Managing Ventilation In Modern Poultry House

Dr A.R Shaukat
Dr Arbab khurshid Ahmad
Dr Waseem Abbas

We rear poultry because
of
 Rapid growth:
Birds are genetically improved to gain maturity in short
period of time to fulfill global protein requirement.
 Cheapest source of protein:
Improved feed conversions and modern techniques have
made it possible to reduce costs to make available low
priced high nutritive quality protein in market.
 Availability:
Due to high rearing density and rapid growth, Higher
production are obtained per unit space as compared to
other live stocks.

Poultry housing
 Hens naturally were wild birds.
 Domesticated with passing time to full fill human protein
requirement.
 Since ages backyard poultry is part of human civilization.
 With rapid increase in human population, the demand for
protein increased enormously which is met by improving
birds efficiency genetically.
 To manage large numbers we confined them.
 Conventional farms were initially built with less width so
that air may cross through natural air current.
 Conventional houses worked a lot in moderate climatic
zones but factors like increase in disease load, noxious
gases, improper control of temperature, decreased
efficiency were questions to be answered.
 Single answer to all these questions was Modern
Environmentally controlled house.

Poultry house ventilation is
necessary because
 Birds need good environment.
 We need more fresh air to full fill the needs due to higher
metabolic rate of birds.
 We need more fresh air to full fill the needs due to higher
stock densities.
 We want to expel excessive heat if any.
 We need dry litter despite high density.
 We want to expel noxious gases e.g. ammonia.
 Ventilation in a poultry house supplies fresh air that is
essential to sustain life. It also helps reduce the extremes of
temperature, humidity and air contamination to tolerable
limits for confined chickens

Environmental conditions in
Pakistan
 We are dependant upon the environmental conditions i.e.
climate of the region in which farm is to be constructed.
 Due to the location, Pakistan Climate is temperate.
 Pakistan has four seasons:
 A cool, dry winter from December through February.
 A hot, dry spring from March through May.
 The summer rainy season, from June through September.
 The fall is a retreating monsoon period of October and
November.
 The onset and duration of these seasons vary somewhat
according to location.

Extreme temperatures and
humidity in Pakistan
 Climate of Pakistan has great regional variation.
 The difference in temperature between day and night is
immensely substantial.
 The Extremely hot temperature may go up to 45°C to
50+°C in the summers.
 The Extremely low temperature may comes to 0°C or
even less in the winters.
 Humidity ranges between 10% to 100%.
 Points of concern are Extreme temperatures and Humidity.

Ventilation systems
 Generally divided into two types:
 (1) Natural air flow system
 Natural air currents are allowed to enter into the house.
 Fit for areas where outside temperature does not exceed 33°C.
 House width may be maximum around 30 feet for this system.
 Conventional farms are built on this principle
 Not best fit for our conditions.
 (2) Mechanical air movement (fans).
 Mechanical air movement is required to ventilate a house in all
climatic conditions. This system suits our climatic conditions.
 Mechanical systems use electric fans as principal components
to exchange air in the building. They can be divided into two
distinct types(Positive pressure and negative pressure).

Positive pressure System:
 In the positive pressure system, fans are arranged to
push fresh air in to the building.
 Creates air velocity which produces wind chill effect.
 For rearing at higher stock densities in extreme
climatic conditions this system is not very much
effective.

Negative Pressure system:
 In the negative pressure system, fans are arranged to
expel air from the building. In doing so, they create a
partial vacuum or negative pressure inside the house.
The pressure difference pulls fresh air through inlets
into the house.
 The location, distribution and size of the fans and
inlets are critical if all areas of the house are to be
ventilated.
 We may term this system best fit for our climatic
conditions.

Negative pressure system
operation in different weathers
 To discuss this system in changing climatic
conditions we may mainly divide it in to;
 1-Cold Weather Ventilation (Minimum ventilation)
 2-Hot Weather Ventilation (Tunnel ventilation)
 3-Optimum weather ventilation (Transitional
ventilation)

Minimum Ventilation
 Minimum ventilation is used to provide fresh air inside the
house during cold weather. It removes excessive moisture and
minimize the heat loss.
 Fans exhaust air out of the house by creating a slight negative
pressure inside the house. Due to the negative pressure, fresh air
is pulled into the house through some planned air inlets.
 The air inlets are installed either in the ceiling or high on the
house side wall. These inlets are designed to direct air across the
ceiling allowing it to mix with warmer air located there and to
heat up before coming into contact with the birds.
 Check temperature and determine the heating necessity. Doing
this will help to minimize heating costs. For large scale
commercial production, you can install automatic computer
controllers.

