Broiler House Tunnel Ventilation Design and Operation

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

Key Takeaways

Tunnel ventilation is critical for broiler heat stress mitigation, achieving optimal wind chill through high-speed airflow (400-600 fpm at bird level) generated by end-wall fans and a properly sized inlet (1 sq ft per 600-800 CFM).
Design airflow targets range from 2.5 to 3.5 CFM per square foot of floor area, with higher rates (up to 5 CFM/sq ft) necessary for hot climates or heavy birds to maintain effective cooling.
Static pressure, measured in inches of water column, is a key diagnostic indicator, typically maintained between 0.08 and 0.12 inches; deviations signal inlet restrictions or fan issues.
Continuous operation of tunnel fans is essential during hot weather to maintain consistent wind chill; cycling fans on and off negates the cooling benefit and stresses birds.
Evaporative cooling pads serve as a secondary cooling measure, activated when air movement alone is insufficient (typically above 85-90°F with all fans running), and require diligent maintenance to prevent mineral scaling and algae growth.
Effective operation necessitates monitoring bird behavior, air speed at bird level, static pressure, and temperature staging, with adjustments made as birds grow and environmental conditions change.

Tunnel ventilation is the backbone of warm-weather broiler production. This guide explains how tunnel ventilation works, how to design a system for a new or existing house, how to operate it day to day, and how to avoid the common mistakes that cost birds and money. It is written for broiler growers, farm managers, and poultry service technicians who want a practical, system-level understanding of tunnel ventilation without wading through engineering textbooks.

At a Glance

Tunnel ventilation moves air lengthwise down the house at high speed to create wind chill, which lets birds cope with heat.
Design for 2.5 to 3.5 cubic feet per minute (CFM) of airflow per square foot of floor area for most broiler houses. Higher rates up to 5 CFM per square foot may be needed in hot climates or for heavy birds.
Target air speed at bird level of 400 to 600 feet per minute (fpm) for broilers, with 500 to 700 fpm for heavy roasters in hot weather.
Use a static pressure of 0.08 to 0.12 inches of water column for a typical tunnel house with a good inlet system.
The tunnel curtain or inlet opening should be sized to match fan capacity. A common rule is 1 square foot of inlet area for every 600 to 800 CFM of fan capacity.
Run tunnel fans continuously in hot weather. Do not cycle them on and off if you can avoid it, because birds lose the benefit of constant air movement.
Measure air speed at bird level, not just at the fan. Air speed at the bird is what creates wind chill.
Check static pressure daily. A sudden drop often means an inlet is blocked or a fan belt is slipping. A sudden rise often means a curtain is stuck or a fan has failed.
Keep evaporative cooling pads clean and dry when not in use. Wet pads that dry out repeatedly accumulate mineral scale and lose efficiency.
Use a controller with a reliable temperature sensor at bird level. Place sensors away from direct sunlight, drafts, and the cooling pad end of the house.

Why Tunnel Ventilation Matters

Broilers are heat-sensitive animals. They have no sweat glands, and they rely on panting and on radiating heat from their skin and comb to stay cool. When air temperature approaches bird body temperature, which is about 106 degrees Fahrenheit, those passive cooling methods stop working. Birds begin to pant heavily, their feed intake drops, and their growth rate slows. In severe heat, birds die.

Tunnel ventilation solves this problem by moving large volumes of air down the length of the house at high speed. The moving air strips heat from the birds' bodies and from the litter, and it increases evaporative cooling from the birds' respiratory tract. The effect is wind chill. A bird standing in a 500 fpm air stream at 90 degrees Fahrenheit experiences an effective temperature several degrees cooler than the actual air temperature. That difference keeps birds eating and growing in conditions that would otherwise stop them.

Tunnel ventilation is not the same as cross ventilation, which moves air across the width of the house using side wall fans. Cross ventilation works well in mild weather when outside temperatures are comfortable. It cannot move enough air to cool birds in hot weather because the air path is short and the air speed at bird level is low. Tunnel ventilation is the only practical way to move enough air through a modern broiler house to keep heavy birds alive and productive in summer.

