This document discusses ventilation and air movement in buildings. It covers natural ventilation strategies like wind patterns, opening positions and sizes, and stack effect. Cross ventilation and the venturi effect are explained as ways to induce air flow. Maintaining indoor air quality by supplying fresh air and removing pollutants requires careful ventilation design considering factors like wind direction, constrictions to increase speed, and opening placement and size. Various techniques are presented, like wind scoops, jets and tunnels, to study air movement and optimize ventilation performance in buildings.

1. Ventilation
Air movement

2. This lecture is about
 Fundamentals of building ventilation
 Natural Ventilation
 Wind patterns
 Openings
 Building strategies

3. Why is it necessary to ventilate?
 Air for breathing
 Adult man has frequency of breathing typically 16 times per minute –8 l/min.
 Respiration

4. Why is it necessary to ventilate?
 Indoor environment in a room has to meet level suitable for
 people and theirs activity.
 In an industrial building ventilation requirements may relate
 also to industrial processes.
 In an agricultural building all focus aims to animals.
Ventilation is one of systems keeping habitable environment.

5. Information about wind patterns and
prevailing wind direction
Functions of ventilation
Three distinctly different functions
- Supply of fresh air
- Convective cooling
- Physiological cooling
Achieved by - air movement
Ventilation
In Architectural terms, Ventilation is the
intentional introduction of outdoor air into a
space and is mainly used to control indoor
air quality by diluting and displacing indoor
pollutants; it can also be used for purposes
of thermal comfort or dehumidification.

6. SUPPLY OF FRESH AIR - Air movement around building
Wind is generated by pressure differences – so an air flow through the building is
result of pressure difference between two sides.
1.The air flow around a building
Development of positive pressure on
windward side and negative pressure
on leeward side of the building
Side elevation
plan

7. Air stream separation at the face of building Reverse flow behind tall block
Air flow grid iron pattern Air flow checkboard pattern
Air movement around building

8. Air movement around building
Form of the buildings, specially in
terms of high rise building should be
carefully planned to help the air
movement in the surroundings

9. 30 St Mary Axe, informally known as
The Gherkin, is a commercial skyscraper in
London's primary financial district.
It was completed in December 2003 and
opened in April 2004.[10] With 41 floors, it is
180 metres (591 ft) tall.

10. Air movement inside the building – opening positions

11. Air movement inside the building – opening positions

13. Cross ventilation
Lack of cross ventilation
Effect of opening positions
Pressure built up at inlet
Air flow in a
two storey
building
Position of openings
Air movement inside the building – opening positions

14. Air movement inside the building

15. Size of the openings
The largest air velocity will be obtained through a small inlet opening with large
outlet. This is partly due to the total force acting on the small area forcing air
through opening at high pressure and partly due to venturi effect.
When the wind direction is not constant and when air flow through whole space is
required , the large inlet opening will be proffered
Controls of openings
Effect of sashes
Effect of louvers
Effect of canopies
Effect ofVenetian
blinds
Air movement in and around building

16. Wind Angle at 75˚
A study done in a residential
building for understanding the
effect of wind angles

17. Wind Angle at 0˚Wind Angle at 30˚

18. CONVECTIVE COOLING – Stack effect
The driving force for the stack effect
The stack effect relies on thermal forces, set up
by the density difference (caused by the
temperature difference)between the indoor and
outdoor air and change in temperature due to
height.)

19. Convective cooling – Stack effect

20. Various techniques for ventilation

21. The Venturi effect is the reduction in fluid pressure that results when a fluid flows
through a constricted section of pipe.
Venturi effect
To increase speed of air
to reduce temperature.

22. when the air flow is channeled and restricted, the pressure rises
and the velocity increases. This is called the venturi effect
By using these principles and
understanding how air moves
and acts similar to a fluid, like
water, we can visualize wind
patterns on different sites and
in different conditions.
Venturi effect
Vegetation creating the venturi effect

23. A local wind created by acceleration
of the airflow through a gap,
constriction, or channel
Changing the direction
by diverting.
A strong, low-level wind through
channel between two structures
Lack of cross ventilation

24. Humidity control
Wind scoop – in hot and dry climate humidification is necessary which
can be associated with evaporative cooling
Functions of wind scoop
controlled air supply
Filtering out sand and dust
evaporative cooling.
humidification

25. Various techniques for ventilation

26. Open jet wind stimulator
On basis of experiments following factors can be isolated which affect the
indoor flow
- Orientation - size of openings
- Cross ventilation - controls of openings
- Position of openings
Experiments to check ventilation in models

27. Closed Wind tunnel