I have an air duct coming off my furnace that supplies heat to two small first floor rooms. It also supplies heat to the upstairs. There has always been incredible air flow coming from the first floor registers, and hardly anything coming from the upstairs registers. A family member who i usually trust when it comes to home issues told me that usually when one air duck branches off another, and goes up, there is some type of shield that forces some air to head up the up air duct instead of going straight through the main air duct. He says that i do not have one of these. It sounds logical to me, but what the heck do i know. Does this sound correct? Thanks.