FREE Delivery On All Orders Over £250 - Conditions Apply

Supplying the poultry industry for three decades

A Guide to Dairy Ventilation

Rowan Burgess |

A well-ventilated dairy is essential for happy, healthy cows, leading to good productivity and yields - as well as a lower carbon footprint.

A quick guide: dairy cows produce a lot of heat - which they dissipate by evaporating moisture from their lungs when exhaling. Add sweat from their skin in warmer conditions, and as the moisture content of the air increases, it becomes ineffective at cooling. Sounds like a great workout!

It’s always worth reviewing your dairy housing to see if improvements can be made to both airflow and ventilation. This protects the milk yield and the health of the herd.

Why is Proper Ventilation Important for Dairy Farming?

An environment where cattle are comfortable and exhibit normal behaviour promotes better health, good milk yield, and higher conception rates. Proper ventilation has a significant impact on animal welfare and productivity as well as carbon footprint. 

Heat and humidity cause problems for dairy farmers all year round; it’s not just a summer problem. Difficulties occur when the cows gather in collection points - both in the heat of summer and the huddling cold of winter.

Dairy cows kept in an environment with the correct temperature and humidity levels have lower respiration rates and produce more milk because they are not affected by heat stress. But overall, they enjoy better health.

There is a direct connection between indoor temperature and optimised Feed Conversion Ratio (FCR). 

FCR is the crucial link between what the cow is eating and how much milk she produces - a focal point for nearly all dairy farmers in an industry where profit margins can be wafer thin.

In a damp, humid environment, heat stress occurs at low temperatures. Indeed, the cow cannot lose moisture from the body into the air to cool herself. Additionally, hot cows drink more water and require greater access to fresh air. Let's get into science for a moment.

Ambient temperature and humidity combined are recorded using a Temperature and Humidity Index or THI. This is an important measurement, as both oestrus and milk yield may be adversely affected.

A THI of 57 or higher may impact fertility - and this high level can be reached with a temperature of just 14 C and 55% humidity. During the colder winter months, humidity in the cow shed often exceeds 55% in our damp British climate.

A THI of above 65 affects conception rates. Bump the temperature to 21 C with 70% humidity, and milk yields and quality could be significantly impacted. 

Adequate ventilation also helps prevent the spreading of diseases -particularly respiratory conditions such as pneumonia - as pathogens can survive longer in humid air.

Diseases like digital dermatitis and mastitis may rise, caused by the increased humidity of the cubicle beds and floors.

What Are the Different Types of Dairy Ventilation Systems?

There are different types of dairy ventilation systems broadly divided into natural and mechanical. A good system will support the existing airflow within the building, promoting ventilation and cooling the cattle.

Ventilation systems can be managed remotely by a climate control unit accessible via a PC to constantly monitor the climate in the housing using THI index values.

The best choice of ventilation system depends upon the type of housing used and the local climatic conditions.

Natural Ventilation

Natural ventilation is based on the design of the building. It may include open ridge ventilation in the roof to remove stale air, ventilation panels, curtains and doors.

Sheds should be as open as possible to the sides. However, cows dislike draughts and use energy to maintain body heat if they get too cold. If you find yourself in this situation, we recommend taking weather precautions and utilising roll-up curtains.

Good shed construction takes advantage of location, as well as different wind forces and directions. It’s essential to consider the right type of system to augment the natural ventilation that is already present in the building.

Tunnel Ventilation

Tunnel ventilation often uses a system of evaporative cooling pads which are wetted by a water tank and pump and supported by a gutter system. 

Extraction fans are placed on the wall opposite the cooling pads drawing cool air from the pads along the housing in a tunnel formation. Tunnel ventilation is rare in the UK.

Cross Ventilation

Cross ventilation uses the same evaporative cooling pads. Extraction fans are placed on the wall opposite the cooling pads creating ventilation from one side of the building to the other.

What Are the Different Types of Dairy Fans?

Fans should both ventilate the shed and cool the cattle, supplementing any natural ventilation.

