Swine Barn Ventilation Design for Grow-Finish Facilities

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-14

Key Takeaways

• Ventilation's dual role: Effectively removing heat, moisture, and gases (ammonia, CO2, H2S) while ensuring fresh air delivery to all pigs is paramount for preventing respiratory disease and maintaining growth rates.
• Minimum ventilation is critical for cold weather: Maintaining a minimum air exchange rate (20-60 CFM/pig depending on weight) is essential to control humidity (target <70% RH) and ammonia (target 10-15 ppm at pig level), preventing respiratory issues.
• Static pressure is a primary diagnostic: Manometer readings outside the typical 0.05-0.15 inches of water column indicate issues with inlet sizing/placement or fan performance, directly impacting air distribution and barn environment.
• Gas monitoring at pig level is crucial: Ammonia and carbon dioxide, being heavier or warmer than ambient air, accumulate near the floor; measurement at pig level (not human height) is necessary for accurate assessment of exposure risks.
• Seasonal management requires distinct strategies: Minimum ventilation for cold, tunnel ventilation for heat (300-500 ft/min air speed for wind chill), and transitional ventilation for spring/fall necessitate precise controller settings and inlet adjustments to avoid drafts and maintain optimal conditions.
• Record-keeping is vital for proactive management: Documenting fan run times, static pressure, gas readings, and pig health observations creates a historical baseline for early problem detection and system optimization.

This guide covers the fundamentals of swine barn ventilation design for grow-finish facilities, from understanding basic air movement principles to selecting equipment, sizing inlets and fans, and establishing a monitoring routine. It is written for farm owners, managers, and employees who are planning a new barn, renovating an existing one, or troubleshooting persistent air quality problems. The focus is on practical decisions you can make on the ground, with clear guidance on when to bring in a specialist.

At a Glance

• Ventilation has two jobs: Remove heat, moisture, and gases from the barn, and deliver fresh air to every pig. Both jobs matter equally.
• Minimum ventilation is the most important setting. It runs during cold weather to control moisture and ammonia. Get this wrong and you will have respiratory problems all winter.
• Tunnel ventilation is for hot weather only. It moves large volumes of air at high speed to create wind chill for pigs. Do not use it in cool weather.
• Inlet sizing and placement control air distribution. The goal is to bring fresh air in at the ceiling and let it mix with warm barn air before it falls to pig level. Avoid drafts on pigs.
• Static pressure is your main diagnostic tool. A manometer reading outside the expected range tells you that inlets, fans, or both need adjustment.
• Measure gases at pig level, not at human height. Ammonia and carbon dioxide are heavier or warmer than room air and collect near the floor.
• Fall and spring are the hardest seasons to ventilate. Temperature swings require frequent adjustments. A good controller automates most of this, but you still need to check the system daily.
• Keep records. Fan run times, static pressure, gas readings, and pig health observations create a history that helps you spot problems early.
• Call a veterinarian if pigs show respiratory signs that do not improve within a few days of fixing ventilation issues. Call an extension agent or ventilation specialist if your system is not performing after you have checked the basics.

Why Ventilation Matters in Grow-Finish Barns

Pigs in a grow-finish barn generate heat, moisture, and gases continuously. The animals themselves are the main source of all three. A 150-pound pig produces roughly 500 to 700 British thermal units of heat per hour, along with about a gallon of moisture per day through respiration and manure. The manure also releases ammonia, hydrogen sulfide, and other gases as it breaks down. Without ventilation, the air inside a barn becomes hot, humid, and toxic within hours.

Ventilation does three things. First, it removes heat. Second, it removes moisture. Third, it dilutes and removes gases and airborne dust. A properly designed system does all three without creating drafts on pigs or wasting excessive energy.

Poor ventilation leads to a cascade of problems. High humidity keeps bedding and floors wet, which increases ammonia production and promotes bacterial growth. High ammonia levels irritate the respiratory tract, making pigs more susceptible to pneumonia and other respiratory diseases. High carbon dioxide levels indicate that the air is stale and that oxygen may be limited in the pig zone. Heat stress reduces feed intake and growth rate, which directly affects your bottom line. In severe cases, poor ventilation contributes to mortality.

The goal of a ventilation system is not simply to move air. It is to maintain an environment that keeps pigs healthy and productive across all seasons. In winter, the system must preserve heat while removing moisture and gases. In summer, it must remove large amounts of heat. In spring and fall, it must handle rapidly changing conditions. A well-designed system manages all of this with minimal human intervention, but it still requires daily attention.

