Passive Strategies: Natural Ventilation (b)

Last week we started our series on Passive Strategies in Buildings. We kicked off with Natural Ventilation (a)Why it’s needed, What needs to be doneHow and Factors important for it.

This week we look at Strategies and related Issues for Natural Ventilation.

  1. Zoning
  2. Orientation and Form
  3. Building Depth
  4. Fenestration
  5. Advanced Strategies

(1) Zoning

Building functions can be zoned according to the ventilation strategy for effective management and energy conservation. This is seen in Akshay Urja Bhavan1 where spaces are divided into zones according to setpoints – Apex, Controlled and Passive. Only around 12% of the area is air-conditioned. Mist cooling systems are used for the Controlled and Passive zones.

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(2) Orientation and Form

Buildings should preferably be oriented between 0o and 30o with respect to the prevailing wind direction2. The building form can incorporate courtyards or verandahs (transitions zones between inside and outside) for increased ventilation and thermal comfort. These features temper down the harshness of the exterior environment, providing shade and cool breezes in summer.

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(3) Building Depth

unit thick principle
Unit Thick Principle in 2 projects by WOHA

A building depth of around 15 meters or less would enable Natural Ventilation and Daylighting. This is an assumption based on our research of many buildings by WOHA applying their Unit thick Principle. Some buildings may not be able to achieve less depth due to larger functions such as Industrial labs.

Solution | Fragmentation of Form – Such buildings could employ courtyards or atriums to break the overall form, thus enabling light to penetrate or air to flow better. (eg. Cleantech One) Fragmentation of form is also seen in Indira Paryavaran Bhavan3, where two North-South oriented blocks are separated by a centrally running  public spine.

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(4) Fenestration

  • Location, Sizing, Area – The location and size of windows, should take into account the wind direction and the ‘Living Zone’. The total area of openings should be a minimum of 30% of floor area2.
  • Window to Wall Ratio – The Window to wall ratio (WWR) should fall between 20-40% for Commercial buildings. In any case, it should not exceed 60%4.
  • Operable windows – The windows should preferably be operable with a staggered alignment. Operable windows may present certain issues. In the case of hotels for example, people might leave windows open when the air-conditioning is on, which would affect energy costs. Operable windows could also have safety implications.

Solution 1 | Sensors – Some hotels install sensors that automatically shut off air-conditioning when windows are opened.

Solution 2 | Individual Project Detailing – Safety concerns would need to be addressed in projects individually, through railing design details, selective openings or special locking mechanisms.

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(5) Advanced Strategies

(i) Air Earth tunnels


A 16 km (once campus completed) tunnel network of Air Earth tunnels, will be running 4 m below the ground in NIIT University, Neemrana Campus. Surface temperature and seasonal variations do not penetrate below this depth, keeping air temperature constant throughout the year. Fans will pull cool air through these tunnels. This would then be taken through precipitators to eliminate dust and would be supplied to the building through ducts. The result! – Pleasant 25oC temperatures indoors, without the use of air-conditioning, when temperatures outside are nearing 50oC5.

(ii) Wind Tower

These are utilized widely in desert climates (eg. Iran, Saudi Arabia). Tall towers are built with openings facing the prevailing wind direction. The openings are narrow and the towers may contain misters or other moisture creating devices. As the tall tower catches winds, air moves down the tower, cooling on the way and is used in the building. A similar system using Shower Towers is used at DPR Office, Phoenix.

(iii) Stack effect

According to the principle, warm air from an area would rise, making space for cooler air. This would generate a loop of air circulation. This effect can be seen at building scale or even at room level. In Indira Paryavaran Bhavan, the central courtyard spine coupled with well placed building punctures, generates the ‘Stack Effect’ at the building scale. The IRRAD Building, although using air-conditioning, is utilizing a similar principle. The vents are placed near the floor, instead of the ceiling. Cool air enters the room at a lower level and it rises as it become warm6.

(iv) Displacement Ventilation

In Neemrana University, the cool air from ducts is introduced at lower levels in rooms. This pushes warm air in the room upwards, which is then exhausted through openings in higher parts of the spaces. It is similar to the stack effect, but here an additional push is being provided by the introduced cool air, to get the circulation loop going.

