REQUIREMENT OF VENTILATION IN THE BUILDING





Ventilation is defined as the process of changing the air in a room. It is not the total volume of air present in a room that matters but the rate of movement of the air. The basic idea of ventilation is to adjust the flow of air currents through the rooms, corridors, etc. in such a manner that constant freshness remains in them. Moreover, neither it should create draught in a room nor staleness of air be perceptible.

Following are the advantages of good ventilation :

(a) It removes foul air (due to respiration) from inside a room and supplies fresh air.

(b) It checks the concentration of bacteria through the continuous change of air.

(c) Unpleasant odor due to humidity and warmth is also removed.

A well-ventilated building is a sign of health and comfort but on the contrary, deficient ventilation leads to discomfort and the germs of various diseases bread.

Ventilation of a building can be achieved by the following two methods or combination of theirs.

Natural Ventilation

In the air by the heat of the sun, convection currents sets in, which result in the movement of air. By providing doors and windows in the opposite walls of a room, cross ventilation of the building is achieved which facilitates quicker movement of air. With respiration, the air present in a room gets heated up and rises up which finds its way out through the ventilators provided just under the head of the roof slab.

For good ventilation and lighting of a room, it is specified that the clear window area should not be less than 1/10 of the floor area or 1/100 of the cubical contents of the room

In addition for every 10-15 cubic meters capacity of a room, a ventilator just below the roof slab (but not above 3.5 m) should be provided which should have an area of 0.15 sq. meter.

Artificial Ventilation

It is also termed mechanical ventilation. Where there are lesser means of natural circulation of air, exhaust fans are provided in a room to expel the air out and in turn, fresh air enters into the room through doors and windows. Similarly, instead of expelling the air, air can be blown into a room. Anyhow, the main aim is the renewal of fresh air without creating a draught. In case of air conditioned buildings, arrangements both for extraction and input of air are provided by mechanical means.

PLANNING OF VENTILATION IN BUILDINGS

The following points should be kept in mind while planning ventilation in residential and public buildings

1. Vent openings in a building should be properly distributed and should be located on the windward side at a low level. The outward opening should be on the leeward side at a higher level near the roof.

2. It is always preferable to have equal size openings for outlet and intel though it is practically not possible. When outlet opening is provided only in the roof, the intel must of a larger area for efficient flow.

3.Normally outlet openings on the shorter side and intel on the longer side of the rooms provide better ventilation.

 4 Inlet and outlet openings should have no obstructions like trees, other buildings, signboards, etc.

5. Cross ventilation (providing doors and windows in the two opposite walls of a room just facing each other) helps in more air changes and hence improves ventilation of the room. But due to cross-ventilation air stagnation pockets are formed and air circulation is restricted only to a limited portion of the room.

6. The height of the room should be in proportion to its size, the number of users, nature of the activity, etc. The efficiency of ventilation depends on the height of a room and the location of outlet and inlet openings.

7. For the exit of smoke or fumes, flue holes should be provided in the roof.

8. All outlet and inlet openings should preferably open in the open spaces or courtyards.

STANDARD NORMS OF NATURAL VENTILATION

For the various type of buildings in our country the National building organization, I.S.I., and Central Building Research Institute have set certain norms and procedures to be followed for natural ventilation. These are :

1. Area of inlet openings should not be less than 1/10th of floor area for residential buildings and 1/8th for buildings such as offices, schools and colleges, hospitals, etc. other than factories, workshops, and chemical industries.

2. There must be at least one window or ventilator in every room.

3. The inlet openings can be permanent or casual. Permanent opening should

be provided by air bricks or cement mesh or steel grills etc.

4. All rooms must have at least one window on the outside wall and this inlet

must be free from any obstruction.

5. The outlet openings should be provided near the roof on the leeward direction preferably, without any obstruction.

COMFORT CRITERIA

The functional planning of any type of building for creating a good atmosphere and providing a living comfort is necessary Man-Made environment is that the environment which is found by the physical surroundings that a man builds for himself for his living, working, and recreation. A good environment is highly essential for the well-being of the people and can be achieved by improving their living conditions through the construction of good houses. Good houses mean houses that are well planned for efficient and comfortable living. Light is one of the criteria for comfortable living. Daylight, free from glare at a desirable time and direction is essential for any type of building. Sun-light promotes healthy and efficient activities particularly industrial building, creates a pleasing environment, helps in eliminating germs of diseases, mosquitoes, and flies. Too much light that too during summer is very much undesirable. For industrial building natural light is a boon as it increases the efficiency of workers and reduces the cost of power on artificial lighting.

Construction and planning of various components of a building are also important criteria of comfort. Sometimes psychological feelings also disturb the comfort of living in a building.

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