Basic Principles of Swine Barn Ventilation

Before you select equipment or adjust controls, you need to understand four concepts: air exchange rate, air distribution, static pressure, and the ventilation curve.

Air Exchange Rate

Air exchange rate is the number of times the barn air is replaced per hour. It is expressed in cubic feet per minute (CFM) per pig, or CFM per head. The required exchange rate depends on the season and the size of the pigs.

For grow-finish pigs, the recommended ventilation rates are usually expressed as a range. The minimum rate, used in cold weather, is typically 20 to 30 CFM per pig for pigs up to 50 pounds, increasing to 40 to 60 CFM per pig for pigs over 150 pounds. The maximum rate, used in hot weather with tunnel ventilation, is 250 to 400 CFM per pig depending on the climate and the size of the pigs. These numbers are starting points. Your local extension service can provide rates specific to your area and building type.

Air Distribution

Air distribution refers to how fresh air moves through the barn. The goal is to bring fresh air into the building, mix it with the warm, moist air near the ceiling, and then let it fall gently to the pig zone. This mixing process is critical in cold weather. If cold outside air falls directly onto pigs, they experience a draft and use energy to stay warm instead of growing.

The mixing process depends on inlet design and placement. Inlets are usually located in the ceiling or high on the sidewalls. They are sized and positioned to create a jet of air that travels along the ceiling for a distance before dropping. The distance depends on the inlet opening size, the static pressure, and the temperature difference between inside and outside air.

In warm weather, the goal changes. You want air to move directly across the pigs to create wind chill. This is the basis of tunnel ventilation, where air enters at one end of the barn and is pulled by fans at the other end.

Static Pressure

Static pressure is the difference in air pressure between the inside and outside of the barn. It is measured in inches of water column. A manometer measures this pressure. Most barns operate at 0.05 to 0.15 inches of water column, depending on the inlet type and fan capacity.

Static pressure is the force that pulls air through inlets. If the pressure is too low, air enters through the path of least resistance, which is often the nearest inlet or a crack in the building. This causes drafts and uneven air distribution. If the pressure is too high, air enters at very high speed, which can create drafts and reduce fan efficiency. The controller maintains static pressure by opening or closing inlets as fans turn on and off.

The Ventilation Curve

A ventilation curve is a graph that shows how fan capacity changes with temperature. The controller uses this curve to decide which fans to run and how fast to run them. In cold weather, only the minimum fans run. As temperature rises, the controller adds more fans or increases fan speed. In hot weather, all fans run at maximum capacity.

The ventilation curve is set during commissioning and adjusted as the season changes. Getting this curve right is one of the most important tasks in barn management. A curve that is set too low leads to stale air and high gas levels. A curve that is set too high leads to drafts and high energy bills.

Types of Ventilation Systems

There are three main types of ventilation systems used in grow-finish barns: negative pressure, positive pressure, and neutral pressure. Most modern barns use negative pressure systems, so this guide focuses on them. However, you should understand the alternatives.

Negative Pressure Systems

In a negative pressure system, fans pull air out of the barn, creating a slight vacuum. Fresh air enters through inlets that are controlled by static pressure. This is the most common system in modern swine barns because it gives good control over air distribution.

Negative pressure systems come in two forms: sidewall exhaust and tunnel ventilation. Many barns use both, switching between them depending on the season.

Positive Pressure Systems

In a positive pressure system, fans push air into the barn, creating a slight positive pressure. Air leaves through openings in the walls or ceiling. These systems are less common in grow-finish barns because they are harder to control and can cause moisture problems in the building structure. They are sometimes used in buildings with special requirements, such as filtered barns.

Neutral Pressure Systems

Neutral pressure systems use both supply and exhaust fans to maintain equal pressure inside and outside. They are more expensive to build and operate, but they offer better control over air filtration and are sometimes used in high-health barns.

Minimum Ventilation for Cold Weather

Minimum ventilation is the backbone of a good ventilation system. It runs continuously during cold weather to remove moisture and gases while preserving as much heat as possible. Getting minimum ventilation right is the difference between a healthy barn and one with chronic respiratory problems.