How Tunnel Ventilation Works

A tunnel ventilation system has three essential parts: exhaust fans at one end of the house, an air inlet at the opposite end, and a control system that manages both. The fans pull air out of the house, which creates a slight negative pressure inside. That negative pressure draws fresh air in through the tunnel inlet at the far end. The air then travels the full length of the house before it reaches the fans and is exhausted.

The key to tunnel ventilation is air speed. The fans must move enough air to create a visible breeze at bird level. In a well-designed tunnel house, you can feel the air moving when you stand at the bird level in the middle of the house. That breeze is what keeps birds cool.

The tunnel inlet is usually a large opening at the gable end of the house opposite the fans. It can be a solid wall with a bank of doors or curtains, or it can be a series of vents that open along the end wall and part of the side walls near the inlet end. The inlet must be large enough to let air enter without creating excessive static pressure, but it must also be controllable so you can adjust the air speed and direction.

Evaporative cooling pads are often installed in the tunnel inlet. These pads are made of a corrugated cellulose or aspen material that holds water. Water is pumped to the top of the pad and allowed to trickle down through the material. Air passing through the wet pad is cooled by evaporation before it enters the house. Tunnel ventilation plus evaporative cooling is the standard system for hot climates.

Design Principles for Tunnel Ventilation

Designing a tunnel ventilation system starts with the house dimensions. You need to know the floor area, the house length, the house width, and the ceiling height. These numbers drive all the other calculations.

Calculate Required Airflow

The first step is to determine the total airflow you need. The standard design target for broiler houses is 2.5 to 3.5 CFM per square foot of floor area. A 40 foot by 500 foot house has 20,000 square feet of floor area. At 3 CFM per square foot, you need 60,000 CFM of total fan capacity. In hot climates or for heavy birds, you may want 4 to 5 CFM per square foot, which would mean 80,000 to 100,000 CFM for the same house.

The higher end of the range is for houses that raise roasters or for regions with prolonged periods of extreme heat. The lower end may be adequate for light broilers in moderate climates. When in doubt, design for the higher airflow. It is easier to slow fans down than to add capacity later.

Select Fans

Exhaust fans are rated by the volume of air they move at a given static pressure. A typical 48 inch tunnel fan moves 20,000 to 25,000 CFM at 0.10 inches of static pressure. A 36 inch fan moves about 10,000 to 12,000 CFM. You need enough fans to reach your total airflow target.

Tunnel fans should be installed in the end wall of the house, or in the side walls within the last 50 to 100 feet of the house. The fans should be spaced evenly across the end wall so the air is pulled uniformly down the house. If fans are clustered on one side, the air will move faster on that side and slower on the other.

Choose fans with a high airflow rating at the static pressure you expect to operate at. Fan performance is published in the manufacturer's catalog and is measured against industry standards. Look for fans that move the most air per watt of electricity, because tunnel fans run for long hours in summer and electricity is a major cost.

Size the Tunnel Inlet

The tunnel inlet must be large enough to supply the fans without excessive static pressure. A common rule is 1 square foot of inlet opening for every 600 to 800 CFM of fan capacity. For a house with 60,000 CFM of tunnel fans, you need 75 to 100 square feet of inlet opening.

The inlet can be a single large opening or a combination of end wall doors and side wall curtains. Many modern houses use a bank of doors on the end wall that open outward or slide upward. Some use a curtain that rolls up from the bottom. The important thing is that the total open area matches the fan capacity.

The inlet should be positioned so the incoming air enters at bird level or slightly above. Air entering at the floor level will pick up dust and ammonia from the litter. Air entering too high will rise to the ceiling and not create good air movement at bird level. A target is to have the inlet centered vertically at about the height of the birds' backs, which is 6 to 12 inches above the floor for broilers.

Design for Air Speed

Air speed at bird level is the product of total airflow divided by the cross sectional area of the house. The cross sectional area is the house width times the average ceiling height. A 40 foot wide house with an 8 foot average ceiling height has a cross sectional area of 320 square feet. If you move 60,000 CFM through that house, the theoretical air speed is 60,000 divided by 320, which equals 187 fpm. That is too slow for broilers in hot weather.