Objectives of minimum
ventilation
 Provide fresh air containing oxygen and exhaust
ammonia, carbon dioxide and other gases.
 Provide an adequate air exchange to control moisture.
 Get rid of excessive heat if any.
 Provide an in house airflow pattern that avoid chilling
birds.
 Reduction in fuel cost by minimizing heat loss.

Modern house:
Tools of minimum ventilation
 To achieve the objectives of minimum ventilation,
certain tools are required based on scientific
principles.
 Most important tools are exhaust fans and air
inlets(vents) and other accessories to operate fans and
vents properly.
 If we construct a new house we may have the
knowledge that how many fans and vents may be
installed in that house.

Exhaust fans
Expel air out of the
building. In market
there are different
types of fans available
with varying capacity.
Normally for
minimum ventilation
9000 CFM capacity
fans are used but we
may also use fans of
any capacity.

Calculation:
number of fans for a house
 Though this topic belongs to tunnel ventilation but to ensure
continuity we have to discuss # of fans to be installed in a
house first. Formula to calculate number of fans is as follows.
No Of Fans = Cross Section x Desired velocity
CFM of one fan
 (Cross section= width * height of the house)
 Desired velocity in our climatic conditions must be more than
length of the house to get less than 1 minute air change.
 CFMs of air expelled by a single fan depends upon the size and
efficiency of fan recommended by the manufacturer.

Controllers: It is an
electronic device that collect
information from different
sensors and execute
scheduled tasks. Static
pressure switch provide
information to controller and
controller operates power
track to open or close vents
accordingly.
Inlets(vents): fresh air is
pulled into the house through
vents. Vents are distributed
through out the house in
uniform pattern. Number of
vents depends upon size of
vent and 40% of total capacity
of fans installed in house so
that air may pass at a velocity
of 700 Feet per minute .

Calculation;
Number of vents for a house
 Area for vents=Total no of fans x cfm of one fan x 40%
700 f.p.m
 Total no of vents=total area for vents
Area of one vent
 (40% of total ventilation is maximum limit of minimum
ventilation).
 (Air should pass across the vent at a speed of 700 fpm).
 We can purchase vent of any dimension from market.
Greater the area of vent, Less would be the number of vents
and vice versa which are supposed to be installed in house
uniformly.

Static pressure sensor:
sensor is installed with
controller to sense static
pressure and give feed back to
controller so that it may open
or close the vent according to
static pressure to avoid
chilling.
Power track : it is an
electrical device attached
mechanically to vents and on
the information of controller,
Operates the vents according
to the static pressure.

Minimum ventilation:
Tools working sequence
 Tunnel Fans : Off
 Min. Ventilation Fans : on
 Cooling Pad : Closed
 Vents : Open
 Evaporative Cooling : Off
 Tunnel door : Closed

Lethal and desirable level of gases.
 One of the most important
objective of minimum
ventilation is to remove
gases in order to provide
quality air to birds.
 Three primary air quality
variables are of utmost
importance.
 Carbon dioxide,
 Humidity,
 Ammonia.
Table 1. Common gas levels in
poultry houses
Gas
Symb
ol
Lethal
Desirabl
e
Carbon
Dioxide
CO2 Above
30%
Below
1%
Methane CH4 Above
5%
Below
1%
Ammonia NH3 Above
500ppm
Below
40ppm
Hydrogen
Sulfide
H2S Above
500ppm
Below
40ppm
Oxygen O2 Below
6%
Above
16%

How much to ventilate
 Knowing how much to ventilate during cold weather is
crucial but to simplify a minimum ventilation value
of 0.588 cubic feet per minute per kg body weight is
suggested. Ventilating too little can lead to poor
air/litter quality, resulting in bird health and
performance issues. Ventilating too much can lead to
drafty conditions and high heating costs.
 Static pressure is of importance to avoid chilling and
its desired value is dependant upon width of house. As
a rule of thumb the width of house in meters is equal
to the static pressure required in Pascal.

Practical application
Minimum ventilation value
 Calculate total live weight in house by multiplying average
weight in kilograms with number of birds present in
house.
 By multiplying total live wt with 0.588, we will have total
cfms required to ventilate house.
 Adjust the fan runtime by dividing total cfms on cfm of
one fan.

