The ventilation system in a barn has three functions and must be designed properly. Do not rely on machines and instruments to determined a barn environment, look at your pigs. Pigs which are cold tend to lie in piles in a warm and draught free area. Pigs which are hot attempt to lie separated from each other with maximum body surface in contact with the floor. The LCT and UCT define the pig’s thermoneutral zone where no energy is wasted to cool or heat the pig. Watch for signs of ill health in your pigs such as sneezing, coughing and increased depth of breathing. Monitor temperature in the barn. Dirty sensors/control systems cannot maintain room conditions within the necessary parameters. Ideally for the average finishing room of 12 pens, there should be three maximum and minimum thermometers fixed in the air-stream above the stock – typically, mid-pen, 3m from the wall and 1.2m above the floor. Very little electrical energy is required to monitor barn conditions.