# Broiler House Air Inlet Design and Placement ## Key Takeaways - **Air circulation pattern is paramount:** Properly designed and placed air inlets control the path of incoming fresh air, ensuring it travels along the ceiling, mixes with warmer air, and drops to bird level uniformly, preventing drafts and stagnant zones. This is achieved by matching inlet opening size to fan capacity to maintain a target air speed across the ceiling of 800-1,200 feet per minute during minimum ventilation. - **Static pressure is the primary adjustment tool:** Maintaining static pressure between 0.05 and 0.15 inches of water column is critical for controlling air speed through inlets. Higher static pressure requires wider inlet openings, while lower static pressure necessitates narrower openings to achieve the desired air velocity and circulation pattern. - **Inlet design and placement are house-specific:** Sidewall inlets are generally preferred for tunnel-ventilated houses, directing air horizontally across the ceiling, while ceiling inlets are suitable for lower roof pitches or specific airflow requirements. Inlet placement must ensure uniform distribution along the house length, with sidewall inlets typically spaced 4-8 feet apart and positioned at or just below the ceiling line. - **Dynamic inlet management is essential:** Inlets must be adjusted weekly or whenever bird weight, outside temperature, or fan staging changes. Failure to adjust inlets leads to suboptimal air quality, characterized by litter capping, elevated ammonia levels, and increased respiratory disease incidence. - **Troubleshooting requires systematic observation:** Common issues like bird huddling near sidewalls or the center, wet litter, or ammonia smell can be diagnosed by assessing static pressure, inlet height, baffle angle, and air leaks, often confirmed with simple smoke or tissue tests to visualize airflow patterns. --- Getting air into a broiler house sounds simple, but the way you design and place your air inlets determines whether your birds get fresh air evenly distributed or whether they huddle in drafts while stagnant air sits over the litter. This guide covers the engineering principles behind inlet design, the step-by-step process for sizing and placing inlets, how to adjust them as birds grow and weather changes, and how to troubleshoot the common problems that show up when inlet design is wrong. It is written for broiler growers, farm managers, and poultry service technicians who want to understand the why behind inlet placement, not just a generic checklist. ## At a Glance - Air inlets control where fresh air enters the house and how fast it travels across the ceiling before dropping to bird level. - Inlet opening size must match fan capacity. Too much opening means low air speed and drafts. Too little opening means high static pressure and reduced fan performance. - Inlet placement should create uniform air distribution along the full length of the house. Sidewall inlets work best for most tunnel houses, while ceiling inlets suit houses with lower roof pitches or where sidewall placement is not practical. - The target air speed across the ceiling is typically 800 to 1,200 feet per minute during minimum ventilation. This speed pushes air to the center of the house before it drops. - Static pressure is your primary adjustment tool. Most broiler houses operate between 0.05 and 0.15 inches of water column during minimum ventilation, depending on house width and inlet design. - Inlets must be adjusted weekly or whenever bird weight, outside temperature, or fan staging changes. Set-and-forget inlet management leads to litter capping, ammonia, and respiratory issues. - A simple smoke test or tissue test can reveal dead zones and drafts that you cannot see with your eyes alone. - If birds show respiratory signs despite correct temperature and ventilation settings, call your veterinarian or extension agent before adjusting inlets further. ## Why Air Inlet Design Matters More Than Fan Power Most broiler growers understand that fans move air out of the house. What gets less attention is that air has to come back in somewhere, and that somewhere determines the path the air takes before it reaches the birds. A house with excellent exhaust fans but poorly placed inlets will still have cold drafts at one end, stale air at the other, and birds that pile or pant in the same room. The physics are straightforward. When an exhaust fan pulls air out of the house, it creates a slight negative pressure inside. The outside air then pushes through any opening it can find. If your inlets are not designed and placed to control that incoming air, the air will find its own way in through cracks, door gaps, and loose curtains. That uncontrolled air enters at low speed and drops immediately to floor level, chilling the birds nearest to the leak. Meanwhile, the center of the house gets little fresh air and the litter goes sour. Air inlets solve this by giving the incoming air a controlled path. When an inlet opens, the air enters at a specific angle and speed. It travels along the ceiling toward the center of the house, picking up heat from the warm air that naturally rises, and then drops to bird level as a warm, oxygenated air mass. This is