Ventilation of Building
1. Introduction
Ventilation is the process of changing the indoor air with out door air. The process is carried
out to maintain the indoor temperature, air motion and humidity. These factors are related to
thermal comfort of the living space. The design of buildings plays a vital role in ventilation.
So, it is necessary for the engineers to keep a close eye on all the aspects of ventilation
while designing a building(Chapter, 2005). The good indoor quality is closely related to
ventilation but there are some other factors which should be kept in mind along with it. For
example: in the air polluted environment, the ventilation alone is not enough to maintain the
thermal comfort of indoor environment. Some kind of air treatment process such as filtration
must be incorporated with ventilation. The design of particulate capture is also important
than the bulk ventilation. The system must have capability to remove enough particulate
matters from indoor air. This process is described as ventilation effectiveness. The sources
of air pollution and their impact must be incorporated while considering overall impact of
ventilation(Standard, 2004).
2. Objective
The objectives of ventilation are as follow
Replacement of indoor air with fresh outside air
Attainment of thermal comfort by maintaining humidity and temperature.
Removal or dilution of particulate matter
3. Natural Ventilation
Natural ventilation is the process of replacing indoor air with out door fresh air. For this
purpose, there is an opening in the roof of the building. This opening serve as a pathway for
the removal of warm and polluted indoor air. This system does not utilize a mechanical
device and uses energy from the wind and buoyancy to replace the indoor air with fresh air.
The pressure difference between different sections of building is the key of natural
ventilation. Natural ventilation can be used to remove the particulate matters and maintain
the thermal environment of the living space. Natural ventilation should be selected because
the process is cheap. Also, there is no carbon production. The modification is not required in
this system because it is directly linked with the environment. The process is used to provide
the cooling effect during night and to lower the indoor temperature during day time(Asfour,
2015).
3.1 Types of Natural Ventilation
There are two types of Natural Ventilation which are explain as follow
Buoyancy Driven
This process utilizes the low density of inside warm air to replace it with fresh air. For
this purpose, there are two openings. One at the top and other at the lower side. The
warm less dense air rises up and escape from top opening. When warm air is removed,
the pressure difference is created which pushes the outside fresh air inside.
Wind Driven
This process of ventilation is simple and depend on the movement of wind. This is also
known as cross ventilation or unilateral ventilation. The direction of wind motion is
utilizing to remove the air from the inside(Siew et al., 2011).
4. Mechanical Ventilation
As the name suggests, this type of ventilation utilizes a mechanical device to remove the
inside polluted or warm air and replace it with fresh air. In most cases, fans are installed
wither on the walls or directly on the windows. Temperature has a key role in this type of
ventilation. For example: in hot weather, a positive pressure system is used which pushes
the air towards the walls and prevent them heating the inside of the room. In cold weather,
negative pressure system is used to prevent condensation. In a positive pressure system,
there is adequate amount of air inside the room while in negative pressure system air is
pushed inside from outside. In between these two extremes, there is a balanced system
which operates between positive and negative pressure system(Kamendere et al., 2013).
4.1 Types of Mechanical Ventilation
There are four types of mechanical ventilation which are explain as follow
Exhaust Only
In this type of mechanical ventilation, the pressure of inside air is reduced which pulls
the fresh air inside throughs leaks of the building. There is no special equipment to pull
the fresh air inside. This system is simple and economical. Only a fan is required which
is installed at the exhaust. This type is feasible for colder climate.
Supply air Only
In this type of mechanical ventilation, the outside air is forcibly pushed inside the
building. The indoor air is pressurized and air from outside is pushed inside by using a
fan. This forced movement of outside air pushes the indoor air outside throughs leaks in
the walls of the building. This system is simple but costly. Central fan integrated system
is required. This type is feasible for hot climate.
Balanced
The combination of supply air and exhaust system forms a balanced system. The
outflow of inside air and inflow of outside air are almost equal in this type of mechanical
ventilation. This system can be unitized in both hot and cold environment.
Energy Recovery
In this type of mechanical ventilation system, waste energy is recovered. This can be
done by supplying heat energy from exhaust air to fresh air to raise its temperature.
This system finds its application in heating ventilation. The cost of heating is reduced to
a large extent because no addition source is utilizing to raise the temperature of
incoming air. During the summer, the cooling price is reduced in the similar way(Babota,
2014).
References
ASFOUR, O. 2015. Natural ventilation in buildings: An overview.
BABOTA, F. 2014. MECHANICAL VENTILATION SYSTEMS WITH HEAT RECOVERY FOR REFURBISHMENT
PROJECTS AND NEW BUILDINGS. Bulletin of the Polytechnic Institute of Jassy, CONSTRUCTIONS.
ARCHITECTURE Section, 60, 39-50.
CHAPTER, T. C. J. I., ATLANTA, GA 2005. Fundamentals Volume of the ASHRAE Handbook. ASHRAE.
KAMENDERE, E., KAMENDERS, A., ŽANDECKIS, A., IKAUNIEKS, J. & ROCHAS, C. 2013. Analysis of
Mechanical Ventilation System with Heat Recovery in Renovated Apartment Buildings.
Agronomy Research, 12, 491-498.
SIEW, C. C., CHE-ANI, A., MOHD TAWIL, N., GOH, N. & MOHD TAHIR, M. 2011. Classification of Natural
Ventilation Strategies in Optimizing Energy Consumption in Malaysian Office Buildings. Procedia
Engineering, 20, 363-371.
STANDARD, A. J. I. 2004. Standard 62.1-2004 Ventilation for acceptable Indoor Air Quality. ASHRAE.