(v) Wind Scoops

Wind Scoops like the one used in CapitaGreen can channel air into a ‘Cool Void’. This brings cool air from a higher altitude, deeper into a high-rise building. Air flow, such as that channeled by CapitaGreen maybe blocked by surrounding buildings in a different scenario.

Solution | City Planning and Studies – This leads to the need for city planning and studies like Computational Fluid Dynamics (CFD) to ensure these strategies are workable at a city level. This would help avoid “dead air zones”, wind canyons and other undesirable wind related events. This becomes especially important in city centers with greater density and multiple high-rise structures.

(vi) Solar Chimney

The DPR Phoenix Regional Headquarters in Pheonix, Arizona use solar chimneys to exhaust warm air from the building.

(vii) Evaporative cooling

This technique utilizes the latent energy used to convert liquid to gas. As water evaporates, its phase changes, which results in a cooling effect. This technique has been used widely in desert coolers.

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That’s all for this week. Hope this was useful! As always, please let us know your thoughts, suggestions, queries, opinions. Your views will make this exploration richer!

Thank you!



  1. BEE, USAID, PACE-D. Case Studies – Akshay Urja Bhawan. NZEB.
  2. BEE, USAID, PACE-D. Knowledge Centre – Natural Ventilation. NZEB. Accessed September 9, 2018.
  3. CA(NDR), CPWD. Sustainable Architectural Built Environment.
  4. GRIHA, TERI. GRIHA V-2015.; 2015. Accessed September 9, 2018.
  5. Bhandari P. Let buildings breathe. Times of India Jaipur. Published 2009.
  6. Somvanshi A. Simply creative. DownToEarth. Published 2015.

E@BS 4/5: Residential – Skyville@Dawson

This is Segment 4 of our Chain of posts focused on ‘Energy @ the Building Scale’.
[Extension of Part 4/5: The Red System (Energy), Singapore – Published: 28th May 2018]

clusters editted
Plan diagrams showing Apartments Clusters

Skyville@Dawson is a 111,106 sq.m., 48-storey1 public housing project by WOHA Architects in Queenstown, Singapore. It is one of two Build-To-Order (BTO) projects commissioned by Singapore’s Housing Development Board (HDB), as part of their “Remaking Our Heartland” initiative (the other being SkyTerrace@Dawson by SCDA Architects)4. This “housing-in-a-park” concept would show transferability in future projects and towns like – Waterway Terraces, Bidadari, Punggol Northshore, Tampines North6. It is the first housing development to be awarded the GreenMark Platinum Rating10. Skyville@Dawson’s Sustainable Design features including Passive Strategies are elaborated below-


    • Orientation
    • Clustering and Modules
    • Unit Thickness
    • Breathability – Horizontal Air Movement
    • Breathability – Vertical Air Movement
    • Horizontal Green
    • Site Integration with Green and Blue



(i) The Building is placed with its longer facades facing the North-South9 directions. This reduces exposure to the East and West directions, that are normally difficult to shade.

shadow studies
Shading Studies for Skyville@Dawson

Clustering and Modules

(i) 8 apartments in plan(as seen in Plan diagrams above), surround a courtyard. This cluster is repeated 2 more times, to create 3 sets of apartments enclosing courtyards. This configuration also provides self-shading, especially from low angle rays from the East and West directions (as seen in the Shadow Studies above).

(ii) In Elevation, 12 clusters form villages, each comprising of 80 apartments.

villages with border
Perspective diagrams showing Apartment Villages

(iii) The apartment layouts are column and beam free4. This provides the possibility of 3 layouts for residents – reducing wastage, allowing flexibility for multiple functions, family size and the future.

(iv) For standardization, efficiency and to reduce wastage, only 5 window types2  have been used in the entire development.

(v) The design uses precast and prefabricated10 elements to avoid errors and reduce wastage. This feature could also contribute towards LEED BD+C v4 CreditConstruction and Demolition waste management. 

