Natural ventilation uses natural forces like wind and buoyancy to introduce fresh air into buildings. It ventilates spaces by providing oxygen, diluting contaminants, and promoting air movement for comfort. There are three main natural ventilation methods: single-sided ventilation using only openings on one wall, cross-ventilation using openings on opposite walls, and stack effect using cooler air intake on the lower sides and warmer air exhaust on the upper sides. Natural ventilation has advantages like energy savings, no need for ducts or machinery, more natural light, lower maintenance costs, and potential health benefits compared to mechanical ventilation. Factors like wind direction, building orientation, topography, vegetation and the size and placement of openings need to be considered for effective

1. Natural ventilation uses the natural forces of wind and
buoyancy to introduce fresh air and distribute it
effectively in buildings for the benefit of the occupants.
The reasons for ventilating a space with air are as follows:
1. Ventilation air provides oxygen that is needed for
human life processes; poor-quality air deficient in
oxygen with consequent high CO2 levels impedes
clear thinking and concentration.
2. Ventilation air dilutes; the contaminants may be CO2
from respiration, odors secreted through the human
skin, cigarette smoke, or emissions from other
process such as dust, allergens, aerosols, toxic gases,
and particulates in general.
3. Ventilation promotes and directs air movement in the
space, removing excessive heat and/or moisture
essential for comfort and well-being.

2. • There are three methods to carry out natural
ventilation:
• Single-sided ventilation
• Cross-ventilation
• Stack effect

3. Single-Sided Ventilation
This method involves having openings only on
one external wall and generally towards the
wind-direction. Air exchange happens through
wind turbulence. Single-sided ventilation is not
used as often as it is ineffective compared to the
other two ways.

4. Cross-Ventilation
In this method, openings are located such that the
ones at the receptive end allow maximum inflow of
fresh air and the outlet openings are placed such that
the air gets circulated in the space efficiently and is
pushed out with the inflow of fresh air.
In areas with high wind speeds, smaller openings are
preferred in the wind-ward directions and larger in the
lee-ward or exhaust direction. In case of lower wind
speeds, the opposite of the previous is preferred to get
better quality air.

5. Stack- Effect
This method is based on the fact that cooler air is light in
weight and hot and stale air is heavier. Receptive openings
are given on the lower sides in the wind-ward directions
and for outlet, openings are given on the upper side.
This arrangement pushes out the stale air from the space
whenever fresh air is drawn inwards.

6. • Advantages Of Natural Ventilation System
• Energy saving
• Buildings are one of the highest energy-consumers and
producers of carbon dioxide. Natural ventilation systems do
not emit carbon dioxide or any other harmful substance.
• They do not require electricity or any other fuel to carry out
ventilation
• No pipelines and ducting
• Unlike mechanical ventilation or air-conditioners, natural
methods do not require pipelines or ducts which incur
extra expenditure and also in some cases spoil the
aesthetics of the building

7. • More natural light
Anything natural is good for health. At least, most of the
times. Large openings not only bring in more natural air but
also more natural light. In case of harsh sunlight, you can
always cover them up with beautiful drapes!
• Efficient use of space
Air handling units or any other machinery require space for
installation, whereas, natural ventilation needs only openings.
The space that could be occupied with machinery can now be
used for various other purposes.
Low maintenance
The absence of pipes, ducts and machinery will need no
maintenance except for regular dusting the openings, which,
is definitely not a herculean task!

8. • Less expensive
Except for spending on frames, shutters and
drapes for openings, there is no expenditure for
anything else. No machinery means, no extra
costs. Fresh air is free, isn’t it?
• Less health-issues
Mechanical ways might cause disorders and
unpleasant sounds (if machines are not
maintained properly). Natural ventilation can
reduce such sick-building syndrome symptoms.

9. • Natural ventilation is dependent on factors like:
• Wind Direction And Orientation Of Building
• North-East and South-West are generally considered as the
direction of winds. Therefore, the placement of openings
should be done considering these directions
• Topography
• An uneven topography may hinder the movement of wind
due to which the placement, size and types of openings may
be altered.
• Vegetation / Landscape
• Having more vegetation definitely cools the surroundings and
absorbs noise. But, apart from these, trees also act as source
of fresh hair.

10. • Size And Types Of Openings
Avoid parallel placing of inlets and outlets and
partitions near inlets. Openable windows are
more efficient as they could be closed and
opened whenever required. Glass panels
could be used for shutters to get sunlight even
while shutters are closed.

11. During the day the sun heats up the structure warming the internal air which
then rises through the wind tower, as illustrated in Fig. At night the cool night
air lowers the temperature of the structure and the internal air and the
heavier air then flows downward cooling the internal spaces after the heat of
the day.

12. Natural ventilation strategies can be integrated into design

13. Thank you