Traditionally, calves are kept individually in outdoor igloo’s. In the Hooibeekhoeve, a research and demonstration farm in Antwerp, Belgium, young calves are individually housed indoors. The air for the ventilation in this calf house is separated from the barn with the adult cows. From the outside of the barn, three inlets draw fresh air from via underground channels through the floor of the calf house. The air then passes through the house and is subsequently extracted at the ceiling and sent to the barn with the adult cows. The separate ventilation for cows serves to prevent infections from the adult cows in the bigger barn to spread to the younger calves. Another benefit of this ventilation system is the ability to keep the room temperature and the humidity of the air constant, in contrast to outdoor igloo’s. It creates a comfortable surrounding for the calves that protects the calves against the cold weather and keeps them warm at all times.