called the air circulation pattern, and it is the single most important concept in broiler house ventilation. The design of the inlet determines three things. First, it determines the direction of the incoming air. Second, it determines the speed of that air. Third, it determines the volume of air that can enter. Get all three right and your ventilation system works efficiently. Get any one wrong and you will spend the whole flock fighting temperature gradients, moisture problems, and bird health issues. ## Understanding the Air Circulation Pattern Before you can place a single inlet, you need to understand how air moves inside a broiler house during minimum ventilation. Minimum ventilation is the mode you use when outside temperatures are below the target house temperature and you are running fans intermittently to control moisture and air quality. During minimum ventilation, the goal is not to cool the birds. The goal is to remove moisture, ammonia, and carbon dioxide while preserving heat. You run a fan for a short period, typically one to five minutes on a timer, then let the fan rest. During the fan-on period, fresh air enters through the inlets, travels along the ceiling, and pushes the stale air down to floor level where the exhaust fan removes it. For this to work, the incoming air must travel far enough along the ceiling to reach the center of the house before it drops. The distance the air travels depends on its speed and the angle at which it enters. Air entering at a steep downward angle will drop quickly. Air entering nearly horizontal to the ceiling will travel further before dropping. The target is for the air to reach the center of the house, where the ridge is highest, before it falls toward the birds. By the time it reaches bird level, it should have mixed with the warm air near the ceiling and be close to house temperature. This prevents cold air from falling directly onto the birds, which is the most common cause of chilling during minimum ventilation. The key measurements are house width and ceiling height. A 40 foot wide house with a 10 foot ceiling needs different inlet placement than a 60 foot wide house with a 12 foot ceiling. The air speed across the ceiling must be high enough to carry the air to the center but not so high that it creates turbulence that disrupts the pattern. ## Types of Air Inlets for Broiler Houses There are two main categories of air inlets used in modern broiler houses: sidewall inlets and ceiling inlets. Within each category there are several designs, and your choice depends on your house configuration, budget, and ventilation goals. ### Sidewall Inlets Sidewall inlets are mounted on the side walls of the house, typically just below the ceiling or eave line. They open outward or inward and direct air across the ceiling toward the center of the house. Sidewall inlets are the most common choice for tunnel-ventilated broiler houses because they work well with the negative pressure created by exhaust fans. There are several designs of sidewall inlets. The most basic is the hinged baffle, which is a simple board or panel that swings open. The angle of the baffle determines the direction of the incoming air. More advanced designs use adjustable vanes or directional louvers that allow you to fine-tune the air direction without changing the opening size. Sidewall inlets have several advantages. They are relatively inexpensive to install, easy to maintain, and work well with automated control systems. They also allow you to direct air along the ceiling regardless of roof pitch, because you can adjust the baffle angle. The main disadvantage of sidewall inlets is that they require adequate ceiling height to work properly. If the ceiling is too low, the air will not have enough distance to travel before it reaches the center of the house. In houses with low roof pitch, sidewall inlets may not provide sufficient air distribution. ### Ceiling Inlets Ceiling inlets are mounted in the ceiling itself, usually in the center of the house or distributed across the ceiling area. They direct air downward into the house, creating a different circulation pattern than sidewall inlets. Ceiling inlets are often used in houses with low roof pitch or where sidewall placement is not practical. Ceiling inlets come in several designs. Some are simple round or rectangular openings with adjustable dampers. Others use a cone or diffuser design that spreads the air in a circular pattern. The most common type in broiler houses is the slot inlet, which is a long narrow opening that runs along the ceiling. Ceiling inlets work best when the air needs to drop relatively quickly, such as in houses with high ceilings or where you want to create air movement at bird level. They are less effective in wide houses because the air does not travel as far horizontally before it drops. The choice between sidewall and ceiling inlets is not always clear-cut. Some houses use a combination of both, with sidewall inlets for minimum ventilation and ceiling inlets for transitional or tunnel ventilation. The best approach is to match the inlet type to your house geometry and ventilation goals. ## Sizing Your Air Inlets The size of your air inlets determines how much air can enter the house at a given