How Minimum Ventilation Works

Minimum ventilation fans run on a timer or a variable speed controller. The timer is set to run the fan for a certain number of minutes per hour, or the variable speed controller runs the fan at a low speed continuously. The goal is to exchange enough air to keep relative humidity below 70 percent and ammonia below the recommended limit of 10 to 15 parts per million (ppm) at pig level.

The minimum ventilation rate depends on the number and size of pigs in the barn. A good starting point is 20 to 30 CFM per pig for pigs under 50 pounds, increasing to 40 to 60 CFM per pig for pigs over 150 pounds. These rates remove the moisture produced by the pigs while minimizing heat loss.

Setting the Timer or Variable Speed

If you are using a timer, set it to run the fan for the minimum number of minutes per hour that keeps humidity and gases at acceptable levels. Start with the manufacturer's recommendation or your extension service's guidance, then adjust based on your actual conditions. Check the barn in the morning, before the sun warms the building, because this is when moisture levels are highest.

If you are using a variable speed fan, set the minimum speed to achieve the same result. The fan should run continuously, but at a low speed. This is generally better than a timer because it provides constant air movement and avoids the temperature swings that come with on-off cycling.

Adjusting Minimum Ventilation

Minimum ventilation needs adjustment as pigs grow and as the weather changes. The rule of thumb is to increase minimum ventilation by about 5 percent per week as pigs grow, and to make smaller adjustments for weather. In practice, you should check the barn daily and adjust the settings when you see signs of moisture buildup, high gas levels, or drafts.

Signs that minimum ventilation is too low include condensation on windows and walls, wet bedding or floors, a strong ammonia smell, and pigs coughing or showing respiratory distress. Signs that it is too high include drafts on pigs, cold floors, and high energy bills.

Minimum Ventilation and Manure Handling

The type of manure handling system affects minimum ventilation requirements. Barns with pits under the floor produce more ammonia and moisture than barns with flush systems or deep bedding. If you have a pit system, you may need to increase minimum ventilation during periods when the pit is being agitated or pumped. Always follow safety procedures when working with manure pits, as hydrogen sulfide can be deadly.

Tunnel Ventilation for Hot Weather

Tunnel ventilation is the most effective way to cool pigs in hot weather. It works by moving large volumes of air down the length of the barn at high speed, creating a wind chill effect that helps pigs dissipate heat.

How Tunnel Ventilation Works

In a tunnel ventilation system, air enters through large inlets at one end of the barn and is pulled by a bank of fans at the other end. The air moves down the barn in a single direction, picking up heat and moisture as it travels. The air speed at pig level is typically 300 to 500 feet per minute, which creates a wind chill effect of 5 to 10 degrees Fahrenheit.

Tunnel fans are located on the end wall opposite the inlet. They are large, high-volume fans, typically 36 to 48 inches in diameter. The number of fans depends on the barn size and the desired air speed. A common rule of thumb is to provide 250 to 400 CFM per pig for tunnel ventilation, depending on the climate and pig size.

Tunnel Inlets

Tunnel inlets are large openings, usually with curtains or doors that open fully during tunnel operation. They are located on the end wall or sidewall near the end of the barn. The total inlet area should be sized so that the air velocity through the inlet does not exceed 500 to 700 feet per minute. This prevents excessive static pressure and ensures even air distribution.

A common mistake is to undersize the tunnel inlets. If the inlets are too small, static pressure rises and fan efficiency drops. The fans move less air, and the pigs do not get the wind chill they need.

Tunnel Curtains and Doors

Tunnel inlets need to seal tightly when not in use. If they leak during cold weather, they cause drafts and reduce the effectiveness of minimum ventilation. Install good quality curtains or doors and check them regularly for wear and gaps.

Combination Systems

Many barns use a combination system that operates in different modes depending on the temperature. In cool weather, the barn uses minimum ventilation with ceiling inlets. As temperature rises, sidewall exhaust fans turn on to provide transitional ventilation. In hot weather, the tunnel fans turn on and the sidewall inlets close. The controller manages the transitions automatically, but you need to set the temperature setpoints correctly.

Transitional Ventilation for Spring and Fall

Transitional ventilation is the most difficult mode to manage because it operates in the temperature range where neither minimum nor tunnel ventilation is ideal. This is typically between about 50 and 70 degrees Fahrenheit, depending on pig size and humidity.

The Challenge of Transitional Ventilation

In transitional weather, the temperature swings widely between day and night. A barn that needs minimum ventilation in the morning may need tunnel ventilation by mid-afternoon. The controller must respond quickly to these changes, and the ventilation system must be able to ramp up and down smoothly.

