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In most climates around the world, poultry houses should have 3 ventilation systems. These are:
Minimum ventilation is used when the house temperature is at or below the required house set- point temperature (bird comfort temperature). It is most commonly used during brooding (chicks).
During minimum ventilation, air should enter through sidewall inlets.
During minimum ventilation the air inlets must operate based on negative pressure (pressure differential). The ideal operating negative pressure for an individual house will vary and depends on:
For a given ceiling shape, the pressure requirement will be lower for a smooth ceiling relative to a ceiling with exposed beams/trusses.
Also, for a given pressure, the ‘throw’ (the distance the air moves into the house) of the air into the house will be further the more the inlet is opened.
A useful guide for estimating operating pressure for a given house is that for every increase in negative pressure of 3 - 4 Pa (0.012-0.016 inches of water column) air is thrown approximately 1 m (3.3 ft) further into the house.
Inlet management is a crucial part of minimum ventilation. Generally, not all air inlets will need to be opened during minimum ventilation and the inlets that are open must be opened equally to ensure a uniform air flow and distribution.
The recommended minimum inlet opening is approximately 5cm/2 in (but not less than 3 cm/1 in).
Having, the correct setting of the air direction plate (above the inlet) is important.
If any one of the 3 factors above is incorrect, air flow will be compromised.
Inlet air flow and operating pressure should be tested, checked and confirmed using a smoke test or the cassette tape method.
How do you decide how many inlets should be used for minimum ventilation? Some people try to calculate this based on the fan capacity. Unfortunately though, this method can be quite
inaccurate because you have no idea how much leakage there is in the house, which is also a form of inlet area.
Assuming your house has sufficient sidewall inlets for transitional ventilation, a practical method to determine the setup is as follows:
The above explanations of setting and managing inlets refer to sidewall inlets. However, the basic principles will apply to most inlet types when being used during minimum ventilation.
The set-point temperature profile should be used as a guideline only.
What to look for when entering house during minimum ventilation
If this information is known, then the amount of cooling and resultant RH level
The table above shows the approximate lower air temperature inside the house measured next to the cooling pad, given the outside temperature and %RH. The values are based on a cooling efficiency of approximately 75 percent, which is average for a 15 cm (6 in) thick cooling pad.
There are 3 pressure range categories of fogging systems:
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