To get 500 fpm in that house, you need 500 times 320, which equals 160,000 CFM. That is a very high airflow rate, and it explains why tunnel ventilation works best in long, narrow houses. A 40 foot wide house is at the upper limit for tunnel ventilation. Wider houses are difficult to ventilate with a tunnel system because the cross sectional area is too large.

Most tunnel ventilated broiler houses are 30 to 40 feet wide and 400 to 600 feet long. The length is important because it gives the air time to accelerate and to develop a uniform flow pattern. Houses shorter than 300 feet may not achieve good air speed at bird level because the air has not had enough distance to become uniform.

Add Evaporative Cooling

Evaporative cooling pads are sized based on the airflow through them. The standard design is 1 square foot of pad face area for every 250 to 350 CFM of airflow. For a 60,000 CFM house, you need 170 to 240 square feet of pad area. The pads are typically installed in the tunnel inlet, covering the entire opening.

Pad thickness is also important. A 4 inch pad is common in moderate climates. A 6 inch pad provides more cooling and is recommended for hot, dry climates. Thicker pads create more static pressure, so the fans must be able to handle the added resistance.

The water system for the pads includes a pump, a distribution pipe along the top of the pad, and a collection gutter at the bottom. The pump recirculates water from a sump tank. The sump should be sized to hold enough water to keep the pads wet during peak operation, typically 1 to 2 gallons per square foot of pad area.

Operating Tunnel Ventilation

Operating a tunnel ventilation system is more than turning on fans when it gets hot. It requires a planned sequence of steps as temperature rises, careful attention to air speed and static pressure, and daily monitoring of the system.

Know Your Temperature Stages

A tunnel ventilation controller operates in stages. Each stage turns on additional fans as the house temperature rises. The stages are set so that the house stays within a target temperature range without large swings.

A typical staging plan for a broiler house might look like this:

Stage 1: One tunnel fan turns on when the house temperature reaches 80 degrees Fahrenheit.
Stage 2: A second tunnel fan turns on at 82 degrees.
Stage 3: A third tunnel fan turns on at 84 degrees.
Stage 4: All remaining tunnel fans turn on at 86 degrees.
Cooling pads turn on at 88 degrees or when the temperature continues to rise with all fans running.

The exact temperatures depend on bird age, outside conditions, and the capacity of the system. The principle is to add airflow gradually as the heat load increases, and to save the cooling pads for when air movement alone is not enough.

Use Minimum Ventilation First

Tunnel ventilation is not for cold weather. In cool weather, you use minimum ventilation to remove moisture and ammonia while conserving heat. Minimum ventilation uses small fans on a timer to exchange air at a low rate. As the weather warms, you transition to transitional ventilation, which uses side wall fans and inlets to increase airflow without creating high air speed at bird level.

The transition to tunnel ventilation should happen when the outside temperature reaches about 70 to 75 degrees Fahrenheit and the birds are showing signs of heat stress. Watch the birds. If they are panting and spreading their wings, they need more air movement. If they are huddled and quiet, they are comfortable.

Set Static Pressure Correctly

Static pressure is the difference in air pressure between the inside and outside of the house. It is measured in inches of water column. A properly operating tunnel house runs at 0.08 to 0.12 inches of water column. The exact number depends on the inlet design and the fan capacity.

Static pressure tells you whether the inlet is sized correctly. If static pressure is too high, the air is entering too fast and may be noisy. If it is too low, the air is entering too slowly and may not reach the far end of the house. Adjust the inlet opening until the static pressure is in the target range.

Check static pressure at the controller. Most modern controllers display it continuously. If you do not have a controller with a static pressure sensor, install a manometer in the middle of the house, away from the inlet and fans.

Adjust Inlets as Birds Grow

The tunnel inlet should be adjusted as the birds grow. Young birds are small and do not need as much air movement. The inlet can be partially closed to reduce air speed. As the birds grow and generate more heat, open the inlet to increase airflow.

