Dr Chandra Sekhar is currently a Professor and Programme Director (M.Sc – Building Performance and Sustainability) and Co-Director (Centre for Integrated Building Energy and Sustainability in the Tropics) in the Department of Building at the National University of Singapore (NUS). He is also a Founding Director of Enhanced Air Quality Pte Ltd., a NUS Spin-off Company incorporated in June 2004, arising out of his research in the fields of indoor air quality (IAQ) and Energy. He has been an IAQ consultant in Singapore since 1993. He received his PhD in Mechanical Engineering from the University of Adelaide, Australia, in the area of energy efficient cooling and dehumidification systems. In 1992, he joined NUS as a Faculty and has since been teaching and conducting research in the areas of thermal comfort, ventilation and indoor air quality, energy efficient air-conditioning and mechanical ventilation systems, building energy analysis and has published about 225 papers in these areas in several international journals and conferences.
Prof Sekhar is an Associate Editor of ASHRAE HVAC&R Research journal, Regional Editor (South East Asia) Indoor and Built Environment and an editorial board member of Energy and Buildings journal (Elsevier), International Journal of Ventilation and International Journal of Sustainable Built Environment. He is a regular reviewer of articles for several international journals, such as, ASHRAE Science and Technology for the Built Environment (formerly HVAC&R Research) Journal and Transactions; Indoor Air; Energy and Buildings; Building and Environment; Energy; Indoor and 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 indoor air quality. He is actively involved in the development of local IAQ, ventilation and energy standards in Singapore and received the SPRING Singapore Merit Award 2012 in recognition for his contributions towards Quality and Standards in Singapore. He is a member of the International Scientific Committee of the Healthy Buildings, Indoor Air, ROOMVENT, CLIMA and IAQVEC series of conferences and was the Technical Co-Chair and member of the organising committee of the Healthy Buildings 2003, the Seventh International Conference in Singapore in 2003. He was the Chair of the Steering Committee for ASHRAE IAQ2010 conference in Kuala Lumpur in 2010 and continues to be on the steering committee of subsequent ASHRAE IAQ conferences (Vancouver, 2013 and Washington DC, 2016).
Prof Sekhar is a Fellow of ASHRAE and a Fellow of ISIAQ. He has been an ASHRAE Distinguished Lecturer since 2006 and is regularly invited as a speaker around the world. He is a recipient of the Environmental Health Award (2014), Exceptional Service Award (2013) and the Distinguished Service Award (2010) from ASHRAE. He is a co-recipient of The Enterprise Challenge award of the Prime Minister’s Office, Singapore in 2004 and ASEAN Energy Award in 2011. He is also a member of the Institution of Engineers, Australia (CPEng, IEAust). Within ASHRAE, he is a past Chair of the Environmental Health Committee (EHC), was a member of the IEQ-Global Alliance Ad Hoc Committee (2013-2016) and is currently a member of SSPC 62.1, TC 2.1, EHC and TC 4.3. He has also served the ASHRAE Singapore Chapter in various capacities, including as its President during 2010-2011 and as a BOG member.
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.
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.
Decoupled ventilation strategies for enhanced IAQ – “Demand cooling” and “Demand ventilation”
The concept of decoupling “ventilation air” from “supply air” is fast emerging as an ideal solution to combat the problems associated with poor indoor air quality (IAQ). This talk will present the Personalized Ventilation (PV) system and the Single Coil Twin Fan (SCTF) system, which show considerable promise in their abilities to provide both good IAQ and energy efficiency. The PV system is fundamentally aimed at improving ventilation in the immediate breathing zones of occupants in the built environment. The SCTF system is a new air-conditioning and air distribution system that improves occupants’ thermal comfort and indoor air quality whilst significantly saving energy. It provides “demand ventilation” and “demand cooling” by dynamically responding to the varying requirements in the individual occupied zones of a building.
Emerging HVAC technologies for energy efficient healthy buildings in hot and humid climates
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.
Integrated IAQ and energy case studies in the tropics
This talk will cover the key features of a comprehensive indoor air quality (IAQ) and energy study conducted in commercial office buildings in a hot humid climate in the mid-to-late nineties and will compare the findings with similar large-scale studies conducted in Europe and USA. An integrated IAQ and energy audit methodology was adopted and the key performance parameters measured include various indoor pollutant concentration levels, ventilation characteristics (such as outdoor air change rate, ventilation efficiency and air exchange effectiveness), energy index and subjective responses (Building Symptom Index, Thermal comfort acceptability, IAQ acceptability).
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.
- Prescriptive Method : Minimum ventilation rates can be found in a table listing values for different types of space
- Analytical Method : Calculation of required ventilation rate on the basis of pollutant type, emission rates and acceptable concentration
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.
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.
Ventilation, IAQ and Energy issues in hot humid climates – Past, Present and Future
This talk will provide an overview of the ventilation, IAQ and energy issues in commercial office buildings in hot humid climates. It presents the design challenges based on climatic differences with due consideration given to local codes and ASHRAE Standards 55, 62.1 and 90.1. Typical HVAC design for different building types in hot humid climates will be covered with emphasis on both design and part load characteristics. The role and importance of cooling and dehumidifying coil and limitations in conventional designs will be highlighted. Effective and practical zone-level ventilation control will be introduced and the notion of energy efficient healthy buildings will be presented.