The main challenge is air distribution. At transitional ventilation rates, the air velocity through ceiling inlets is too low to mix properly with the warm air at the ceiling. This leads to cold air dropping directly onto pigs, creating drafts. Many barns use sidewall inlets or a combination of ceiling and sidewall inlets to handle this problem.

Sidewall Inlets for Transitional Ventilation

Sidewall inlets are located in the sidewalls, usually above the pigs. They open outward and direct air upward toward the ceiling, where it mixes with warm air before falling back down. These inlets work well at intermediate ventilation rates.

The number and spacing of sidewall inlets depend on the barn width and the fan capacity. A common arrangement is to place inlets every 8 to 12 feet along each sidewall. The total inlet area should be sized to match the fan capacity at the static pressure you want to maintain.

Managing Temperature Swings

The key to managing transitional ventilation is to anticipate temperature changes. Check the weather forecast daily and adjust your controller setpoints accordingly. On days with large temperature swings, you may need to adjust the setpoints more than once.

Another strategy is to use a variable speed fan for transitional ventilation. This allows the fan to ramp up and down smoothly as temperature changes, rather than cycling on and off. Variable speed fans are more expensive, but they provide better control and reduce temperature fluctuations in the barn.

Selecting Fans for Your Barn

Fan selection is one of the most important decisions in barn design. Fans must be sized correctly, installed properly, and maintained regularly to perform at their rated capacity.

Fan Types

There are two main types of fans used in swine barns: axial fans and centrifugal fans. Axial fans move air parallel to the fan shaft and are the most common type used in barn ventilation. They are efficient and relatively inexpensive. Centrifugal fans move air perpendicular to the fan shaft and are used in applications where higher static pressure is needed, such as in some ducted systems.

Axial fans come in two configurations: direct drive and belt drive. Direct drive fans have the motor connected directly to the fan blade. They are simpler and require less maintenance, but they are less efficient at low speeds. Belt drive fans have a motor connected to the fan blade through a belt and pulley system. They are more efficient at low speeds and allow you to adjust the fan speed by changing the pulley size.

Fan Sizing

Fan sizing is based on the total ventilation requirement of the barn. This is calculated by multiplying the number of pigs by the ventilation rate per pig for each season. For example, a barn with 1,000 pigs at an average weight of 150 pounds needs about 50,000 CFM for minimum ventilation and 300,000 to 400,000 CFM for tunnel ventilation.

The total fan capacity should be divided among several fans of different sizes. This allows the controller to match fan capacity to the ventilation requirement more precisely. A common arrangement is to have one or two small fans for minimum ventilation, several medium fans for transitional ventilation, and two or more large fans for tunnel ventilation.

Fan Efficiency

Fan efficiency is measured in CFM per watt. More efficient fans move more air per unit of electricity, which reduces operating costs. Look for fans with the highest efficiency rating that fits your budget. High-efficiency fans cost more upfront but typically pay for themselves in energy savings within a few years.

Fan Maintenance

Fans need regular maintenance to perform at their rated capacity. Dust buildup on blades and shutters can reduce airflow by 20 to 30 percent. Belts stretch and need adjustment. Motors wear out and need replacement.

Establish a maintenance schedule for your fans. Clean blades and shutters at least twice a year, check belt tension quarterly, and lubricate motors according to the manufacturer's recommendations. Replace worn belts and bearings promptly. A fan that is not performing at its rated capacity is wasting energy and compromising the barn environment.

Inlet Design and Placement

Inlets are the other half of the ventilation equation. Fans create the pressure difference that pulls air into the barn, but inlets determine where that air goes. Poor inlet design or placement can undermine an otherwise good ventilation system.

Types of Inlets

There are several types of inlets used in swine barns. Ceiling inlets are the most common for minimum ventilation. They are located in the ceiling and direct air along the ceiling surface, where it mixes with warm air before falling to the pig zone.

Sidewall inlets are located in the sidewalls, usually above the pigs. They are used for transitional ventilation and direct air upward toward the ceiling. Some sidewall inlets are adjustable, allowing you to change the direction of the air jet.

Tunnel inlets are large openings at the end of the barn used for tunnel ventilation. They are typically curtained or covered with doors that open fully during tunnel operation.

