This document discusses different types of ventilation for buildings. It defines ventilation as replacing or circulating air to provide good indoor air quality. The main types discussed are natural ventilation, mechanical ventilation, and hybrid/mixed-mode ventilation. Natural ventilation uses openings to allow air flow via pressure differences without fans. Mechanical ventilation uses powered fans or blowers. Hybrid systems allow controlled introduction of outdoor air using both mechanical and passive means. The document also outlines purposes of ventilation like maintaining comfort, removing odors and contaminants, and creating air movement.

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Building Services
Ar. Inam Ullah
CECOS UNIVERSITY OF INFORMATION TECHNOLOGYAND EMERGING SCIENCES

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Ventilation
Replacing/circulating air in any space to provide high indoor air
quality is called ventilation.
Ventilation includes both the exchange of air to the outside as well
as circulation of air within the building.

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Ventilation

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Ventilation

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Ventilation

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Purpose of Ventilation
• Maintain human comfort and health.
• Provide sufficient air/oxygen for human/livestock during
overcrowding in the office.
• Remove products of respiration and bodily odor.
• Remove contaminants or harmful chemicals.
• Remove heat generated indoor.
• Create air movement (feeling of freshness/comfort)
• Moisture problems, as indicated by visible fungal growth in
corners.
• Removal of smoking
• Control airborne bacteria

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Types of Ventilation
 Natural Ventilation
 Mechanical Ventilation
 Hybrid/ Mix Mode Ventilation

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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.
 Openings such as windows, louvers, ventilators and doors are
installed in the periphery of the building/room for natural
ventilation.
There are two types of natural ventilation;
• Wind driven ventilation and
• Buoyancy-driven ventilation.

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Natural Ventilation
 Wind driven ventilation arises from the different pressures created
by wind around a building or structure, and openings being formed
on the perimeter which then permit flow through the building.
 Buoyancy-driven ventilation occurs as a result of the directional
buoyancy force that results from temperature differences between
the interior and exterior. Since the internal heat gains which create
temperature differences between the interior and exterior are created
by natural processes, including the heat from people, and wind
effects are variable, naturally ventilated buildings are sometimes
called "breathing buildings".

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Natural Ventilation

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Natural Ventilation

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Mechanical Ventilation
A building ventilation system that uses powered fans or blowers to
provide fresh air to rooms when the natural forces of air pressure and
gravity are not enough to circulate air through a building
Example: Ceiling fans

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Mechanical Ventilation

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Mechanical Ventilation

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Hybrid/ Mix Mode Ventilation
A hybrid ventilation system allows the controlled introduction of
outdoor air ventilation into a building by both mechanical and passive
means.
There are two variants of hybrid ventilation:
The Changeover Type: spaces are ventilated either mechanically or passively, but
not both simultaneously.
Can switch between mechanical and passive ventilation seasonally, diurnally (Active
Mainly during Day).
The Concurrent Type: both methods provide ventilation simultaneously.
Appropriate controls are needed to prevent “fighting” between the two ventilation
methods.

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Hybrid/ Mix Mode Ventilation

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Hybrid/ Mix Mode Ventilation

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Basic elements of Ventilation
Building ventilation has three basic elements:
Ventilation rate — the amount of outdoor air that is provided into the
space, and the quality of the outdoor air.
Airflow direction — the overall airflow direction in a building, which
should be from clean zones to dirty zones; and
Air distribution or airflow pattern — the external air should be
delivered to each part of the space in an efficient manner and the
airborne pollutants generated in each part of the space should also be
removed in an efficient manner.