WEEK 11A — VENTILATION

Ventilation

the exchange of air in a building with fresh air from outside. Heat

air exchange and air distribution

Ventilation has two basic functions:

Air Exchange

function of ventilation that may be summarized simply as the cycle of fresh air in, stale air out

Air Distribution

the process of delivering fresh air to all.

Ventilation Systems

are designed to maintain air quality during cold weather and to regulate temperature during hot weather.

Heating and cooling systems

what compliment ventilation to maintain a productive environment.

Maintain the oxygen content in the area

Reduced the carbon dioxide content

Controlling humidity in a room.

Prevent the heat from the outside

Prevent the heat intensity of the machines

To maximize heat loss in space

Eliminate odor and dirty air content

Provides freshness and convenience

Cooling the temperature in the area

Give Purposes of Ventilation (9)

Natural and Mechanical Systems

2 Types of Ventilation Systems

wind driven ventilation

pressure driven flows

stack vent/stack effect

types of ventilation systems under natural systems

natural inflow & outflow

natural inflow & mechanical outflow

mechanical inflow & natural outflow

mechanical inflow & outflow

types of ventilation systems under mechanical systems

natural ventilation

Passive ventilation is also called as what

passive ventilation

makes use of natural forces, such as wind and thermal buoyancy, to circulate air to and from an indoor space

passive ventilation

these ventilation systems works to regulate the internal air temperature as well as bring fresh air in and stale air out

passive ventilation

this is largely achieved through the opening and closing of windows and vents which acts as a source of air as well as an exhaust

wind driven ventilation

pressure driven flows

stack vent / stack effect

3 types of passive ventilation

Wind Driven Ventilation

depends on wind behavior, on the interactions with the building envelope and on openings or other air exchange devices such as inlets or chimneys

surface wind hedges

what is in low or negative pressure in wind driven ventilation?

front surface of the wind

what is in high or positive pressure in wind driven ventilation?

wind driven ventilation

occurs when the wind blows toward the house or building and create pressure

Pressure Driven Flows

Wind pressures are generally high/positive on the windward side of a building and low/negative on the sheltered side.

windward side

Wind pressures are generally high/positive on what side of a building?

sheltered side

Wind pressures are generally low/negative on what side of a building?

wind speed and wind direction relative to the building

the location and surrounding environment of the building

shape of the building

The occurrence and change of wind pressures on building surfaces depend on

. For a building with numerous partitions and openings

it is under various pressures depending on the relative sizes of the openings and the wind direction. With large openings on the windward face

Stack Vent / Stack Effect

Stack effect is temperature induced. When there is a temperature difference between two adjoining volumes of air

Advantages of Natural Ventilation - 1

Does not require any mechanical appliances.

Advantages of Natural Ventilation - 2

Non operational cost.

Advantages of Natural Ventilation - 3

Non maintenance cost for the appliances/equipment.

Advantages of Natural Ventilation - 4

Silent processes.

Advantages of Natural Ventilation - 5

Combination benefit of ventilation

Disadvantages of Natural Ventilation - 1

The system is uncontrolled: …in terms of speed & distribution …high rise building received strong velocity thus windows should be kept closed. …slow wind velocity during rainy season

Disadvantages of Natural Ventilation - 2

Internal temperature cannot be monitored: …difficult to achieved the required human comfort temperature.

Disadvantages of Natural Ventilation - 3

Rate of air humidity is uncontrolled: …depends on the existing external humidity

Disadvantages of Natural Ventilation - 4

Uneven uniform distribution: …ventilation rate depends on sizes of opening. …distribution is maximum at the area/space nearby the opening. …low ventilation rate for rooms further inside a bldg.

Disadvantages of Natural Ventilation - 5

Quality of fresh & clean wind cannot be assured …maybe contaminated from the external harmful element such as smoke and dust.

Mechanical Ventilation

through an air handling unit or direct injection to a space by a fan. A local exhaust fan can enhance infiltration or natural ventilation

Methods of Mechanical Ventilation

a) NATURAL INFLOW & OUTFLOW b) NATURAL INFLOW & MECHANICAL OUTFLOW c) MECHANICAL INFLOW & NATURAL OUTFLOW d) MECHANICAL INFLOW & OUTFLOW

Natural Inflow & Mechanical Outflow

Winds enter the room naturally without assistance from appliances. Internal air is force out with fan which normally fixed at the building component such as : - roof - wall - window Suitable for factory

Mechanical Inflow & Natural Outflow

External air brought into the building by application of suction fan. Consumed indoor air will exit naturally through the openings which positioned at the lower level of the building. The methods allows the external air to be filtered before entering the internal space. Recommended for small factory building

Mechanical Inflow & Outflow

External air enters and exit the internal space by applications of mechanical fan. The building need to be properly concealed from noise

Plenum System

Comprises of air filter

Requirement for Mechanical Ventilation - Safety

Safety from surrounding environment- such as from contaminated air

Requirement for Mechanical Ventilation - Natural System

Natural system is ineffective in terms of quantity and quality

Requirement for Mechanical Ventilation - Building Use

Types of building usage or space requirements skyscrapers

Requirement for Mechanical Ventilation - Building Location

Building/space location makes natural vent impossible – i.e: basement space or hidden corner

Why Is Proper Air Circulation Important?

Air flowing freely throughout your STRUCTURE helps to regulate temperature