The rule of thumb is to set the inlet so the air enters at about 800 to 1,000 fpm at the inlet. This creates enough velocity to throw the air down the house and to mix with the room air. If the inlet is too open, the air enters slowly and falls to the floor near the inlet. If it is too closed, the air enters too fast and creates drafts.

Use Cooling Pads Wisely

Evaporative cooling pads should be the last line of defense, not the first. They work by adding moisture to the air, which increases humidity. In humid conditions, evaporative cooling is less effective because the air cannot hold much more moisture. In very humid weather, running the pads may make the birds more uncomfortable by raising the humidity without cooling the air much.

Run the pads only when the temperature is high enough that air movement alone cannot keep the birds comfortable. A common threshold is 85 to 90 degrees Fahrenheit with all tunnel fans running. When you turn on the pads, start with a short cycle to wet the pads, then let them dry before the next cycle. This prevents the pads from staying wet continuously, which can lead to algae growth and mineral buildup.

Monitor the water quality in the sump. Hard water leaves scale on the pads that reduces airflow. Algae can grow in the sump and clog the distribution system. Clean the sump regularly and replace the pads when they become clogged or deteriorated.

Watch Bird Behavior

The birds are the best indicator of whether the ventilation is working. Learn to read their behavior.

Comfortable birds are spread evenly across the house. They are eating, drinking, and moving around normally.
Birds that are too warm pant, hold their wings away from their bodies, and crowd toward the inlet end of the house or toward the side walls where air movement is strongest.
Birds that are too cool huddle together, stay away from drafts, and may pile in corners.

If birds are crowding toward the inlet, the air speed at the far end of the house is too low. This can happen if the fans are not moving enough air, if the inlet is not directing air properly, or if the house is too wide for the airflow. Check the air speed at bird level in the middle and far end of the house with an anemometer.

Common Mistakes in Tunnel Ventilation

Many tunnel ventilation problems are caused by a few common mistakes. Recognizing these can save you time and birds.

Inlet Misalignment

The most common mistake is having the tunnel inlet and the fans misaligned. If the inlet is on the end wall but the fans are on the side walls, the air will not travel straight down the house. It will swirl and create dead zones where air speed is low. The fans should be on the end wall opposite the inlet, or the inlet should be extended along the side walls near the fan end to create a uniform flow.

Inlet Too Small

An inlet that is too small creates high static pressure and reduces fan performance. The fans cannot move their rated airflow because they are fighting the inlet restriction. The result is low air speed at bird level even though the fans are running at full speed. Measure the inlet opening and compare it to the fan capacity. If the inlet is less than 1 square foot per 800 CFM of fan capacity, enlarge it.

Fans Too Few or Too Far from the Inlet

If you do not have enough fan capacity, you cannot achieve the air speed you need. Adding more fans is the only solution. Also, fans that are located too far from the end wall, more than 50 to 100 feet, do not pull air uniformly down the house. The air will tend to enter through the nearest side wall openings instead of the tunnel inlet.

Poor Air Distribution at Bird Level

Air entering the tunnel inlet may rise to the ceiling and not reach the birds. This happens when the inlet is too high or when the air enters at too steep an angle. The air should enter nearly horizontal, at bird level, so it sweeps across the floor. If the air is rising, adjust the inlet direction or install baffles to redirect the air downward.

Running Fans on Timers in Hot Weather

Some growers try to save electricity by cycling tunnel fans on and off. This is a mistake. When the fans turn off, the air movement stops and the birds immediately begin to heat up. The stress of cycling between hot and less hot is worse for the birds than running the fans continuously. In hot weather, run tunnel fans continuously.

Ignoring Static Pressure

Static pressure is the diagnostic tool for the whole system. If you do not check it, you will not know when the inlet is blocked, a fan belt is slipping, or a curtain has come off its track. Check static pressure at least daily during tunnel season.

Neglecting Pad Maintenance

Evaporative cooling pads that are dirty, scaled, or clogged with algae move less air and cool less effectively. Pads should be inspected weekly during hot weather. Clean the sump, check the water distribution, and replace pads that are worn out.

