Ventilation is the intentional movement of air into and out of a building. It provides acceptable indoor air quality by removing odors and delivering fresh air either naturally through forces like wind and stack effect, or mechanically. Standards for ventilation are based on factors like floor area, cubic footage of air per person, and recommended air changes per hour. Proper ventilation is important for thermal comfort, indoor air quality, and health.

2. Dictionary --‘intentional movement of air from outside
a building to inside’
Excess of ventilation - discomfort
Control of the quality of air - by modifying the
temperature, humidity and purity
Aim –
a. provide an environment, which is thermally
controlled and comfortable,
b. gives a sense of well-being and
c. reduces the risk of transmission of airborne
diseases.

3. VENTILATION AIR
The air used to provide acceptable indoor air
quality
It removes the bad odours
Delivered either naturally or by means of
mechanical ventilation
Can change the temperature of air or its moisture
content depending on the requirement inside
the building.
Air exchange rate.

4. VENTILATION STANDARDS
To achieve a sense of freshness in a room and remove body
odours.
(a)Floor space :
the product of the length and breadth
optimum floor space requirements per person - 50 to 100 feet.
(b) Cubic space of area :
Earlier prescriptions - fresh air supply of 3000 cu feet of air
per person per hour.
beyond 12 feet, not taken into account
Current standards - 1000 to 1200 cu feet per person per hour
(c) Air change
The recommended number of air changes
living room - 2 to 3 in an hour,
Work rooms and assemblies - 4 to 6 per hour.

6. NATURAL
forces of nature such as wind,
ambient temperature and air
pressure
• Diffusion / infiltration
• Wind driven
• Stack driven

7. DIFFUSION / INFILTRATION
Through openings, joints and cracks
Buildings - kept under slightly positive pressure
Helps in moisture management and humidity
control inside the rooms

8. WIND DRIVEN VENTILATION
Perflation
Aspiration
Cross ventilation.
It creates areas of positive pressure on the windward side of
the building and negative pressure on the leeward side
and the sides of the building.
The shape of the building is crucial in creating wind
pressures that will drive air flow through its apertures.
Simple shapes - improve the ventilation
Complex shapes - turbulent air flows
Adv - readily available, economic to implement, could be
controlled
Dis- unpredictability in speed and directions, air quality is
not controlled and could introduce pollutants & may
create draughts and discomfort

9. STACK DRIVEN VENTILATION
The warmer air will have lower density and be more
buoyant and thus will rise above the cold air,
creating an upward stream.
To have optimum ventilation – the inside and outside
air temperatures must be different
The greater this temperature difference the greater the
stack effect.
ADV - does not rely on wind , flow is relatively stable
with a greater control.
DIS - lower magnitude, reliance on temperature
differences, restrictions due to building designs &
may introduce pollutants.
Used in mills, boiler rooms, warehouses and industrial
plants.

11. CEILING FANS, TABLE OR FLOOR FANS
Used to circulate air within a room for the purpose
of reducing the perceived temperature,
because of evaporation of perspiration from the
skin of occupants.
Do not introduce outside air inside the room
Air-coolers are used in hot & dry conditions
They comprise of a chamber whose walls are
made of straw, which is kept cool by pouring
water & evaporation of water .
A cool environment is thus created inside the
chamber and a fan blows cool air inside the
room

12. EXHAUSTS
The indoor air is extracted out with the help of
mechanically driven fans.
Used in combination with the doors and windows
since exhaustion of air outside the room
creates a vacuum and this needs to be replaced
by fresh air
Exhausts are useful in industries especially where
excess heat is generated.
In residential areas - for extricating smoke or
odours.
The exhaust blades should be cleaned & well
maintained to ensure Their long life

13. PLENUM VENTILATION
Air is blown inside a room by the use of fans and
it enters through ducts.
Creates a positive air pressure inside the room.
Combined with exhaust mechanism it creates
‘balanced ventilation’.
Used along with air conditioners, to supply air
inside the building such that fresh air is
circulated to leave out the odours and
pollutants.

14. AIR CONDITIONING
A system which provides a combination of cooling,
ventilation and control of humidity
The system has a refrigerant providing cooling through
a ‘refrigeration cycle’. This cycle comprises of four
elements
Compressor , condenser, Evaporator-dehumidifier &
fan.
Can be stand-alone systems or a part of central air-conditioning
systems.
Central air-conditioning system should be installed at
the time of construction,
The split air-conditioning where the fan coils are
connected to remoter condenser unit using piping
instead of ducts.

15. DEMAND CONTROLLED VENTILATION
Reduces the energy consumption in a building,
while maintaining adequate air quality.
No fixed air replacement rate
Carbon-dioxide sensors control the ventilation
rate dynamically
based on emissions of actual building occupants.

16. HVAC
HVAC stands for ‘Heating, Ventilation and Air-
Conditioning’.
Important in those places where humidity and
temperature must be closely regulated while
maintaining healthy and safe conditions inside
buildings.
To ensure thermal comfort, accessible indoor
quality at reasonable installation, operation and
maintenance costs.
HVAC systems determine the room air
distribution i.e. how air is delivered to and
removed from room spaces.

17. VENTILATION REQUIREMENTS
. The factors which determine the difference in
ventilation are :
●● Type of buildings
●● Size of the buildings and the floor areas.
●● Type of roof
●● Locally prevalent wind directions
●● Number of persons occupying the room
●● Proximity to commercial or industrial areas
●● Sanitation of the surrounding area
●● Nature of work being carried out inside the
buildings
●● Geographical locations such as closeness to
sea, large water bodies, hilly areas