static pressure. If the total inlet area is too small, the fans will struggle to pull air through the openings, creating excessive static pressure and reducing fan performance. If the total inlet area is too large, the air will enter at low speed and drop before reaching the center of the house. The general rule is that the total inlet area should be sized to match the total fan capacity. A common guideline is to provide 1 square foot of inlet area for every 500 to 700 cubic feet per minute of fan capacity. For example, a house with 100,000 CFM of fan capacity would need between 143 and 200 square feet of total inlet area. This ratio is a starting point. The actual requirement depends on the static pressure you want to maintain, the design of your inlets, and the air speed you need for proper circulation. A better approach is to calculate the required inlet area based on the air speed you want to achieve. The formula is simple. Divide the total fan capacity in cubic feet per minute by the desired air speed in feet per minute to get the total inlet area in square feet. For example, if you have 100,000 CFM of fan capacity and you want an air speed of 800 feet per minute through the inlets, you need 125 square feet of total inlet area. In practice, most growers size their inlets to achieve an air speed of 800 to 1,200 feet per minute through the inlet opening. This speed range gives good air circulation along the ceiling without creating excessive turbulence or noise. The inlet opening area changes as the inlet opens and closes. A fully open inlet has a larger opening than a partially open inlet. The control system should adjust the inlet opening based on the number of fans running and the static pressure in the house. This is where the static pressure sensor and the inlet controller work together. ## Determining Inlet Placement Once you know how much total inlet area you need, the next step is deciding where to put the inlets. The goal is uniform air distribution along the entire length of the house. If you concentrate all your inlets at one end, the far end of the house will get little fresh air and the near end will get too much. For sidewall inlets, the standard approach is to space them evenly along both side walls. The spacing between inlets depends on the width of the house and the air speed you are trying to achieve. A common spacing is 4 to 8 feet between inlets, with inlets placed on both sides of the house. The vertical placement of sidewall inlets is also important. The inlet should be positioned so that the incoming air travels along the ceiling. This means the top of the inlet opening should be at or slightly below the ceiling line. If the inlet is too low, the air will drop too quickly. If it is too high, the air may hit the ceiling and create turbulence. For ceiling inlets, the placement depends on the design of the inlet and the roof pitch. In a house with a gable roof, ceiling inlets are often placed along the ridge line. In a house with a flat or low-pitch roof, ceiling inlets may be distributed across the entire ceiling area. The distance from the inlet to the nearest exhaust fan also matters. Inlets should not be placed too close to fans, because the fan will pull air directly through the inlet without allowing it to circulate across the ceiling. A common guideline is to place inlets at least 10 feet away from the nearest fan. ## The Role of Static Pressure Static pressure is the difference in air pressure between the inside and outside of the house. It is measured in inches of water column, and it is the force that pushes air through the inlets. Static pressure is created by the exhaust fans pulling air out of the house faster than it can enter through the inlets. During minimum ventilation, the target static pressure is typically 0.05 to 0.15 inches of water column. The exact target depends on the width of the house and the design of the inlets. Wider houses need higher static pressure to push air all the way to the center. Houses with ceiling inlets may need different static pressure than houses with sidewall inlets. Static pressure is your primary tool for controlling air speed through the inlets. If the static pressure is too low, the air enters slowly and drops before reaching the center. If the static pressure is too high, the air enters at high speed and may create drafts at bird level. The relationship between static pressure and inlet opening is inverse. When the static pressure is high, the inlets should be opened wider to allow more air in. When the static pressure is low, the inlets should be closed down to increase the air speed. Your controller should manage this automatically, but you need to understand the relationship so you can troubleshoot when something goes wrong. To check your static pressure, use a manometer or a digital static pressure sensor. Place the sensor in the center of the house, away from doors and fans, to get an accurate reading. Check the static pressure at different fan stages and adjust your inlet openings accordingly. ## Step-by-Step Guide to Designing Your Inlet System If you are building a new house or retrofitting an existing one, follow these steps to design and install your air inlet system. ### Step 1: Measure Your House