Horsebox Heat and Ventilation
Without question, there are plenty of research articles on the effects of prolonged exposure to high temperatures and how it causes heat stress, heat stroke, dehydration, muscle spasms, and colic in horses. Effective heat removal and adequate ventilation are essential components of any horse facility. Unfortunately, these factors are often overlooked, despite their significant impact on equine health and comfort.
We have noted significant changes in UK weather patterns including recent heatwaves, and we have dedicated more resources to understanding the climate challenges impacting our horse areas. From our findings, we have upgraded our design considerably to provide better air flow, much improved heat removal and an understanding of how it all works, so we can better inform our customers.
Lazy Air
Air is lazy, always taking the shortest route in and out of the horse area. This adds a level of complexity to designing efficient airflow for horses.
A brief example using an extraction fan in the ceiling (bearing in mind our goal is to remove hot air and draw cooler, fresh air around hot horses). Imagine that it is a hot day and you are loaded with horses, all the windows are fully open, and you turn on the extraction fan to keep them cool. Now, Mr Lazy Air can’t be bothered to travel all the way around your horses and cool them, his preferred choice would be a direct route from the nearest open window and straight to the extraction fan. Some hot air will still be removed, but the cooling effect on your horses will be much reduced. The better option by far is to narrow the openings on the nearest windows to the extraction fan and make the furthest window openings larger. Now, he has no easy route to the extraction fan because all his options are the same effort. This will pull cooler fresh air across the horses, giving a better cooling effect.
Our research findings
Our research closely examined heat from conduction, convection, and thermal radiation in the horse area. We began by considering the volume of the horse area and where heat collected. Using a thermal scanner, we noted hot areas and how darker outside paint colours transferred considerable heat into the horse area. Interestingly, the hottest part was the top third around and above the horse’s head.
We noted that the placement of the horse area windows, and roof vents are essential for quality air flow, as well as heat removal. We used a fog generator to understand air movement through these windows and vents. This greatly aided in determining dead air spots and the amount and placement of windows, roof vents, and our new low-level vents. This testing method was a revelation and led to a total redesigning of our horse areas.
We considered solar heat gain through windows and how it significantly impacts on internal temperatures from direct sunlight. Once testing was underway, it was also noted that customers had no way to gauge heat build-up in the horse area!
Redesigning the horse area in our horseboxes
Fortunately, our horse areas are all stalled for the largest horses with our Aeos range having 2.43 metres (8’) internal height and our Helios range from 2.51 metres (8’3”) to 2.59 metres (8’6”) internal height. This larger volume helps somewhat in keeping the very hottest air up above horse’s head. To passively help remove some of this heat, we install the horse area windows as high as feasible. The size and placement of the widow openings plays a crucial part in the overall cooling effect, as they draw fresh, cool air across the horses. If we consider the window size, an efficient design will see large horse head windows with smaller tail end windows. This differential in window size is crucial. It allows air flowing past a moving horsebox to cause a greater vacuum at the larger head windows than the smaller tail ones. This vacuum effect draws air into the horsebox through the small windows, across the horses and out of the larger head windows and roof vents.
It is worth noting that window opening sizes play a crucial role for a moving horsebox. Ideally window openings should be as large as possible. However, if the roof vents were closed and if both head and tail windows were the same size, the air pressure would be equal on both sides of the horsebox, and little to no air would move inside the horse area. It is also noteworthy that for hot or stale air to leave the horse area, fresh clean air must have an easy route in.
Even with insulated sides, in direct sunlight, testing showed darker paintwork transfers considerably more heat than a light colour. The colour choice always lies with the customer, and we just advise that lighter colours transfer less heat.
For all our models we include a white roof as standard!
Testing with a fog generator highlighted how quickly the air refreshed, it also highlighted air dead spots (still air). Having found these dead air spots, we designed low level vents to blow cool air under each horse. Our Aeos horsebox range now includes these low-level vents, and they deliver cool, fresh air underneath each horse. The cool air is then drawn up around each horse towards the windows and roof vents or extraction fan.
By testing different roof vent configurations, along with our new low-level ventilation system and windows, we found that three roof vents were the optimum and that they worked perfectly. This groundbreaking design has removed dead air areas and vastly increased air circulation and cooling for customers precious horses. When the horsebox is moving with the roof vents opened at an angle, air moving over the external side of roof vents causes a vacuum, air is then drawn from the head/tail windows and low-level vents, around the horses and out of the roof vent. This arrangement removes the most heat from the horse area and replace it with cooler fresh air.
To minimise sun exposure and heat build-up through the windows, we have chosen deeply tinted glass that effectively lowers solar gain while providing a sleek, modern look. Mirrored glass is more effective as it reflects the most sunlight. We thought this might have been a step too far!
Once testing was underway, it quickly became apparent that customers would benefit greatly from temperature readings in the horse area. Therefore, we have designed a robust heat probe system for the horse area with a digital display in the cab, so customers can monitor temperature fluctuations.
We noted that using an extraction fan with roof vents open had little to effect in the removal of heat. For optimal performance, the roof vents must be fully closed when the extraction fan is used. This prevents air being drawn directly from the roof vents straight to the fan, missing the horses completely!
From customer feedback, we noted that however hot the weather, sometimes a trip to the vet is unavoidable. Taking this into account, and where possible, we have moved the horse wash attachment point to the locker closest to the horses. In an emergency this allows the hose to reach each horse with cool water.
Finally, as part of an overall heat and ventilation strategy, when we hand over a new KPH horsebox, we have added an in-detail explanation of air flow and heat removal.
Food For Thought…
We believe our comprehensive approach, including thermal scanning and air flow visualisation, has resulted in improved horsebox designs that prioritise the comfort and well-being of customers horses. As always safety, and primarily horse safety is at the forefront of everything we do.
Thank you for being part of our journey and we would greatly appreciate your thoughts on this blog post! If there’s anything we might have overlooked or if you have additional insights to share, we would love to hear from you. Please feel free to send your feedback to kevin@kphltd.co.uk.
Thank you for helping us improve!
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