I recently enclosed a back porch and made it a regular room. I need to get an air return installed since the room doesn't maintain temperature although it has double pane windows, insulated walls and insulated floor. I have an air return close to where I want to install a return for the room. It is 12 inch flexduct and is about 10 feet from the main return where it is connected. Can I "T" into that flexduct with the new return and still accomplish my goal of more air return for the new room?