Ventilation fans are indirectly open to outside air. They contain a damper to limit the back-flow of cold air. The damper is balanced to allow exhaust air to escape freely and fall back to a closed position when the fan is turned off. By design, they are not completely effective at eliminating cold air infiltration. During gusty winds, the damper may flutter as it adjusts to fluctuating air pressure. This is normal. Exhaust fans will accumulate dust and airborne debris over time that can impair fan efficiency, obstruct the damper and create excess noise. The fan is connected to ductwork that ends with a screen at an outside vent hood. Clean the fan housing and the screen of the hood vent regularly. Exhaust fans will accumulate dust and airborne debris over time that can impair fan efficiency, obstruct the damper and create excess noise. How do I maintain my kitchen/ bath fans and can I stop cold air infiltration from these vents? 112 ANHWP.COM • ALBERTA NEW HOME WARRANTY PROGRAM