When my home was built in 2016 the HVAC runs from the furnace in the basement up through the house uses 7" R4.2 insulated flex duct.
I am in the process of finishing my basement and I would like to tap into the existing runs. I am not sure what type of register to use to blow downward from the ceiling perimeter of the main room or how to accomplish this. Any help would be greatly appreciated.
Attached are a couple pictures
Best Answer
I don't believe 7" or 8" ducts are trunks, and therefore you shouldn't be splitting them. Each vent requires its own branch duct from the trunk.
Trunk lines are almost always rigid rectangular duct of 10x12" or larger. You install a starting collar and connect your flex duct to that.
If your builder didn't properly facilitate new connections for your basement, you may need to have a tinbender come in and extend the trunk appropriately.