Leaving the door open in a piggery - whether through forgetfulness or to 'improve' ventilation - can cost producers a small fortune, according to Nick Bird, director of Reading-based farm energy specialists, Farmex.
The cost of wasted heat has emerged from the company's energy monitoring project on UK farms. On one farm a faulty latch to a weaner room added an extra £5 per day to the heating costs. The monitoring system showed peaks of electricity use due to the door swinging open during the day and again at night.
"The heating came on to maintain room temperature and an extra 4.5 kW was needed to maintain room temperature," commented Nick.
Sometimes leaving the door open is intentional, perhaps with the idea of switching the fans off to save money or through the belief that this form of ventilation is somehow 'better' he surmised. But the heat loss can be surprising, he pointed out.
"The amount of heat loss through a door can be as much as 6 kW at 10°C outside temperature and this increases to a massive 13 kW at 0°C," he said. "Even in our mild British climate an open door can lose a staggering £1,700 worth of heat a year."
Apart from emergencies, it is generally better to use fan ventilation since this is controllable and provides better air mixing so that heat is spread through a room and doesn't just rise to the ceiling. Open doors simply allow cold air to come in at pig level.
"Our data confirms just what granny always told us: 'Shut that door!'" said Nick.
