The vent fans in our bathrooms make loud clapping noises when it's windy. I can open/close the doors to the bathroom quickly and hear the flap clapping because of the pressure change. Is this something I should be concerned about? The house is less than a year old and I'd like to take it up with the warranty department if it is going to cause an issue. I've never had this issue in any other place I've lived.
There is nothing wrong, when you have a small space like a bathroom and you open the door quickly the pressure is enough to open the back draft dampers in the exhaust fan. The same thing happens when you turn on the fan the damper(s) open allowing air out. If a high wind blows across the external duct it can cause noise but that is also normal and nothing a warranty could do anything about. After some time you get used to it adding construction cloth around the opening can help reduce the noise but is an extra cost. Construction is a wire grid that is wrapped around the openings like this to keep critters out and it also reduces whistling,