Natural Ventilation

Ar. Medha Deshmukh.

Masters in Environmental Architecture

Natural ventilation is the intentional flow of outdoor air

through an enclosure under the influence of wind and

thermal pressures through controllable openings.

It can effectively control both temperature and

contaminants, particularly in mild climates.

• Natural Ventilation systems rely on natural driving forces,

– Wind

– Temperature difference between a building and its environment,

• Both work on the principle of air moving from a high pressure to a low

pressure zone.

• Mixed mode or hybrid ventilation buildings

– Natural ventilation systems integrated + mechanical support;

• It can save substantial amounts of energy.

• It may also improve the building’s indoor air quality.

• Provide very comfortable and pleasant environments for the

occupants.

Two fundamental approaches:

• Cross ventilation which uses air-pressure differentials caused by wind

• Stack ventilation which uses the increased resilience of air as it warms

up.

Cross ventilation

• Cross ventilation depends on

two continuously changing

factors: wind availability and

wind direction.

• Consequently, it is a somewhat

unreliable source for providing

air flow and thermal comfort.

Considerations when designing for cross ventilation:

• Will work well if the room is up to 5 times the width of the ceiling height.

• If cross ventilation is not possible placing windows on adjacent walls, at 90

degrees to each other, will work but limit room size to 4.5 m x 4.5 m.

Partitions should not obstruct

air path.

Design spaces so that they

are parallel to main ventilation

path.

• In stack ventilation, air movement is created by cool air being drawn into

the space low down to replace warmer air that naturally rises as it is

warmed and is then exhausted at the top.

• Stack ventilation works best in spaces with high ceilings and where cross

ventilation is not feasible.

Important points

• Climate limits the effectiveness of ventilation systems.

• The exterior air must be cooler than the interior air.

• Thus, making it only possible to reduce the indoor temperature to

around 3 degrees HIGHER than the outdoor temperature.

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Types of Natural Ventilation Openings

• Windows :

• There are many types of windows.

• Windows sliding vertically, sliding horizontally, tilting,

swinging.

• Doors, monitor openings and skylights.

• Roof Ventilators (weather proof air outlet).

• Stacks connecting to registers.

• Specially designed inlet or outlet openings.

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Natural Ventilation Rules• Buildings and ventilating equipment should not usually be oriented for a particular

wind direction.

• Inlet openings should not be obstructed by buildings , trees, signboards, or indoor

partitions.

• For temperature difference to produce a motive force, there must be vertical distance

between openings; vertical distance should be as great as possible.

• Openings in the vicinity of the neutral pressure level are least effective for ventilation.

• Openings with areas much larger than calculated are sometimes.

• The openings should be accessible to and operable by occupants.

• THIRD YEAR B. ARCH.

• Building Services &Sciences II

• Paper 100 Sessional 100 Total 200

Course Outline:

1. Natural Ventilation (passive.)

- Factors affecting comfort conditions.

- Functions, requirements, mechanism

and design

factors.