Common Ways to Move Air

For confined livestock, ventilation is of utmost importance. Proper ventilation in pig barns improves the air quality and reduces the chance for illness, decreased pig productivity, and loss of profits. The two basic forms of ventilation are natural and mechanical systems. Negative pressure mechanical ventilation, the most common form of pig barn ventilation utilizes a combination of inlets and fans to allow fresh air into the pig barn while exhausting stale air. The goal is to introduce fresh air to all parts of the facility, control humidity and temperature levels, and reduce the presence of ammonia.

The Function of Insulation in The Pig Barn

The main function of insulation in the pig barn is to prevent condensation inside the building. In the production facility, the insulation only needs to maintain a surface temperature above dew-point temperature. Walls do not require an R-value higher than the mid-teens and ceilings in the mid-twenties.

A significant amount of cold-weather heating will be lost, regardless, via the normal ventilation air-exchange needed to maintain good air quality and keep moisture levels low. Because the purpose is to prevent condensation, the insulation does not need high R-value, and will have little benefit beyond the above-mentioned numbers.

To prevent insulation from absorbing moisture, a vapor barrier must be used. This prevents moisture inside the barn from creating condensation inside the walls. Insulation must likewise be protected from rodents. Crushed stone or ample baited traps at the base of exterior walls will help prevent rodents from getting in the walls and destroying insulation.

Rigid-board insulation two to three feet below ground level is another excellent measure for controlling humidity and preventing condensation inside the facility. For board insulation, an R-value between six and eight is sufficient. This will help keep floor-level temperatures more comfortable for pigs during cold months.

Natural Ventilation

A natural ventilation system is typically comprised of ridge or roof vents and side inlets. Warm air inside a building is not as heavy as cool outside air entering the building. Warm air rises to the ceiling creating a negative pressure that draws cold outside air into the building. Cool air may also enter via inlets on the side of the building when pushed by wind.

In a natural ventilation system, the amount of ventilation can’t be controlled because it depends on the indoor and outdoor air temperatures and the wind, if any. When outdoor and indoor temperatures are the same, or when outdoor temperatures are higher than indoor temperatures, there is very little ventilation.

Consequently, natural ventilation airflow is difficult to control.

Mechanical Ventilation

In mechanically ventilated production facilities, fans are used to exchange air, creating the air pressure difference between the inside and outside of the barn. This process is usefully broken into three different systems: positive, neutral, and negative pressure systems.

Positive Pressure

In a positive pressure system, fans draw outside air into the facility, forcing the inside air out of the facility through exhaust pipes or ducts. Positive pressure systems are not common in pig facilities because of the chance for warm, humid outside air to enter the structure, leading to possible condensation.

Neutral Pressure

A neutral pressure system utilizes fans both for drawing air in and exhausting air out of the building. The neutral pressure system does not make use of structural elements like inlets or windows. Instead, vertical inlet ducts distribute air evenly throughout the building with directional air vents pointed at the walls and corners of the building. The larger air vents are pointed at the corners, typically the greatest distance from the vertical duct, and the smaller vents are directed at the walls. This will help prevent drafts. Inlet fans should be evenly distributed in the center of the room. Exhaust fans placement is less important as they do not affect airflow patterns.

Neutral pressure systems are expensive to operate and maintain, as they require twice as many fans as other mechanical ventilation systems.

Negative Pressure

The negative pressure system is probably the most common method for ventilating pig barns—they’re easily controlled and cost efficient when compared with the other forms of mechanical ventilation. A standard system makes use of sidewall inlets and a central exhaust fan. Cold air enters the facility and mixes with the warm interior air before reaching the animals. During cold months, inlets should direct the incoming cold air up, toward the ceiling, and down, toward the floor, during warm months.

For wider buildings, inlets can be installed in the ceiling. In this case, air enters through the roof.

Some buildings use floor ventilation in combination with standard negative pressure wall inlets. The advantage of floor venting is that a substantial percentage—up to 50 percent—of stale air is removed below floor-level. This is advantageous as most ammonia is removed before rising to pen-level in slatted facilities, reducing odors, providing an improved working environment and a healthier living space for swine, especially when combined with pit fans.

The Importance of Ventilation Fan Maintenance

Any mechanical ventilation system is only as good as the fans. Performing regular inspections and following a maintenance checklist—at least at the start of fan season—will help assure producers that their fans are performing at peak levels. Regularly inspecting blades, bearings, belts, and sheaves for wear, and fixing any mechanical issues will allow the facility ventilation to be as efficient and effective as possible. Even a little accumulated dust can dramatically reduce a fan’s efficiency. A company like DURAFAN, that offers a wide variety of high-quality fans and replacement parts, is a great choice for consistent, high-performance ventilation.

Does your facility use a negative pressure system? Or something else? Tell us in the comments section!