I am currently in the process of finishing my basement. I have done the framing, run the electric and I am in the process of running the plumbing. Next step will be deciding if I can add a couple vents to the area. I admit I do not know much about HVAC. I am in the process of doing my homework now.

(forgive my HVAC vocabulary)
In the basement celing between the joists I can see the vent chambers running from the main chamber (a rectangular shaped chamber ). The main chamber runs perpendicular to the other vent chambers. I can see 2 on each side that feed the 2 kitchen vents and 2 living room vents. I have easy access to 2 of them the other 2 are behind the ceiling that a previous inhabitant installed.

I would like to install 2 vents in the basement mainly for heat, I would keep them closed during the summer. I want to ask if I can't tap into 2 of the existing chambers and run vents pointing down? I know this would split the flow between the 2 vents by some proportion but I do not know in what ratio.
The better question to ask is what are my options? I can provide a few pics if needed. The heating and colling units should able to handle the additional finished space. My neighbor has the same HVAC unit and has a finished basement.

Thanks in advance

Doug

You could just branch off one of the other runs although like you said it will reduce the pressure going to the other vents. You should also be adding return air ducts which I think are just as important for increasing the heat in a basement. The return ducts should be just off the floor to suck in cold air. It will not be nearly as effective if you just blow the warm air down there from the ceiling.

For branching I was hoping to be able to put an in-line vent into the duct a few feet before the terminal duct. The reason being is the ducts are run snug between 2 joists and it's the only way I can think of unless they may a dual vent (top and bottom openings) terminal end. Do they make inline vents or dual terminal vents ?

Unfortunately I don't think I can run a cold return. The return duct is not accessible to me so that I could tie into it. I assume I would have to run a duct from the return main duct down near the floor?

Thanks