Passive Strategies: Natural Ventilation (a)

Last week we were in conversation with Sustainability Professional Steven Lee from Malaysia. He is currently Principal at Edisi Hijau Sdn Bhd, Kuala Lumpur, Ipoh. Steven has been working with the IT industry for over 20 years, before making the move to Green Technology in 2007. (You could connect with him here – LinkedIn, Twitter)

Our discussion started with the post on Passive Strategies used in CapitaGreen, Singapore and the viability of such strategies in other projects and countries.

Today, we sum up points from this discussion and others that we think could be useful to our readers. We will focus on 3 Essential Passive Strategies – Natural Ventilation, Integration with Greens & Water and Daylighting. This part starts with Natural Ventilation.

Natural Ventilation


Natural Ventilation

Why it is needed ?


Buildings account for 33% of the total electricity consumption in India. (Domestic 24%, Commercial 9%)1. Of this,  HVAC is one of the highest loads accounting for almost 50-60%2.

What needs to be done and effects ?

reduce need

Our effort should be to reduce the need for Air-conditioning, to help reduce energy loads. Less AC use or using air-conditioning at higher setpoints, could result in saving energy. In Residential scenarios for example, after 22oC, every 1oC higher set point equals 3-5% less energy use3.

How ?

Through design, planning, passive strategies like Natural Ventilation, integration with greens and water, we can increase thermal comfort. Thus people will want to use less air-conditioning and this will result in energy use reduction.

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Factors important for Natural Ventilation

(i) Climate

Climate is one of the chief factors determining the feasibility of Natural Ventilation. For example, Natural Ventilation is quite effective in Moderate climates and it may provide considerable relief in Hot and Humid conditions4. However, it could bring discomfort and dust in Hot and Dry Climates. Cold Climates also need protection from chilling exterior winds and might need enclosed conditions.

(ii) Wind direction

The wind direction determines design and viability of Natural Ventilation. Wind rose diagrams are used to understand prevailing directions, frequency, speed and other factors related to wind conditions in any particular area.

(iii) Thermal Comfort and Perception

Thermal Comfort is a complex, often subjective issue determined by multiple factors. Before the advent of AC, buildings were designed according to climate and context. People enjoyed the benefits of fresh air. Now, many occupants prefer fully air conditioned spaces since they have become used to such an environment. There might be instances when the AC is too cold for comfort, but this has become the norm. Enclosed buildings behave like greenhouses2, which then need air-conditioning to cool them down. So, the need is not only to improve thermal comfort , but also address people’s perception related to it.  To address this complex issue, we could look at the following solutions.

Solution 1Custom Thermal Comfort Models – Countries could develop customized thermal comfort guidelines for Design. An example is the ‘Indian Adaptive Comfort Model’ developed by CEPT university. This is part of the GRIHA manual5 and is adapted to Indian local conditions. For example, it provides Indoor Operative temperature values for all cities in India. These are setpoints which are required as per standards to achieve thermal comfort. They are to be monitored during the operation of the building. These models could help optimize setpoints and engage in better AC design.

Solution 2 Hybrid systems – DPR Office in Phoenix, Arizona uses a hybrid cooling system. They have special High Velocity Low Speed (HVLS) fans and operable windows. Cooling is provided by moist air through Shower Towers on the facade. There is also a Solar Chimney exhausting warm air. Only when the conditions are too extreme, they switch on the air-conditioning6. A hybrid cooling system is also being designed for the new School of Design and Environment building NZEB in the National University of Singapore7. The NZEB at CEPT University is planning to utilize optimized natural ventilation coupled with a radiant cooling system2.

Solution 3Common areas could be Naturally Ventilated, (fully or partially) for starters. Since occupants spend lesser time in spaces like corridors, washrooms, lobbies, parking – such efforts might help the acclimatization process. An example can be seen in ParkRoyal Hotel @ Pickering.

park royal

(iv) Pollution and Location 

Natural Ventilation may not be possible if the outside air is polluted. Pollution could be due to traffic, dust from a construction site or other harmful substances, such as emissions from a factory.

Solution 1 | Location – Sensitive functions like schools or hospitals would ideally be located away from such areas.

Solution 2 | Natural Filters/ Barriers – If this is not possible, window opening design could be clubbed with strategies like Vegetation or Earth mounds, to act as noise barriers or to filter pollution.

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That’s all for today. We hope you enjoyed reading the article!

Next week we look at Passive Strategies: Natural Ventilation (b) in which we cover Strategies and related Issues of Natural Ventilation.

For now we leave you with these questions.

Do you know of other Commercial or large projects that are using Passive Strategies?

What do you think of the Passive Strategies mentioned above? Can you spot further practical issues that might arise?

Please share your Sustainability knowledge and experience. Our search for answers continues…..

See you next week.



  1. Rakheja A. Case Study EcoCommercial Building, Noida, India – Adapting To Climate. High Perform Build. 2013:44-52.
  2. USAID India. Net Zero Energy Buildings Initiative.; 2011. Accessed September 9, 2018.
  3. Majumdar M. Sustainable Habitats: Cooling homes…heated pockets. The Economic Times Blogs. Published 2013.
  4. BEE, USAID, PACE-D. Knowledge Centre – Natural Ventilation. NZEB. Accessed September 9, 2018.
  5. GRIHA, TERI. GRIHA V-2015.; 2015. Accessed September 9, 2018.
  6. GreenCE. Aggressively Passive: Confronting the Comfort Status Quo. Accessed September 9, 2018.
  7. NUS S. NUS breaks ground on its first Net-Zero Energy Building today! Published 2016. Accessed September 9, 2018.