My folks have an occasional back draft/ downdraft problem based on the direction of the wind versus a roof line on the home that is a considerable distance away from the top of the chimley.... they’ve been considering a directional cap, as well.... Being that my 70 YO dad is as stubborn as a mule, I doubt they buy one.
We were ~37* in 2014, (not including wind chill), no furnace, woo hoo both smoke dragons were choochin'!!
We have the storm shield cap that was highly recommended by a member here. It’s been great for us. Volko chimney caps... stormshield... draft and ventilation solutions.