Forgetting About Bird Age

Ventilation needs change as birds grow. A 1 pound bird generates much less heat than a 6 pound bird. The ventilation system must be adjusted for bird age. Young birds need less airflow and can be chilled by high air speed. Older birds need maximum airflow and benefit from high air speed. Adjust the staging temperatures and the inlet opening as the flock grows.

Monitoring and Recordkeeping

Good tunnel ventilation requires daily monitoring and careful records. The records help you spot trends and diagnose problems before they become serious.

Daily Checks

Walk the house at least twice a day during hot weather. Check the following:

Static pressure at the controller. It should be stable and in the target range.
Air speed at bird level in the middle and at the far end of the house. Use an anemometer. It should be at least 400 fpm for broilers.
Temperature at bird level in several locations. The temperature should not vary by more than a few degrees from the inlet to the fan end.
Fan operation. Look for fans that are not running, belts that are slipping, and shutters that are stuck.
Inlet operation. Make sure the inlet is open to the correct position and that nothing is blocking it.
Pad condition. Look for dry spots, algae, and mineral scale.
Bird behavior. Note any panting, crowding, or huddling.

Weekly Checks

Once a week, do a more thorough check:

Clean the fan blades and shutters. Dust buildup reduces fan performance.
Check fan belts for wear and tension. Replace belts that are cracked or loose.
Check the water system for the pads. Clean the sump and check the pump.
Calibrate the temperature sensors in the controller. Compare them to a known accurate thermometer.
Check the emergency alarm system. Make sure it is working and that you will be notified if the power fails or the temperature goes out of range.

Keep Records

Keep a daily log of the following:

Outside temperature and humidity
House temperature at bird level
Static pressure
Number of fans running
Pad operation
Bird condition and mortality
Any equipment problems and repairs

The records help you see patterns. If the static pressure has been creeping up over several weeks, the pads may be clogging. If the house temperature has been rising at a lower outside temperature, the fans may be losing performance. Catching these trends early prevents major problems.

Use the Controller Data

Modern controllers record temperature, static pressure, and fan operation continuously. Review the data regularly, especially after a hot day. Look for periods when the temperature exceeded the set point, when the fans were running at full capacity, and when the pads were operating. This information tells you whether your system is adequate for the conditions you experienced and whether you need to adjust the staging.

When to Call a Veterinarian or Extension Agent

Most tunnel ventilation problems are mechanical and can be solved by the grower. However, there are times when you should call for help.

Call a veterinarian if you see signs of heat stress that do not improve with ventilation, such as:

High mortality that continues even when the ventilation is running at full capacity
Birds that are severely panting, with open beaks and rapid breathing, and that do not recover when moved to a cooler area
Birds with signs of respiratory disease, such as coughing, sneezing, or nasal discharge, in addition to heat stress
Birds that are lethargic, uncoordinated, or unable to stand

Call an extension agent or a ventilation specialist if you have persistent problems that you cannot solve:

Air speed at bird level is below target even with all fans running
Static pressure is too high or too low and you cannot adjust it to the target range
Temperature varies significantly from one end of the house to the other
You are not sure whether your fan capacity or inlet size is adequate for your house

A ventilation specialist can measure airflow, check fan performance, and make recommendations for improving the system. This service is often available through the extension service or through equipment dealers.

Tunnel Ventilation vs Cross Ventilation

Understanding the difference between tunnel and cross ventilation helps you know when to use each system.

Cross ventilation uses fans mounted in the side walls to move air across the width of the house. Air enters through inlets on the opposite side wall. The air path is short, typically 30 to 40 feet. Air speed at bird level is low, usually 100 to 300 fpm. Cross ventilation is useful in mild weather when you need to remove moisture and heat but do not need high air speed.

Tunnel ventilation uses fans in the end wall to move air down the length of the house. The air path is long, 400 to 600 feet. Air speed at bird level is high, 400 to 700 fpm. Tunnel ventilation is essential in hot weather when birds need wind chill to survive.

The two systems are complementary. A well designed house has both. Cross ventilation fans handle mild weather, and tunnel fans handle hot weather. The controller switches between them based on temperature.