Inlet Sizing

Inlet sizing is critical for proper air distribution. The total inlet area must match the fan capacity at the desired static pressure. A common rule of thumb is to provide about 1 square foot of inlet area for every 300 to 400 CFM of fan capacity. However, the exact sizing depends on the inlet type, the static pressure, and the desired air velocity.

If the inlets are too small, static pressure rises and fan efficiency drops. If they are too large, static pressure falls and air distribution becomes uneven. The goal is to maintain a static pressure of 0.05 to 0.15 inches of water column, depending on the inlet type and the season.

Inlet Placement

Inlet placement determines how air moves through the barn. For minimum ventilation, inlets should be spaced evenly along the barn to ensure uniform air distribution. Inlets near the ends of the barn may need to be smaller or farther apart to avoid air short-circuiting from the end walls.

For tunnel ventilation, the inlet should be located at the end of the barn opposite the fans. The inlet should be as large as practical to minimize static pressure and maximize air speed at pig level.

Adjustable Inlets

Adjustable inlets allow you to control the direction and velocity of the incoming air. In cold weather, you want the air to travel along the ceiling for as long as possible to mix with warm air. In warm weather, you want the air to drop more quickly to the pig zone.

Most adjustable inlets are controlled by the barn controller, which opens or closes them based on static pressure. Some are manually adjustable, requiring you to change the setting as the season changes. Manual inlets are less expensive but require more management.

Static Pressure Management

Static pressure is the force that pulls air through inlets. It is measured in inches of water column and is one of the most important diagnostic tools in barn ventilation. Understanding and managing static pressure can solve many ventilation problems.

How Static Pressure Works

When fans exhaust air from the barn, they create a slight vacuum. This vacuum pulls air through the inlets. The speed of the air entering through the inlets depends on the static pressure. Higher static pressure means faster air entry, which means the air travels farther along the ceiling before falling.

The controller maintains static pressure by adjusting inlet openings. When fans turn on, static pressure rises and the controller opens the inlets. When fans turn off, static pressure falls and the controller closes the inlets. The target static pressure is set during commissioning and adjusted as needed.

Measuring Static Pressure

Static pressure is measured with a manometer. There are two types: analog and digital. Analog manometers use a tube of water and a scale. Digital manometers use a pressure sensor and display the reading on a screen. Digital manometers are more accurate and easier to read, but they require batteries and can fail.

Place the manometer in a location that represents the average pressure in the barn. Avoid placing it near doors, inlets, or fans, where pressure readings can be distorted. The sensor tube should be open to the barn interior, not blocked by dust or debris.

Troubleshooting Static Pressure

If static pressure is too high, the air enters through the inlets at very high speed. This can create drafts and cause the air to fall to the pig zone too quickly. High static pressure also reduces fan efficiency, which means the fans move less air.

Common causes of high static pressure include dirty filters, blocked inlets, undersized inlets, and closed or partially closed shutters. Check these items first.

If static pressure is too low, the air enters through the inlets at low speed. This means the air does not travel far enough along the ceiling and falls to the pig zone too quickly, creating drafts. Low static pressure also means that air is entering through unintended openings, such as cracks in the walls or around doors.

Common causes of low static pressure include oversized inlets, open doors, and leaks in the building envelope. Check for these problems and seal any leaks you find.

Air Quality Monitoring

Air quality in a swine barn is determined by the levels of gases, dust, and moisture in the air. Monitoring these factors helps you identify problems before they affect pig health.

Ammonia

Ammonia is produced by the breakdown of urea in manure. It is a respiratory irritant that damages the lining of the respiratory tract, making pigs more susceptible to disease. The recommended limit for ammonia in a swine barn is 10 to 15 parts per million (ppm) at pig level. Levels above 25 ppm are considered hazardous.

Ammonia levels are highest near the floor and in the manure pit. Measure ammonia at pig level, not at human height. Use a gas detection tube or an electronic sensor. Calibrate electronic sensors regularly according to the manufacturer's instructions.

If ammonia levels are high, increase minimum ventilation, manage the manure pit more frequently, and check for wet areas in the barn. Ammonia production increases with temperature and moisture, so controlling moisture is key.

Carbon Dioxide

Carbon dioxide is produced by pig respiration and manure decomposition. It is not directly toxic at typical barn levels, but it is a good indicator of air quality. High carbon dioxide levels mean that the air is stale and that other gases and dust are likely accumulating.