Practical application of static
pressure value:
 Lets say width of house is 45 feet.
 Divide 45 by 3.2808 to convert it into meters.
 45/3.2808 gives 13.71.
 So 13.71 Pascal pressure is required.
 Divide 13.71 by 249 to convert it into inches of water
column.
 So 0.055 inches of water column static pressure is
required to pull the air up to the center of house.

Example To Elaborate Minimum
Ventilation
 Let suppose we have a house of Length 500 ft, Width 45 ft,
Total number of birds are 40,000 and average weight of the
bird is 500 grams. Capacity of one minimum ventilation fan
is 9000 CFM. Outside temperature is 2 Degree Centigrade.
How to calculate its ventilation?
 Calculation of minimum ventilation:
 40,000 x 500= 20,000 kilograms
1000
 20,000 x 0.588= 11760 CFM required
 11760 = 1.30 Fans
9000

Example To Elaborate
Minimum Ventilation
 1.30 fans mean that we may operate one fan
continuously and one fan on 30% timer. We may also
operate 2 fans on 65% timer or operate 3 fans on 43%
timer.
 Static pressure:
 45 / 3.2808 = 13.71 Pascal
 13.71 / 249 = 0.055 inches of water column(1’’ of water
column =249 Pascal)

Age wise recommended minimum
ventilation Per Bird rates.
Some studies recommend
typical minimum ventilation
rates per bird depending upon
the age of the broilers.
This table is added specifically
due to the reason that
minimum ventilation at day
first is a little bit tricky on
body weight basis.

How to avoid chilling
The critical factor for successful minimum
ventilation is making sure that in coming
cold air mixes uniformly with and is
warmed by in house air before coming in
contact with the bird.
The setup that most constantly meets this
requirement is a negative pressure system
using side walls exhaust fans with
adjustable air inlets.
The partial vacuum created in the house(
static pressure 0.05---0.1 inches of water
column) pulls air in evenly and at the
same high velocity through all inlets so
that the mixing of outside and in house
air is uniform through out the house.

Transitional ventilation
 Fall and spring are transitional seasons when difference
between day and night temperature may range from 15 to
20 degree centigrade. So this is a difficult time for farmers
to manage poultry house ventilation.
 Farmer must be alert to need for ventilation setup changes
and manage the transition smoothly.
 Transitional ventilation goal is to maintain in house
optimum temperature that support best bird performance.
 In transitional weathers wind chill is required at day time
but may hurt bird performance at night. So keep on
switching between minimum and tunnel depending upon
outside temperature is necessary.

Objectives of Transitional
ventilation
 Transitional ventilation fills gap between hot weather
and cold weather ventilation needs.
 Maintaining in house temperature that support best
bird performance during changing weathers.
 Switching between minimum ventilation and tunnel
ventilation to get wind chill when required in any part
of day and stopping when required.
 Switching between side wall fans and tunnel fans as
required.

Tools of transitional
ventilation
 Side wall fans
 Tunnel fans
 Inlets/vents
 Static pressure switch
 Temperature sensors
 Controllers
 Power track
 Tunnel doors
 Tunnel air inlets

Transitional ventilation:
 Tunnel Fans : Occasionally On
 Min. Ventilation Fans : On
 Cooling Pad : Occasionally Open
 Vents : Occasionally Open
 Evaporative Cooling : Off
 Tunnel door : Occasionally Open

Optimum
temperature
requirement of
broiler as grow out
progresses
•Our goal in ventilation is to
keep in house temperature at
right levels.
•The chart shows the daily
temperatures that produce
the best broiler feed
conversion as a grow out
progresses.
Age In
days
Temp in
centigrade
1 33
3 32
5 31.5
7 31
9 30
13 28
17 27
21 26
25 24
29 22
33 22
35 22
39 22
42 22

Tunnel ventilation
 For keeping the birds cool during hot weather, we use
tunnel ventilation.
 Tunnel ventilation system in the broiler house consists of
large air inlets at one end and fans at the opposite end. The
fans used in one end pull air the length of the house at a
velocity of 500 ft per minute or more.
 This system removes excessive heat from the building very
fast and make a wind chill that provides the birds
additional cooling.
 Evaporative cooling system is also used for cooling the
house, when tunnel ventilation system alone is not
sufficient enough.

Tunnel ventilation Objectives
 Main goal of Tunnel ventilation is cooling birds.
 Maintain end to end temperature difference as low as
possible.
 Maintaining low humidity during extreme hot and
humid weather.
 Get rid of immense heat dissipated by the birds.
 To obtain wind chill effect as per requirement of the
birds.

