Horsebox Ventilation
Horsebox ventilation and how to keep your horses cool
When transporting horses, ensuring proper ventilation in your horsebox is vital for their well-being, especially during warmer months. It is important to understand how to manage airflow and heat effectively. We know there is a considerable risk of prolonged exposure to high temperatures and these including heat stress, dehydration, and muscle spasms. Addressing these issues with a solid ventilation strategy can make a significant difference in protecting your horses’ health during travel.
What started as a research project to improve airflow and heat removal in our horseboxes quickly turned into an in-depth investigation using a portable smoke generator and temperature recording equipment. We tested both stationary and moving horseboxes and this approach provided valuable insights into how air moves within the horse area. It revealed some unexpected findings that can help keep your horses cool and comfortable while ensuring they have fresh, clean, cool air.
How hot?
Whilst testing for heat, we found it very beneficial to record temperatures in the horse area. This made us think how do customers know how hot their horses are. We think it is an important safety feature, so in our smaller horse areas we now install two temperature probes with a readout in the cab. This is most definitely something you can add to your horsebox.
Heat and colour
We thoroughly examined the link between heat absorption and horsebox paint colour, offering key insights for managing heat inside the horse area. Dark paint colours soak up much more heat from sunlight than light ones, which can make horseboxes quite hot.
Research consistently showed that white or light-coloured surfaces, especially on roofs, are far better at reflecting sunlight away, thus keeping things cooler and reducing heat build-up. This finding underscores the importance of colour choice in horsebox design for maintaining a comfortable environment for horses during transport.
Head room
We all know heat rises and that the hottest part of the horse area is always going to be nearest the ceiling. By logging temperatures at various heights in the horse area, we discovered that the higher the ceiling, the cooler the air around the horse’s head.
As an example, to understand why headroom is so important for horses in hot weather. Picture a horse that’s about 16 hands high (around 1.6 meters at the shoulder). On a day when it’s 30°C (86°F) outside, the temperature near the horse’s head can change dramatically in just a small space. We found that a ceiling at 2.3 meters and one at 2.5 meters high – a difference of only 20 centimetres – had a temperature dropped by about 7°C (12.6°F)! This shows why giving horses enough headroom is crucial for keeping them cool and comfortable. It’s a key part of any good plan for managing heat and ventilation in horse areas.
Windows and air flow
Glass and especially colour play an important part again and tinted glass is preferable. It reduces direct sunlight that adds extra heat to the horse area. So tinted glass is good as long as it remains clear enough for the horses to see out.
Widows are basically the starting place for good air flow and heat removal. Window size plays an important part in the cooling effect of air drawn over the horses. A good design will see one large horse window for each horses head and smaller higher windows at the tail. This window size difference is crucial as it allows air flowing past a moving horsebox to cause a greater vacuum on the larger windows than the smaller ones. This vacuum effect draws air into the horsebox through the small windows, across the horses and out of the larger head windows.
However, it is worth noting that if both windows were the same size, air pressure would be equal both sides of the horsebox and little to no air would move inside the horse area. This effect is mostly for a moving horsebox with all the windows open. For a stationary horsebox very little air moves across the horses apart from that caused by any breeze. It is also noteworthy that for hot or stale air to leave the horse area, fresh clean air must have a way in. For example, closed tail end windows would stop air flowing in and being drawn over the horses, so no cooling effect would be present.
Roof vents and air flow (stationary)
Let’s start with a hot horse area and a stationary horsebox. The hottest air is at the ceiling and cooler air low down. Opening a roof vent fully will allow hot air to flow up and out causing cooler air to flow in through the windows. A clever trick here and one we use in our own horsebox design maximises this effect by allowing much cooler air to flow in at floor height.
Roof vents and air flow (moving)
For a moving horsebox with a hot horse area, things get more complicated still. Opening the roof vent and windows fully will remove some hot air, however, there is a way to move much more hot air out by tilting the vent. Actually opening fully the rear most part of the vent and closing the cab end of the vent fully will cause a considerable vacuum effect as air passes over the horsebox roof and tilted vent. At speed this vacuum effect will be considerable and as long as the windows are open the cooling effect will also be considerably increased, even removing more hot air more than an extraction fan!
Intake and extraction fans
Intake and extraction fans play a crucial role in horsebox ventilation, especially when natural airflow is limited. While tilted roof vents may be more effective for air removal in moving horseboxes, fans excel in stationary conditions. During parked situations, heavy traffic, or ferry and tunnel crossings, where air movement is minimal, these fans become indispensable for maintaining a comfortable environment for horses.
Fans actively circulate air, removing hot, stale air and bringing in fresh air, even when the vehicle is not in motion. This is particularly important for preventing heat buildup and ensuring proper air quality in enclosed spaces.
For smaller horseboxes with open windows, one extraction fan is often sufficient. Larger horseboxes may benefit from a combination of intake and extraction fans, negating the need for open windows and providing more controlled ventilation.
However, it’s important to consider that fans consume considerable power, which can drain batteries if the engine is not running. Therefore, a balanced approach, using a combination of passive ventilation methods and powered fans, is often the most effective strategy for maintaining optimal conditions in a horsebox across various travel scenarios.
Wall fan
Getting the heat out of the horse area should be the primary goal, but If you have power to spare, wall fans can be a great addition to cooling your horses. Ideally these should be placed on the rear wall and blowing over the horses.
Air conditioning (AC)
This is the most controllable option and one we use for our largest HGV horseboxes. These only work as long as every window and vent is closed. They work by drawing fresh air in and cooling it to a set constant temperature for the horse area. These are a very good option, but they are expensive, heavy and power hungry!
Lazy air
Air behaves like a lazy traveller, always seeking the path of least resistance when moving through a horse area. This natural tendency creates a significant challenge for effective ventilation. Picture a hot day with horses inside and an extraction fan running: without careful design, the air will rush directly from the nearest window to the fan, completely bypassing the horses.
The key to overcoming this lazy air behaviour is strategic window management. By carefully adjusting window sizes – narrowing openings close to the fan and widening those farther away – you can force the air to take a more comprehensive route. This approach ensures that cooler, fresh air is drawn across the horses, providing a much more effective cooling effect.
It’s essentially tricking the air into doing a complete circuit of the space, rather than taking its preferred shortcut. The result is a more uniform and efficient cooling system that actually benefits the horses, rather than just moving air from point A to point B with minimal impact.
Remote temperature sensor
This is a very sensible addition to any horsebox and with a quick glance of the horse area temperature you remove any guess work.
Worth a mention
One of the most surprising discoveries whilst testing with the portable smoke machine was that we noticed areas under the horses where the smoke did not move at all (still/dead air)!
This initiated further research and a redesign of our horse areas to better ventilate underneath the horses. We designed low level air vents that remove any water and blow fresh cool air underneath each horse.
Testing
These are all just pointers and they are not meant as a replacement for common sense. If you are in any doubt whatsoever please don’t take any risks with your precious companions.
Now you have some testing ahead of you to get this working properly. If you start by partly closing the nearest windows to the fan or roof vent, and fully opening the ones furthest away, you should be able to even-out air flow from each window, so air must travel over your horses to reach the exit fan or vent.
For testing we did all this with a smoke machine and it was still surprisingly difficult, but very enlightening.
There you go, complicated, but something that should point you in the right direction and I hope it helps a little for the hotter days.
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