Start by measuring the width, length, and ceiling height of your house. You also need to know the roof pitch and the type of ceiling you have. Write these numbers down, because you will use them for all your calculations. ### Step 2: Determine Your Fan Capacity Add up the rated capacity of all your exhaust fans. This is usually expressed in cubic feet per minute at a specific static pressure, such as 0.10 inches of water column. Use the capacity at the static pressure you plan to operate at, not the free-air rating. ### Step 3: Calculate Total Inlet Area Divide your total fan capacity by your target air speed. For most broiler houses, use 800 to 1,000 feet per minute as your target. This gives you the total inlet area in square feet. ### Step 4: Choose Your Inlet Type Decide whether you will use sidewall inlets, ceiling inlets, or a combination. Consider your ceiling height, roof pitch, and budget. Sidewall inlets are the most common and usually the most effective for tunnel houses. ### Step 5: Determine Inlet Spacing Divide the total inlet area by the area of each individual inlet to get the number of inlets you need. Then divide the length of each wall by the number of inlets to get the spacing. For sidewall inlets, space them evenly along both walls. ### Step 6: Position the Inlets Vertically For sidewall inlets, position the top of the inlet opening at or just below the ceiling line. The inlet should direct air along the ceiling toward the center of the house. Adjust the baffle angle to achieve the desired air direction. ### Step 7: Install Static Pressure Control Install a static pressure sensor in the center of the house and connect it to your inlet controller. The controller should automatically adjust inlet openings based on the static pressure reading. ### Step 8: Test and Adjust Run your fans and check the air distribution using a smoke test or tissue test. Adjust inlet angles and openings until you get uniform air distribution with no dead zones and no drafts at bird level. ## Adjusting Air Inlets for Different Ventilation Stages Broiler houses operate in three main ventilation stages: minimum ventilation, transitional ventilation, and tunnel ventilation. Each stage requires different inlet management. ### Minimum Ventilation During minimum ventilation, you are running a small number of fans on a timer to control moisture and air quality. The inlets should be opened just enough to match the fan capacity. The static pressure should be at your target level, and the air should travel across the ceiling to the center of the house. The inlet opening during minimum ventilation is typically small, often only 1 to 3 inches. The exact opening depends on the number of fans running and the static pressure. Your controller should adjust this automatically, but you should check it regularly. As birds grow, they produce more moisture and more heat. You will need to increase the ventilation rate, which means running fans longer or adding more fans. When you change the fan settings, you must also adjust the inlet openings to maintain the correct static pressure. ### Transitional Ventilation Transitional ventilation is used when outside temperatures are moderate and you need more air movement than minimum ventilation provides but less than full tunnel ventilation. In this stage, you may run fans continuously and use a combination of sidewall inlets and tunnel inlets. During transitional ventilation, the inlets should be opened wider than during minimum ventilation. The goal is to increase air movement at bird level without creating cold drafts. You may need to adjust the inlet angle to direct air more downward as the ventilation rate increases. ### Tunnel Ventilation During tunnel ventilation, all the exhaust fans are running and air enters through the tunnel inlet at one end of the house. The sidewall inlets should be closed during tunnel ventilation to force all the air to enter through the tunnel inlet. Some houses use a combination of tunnel and sidewall inlets during hot weather. This is called tunnel-plus or evaporative cooling mode. In this mode, the sidewall inlets may be partially open to allow additional air entry, but the majority of the air should still enter through the tunnel inlet. ## Common Mistakes in Air Inlet Design and Placement Even experienced growers make mistakes with air inlets. Here are the most common problems and how to avoid them. ### Inlet Area Too Small The most common mistake is not providing enough total inlet area. This creates excessive static pressure, reduces fan performance, and limits the amount of fresh air entering the house. The birds may show signs of oxygen deprivation, and the litter will become wet and ammonia levels will rise. Solution: Calculate your total inlet area based on your fan capacity and target air speed. Add more inlets if needed. ### Inlet Area Too Large The opposite problem is too much inlet area. This causes the air to enter at low speed and drop before reaching the center of the house. You get cold drafts near the sidewalls and stale air in the center. Solution: Close down some inlets or reduce the opening of each inlet. Your controller should adjust this automatically, but check it manually if you suspect a problem. ### Inlets