Purge Ventilation or Continuous Ventilation in Hog Barns?

( Jennifer Shike, Farm Journal's PORK )

When it comes to ventilation, there’s no substitute for paying attention to what your pigs are telling you, said Doug Owens, senior service manager for New Fashion Pork. 

“You may need to over- or under-ventilate based on given weather periods over a pattern of time,” Owens said during the 2020 Iowa Pork Congress on Wednesday. Owens discussed the advantages and disadvantages of using purge ventilation versus continuous ventilation. 

Purge ventilation uses a cycle time to run fans and shut fans off to get the required cubic feet per minute (cfm) of air moved in your barn, he explained. Continuous ventilation, on the other hand, allows your fans to run continuously at a set percentage. Owens broke down these ventilation types and shared his thoughts on the advantages and disadvantages of each type. 

Advantages of Purge Ventilation:
1. You know the exact speed of your air every time the fan runs.
2. Possible liquid propane (LP) savings.
3. Fan always runs at 100% so you don’t have to worry about burning fan motors out from running fans too slow.
4. When running automatic inlets, there is zero influence from a pressurized attic.

Disadvantages of Purge Ventilation:
1. Fans can freeze up, seasonally.
2. During the off cycle, there can be a back draft of air up into the attic which can create moisture on your roof steel, causing roof to rust prematurely if not insulated.

Advantages of Continuous Ventilation:
1. No updraft into your attics.
2. Easier to teach to new employees.
3. Not opening/closing automatic inlets as much so little less wear on that equipment.

Disadvantages of Continuous Ventilation:
1. Inlets are open 100% of time, so if you run into a positive pressure situation, you may over-ventilate your barn for a period of time.
2. Need to remember to plug your second pit fan in and also readjust your minimum ventilation.

New Fashion Pork runs continuous ventilation throughout their system, Owens said. However, there are always exceptions and some one-off situations, including older, more traditional nurseries where they use purge ventilation. They also may use purge ventilation when they have a half-stocked barn for a short period of time. 

In addition, they have used modified continuous ventilation on random grow-finish sites that they’ve struggled to ventilate, he added.

“The number one reason we switched to continuous ventilation was to preserve our roof steel,” he said. 

He added that he watches LP cost and savings closely.

“But at the end of the day we have to realize we’re in northwest Iowa and southern Minnesota raising pigs. Sometimes you will just have to burn propane to raise pigs right,” Owens said. 

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