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.

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.

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.

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.

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.