems do consume a significant proportion of national energy budget in any country irrespective of whether the HVAC design is “Cooling Driven” or “Heating Driven”. Hence, the notion of Energy Efficient Healthy Buildings is gaining popularity worldwide in the context of sustainable design and it is even more challenging in hot and humid climates that have all-year air-conditioning demand in the form of energy intensive cooling and dehumidification. It is quite apparent that Climate Change effects are only going to make the HVAC designer’s job even more challenging in the future.  Whilst SOURCE CONTROL is commonly advocated as the fundamental approach to eliminating or containing the contaminant levels inside the building, a more practical and often necessary approach is likely to be EXPOSURE CONTROL.  Thus, ventilation plays an important role in providing a quality built environment.  Two considerations are highlighted in order to achieve “good” indoor air quality (IAQ) and energy efficiency – the enhanced dehumidifying performance of cooling coils and the effectiveness of air distribution strategies.  The concept of decoupling “ventilation air” from “supply air” is fast emerging as an ideal solution to combat thermal comfort and indoor air quality (IAQ) issues in a sustainable manner. This talk will highlight some of the current and future technologies for air-conditioning and air-distribution that can collectively contribute to the design of energy efficient healthy buildings.  The air-conditioning technologies reviewed include the Low Face Velocity-High Coolant Velocity (LFV-HCV) system; outside air pre-treatment system; single coil twin fan (SCTF) system employing a compartmented cooling coil; desiccant dehumidification system and heat pipe.  The air-distribution systems reviewed include SCTF system with independent “ventilation” and “thermal cooling” on zone-based demand; personalized ventilation system coupled with secondary ambient air distribution system and dedicated outdoor air system (DOAS) coupled with chilled beams or radiant chilled ceiling.

An overview of ASHRAE Standard 62.1

ANSI/ASHRAE Standard 62.1 – Ventilation for acceptable indoor air quality, was first published in 1973 as Standard 62, and is now updated on a regular basis using ASHRAE’s continuous maintenance procedures.  This means that the standard is continuously revised by addenda that are publicly reviewed, approved by ASHRAE and ANSI, and published in a supplement approximately 18 months after each new edition of the standard, or in a new, complete edition of the standard, published every three years.  Standard 62.1 has undergone some key changes over the years, reflecting the ever-expanding body of knowledge, experience, and research related to ventilation and indoor air quality. While the purpose of the standard has remained consistent— to specify minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects—the means of achieving this goal have evolved.  This talk will provide an overview of the standard and highlight some of the recent revisions to the standard.

ASHRAE Standard 241-Control of Infectious Aerosols
ASHRAE, through its Epidemic Task Force, provided timely leadership in responding to the COVID19 pandemic from March 2020 through June 2022. At the request of the White House, ASHRAE undertook its own project Warp Speed to build on that expertise for the future. In December 2022, the ASHRAE Board committed to quickly writing a standard to make buildings more resilient against infectious aerosols ahead of the next epidemic. In only four months the project committee created and won approval for ASHRAE Standard 241-2023. In this Lecture a member of the 241 project committee will provide a summary of the standard including its purpose, scope, and key requirements with supporting background.