The recommended limit for carbon dioxide in a swine barn is 3,000 ppm. Levels above 5,000 ppm indicate a serious ventilation problem. Carbon dioxide is heavier than air, so it collects near the floor. Measure it at pig level.

Hydrogen Sulfide

Hydrogen sulfide is produced by manure decomposition and is highly toxic. It has a characteristic rotten egg smell at low levels, but at high levels it can deaden the sense of smell, so you cannot rely on your nose for safety. The recommended limit for hydrogen sulfide is 10 ppm for short-term exposure.

Hydrogen sulfide is most dangerous during manure pit agitation and pumping. Never enter a barn during these operations without proper respiratory protection. If you smell rotten eggs, leave the barn immediately and ventilate it thoroughly before re-entering.

Dust

Dust in a swine barn is a mixture of feed particles, dried manure, skin cells, and mold spores. It irritates the respiratory tract and can carry pathogens. High dust levels are associated with increased respiratory disease in pigs.

Dust levels are difficult to measure without specialized equipment, but you can assess them visually. If you can see dust in the air when light shines through a window, the dust level is too high. Increasing ventilation and reducing feed dust can help.

Relative Humidity

Relative humidity is a measure of moisture in the air. The recommended range for a swine barn is 50 to 70 percent. High humidity promotes the growth of bacteria and molds and increases ammonia production. Low humidity causes dust to become airborne and irritates the respiratory tract.

Relative humidity is measured with a hygrometer. Place it at pig level, away from water sources and inlets. If humidity is consistently above 70 percent, increase minimum ventilation. If it is consistently below 50 percent, you may need to reduce ventilation or add moisture.

Ventilation Controllers

Modern swine barns use electronic controllers to manage ventilation automatically. A good controller monitors temperature, static pressure, and sometimes humidity, and adjusts fans and inlets to maintain the desired environment.

Controller Functions

The main function of the controller is to maintain the target temperature in the barn. It does this by turning fans on and off, adjusting variable speed fans, and opening and closing inlets. The controller also monitors static pressure and adjusts inlets to maintain the target pressure.

Most controllers have multiple temperature setpoints that define the ventilation curve. For example, the controller might be set to run minimum ventilation below 60 degrees, transitional ventilation between 60 and 75 degrees, and tunnel ventilation above 75 degrees. The exact setpoints depend on your barn and your pigs.

Setting the Controller

Setting the controller correctly is one of the most important tasks in barn management. Start with the manufacturer's recommendations or your extension service's guidance, then adjust based on your actual conditions. Check the barn at different times of day and in different weather conditions to see how the controller responds.

The most common mistake is setting the temperature setpoints too high or too low. If the setpoints are too high, the barn stays too warm and pigs are heat stressed. If they are too low, the barn is over-ventilated and pigs are exposed to drafts.

Controller Alarms

Controllers have alarms that alert you to problems. Common alarms include high temperature, low temperature, power failure, and static pressure out of range. Test your alarms regularly to make sure they work, and make sure someone is available to respond to alarms at all times.

Backup Systems

A power failure in a swine barn is a serious emergency. Pigs can die from heat stress within hours in hot weather. Install a backup generator that is large enough to run the critical fans and controller. Test the generator monthly and keep it in good working order.

Some controllers have a backup battery that powers the controller during a power failure. This allows the controller to sound an alarm and maintain its settings when power is restored.

Common Ventilation Mistakes

Even well-designed ventilation systems fail when they are not managed properly. Here are the most common mistakes I see on farms.

Setting Minimum Ventilation Too Low

The most common mistake is setting minimum ventilation too low to save energy. This leads to high humidity, high ammonia, and respiratory disease. The energy savings are small compared to the cost of reduced pig performance and increased medication.

Ignoring Static Pressure

Static pressure is the most important diagnostic tool in barn ventilation, yet many farmers ignore it. If your manometer is broken or missing, replace it immediately. Check it daily and investigate any readings outside the expected range.

Blocking Inlets

Inlets are often blocked by feed bags, tools, or other equipment. This prevents air from entering the barn properly and causes static pressure to rise. Keep inlets clear at all times.

Failing to Maintain Fans

Dust buildup on fan blades and shutters can reduce airflow by 20 to 30 percent. Dirty fans waste energy and fail to provide adequate ventilation. Clean fans at least twice a year and check them monthly.

