Natural Ventilation of Buildings in India

Natural ventilation:

➢Natural ventilation is the process of supplying air to and

removing air from an indoor space without using mechanical

systems.

➢It refers to the flow of external air to an indoor space as a

result of pressure differences arising from natural forces.

Philosophy of natural ventilation:

➢ Thermal comfort requirements of building occupants

➢ Thermal performance of the building structure

➢ Impact of the buildings form and its openings

➢ Constraints of the local and regional climate

Functions of ventilation:

➢ The main functions of ventilation are:

▪ The supply of fresh air,

▪ Physiological cooling,

▪ Removing heat from, on adding it to.

Natural ventilation:

➢ Natural ventilation is run by itself by the force of wind

and temperature.

➢ It creates pressure inside and outside of the building so

the ventilation work.

➢ Wind pressure on a building depends on wind direction,

speed and the shape of the buildings.

➢ Temperature differs between indoor and outdoor as there

is different type of air and pressure.

➢Air flows through opening in ventilation.

➢ The pressure created is used to balance the flow of air

through openings as the air root through the building.

Wind effect:

➢ Wind is one of the main

source of ventilation.

➢ The wind pressure

differs from the height of

the building.

➢ In cities there are huge

buildings, so the wind is

4m/s.

➢ In sub urban area

buildings are of less height,

so wind speed is 6.5m/s.

➢ In open countries there

are less buildings so wind

speed is 10m/s.

Temperature effects:

➢ This effect is also

known as stack

ventilation .

➢ This creates vertical

pressure as the hot air

rises.

➢ For each degree of

temperature difference

between indoor and

outdoor.

➢A pressure

difference is set up of

above 0.04 Pa per

meter of building

height.

Types of ventilation:

➢ Single sided ventilation

➢ Cross ventilation

➢Stack effect

➢Reverse stack effect

There are four main ways in which buildings are naturally

ventilated:

Single sided ventilation:

➢ Single sided ventilation occurs when large ventilation openings are situated on one

external wall only.

➢ Exchange of air takes place by wind , by outward openings interacting with the

local external airstreams, and by local stacks.

single sided ventilation

Cross ventilation:

➢ Cross ventilation depends

on windows or other openings

on opposite sides of the

building being sufficiently

opened which demands the

cooperation of the occupants.

Cross ventilations

Stack and reverse stack ventilation:

➢ On a hot summer afternoon with little wind the wind tower

will be hot inside because of a stack effect that draws the

warmer air up the tower which is replaced in a summer room

below by cool air from the courtyard.

➢ On summer windless mornings the inside of the tower

having been cooled by the night air will draw air in from the

warmer outside in a reverse stack effect pushing the north

uncomfortable air through the summer room in reverse .

In the tower heats up the stack reverses and cooler courtyard

air again is used.

➢Wind tower design are now being use for construction in

temperate regions.

Hotter region

➢People are experimenting with soar chimney in which

transparent wall in the wind tower facing the sun introduces sun

light in to the tower shaft and heats the opposite high mass

wall.

➢The increase heat build up in the tower enhances the stack

effect and leads to a faster draw of air .

➢The sunlight penetration should not be excessive.

➢Example of cool tower driven by the reverse stack effect is

that at the desert architecture research unit in Israel. Water

spread in the center of the building cools the air which leads to

a drop in temperature and introduces cool air while venting the

hot air form the apex of the adjacent wall of the building.

cooler region