To Stop Drafts: Backdraft Dampers
Backdraft dampers or butterfly damper play a big role in energy efficiency. Usually acting as an air valve that only opens one way they are used to prevent the air outside from invading your home. When air is exhausted through a dryer or a Range Hood vent, a backdraft damper will make sure that the air goes only to the outside.
The Design of Back draft dampers
The Butterfly damper is the most common design for backdraft damper. It can be made from either aluminum, galvanized steel, or stainless steel cylinders. Inside of the backdraft damper are one or two pivoting blades that are inside. The blades move in opposing direction, and this is how its gets its name (butterfly wings) When the air flows, the blades wills stay open but will close when the air flow stops. For example, when the Range hood vent is turned off. A successful Butterfly damper can stop up to 99.9 % of the incorrect air flow. Cylindrical Sidewall hooded dampers can also be purchased. These damper from direct wind and rain.
Newer models of back draft dampers have a fabricated sleeve that is called a “Cape” The cape allows air flow to go without impedance when it is flowing in the right direction , but the fabric stops it in the opposite direction. These have a larger free area, and so because the flow is not blocked, the vent flows more freely. Also this vent makes less noise because there are no moving parts.