Stores that sell roof vent caps include Grainger, The Home Depot and Lowe's. As of March 2015, Grainger carries over 40 different kinds of roof vent caps from such brands as Ameri-Vent, Broan and Dayton. The vent caps range in price from around $25 to over $200.
The least expensive roof vent caps sold by Grainger are those manufactured by Broan that are designed to fit over 3- or 4-inch duct sizes. The most expensive are the galvanized steel, 12-inch roof vent caps made by Fantech.
The Home Depot stocks over 60 different models of roof vent caps from Master Flow, Active Ventilation and Speedi-Products, among others. The caps range in price from about $10 for a Master Flow 3-inch vent cap, to over $220 for a Speedi-Wind 12-inch round wind directional chimney cap. Customers who decide to purchase roof vent caps through The Home Depot's website can choose to either pick up the caps from the store, or have them shipped home. Both options are free.
Lowe's carries over 80 roof vent caps that are priced between $8 for a Air Vent plastic roof vent cap that fits 9-inch ducts, and over $100 for high-end Broan aluminum roof vent caps.