Extracted air is better than recirculating air. this new award winning ducting valve will stop any backdraft coming back into your kitchen or bathroom, this self-opening valve and will open and close when your extractor is turned on or off, this will save on any cold air returning back into your room, No electrical connection is necessary and simply fit into either a 150mm ducting pipe or a 125mm ducting pipe. if your house is prone to windy conditions this new unit will put an end to noisy flapping outside vents proventing the cold air returning back into your kitchen.