Tunnel ventilation:
 Tunnel Fans : On
 Min. Ventilation Fans : off
 Cooling Pad : Open
 Vents : Closed
 Evaporative Cooling : On
 Tunnel door : Open

Principles of tunnel
ventilation
 Pulling air in a single direction from one end to the other
end produces a certain velocity. This air movement from one
end to the other carries all the excessive heat dissipated by
the birds and excessive humidity, gasses outside the house.
 With increasing air velocity effective temperature felt by the
bird is decreased.
 Evaporative cooling system decreases the temperature by
adding humidity in the house. It is very important to realize
that the evaporative cooling produces far less cooling than
does the air speed.

Points to be considered in
tunnel ventilation
 Ventilate with Tunnel, only when cooling the birds is
the goal.
 Turn on the right number of fans for cooling needed,
depending upon the age of the birds.
 Watch the birds not only thermometer to see how
much cooling is needed.
 Do not run fewer than half of the installed tunnel fans
if you intended to be tunnel ventilating .
 Monitor and maintain adequate air flow.
 If running evaporative pad cooling static pressure
should be 0.05 to 0.1 inches of water column.

Tools of tunnel ventilation
Exhaust fans:
Expel air out of the building
and combination produces
velocity of air in the house.
Number of fans are
determined through cross
section of the house and
desired velocity.
No of fans = Cross Section x Desired Velocity
CFM of one fan

Tools of tunnel ventilation
 Cooling pads: it is a pad
made up of cellulose with
different flute angles.
When we pour water upon
pads and air pass through
the wet flutes, air cools
down due to addition of
humidity. That cooled air is
pulled in a single direction
by exhausts fans through
out the house.
 Air velocity across the pad
must be 350fpm with
operation of all fans.

Number of Cooling Pads in a
Modern House
When we have desired # of fans what may be the pad area to
support these fans properly in extreme hot weather.
Area of cooling Pad= Total no of fans x CFM of one fan
350 fpm
Total No of pads=total area for pads
Area of one pad
 (Air should pass across the cooling pad at a speed of 350 fpm).
 Number of pads may be determined by dividing total area
required by area of 1 pad.

Tools of Tunnel
ventilation
•Tunnel door
•Cooling pads motor
•Power track for the
operation of tunnel
door
•Controller
•Temperature
sensors
•Humidity sensor
•Humidity switch

Ventilation during hot and dry
weather
 With increase in temperature a poultry house needs higher
ventilation.
 With increasing age and temperature we may keep on
operating more fans until we reach to a velocity of 1 minute
air change.
 If the effective temperature felt by the bird is still high then
we have to operate cooling pads.
 When the air passes through the wet cooling pads it is
cooled down in dry weather and directed towards the
ceiling of the house to avoid chilling of the birds at pads
area.

Ventilation during hot and dry
weather
 The cooled air would be transported to the end of
the house in 1 minute.
 So the temperature of the house would come down
quickly and it would be sensed by the sensors and
conveyed to the controller. The controller would
bring down the air velocity by shutting off fans to
avoid chilling by combined effect of low
temperature and wind chill.

End to end temperature
difference
•In tunnel ventilation end to end temperature difference must be as
low as possible.
•Higher the air velocity lower would be the end to end difference.
•In the given diagram the end to end difference is almost 2 degree
with an air velocity of 550 fpm.
•it also depends upon insulation of the house.
•Poor the insulation higher would be the end to end difference.

Ventilation during hot and
humid weather
 This is the most challenging weather in Pakistan
for poultry farmers.
 As we approaches the month of July in Pakistan
there is a sudden increase in the relative humidity
outside due to Moon Soon.
 In this weather our tool of minimizing house
temperature through evaporative cooling does not
work properly due to increased humidity.
 We are supposed to increase the air velocity as
much a possible in this type of condition.

Ventilation during hot and
humid weather
 But still despite achieving the maximum possible air
velocity, we do need to decrease the temperature by a
certain degree due to the fact the temperature goes beyond
35 degree centigrade.
 In such conditions we operate pads on timer basis.
 Off time of the pad is calculated by observing the time in
which the pad is dried off and the on time is determined on
the basis of observation that in how much time the pads
become completely wet.
 Increasing air velocity to 40 seconds air change or less may
give good results.

Managing Ventilation In Modern Poultry House

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