Of course, dairy fans have a power cost, but this is more than outweighed by the advantages of optimal milk yield and improved health.

There are several types of fans suitable for dairy cattle housing. The right choice depends upon the natural ventilation already present in the shed, the size of the shed, the number of cattle and whether there are any hotspots.

Basket Fans

Basket fans have a wide airflow, making them ideal for creating a refreshing airflow indoors. As a result, this fan is widely applicable in agricultural settings.

Thanks to their design, Basket fans tend to cover a wide area. Basket fans are usually easy to install and set up to create the right airflow direction. 

This is ideal for creating a uniform indoor climate or a wind chill effect for livestock and employees during hot summers.

Basket fans are available in various sizes to suit shed roof heights.

Belt-driven Fans

Belt-driven fans can appear both looming and massive, up to two metres in diameter. Typically hung above the cubicles in rows, the air then passes over the backs of the cattle and exits the building. Refreshing!

These fans have a protective casing to stop the air from dissipating and are hung at slight angles to direct air over the backs of the cows. Why? The idea here is to blow air in the same direction as the prevailing wind.

Belt-driven fans produce a lot of airflow for a small amount of electricity. They can be used as a complete system or in isolation to deal with specific hot areas in the shed. However, keep in mind that they’re not always suitable for low sheds.

Because of the casing that directs the air forwards, several rows may be needed in large sheds.

High-volume low-speed fans

These are large rotating fans - like helicopter rotors which blow air down and outwards. 

High-volume low-speed fans aren't always the most effective system and may mix the air up rather than cool the cattle. Additionally, they disrupt air movement in sheds, which have good natural ventilation and don't specifically target the cattle. They may be right for your farm, so be sure to personalise them to your needs. 

Panel Fans (Plate Fans)

Panel fans sit within one of the end walls of the shed and suck air from outside into the building. Panel fans work well in hotspots but aren't so good at cooling large areas.

Good news, though. They can be augmented with a positive pressure tube in low sheds to propel air throughout the whole building. The height of a plate fan is important because if it is too high, your animals won’t get the cooling they need.

Panel fans don’t produce a huge volume of air, so it’s usually necessary to install quite a few to achieve adequate ventilation and cooling.

What To Consider When Designing a Dairy Ventilation System

Natural Ventilation

Always make the most of natural ventilation before installing fans or other systems. Circulating stale air is never as effective and will inhibit the performance of any cooling system.

Any installed system should enhance natural ventilation in the building and not disrupt it.


Use inexpensive humidity loggers to work out the location of your building’s pain points. Hint: they’re usually where the cows tend to congregate. This helps inform the most effective design.

Expert installers can recommend the best location and height of the fans.

Install a variable-speed control box so that the fans can be responsive to different requirements. This helps save energy use and keeps bills as low as possible.

After working out the optimal location for the fans, consider where the dirty air will exit the building. 

Stocking Level

The stocking rate of a shed will impact the ventilation. If the shed is overcrowded, then the airflow may be static. 

However, low stocking rates in large sheds can also be a problem as this can fail to create a stack effect which drives stale air to the vents in the roof where it can escape. This is a classic scenario where fan installation will help.

Maintaining Your Dairy Ventilation System

Good maintenance of your dairy ventilation system is important for herd health and productivity. Monthly cleaning ensures the system is working effectively and not creating higher than necessary running costs.

Poor hygiene and maintenance can reduce efficiency by as much as 40%. Even a small amount of dirt on fan blades reduces their performance.

Energy bills remain the same, but effective cooling and ventilation diminish, impacting herd health and productivity.                         

Final Thoughts

Proper ventilation in cattle housing is essential for the optimal maintenance of a happy and healthy dairy herd with good conception rates and milk yield. This is what we’re all after!

Dalton Engineering is a proud supplier of high-quality dairy ventilation systems with products to suit all types of farming arrangements and cattle housing. 

We supply premium branded equipment to the dairy industry backed by sound, professional advice and expertise, helping farmers achieve high milk yields and productivity. We’d be glad to help you and your cows through this season and the next!