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WINTER VENTILATION:
WHAT IS
THE OBJECTIVE?
Dr. William D. Weaver, Jr.
Professor and Head
Department of
Poultry Science
Maintaining desirable air qual
ity in the poultry house during the
winter months can challenge the
most experienced producers.
On the one hand, they are
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required to tighten up their houses
to eliminate drafts and reduce heat
lost. However, on the other, they
are asked to run their ventilation
fans, which brings in cold outside
air, in order 10 reduce moisture and
control ammonia.
This almost seems paradoxical
—a producer is expected to seal up
his house but then run his fans to
bring in cold outside air.
Is the objective to minimize fuel
usage, or is it to completely rid the
house of ammonia? Most growers
would agree that it is neither of
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these, but rather it is to create an
environment that will allow for the
efficient and economical produc
tion of meat and eggs.
In order to accomplish this,
growers must bring in adequate
quantities of outside air, which in
the case of growing birds will
increase fuel consumption, in
order to remove moisture and con
trol ammonia. The keys to creating
the proper environmental condi
tions are to:
• Provide adequate insujation
(at least Rl9 in ceiling and if 12 in
sidewalls).
• Eliminate all locations where
outside air can infiltrate.
• Allow outside air to enter only
through properly designed air
inlets located at the eaves on both
sides of the house.
• Direct the incoming air across
the ceiling, allowing it to mix with
the warmer inside air before it
reaches the birds and the litter.
• Ensure that outside air is
brought in at the proper velocity
(minimum of 600 feet per minute
Lancaster Farming, Saturday, November 6, 1993-C3
or from .08 inch to .10 inch static
pressure), allowing it to move
across the ceiling.
Even though the outside air
maybe cold and possibly high in
relative humidity, it can be used to
ventilate the poultry house during
the winter months. The goal is to
control ammonia by removing
moisture. This is accomplished by
bringing in cold outside air,
increasing its temperature by mix
ing it with warmer inside air,
allowing it to pick up moisture
from the litter, and then exhausting
the moisture laden air from the
house.
A rule to remember is that the
moisture-holding capacity of air
approximately doubles for each 20
degree Fahrenheit (F) increase in
temperature. For example: otuside
air at 32 F and 100 percent RH
(raining) can be brought into the
house and warmed to 72 F, repre
senting a 40 F increase in tempera
ture. During the warming process,
the relative humidity of the air is
'*•
reduced from 100 to 25 percent,
which, when moved across the lit
ter, has tremendous ability to take
up and remove large quantities of
moisture.
Blindness among birds, ascites
(excess fluid in the body cavity),
skin irritations (ammonia bums),
breast blisters, leg abnormalities,
and severe respiratory infections
are all directly attributed to
increases in ammonia and litter
moisture during the colder months.
Properly designed and operated
ventilation systems that bring in
and exhaust the correct amount of
air will minimize both ammonia
and moisture, creating desirable
environmental conditions. Ammo
nia should not be allowed to
increase above 25 ppm (about the
level most people start smelling
the gas) and litter moisture above
30 percent (slightly moist with no
caking).
Therefore, the objective is to
maintain desirable air quality in
the poultry house by controlling
ammonia and moisture through
bringing in small quantities of out
side air. This can be done most
efficiently in adequately insulated
houses with properly designed and
operated negative pressure ventila
tion systems.
STANLEY M. WENSEL
Box 24 Barra* A
Alexandria, PA 16611 VV
814-669-4558
• Fax 814-060-0416