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Unit Thickness

(i) The individual apartments are approximately 11 meters across in width, thus applying the Unit Thick Principle. Apartments also have openings in all directions. They are thus naturally ventilated and day lit, reducing artificial cooling and lighting costs.

unit thick
Plan diagram showing Unit Thick apartment blocks

Breathability – Horizontal Air Movement

(i) The clustering arrangement around courtyards, and the repetition of this module linearly, enables horizontal air circulation.

hori air movt
Plan diagram showing Horizontal air movement through courtyards and building block gaps

(ii) Common areas (Lobbies, Corridors, Staircases) and Apartments are naturally ventilated. Many units have not installed Air-conditioning3.

Breathability – Vertical Air Movement

(i) With minimal obstructions and the creation of Canyon like spaces, air moves vertically through the towers – accentuating the breezy atmosphere. The interaction of this air with greenery from sky gardens at intermediate levels, cools this air through evapotranspiration.

vertical air movt
Section diagram showing Vertical air movement through the towers

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Horizontal Green

(i) ‘Sky Terraces’7 are located every 12 floors. These are designed as community spaces, where people can collect to interact with neighbors or simply visit to relax and enjoy the lush greenery.

hori greenery
Sky Gardens and Rooftop Garden

(ii) A ‘Sky Park’7 on the roof has planters, hedges, and beautiful city views. Photovoltaics3 power the common area lighting.

Site Integration with Green and Blue

(i) A 150 m long bio-swale (gently sloping ditch with specific plants) filters and treats site stormwater before discharging it into the city drainage system5. Another example of a bio-swale – water treatment and recycling loop can be seen in Kampung Admirality.

site green blue
Site Plan diagram showing location of Parks, Plaza and Bio-swale

(ii) The site is an ungated3 community, with Public Parks and Amenities that cater to the residents as well as the general public.

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(i) Monsoon windows8 on the facade can be kept open during rains, thus providing cool breeze without wind-blown rain entering the home. A similar more advanced Monsoon Window design is utilized in another high-rise residential building – 1 Moulmein Rise, Singapore.

(ii) The walls on the facade have horizontal and vertical sunbreakers5. Balconies or horizontal ledges9 are used to provide shading for openings.

(iii) Double-height verandas10 on the ground level provide pleasant public spaces overlooking the parks.

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That’s all for today! We hope you enjoyed this segment. As always, we would love to hear your thoughts, suggestions, queries, opinions.

Thank you!

See you next week.

Graphics : Selected graphics are produced as part of a team project for M.Sc. Integrated Sustainable Design at National University of Singapore (Building Semester – Stage 1 – Complex Living Systems). Group Members – Gajender Kumar Sharma, Aditi Bisen, Huang Hongbo, Zhao Yanming
Text: Aditi Bisen

References/ Additional Reading:

  1. CTBUH. SkyVille @ Dawson – The Skyscraper Center. Accessed July 18, 2018.
  2. Furuto A. SkyVille @ Dawson / WOHA. ArchDaily. Published 2012. Accessed July 18, 2018.
  3. ArchDaily. SkyVille / WOHA. Published 2017. Accessed July 18, 2018.
  4. HISTORYSG. SkyVille@Dawson and SkyTerrace@Dawson are launched – Singapore History. Published 2015. Accessed July 18, 2018.
  5. Australian Design Review. An exploration in affordable housing: Skyville @ Dawson. Published 2016. Accessed July 19, 2018.
  6. Zachariah NA. Dawson’s SkyVille and SkyTerrace projects are raising the bar for stylish public housing. The Straits Times. Published 2015. Accessed July 19, 2018.
  7. Willis C. The Skyscraper Museum: GARDEN CITY | MEGA CITY: WOHA rethinks cities for the age of global warming. Accessed July 24, 2018.
  8. Pearson CA. SkyVille@Dawson|Gardens in the Sky. Architectural Record. Published 2013. Accessed July 24, 2018.
  9. BCA Singapore. BCA GreenMark Buildings Directory | Skyville @ Dawson. Accessed July 26, 2018.
  10. world-architects. SkyVille @ Dawson WOHA. Accessed July 26, 2018.