There are still a few producers who ventilate their piggeries without the assistance of power. These notes may help them get the process as efficient as nature permits.
Natural ventilation moves air both through adjustable and fixed openings. ‘Adjustable’ includes windows, eave panels, ridge openings and ventilated doors. ‘Fixed’ openings use open points in the building, especially continuous ridge and eave gaps as well as lattice sides to big courts.
Natural vs mechanical ventilation – a dramatic trial
While manually operated natural ventilation is much cheaper than mechanical ventilation, manually altering such systems is never frequent enough, so cannot match that of mechanical control. Many years ago I was able to record some figures from a client’s unit as he changed from a natural manually-operated system to a modern fan installation with a control correctly operated by a sensor. We had four weeks to measure temperatures both inside and out, in two adjacent barns with pigs of similar weights when both systems were running concurrently. The averaged results on a weekly basis, as Table 1 shows, were clear and dramatic.
Naturally we followed both barns to slaughter to see if just one month’s comparison made much of a difference, and even for this short winter period – it did.
In the 24 hours the naturally-ventilated pigs remained too cold much longer, despite diligent morning and evening adjustment of the exit flaps.
How to calculate naturally-ventilated openings?
Note: Inlet and outlet allowances can vary from source to source, i.e. up on a ridge or down in a dip or sheltered spot. My figures are a compromise and have worked well in non-extreme conditions. If in doubt seek help from a ventilation expert – who sadly are rare birds these days.
[Source: Pig Progress magazine Vol 30 nr 4, 2014 – ‘What the textbooks don’t tell you about…’ series]