Not Adjusting for Pig Growth

Ventilation requirements increase as pigs grow. A setting that is correct for 50-pound pigs is inadequate for 200-pound pigs. Adjust your settings weekly as pigs grow.

Closing the Barn Too Tightly

Some farmers close the barn too tightly in cold weather to save heat. This leads to high humidity and gas levels. The barn needs a minimum amount of air exchange even in the coldest weather.

Ignoring the Weather Forecast

Spring and fall weather is unpredictable. A barn that is comfortable in the morning can be overheated by afternoon. Check the weather forecast daily and adjust your controller setpoints accordingly.

Seasonal Management Checklist

Ventilation management changes with the seasons. Use this checklist to stay on top of the key tasks.

Spring

• Clean fans and shutters after winter use
• Check belts and replace worn ones
• Adjust minimum ventilation as pigs grow
• Increase ventilation as temperatures rise
• Watch for temperature swings between day and night
• Check tunnel inlets for proper operation

Summer

• Test tunnel fans and inlets before hot weather arrives
• Check backup generator and test it monthly
• Monitor static pressure during tunnel operation
• Watch for hot spots in the barn
• Adjust tunnel inlet openings as needed
• Check water supply and drinker flow rates

Fall

• Transition from tunnel to transitional ventilation
• Adjust minimum ventilation as temperatures fall
• Seal leaks in the building envelope
• Check heaters and thermostats
• Adjust ventilation curve for cooler weather
• Monitor humidity as temperatures drop

Winter

• Check minimum ventilation settings weekly
• Monitor ammonia and humidity at pig level
• Watch for condensation on walls and windows
• Keep inlets clear of snow and ice
• Check heaters and fuel supply
• Adjust minimum ventilation as pigs grow

When to Call a Veterinarian or Extension Agent

Ventilation problems often show up as pig health problems. If you see respiratory signs in your pigs, do not assume it is just a ventilation issue. Call your veterinarian.

Signs that warrant a veterinary call include:

• Coughing or sneezing in multiple pigs
• Labored breathing or open-mouth breathing
• Nasal discharge or eye discharge
• Reduced feed intake or slowed growth
• Increased mortality
• Pigs huddling or spreading out in the pen

Your veterinarian can help you determine whether the problem is caused by ventilation, infectious disease, or both. In many cases, both are involved. Poor ventilation stresses pigs and makes them more susceptible to disease.

Call your extension agent or a ventilation specialist if:

• Static pressure readings are consistently out of range
• Air distribution is uneven, with hot or cold spots in the barn
• You cannot control humidity or gas levels despite adjusting the system
• You are planning a new barn or major renovation
• Your energy bills are significantly higher than expected

A ventilation specialist can measure airflow, check fan performance, and recommend adjustments or equipment upgrades. This is a worthwhile investment if you have persistent ventilation problems.

Designing a New Grow-Finish Barn

If you are planning a new barn, ventilation design should be part of the initial planning process. The following steps will help you get it right.

Step 1: Determine Your Ventilation Requirements

Calculate the ventilation requirements based on the number of pigs, the expected weight range, and your local climate. Your extension service can provide climate-specific recommendations.

Step 2: Choose the Ventilation System

Decide whether you need tunnel ventilation, and whether you want a combination system. Most grow-finish barns in warm climates benefit from tunnel ventilation. Barns in cool climates may be able to rely on sidewall ventilation alone.

Step 3: Size the Fans

Select fans that provide the required ventilation rates for each season. Use high-efficiency fans to reduce operating costs. Include a mix of fan sizes to allow the controller to match capacity to demand.

Step 4: Design the Inlets

Size and place inlets to match the fan capacity and the barn layout. Consider the air distribution needs for each season. Work with a ventilation specialist to get this right.

Step 5: Select the Controller

Choose a controller with the features you need, including temperature setpoints, static pressure control, variable speed fan control, and alarms. Make sure it is compatible with your fans and inlets.

Step 6: Plan for Maintenance

Design the barn with maintenance in mind. Provide access to fans for cleaning and servicing. Install a manometer in a convenient location. Plan for a backup generator.

Renovating an Existing Barn

If you are renovating an existing barn, the principles are the same, but the constraints are different. You may be limited by the existing structure, the fan openings, and the electrical system. Work with a ventilation specialist to develop a renovation plan that fits your barn.