Designing a New Tunnel Ventilation System

If you are building a new house or retrofitting an existing one, follow these steps:

Step 1: Measure the House

Get the exact dimensions of the house: length, width, and ceiling height. Measure the ceiling height at the lowest point and at the highest point. The average ceiling height is used for the cross sectional area calculation.

Step 2: Calculate Floor Area

Multiply the length by the width to get the floor area. A 40 by 500 foot house has 20,000 square feet.

Step 3: Determine Required Airflow

Multiply the floor area by the target airflow rate. For most broiler houses, use 3 to 4 CFM per square foot. For hot climates and heavy birds, use 4 to 5 CFM per square foot.

Step 4: Select Fans

Choose fans that can deliver the required airflow at 0.10 to 0.12 inches of static pressure. Count the number of fans needed by dividing the total airflow by the airflow per fan. Add one extra fan for redundancy if possible.

Step 5: Size the Inlet

Multiply the total fan capacity by 1 square foot per 600 to 800 CFM to get the inlet area. For 60,000 CFM, the inlet should be 75 to 100 square feet.

Step 6: Position the Inlet

Place the inlet on the end wall opposite the fans. If the house is very wide, extend the inlet along the side walls for the first 20 to 40 feet to improve air distribution.

Step 7: Design the Pad System

If you are installing evaporative cooling, size the pads at 1 square foot of pad face area per 250 to 350 CFM of airflow. Choose 4 inch or 6 inch pads based on your climate.

Step 8: Install the Controller

Choose a controller that can manage multiple stages of fans, control the inlet, and operate the cooling pads. The controller should have alarms for high temperature, power failure, and static pressure problems.

Step 9: Test the System

After installation, run the system and measure air speed at bird level in several locations. Adjust the inlet and fan staging until the air speed is uniform and adequate.

Retrofitting an Existing House

Many older houses were not designed for tunnel ventilation. Retrofitting is possible but requires careful planning.

The main challenges are:

The house may be too wide for effective tunnel ventilation. Houses wider than 40 feet are difficult to ventilate with a tunnel system.
The ceiling may be low, which reduces the cross sectional area and increases air speed for a given airflow. This can be an advantage or a disadvantage depending on the house.
The existing fans may not be adequate. You may need to add tunnel fans to the end wall.
The existing side wall inlets may interfere with the tunnel airflow. You may need to close or seal them during tunnel operation.

A ventilation specialist can help you assess whether your house is a good candidate for a tunnel retrofit and can design a system that works with your existing structure.

Economics of Tunnel Ventilation

Tunnel ventilation costs money to install and operate. The main costs are:

Fans: A 48 inch tunnel fan costs $800 to $1,500. A house with 6 to 8 fans will cost $5,000 to $12,000 for fans alone.
Inlet system: Motorized curtains or doors cost $2,000 to $5,000.
Evaporative cooling: Pads, pumps, and piping cost $0.50 to $1.00 per square foot of floor area.
Controller: A good controller with sensors and alarms costs $1,000 to $3,000.
Electricity: Tunnel fans use 1 to 2 kilowatts each. Running 6 fans for 12 hours a day at $0.12 per kilowatt hour costs about $10 to $17 per day.

The benefits are reduced mortality, better feed conversion, and higher growth rates during hot weather. In a severe heat wave, tunnel ventilation can be the difference between losing a few birds and losing thousands. The investment typically pays for itself in one to three hot seasons.

Maintaining Tunnel Ventilation Equipment

Regular maintenance keeps the system running at peak efficiency. Follow the manufacturer's recommendations for each piece of equipment, and add these tasks to your routine:

Fans

Clean fan blades and shutters monthly during the cooling season. Dust on the blades reduces airflow significantly.
Check belts monthly. Replace belts that are cracked, glazed, or stretched. Keep spare belts on hand.
Lubricate fan bearings according to the manufacturer's instructions.
Check the electrical connections and the motor for signs of overheating.

Inlets

Check the inlet curtains or doors for proper operation. Repair any tears or gaps that let air enter where it should not.
Lubricate hinges and tracks.
Check the inlet position sensors and adjust them if needed.

