Clear the air: How good ventilation improves calf welfare
December 3, 2025
Fresh air is a natural disinfectant and improving air flow in your sheds will provide multiple benefits for years to come. Good ventilation is essential for calf health, acting as a natural disinfectant by helping to remove airborne pathogens and moisture. CAFRE Beef and Sheep Adviser, Gareth Beacom explains how improving airflow in calf sheds can deliver long-term benefits for animal welfare and farm performance.
With store calf prices rising by over 50% in the last 12 months ensuring the health and welfare of these calves has arguably never been more crucial. Whether calves have already been bought, are yet to be sold, or are being kept for grazing next year, their health over the winter months will directly impact their physical performance – and your bottom line.
“Ventilation is key to an animal’s health over the coming months,” comments Gareth. “The two key components of ventilation are that there is sufficient outlet and inlet areas and that the inlet is above the head height of the animal for effective ventilation whilst not causing a draught to the animals.”
Outlet ventilation
The amount of outlet required in your shed depends on two key factors: the stocking density and the distance between the air inlet and outlet. While this distance can be tricky to measure precisely, you can estimate it using reference points on the gable end, such as rows of blocks or sheets of tin. Once you’ve got a rough measurement, you can calculate the outlet size needed for your specific shed and the type of stock housed in it.
A general rule of thumb based on recommended stocking densities and a distance of 2 metres between the outlet and inlet is that animals over 500 kg require 0.1m2 per animal (as well as 0.04m2 for young calves). For example, a five bay shed approximately 23 metres long with a ridge gap of 0.2m (8 inches) will have an outlet of 4.6m2. This would be enough of an outlet for 46 cattle over 500 kg or 32 cows and calves.
Ideally the open ridge would be left open to not restrict any air flow, however if it needs to be covered, to prevent rain coming in then the height of the cover should be 50% of the width of the ridge (i.e. if the ridge is 0.3m in width then the cover should be at least 0.15m clear from the roof).
Angled uprights from the ridge gap offer a great alternative to traditional ridge covers. They provide far better ventilation while keeping out most of the rain. If an open ridge isn’t an option, spaced sheeting can provide an effective outlet provided it is adequately spaced throughout the building.
Inlet ventilation
Once you have calculated the outlet area the inlet area can then be calculated as the inlet area should be at least twice and preferably four times the outlet area (0.2 – 0.4m2 per animal over 500 kg).
To avoid draughts the inlet should be positioned above the head height of the animals. These are typically created either by spaced boarding or Yorkshire boarding along the length of the building. Inlets along the sides of the building are usually sufficient unless your shed is excessively wide (over 25 metres in width), in that case inlets along the gable ends will be needed also. In comparison to spaced boarding and Yorkshire boarding, vented sheeting offers considerably less air flow and hence inlet for the building. Spaced boarding is generally achieved by a 100mm board with a 10mm gap in between, as can be seen in Figure 1. Yorkshire boarding is usually constructed using 150mm boards with a 50mm gap between (see Figure 2). This allows more air to enter via the larger spaces and with the overlapping rows blocking most of the rain out also.
If designing a new shed, the positioning of the shed is crucial to maximise airflow. To take advantage of prevailing winds, the shed should be oriented at a right angle to the wind direction and placed away from obstructions such as buildings and tall trees. This setup enhances airflow through designated inlets. However, if it is an open sided building then the open side should be positioned wherever it gets the most protection from the prevailing wind whilst still allowing adequate airflow.
Improving ventilation on existing buildings
If ventilation issues arise in existing sheds, several modifications can help alleviate the problem. One effective solution is to increase the size or efficiency of the air inlets by replacing spaced boarding or solid side sheets with Yorkshire boarding, to allow better airflow. Windbreakers are a flexible option to enable controlled ventilation while preventing rain from getting in. Alternatively, the bottom edge of the side cladding or sheets can be angled outward from the wall, creating a clear gap between the wall and the cladding. This design channels incoming air upward as it enters, improving internal air circulation.
Modifying the outlet for ventilation can be more challenging, but there are practical solutions. One approach is to raise one or two roof sheets per bay to create additional outlet space. These sheets can be replaced with wider ones to allow for overlapping, which helps prevent rain ingress. Alternatively, if the roof has a ridge cap, it may be possible to raise it or widen the existing gap to improve airflow. Both methods can enhance ventilation while maintaining weather protection.
Mechanical ventilation systems are becoming increasingly common on farms, with two main types in use, ventilation fans and extractor fans. Ventilation fans draw in fresh air from outside hence a good outlet is essential. These are particularly useful in stuffy conditions when airflow is poor or when the sitting of a shed doesn’t allow for much natural ventilation. They can also be used where there isn’t enough of a stocking density in the building to create a ‘stack effect’ i.e. in calf sheds or understocked sheds.
Extractor fans on the other hand, assist with the extraction of moist air from the ceiling areas of sheds with poor outlets. These work better in smaller confined areas however various sizes of extractor fans are available.
While there is an upfront cost associated with ventilation improvements, the long-term benefits make it an extremely worthwhile investment. The health benefits from increased airflow can lead to increased daily live weight gain, reduced reliance on medication, and in severe cases, lower mortality rates. Considering the lifespan of most farm buildings, these gains are significant.
Fresh air acts as a natural disinfectant, helping to kill viruses and remove harmful bacteria and dust from the shed environment. Therefore, maximising the movement of fresh air through sheds is essential for maintaining animal health and overall productivity. It’s also important to remember that repairs to livestock buildings are tax-deductible, which can help offset the initial investment.
Gareth concludes, “Given the value of calves this year it is easy for any suckler farm, regardless size, to justify spending time and money on improving the ventilation of their sheds.” He adds, “Regardless of what type of livestock shed you are working with the target is always the same, maximise air flow and ventilation on a still day without leaving the animals exposed to a draft on a windy day.” You can discuss all aspects of shed ventilation with a local CAFRE Beef and Sheep Adviser by contacting your local DAERA Direct office.