The most common renovations are:

• Replacing old fans with high-efficiency models
• Adding tunnel ventilation to an existing barn
• Improving inlet design and placement
• Upgrading the controller
• Sealing leaks in the building envelope

Prioritize renovations based on the biggest impact on pig health and energy efficiency. A ventilation specialist can help you identify the most cost-effective improvements.

Monitoring and Recordkeeping

Good recordkeeping is essential for managing ventilation. Keep a log of the following items and review it regularly:

• Fan run times and settings
• Static pressure readings
• Temperature and humidity readings
• Ammonia and carbon dioxide levels
• Pig health observations
• Medication use
• Energy consumption
• Maintenance performed

Record this information daily or weekly, depending on the item. Review the records monthly to identify trends. For example, if ammonia levels have been creeping up over several weeks, you may have a manure management problem or a ventilation system that is degrading.

A good recordkeeping system does not need to be complicated. A notebook or a spreadsheet works fine. The key is to be consistent and to review the records regularly.

Frequently Asked Questions

What is the ideal static pressure for a swine barn?

The ideal static pressure depends on your inlet type and fan capacity. Most barns operate at 0.05 to 0.15 inches of water column. Ceiling inlets typically work best at 0.08 to 0.12 inches. Tunnel inlets work best at lower pressures, around 0.04 to 0.06 inches. Check your inlet manufacturer's recommendations and adjust based on how the air distributes in your barn.

How often should I clean my fans?

Clean fans at least twice a year, ideally in spring and fall. Dust buildup on blades and shutters can reduce airflow by 20 to 30 percent. In dusty environments or during periods of high feed dust, you may need to clean more often. Check fans monthly and clean them when you see visible dust buildup.

What is the maximum ammonia level for pigs?

The recommended limit for ammonia in a swine barn is 10 to 15 parts per million (ppm) at pig level. Levels above 25 ppm are considered hazardous and will cause respiratory damage. If ammonia levels are consistently above 15 ppm, increase minimum ventilation and address the source of ammonia, which is usually the manure.

How do I know if my minimum ventilation is set correctly?

The best indicators are relative humidity and ammonia levels. Relative humidity should be between 50 and 70 percent. Ammonia should be below 15 ppm at pig level. If humidity is above 70 percent or ammonia is above 15 ppm, increase minimum ventilation. If pigs are showing signs of drafts, such as huddling or shivering, decrease minimum ventilation.

What air speed do pigs need in tunnel ventilation?

Pigs need an air speed of 300 to 500 feet per minute at pig level for effective wind chill in hot weather. The exact speed depends on the pig size and the temperature. Larger pigs need more air speed than smaller pigs. If you cannot achieve this air speed, you may need more fans or larger tunnel inlets.

Should I run minimum ventilation fans continuously or on a timer?

Continuous operation with a variable speed fan is generally better than timer-based operation. Continuous operation provides constant air movement and avoids temperature swings. If you are using a timer, set it to run the fan for the minimum number of minutes per hour that keeps humidity and gases at acceptable levels. Check the barn in the morning to see if the settings are adequate.

How do I measure ammonia in my barn?

Use a gas detection tube or an electronic sensor. Measure at pig level, not at human height. Ammonia is heavier than air and collects near the floor. Calibrate electronic sensors regularly according to the manufacturer's instructions. Gas detection tubes are accurate but are single-use and can be expensive for regular monitoring.

What should I do if the power goes out in my barn?

If you have a backup generator, start it immediately and connect it to the critical fans and controller. Check the barn for signs of heat stress, especially in hot weather. If you do not have a generator, open doors and windows to provide natural ventilation. Monitor the barn continuously until power is restored. A power failure is a serious emergency, and you should have a plan in place before it happens.

Related Farming Guides

• Swine Barn Ventilation: Designing for Thermal Comfort and Air Quality

This section will be populated with links to related farming guides on pig housing, swine health, and barn management topics. Check back for updates.

Related Clinical & Scientific Guides

• Pig Enrichment Programs and Behavior Monitoring
• Swine Handling Facility Design for Safe Pig Movement
• Swine Feeding Management for Grow-Finish Pigs

References

• National Pork Board: https://www.pork.org/
• USDA APHIS Swine Health: https://www.aphis.usda.gov/livestock-poultry-disease/swine
• FAO Pig Production: https://www.fao.org/pig-production-and-products/en/
• FAO Animal Production and Health: https://www.fao.org/animal-production/en/
• WOAH (World Organisation for Animal Health): https://www.woah.org/en/home/

This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.