Evaporative Cooling Pads

Inspect the pads weekly during the cooling season. Look for dry spots, algae, and mineral scale.
Clean the sump weekly. Remove debris and algae.
Check the water distribution pipe for clogs. Clean the holes if needed.
Replace the pads when they become clogged, deteriorated, or lose their rigidity. Pads typically last 3 to 5 years with proper care.

Controller

Check the temperature sensors for accuracy. Calibrate them against a known thermometer.
Check the static pressure sensor for accuracy.
Test the alarms to make sure they work.
Keep the controller clean and dry.

Emergency Procedures

Even with a well designed and maintained system, emergencies happen. Power outages and equipment failures can kill birds quickly in hot weather.

Power Outage

Have a backup generator that can run the tunnel fans and the cooling pad pump. Test the generator monthly and keep enough fuel on hand for at least 24 hours of operation. Wire the generator to automatically start when the power goes out, or have a plan to start it immediately.

Fan Failure

If a fan fails, the air speed drops and the birds at the fan end of the house suffer. Have spare motors and belts on hand. Replace failed fans immediately. If you cannot fix the fan quickly, open the side wall inlets and run the remaining fans to provide some air movement.

Inlet Failure

If the inlet will not open, the static pressure rises and the fans cannot move enough air. Check the inlet mechanism and repair it. If you cannot fix it, open the side wall inlets manually to provide an alternate air path.

Pad Failure

If the pad pump fails, the pads dry out and lose their cooling effect. Have a spare pump and check the pump strainer regularly. If the pads fail completely, run the fans without the pads. The birds will still benefit from the air movement, though the temperature will be higher.

Frequently Asked Questions

How do I know if my tunnel ventilation is working properly?

Measure air speed at bird level in the middle of the house and near the fan end. It should be at least 400 fpm for broilers. Also check static pressure, which should be 0.08 to 0.12 inches of water column. Watch the birds. If they are spread evenly and not panting heavily, the system is working.

What is the ideal air speed for broilers in a tunnel house?

Most broiler houses are designed for 400 to 600 fpm at bird level. Heavy roasters in hot weather benefit from 600 to 700 fpm. Air speed above 700 fpm is rarely needed and can cause birds to use energy fighting the wind instead of growing.

How many tunnel fans do I need for my house?

Calculate the floor area and multiply by 3 to 4 CFM per square foot. Then divide by the airflow of the fans you plan to use. For example, a 20,000 square foot house at 3 CFM per square foot needs 60,000 CFM. If each fan moves 20,000 CFM, you need 3 fans minimum, but 4 to 5 is better for redundancy and for hot weather.

Should I run tunnel fans continuously in hot weather?

Yes. In hot weather, run tunnel fans continuously. Cycling them on and off reduces the wind chill benefit and stresses the birds. Use the controller to stage the fans so they come on as the temperature rises, and leave them on once they are running.

When should I turn on the evaporative cooling pads?

Turn on the cooling pads when the temperature rises above the point where air movement alone can keep the birds comfortable. This is typically 85 to 90 degrees Fahrenheit with all tunnel fans running. In humid weather, the pads are less effective and may need to be used sparingly.

How do I clean evaporative cooling pads?

Rinse the pads with clean water to remove dust and debris. Clean the sump and the distribution pipe. Use a mild acid cleaner to remove mineral scale, following the manufacturer's instructions. Do not use bleach or other harsh chemicals that can damage the pads.

Why is the air speed at the far end of the house lower than at the inlet end?

This is normal to some degree, but a large difference indicates a problem. Possible causes are insufficient fan capacity, an inlet that is not directing air properly, or the house being too wide for the airflow. Measure the air speed at several points to identify where the drop occurs.

What should I do if the static pressure is too high?

High static pressure means the inlet is too small or blocked, or the fans are fighting against a restriction. Check the inlet opening and make sure it is fully open. Check for obstructions such as curtains, nests, or debris. If the inlet is sized correctly, check the fans for belt slippage or other mechanical problems.

Related Farming Guides

Additional poultry house ventilation and management guides will appear here. Check back for updates on minimum ventilation, evaporative cooling, and broiler health management.

Related Clinical & Scientific Guides

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.