Alabama Poultry Monthly pg 9

By Jim Donald
Extension Agricultural Engineer
and Professor Biosystems Engineering
Department Auburn University
(334) 844-4181
(334)-844-3548 fax
jdonald@acesag.auburn.edu

We have had a fairly mild early winter in Alabama so far, but that is likely to change as we get into the coldest months of the year. Wintertime broiler house ventilation requires very different management methods from summertime, and I often receive calls, letters and emails from growers asking questions about various aspects of cold weather ventilation. Growers want to keep flock performance up, but don't want to burn any more heating fuel than necessary, and they ask what factors or methods are really important to reaching this goal. The following key points briefly outline what industry experience and university research have shown to be the cardinal rules for efficient wintertime broiler house ventilation.

The Cardinal Rules:

1. Seal all house air leaks. You cannot properly ventilate a loose house. We want all air to come in through the inlets, not through leaks and cracks. Cold air falls, and cold outside air leaking through cracks, curtains, holes and any other unwanted opening drops toward the floor, causing condensation, wet litter, cake and poor bird performance. Test house tightness by static pressure: with all doors, curtains and inlets of the house closed and one 48-inch, 20,000-cfm fan turned on, we should be able to pull a negative static pressure of 0.15 inches. If the number is lower than 0.15, too much air is coming through leaks and cracks. The higher the number from the static pressure test the tighter the house.

2. Insulate before you ventilate. We cannot maintain good environment in a poultry house in cold weather if we have no way to keep the heat in. Ceiling

insulation should be approximately R-19. Check your insulation for tears, holes and places where insulation may have shifted and there is no insulation at all. Consider insulating end walls, end doors and other parts of the house that are not currently insulated.

3. Set the fan timer for the right
minimum ventilation rate, according
to bird age. Be sure all fans are
controlled by a singletimer. The
ventilation rate needed
usually ranges from
about 0.10 cfm/bird in
week one to about 0.90
cfm/bird by week eight.
In week one, for example,
with 24,000 birds, you
would need one-tenth
of 24,000, or 2,400 cfm on
average. We say "on
average,"because you
can't run a 2,400 cfm fan.
You use the timer to run,
say, two 10,000-cfm 36-
inch fans the percentage
of time needed to average
out at 2,400 cfm. You find
the percentage needed
simply by dividing the
cfm's needed by the cfm
capacity of the fans you
will be running. In this
example, 2,400 cfm divided
by 20,000 fan cfm's equals
0.12. You multiply that
percentage times the five
minutes in the timer cycle,
and set for 36 seconds
run-time out of a five minute
cycle (36 seconds on-time out of 300
seconds = 0.12). Never ventilate with
less than two 36-inch fans. Single 36-
inch fan ventilation usually will not
yield a high enough static pressure to
ventilate properly. Heat moves toward
fans, so ventilating with a single 48-
inch fan concentrates heat in that
end of the house. Running two or
more minimumventilation fans helps
maintain temperature

uniformity, and that will boost flock
performance.

4. Increase fan timer settings (ventilation
rate) each week from day one through catch. Fan run-time must be increased weekly to handle the increased moisture birds give off as they grow. As noted in Rule #3, the rate needed typically increases from about one-tenth a cfm per bird to almost a full cfm per bird. Note that having a properly set minimum ventilation timer                               is just as important at the
                              end of the growout
                              as it is in the beginning
                              of the growout.
                              Later in a growout,
                              thermostat control
                              usually will override
                              the timer control most
                              of the time. However,
                              the minimum ventilation
                              timer must remain
                              properly set to take
                              care of air quality if and
                              when higher temperatures                               no longer trigger                               thermostat control.

                              5. Maintain minimum
                              ventilation no matter
                              what the outside or
                              inside conditions are.
                              Without at least the
                              minimum ventilation
                              rate, inside air quality
                              will deteriorate and litter                             moisture and ammonia                               problems will occur. The amount of house heat lost because of minimum ventilation is small, and well spent to avoid moisture problems. Remember also that you can and must ventilate even if a cold rain is falling outside. When cold air is heated its moisture holding capacity increases. When air is heated 20 degrees its relative humidity will be cut about

                RULES continues on page 10