Placed Too Low If sidewall inlets are placed too low on the wall, the incoming air drops to bird level too quickly. This creates cold drafts and chilling, especially during minimum ventilation in cold weather. Solution: Move the inlets up so the top of the opening is at or just below the ceiling line. If you cannot move the inlets, adjust the baffle angle to direct air more horizontally. ### Inlets Placed Too Close to Fans When inlets are placed too close to exhaust fans, the fan pulls air directly through the inlet without allowing it to circulate across the ceiling. This creates a short circuit, where fresh air enters and immediately exits without mixing with the house air. Solution: Keep inlets at least 10 feet away from the nearest fan. If your house layout does not allow this, consider using ceiling inlets in the area near the fans. ### Not Adjusting Inlets as Birds Grow Many growers set their inlet openings at the start of the flock and never touch them again. This is a mistake. As birds grow, they produce more heat and moisture, and you need to increase the ventilation rate. The inlet openings must be adjusted to match the increased fan capacity. Solution: Check your inlet openings at least weekly and adjust them whenever you change fan settings. Keep a log of your settings so you can see the trend. ### Ignoring Static Pressure Readings Static pressure is your best indicator of whether your inlets are set correctly. If the static pressure is too low, your inlets are too open. If it is too high, your inlets are too closed. Ignoring the static pressure reading is like driving without a speedometer. Solution: Check static pressure daily and adjust inlet openings to maintain your target. Calibrate your static pressure sensor regularly. ## Monitoring and Recordkeeping Good inlet management requires regular monitoring and careful recordkeeping. You cannot manage what you do not measure. ### Daily Checks Check the following items daily: - Static pressure reading in the center of the house - Inlet opening position on several inlets throughout the house - Air speed across the ceiling using an anemometer - Temperature at bird level in several locations - Litter moisture and condition - Bird behavior, especially distribution and activity level ### Weekly Checks Check the following items weekly: - Inlet baffle angles and direction of incoming air - Condition of inlet seals and hinges - Operation of inlet actuators and controllers - Calibration of static pressure sensor - Fan performance and belt condition ### Recordkeeping Keep a log of the following information for each flock: - Date and bird age - Outside temperature and weather conditions - Number of fans running and fan stage - Static pressure reading - Inlet opening position - House temperature at bird level - Litter moisture and ammonia levels - Bird weight and condition - Any problems observed and corrective actions taken This record will help you identify trends and make better decisions in future flocks. It will also help your veterinarian or extension agent diagnose problems if they arise. ## Troubleshooting Common Inlet Problems When something goes wrong with your ventilation, the symptoms show up in bird behavior and house conditions before they show up in your equipment. Here are common problems and their likely causes. ### Birds Huddle Near the Center of the House If birds are piling in the center, they are likely trying to get away from cold drafts along the sidewalls. This usually means the incoming air is dropping too quickly, either because the inlets are too low, the baffle angle is too steep, or the air speed is too low. Check your inlet height and baffle angle. Increase the static pressure by closing the inlets slightly. This will increase the air speed and push the air further across the ceiling. ### Birds Huddle Near the Sidewalls If birds are gathered along the sidewalls, they may be seeking warmth or avoiding drafts from the center. This can happen if the air is traveling too far and dropping on the opposite side of the house, creating a cold spot. Check your static pressure. If it is too high, the air may be moving too fast and dropping at the far side. Reduce the static pressure by opening the inlets slightly. ### Wet Litter in the Center of the House Wet litter in the center usually means the air is not reaching the center to dry the litter. This can happen if the air speed is too low or the inlets are not directing air properly. Increase the air speed by closing the inlets slightly or adding more fans. Check the baffle angle to ensure air is directed along the ceiling. ### Wet Litter Along the Sidewalls Wet litter along the sidewalls often means air is entering through cracks or poorly sealed inlets, dropping immediately to the floor. Check for air leaks around inlet frames and door seals. ### Ammonia Smell Despite Adequate Ventilation If you smell ammonia even when your ventilation seems adequate, the air may not be reaching the litter surface. This can happen when the air circulation pattern is poor, with fresh air moving across the ceiling and out the exhaust fans without dropping to floor level. Do a smoke test to visualize the air pattern. Adjust inlet angles and static pressure until you see the air dropping