NATURAL VENTILATION STRATEGIES IN TROPICAL CLIMATE

INTRODUCTION - 

Natural Ventilation is not new.

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Only 150 years ago mechanical ventilation has been introduced/used.

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Prior to that period, all enclosure occupied by humans were naturally ventilated.

EARLY DESIGN OF NATURAL VENTILATION - 

Early designs of natural ventilation were evolved from experience (long-term experiments at full scale).

What are the challenges of ‘Natural Ventilation’ in modern buildings? - 

Modern buildings are more demanding

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Standards for health and comfort have to be met

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Satisfying requirements for low energy consumption and sustainability

TRADITIONAL APPROACHES Hot Air

Stack Effect

Fresh Air

Hot Air

Wind-Driven Cross Ventilation

Fresh Air

Hot Air Fresh Air

Wind-Driven Cross Ventilation

PASSIVE DESIGN STRATEGIES IN TMH Natural Ventilation

Control Solar Radiation

Low Thermal Material

Control Solar Glare Protect Against Heavy Rain

Traditional Malay House strategies to attain optimal climatic control which include; 1. Allowing adequate ventilation for cooling and reduction of humidity. 2. Using of low thermal capacity building materials so that little heat is transmitted into the building. 3. Controlling direct solar radiation 4. Controlling glare from the open skies and surroundings 5. Protecting against heavy rain 6. Assuring adequate natural vegetation in the surroundings to provide a cooler microclimate

What are government buildings that using natural ventilation? - 

Schools (Classroom,s workshops, canteen, etc)

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Mosque, surau

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Quarters etc.

ADVANTAGES & DISADVANTAGES OF NATURAL VENTILATION Advantages

Disadvantages

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-  Limited to provide cooling in hot and humid climates. -  May need to combine with some sustainable cooling system to achieve comfort. -  Errors in the design of Natural Ventilation may be difficult to correct -  Air flow rates and the pattern of air flow are not constant -  Deep plan and multi-roomed buildings may not be possible -  Unsuited to noisy and polluted locations -  Some designs may present a security risk

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Suitable for many types of buildings Contributes to a sustainable building environment Reduces capital and operating costs No electricity; reduces energy Less maintenance Occupants have control over their environment Does not require space for plant rooms or ducts No fan or system noise

NATURAL VENTILATION DRIVING FORCES The air motion in a room is generated by sources of 1.  Momentum (wind velocity) 2.  Buoyancy (temperature difference) MOMENTUM -  - 

The air flows through the openings Vary according to some factors; wind speed, wind direction, opening size etc.

Larger opening size = Higher airflow Greater pressure difference = Higher airflow

NATURAL VENTILATION DRIVING FORCES (CONT.) BUOYANCY -  Heat transfer at solid surfaces is the major source of buoyancy -  Warm air is less dense than cool air (more buoyant); works when indoor air is warmer than outdoor air.

Hot Air - - - (Less Dense)

-  Variations of the internal temperature can effect the flow rates Cool Air ++++ (More Dense)

MALAYSIA’S WIND SPEED DATA

Wind Speed - 

Average wind speed is low (