to floor level in the center of the house. ## When to Call a Veterinarian or Extension Agent Most inlet problems can be solved with adjustments and troubleshooting. However, there are times when you need professional help. Call your veterinarian if: - Birds show respiratory signs such as coughing, sneezing, or gasping despite correct ventilation settings - Bird mortality increases suddenly or gradually without an obvious cause - Birds are not gaining weight as expected and you have ruled out feed and water problems - You see signs of eye irritation, conjunctivitis, or sinusitis that may indicate high ammonia or poor air quality Call your extension agent if: - You are designing a new house or major retrofit and need help with inlet sizing and placement - You have persistent ventilation problems that you cannot solve with adjustments - You want to upgrade your ventilation control system - You need help interpreting your ventilation records or troubleshooting a specific problem Your veterinarian and extension agent are there to help you. Do not wait until you have a major problem to call them. ## Frequently Asked Questions ### How do I know if my air inlet area is correct? The best way to check is to measure the static pressure in your house while your fans are running. If the static pressure is within your target range of 0.05 to 0.15 inches of water column, your inlet area is likely correct. You can also use the calculation method: divide your total fan capacity by your target air speed of 800 to 1,000 feet per minute to get the required inlet area in square feet. ### What static pressure should I maintain during minimum ventilation? The target static pressure depends on your house width and inlet design. For most broiler houses, 0.05 to 0.10 inches of water column works well for 30 to 40 foot wide houses. Wider houses of 50 to 60 feet may need 0.10 to 0.15 inches. Start at the lower end and increase until you see good air circulation across the ceiling. ### Should I use sidewall inlets or ceiling inlets? Sidewall inlets are the most common choice for tunnel-ventilated broiler houses. They work well when you have adequate ceiling height and want to direct air across the ceiling to the center of the house. Ceiling inlets work better in houses with low roof pitch or where you want air to drop more quickly. Some houses use a combination of both. ### How often should I adjust my air inlets? You should check your inlets at least daily and adjust them whenever you change fan settings, which is typically every few days as birds grow. The inlet opening should match the fan capacity to maintain the correct static pressure. Many growers adjust inlets weekly as part of their routine management. ### Why is my static pressure reading different at different ends of the house? It is normal for static pressure to vary slightly along the length of the house. The pressure tends to be lower near the exhaust fans and higher near the inlets. If the variation is large, more than 0.03 inches of water column, you may have uneven inlet distribution or air leaks. Check for leaks and adjust inlet spacing if needed. ### Can I use my tunnel inlet for minimum ventilation? You can, but it is not recommended. The tunnel inlet is designed for high air volume and creates a different air pattern than sidewall inlets. Using the tunnel inlet during minimum ventilation can create cold drafts at bird level and poor air distribution. It is better to use sidewall inlets for minimum ventilation and reserve the tunnel inlet for tunnel mode. ### How do I do a smoke test to check air circulation? Light a smoke candle or use a smoke generator in the center of the house and watch how the smoke moves. It should travel along the ceiling toward the center of the house, then drop to floor level and move toward the exhaust fans. If the smoke drops immediately or moves erratically, your inlet settings need adjustment. ### What is the minimum air speed I need across the ceiling? The minimum air speed across the ceiling should be about 500 to 600 feet per minute to carry air to the center of a 40 foot wide house. For wider houses, you need higher speeds, up to 1,200 feet per minute for 60 foot wide houses. If your air speed is too low, the air will drop before reaching the center. ## Related Farming Guides This section will be populated with links to related farming guides on broiler house ventilation, litter management, and poultry health topics. Check back for updates. ## Related Clinical & Scientific Guides * [Poultry Farm Fencing: Materials, Design, and Predator Exclusion](/knowledge/animal-farming/poultry/poultry-farm-fencing-materials-design-predator-exclusion) * [Broiler House Wind Speed and Airflow Measurement](/knowledge/animal-farming/poultry/broiler-house-wind-speed-airflow-measurement) * [Broiler House Heating Systems: Types and Efficiency](/knowledge/animal-farming/poultry/broiler-house-heating-systems-types-efficiency) ## References - [FAO Poultry Production](https://www.fao.org/poultry-production-products/en/) - [USDA APHIS Poultry Health](https://www.aphis.usda.gov/livestock-poultry-disease/avian) - [WOAH Avian Influenza](https://www.woah.org/en/disease/avian-influenza/) - [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.