running HVAC ducts for newly finished basement room
I have a related post going, but I got some advice so this modifies my original idea. I've got an unfinished room in my basement that's about 15x25 feet. There is presently another 15x25 foot totally finished room down there as well. It's heated/cooled from the same unit that does our first floor.
I'm about to begin finishing this unfinished 15x25 room down there. It happens to have the HVAC air handler sitting in it. I'll box it in to code and put a vented door on it, etc.
Our units are older but in top working shape, so we're not going to replace them now.
That being said......
I've gotta heat/cool this new room. I want to tap into the existing unit and run perhaps 2 vents and one return. There are also two vents and a return in the other finished room.
I know I'll replace the HVAC unit at some point. So my question is before I frame, do I need to do anything special for that in terms of vents? I want it vented properly so it can work now with the older/present system. Then at some unknown future point, I can have a new HVAC unit installed but my venting will already be right.
And final question - is there preferred placement for these new vents? I assume above windows/doors. There is an exterior door and a double window. So two new runs to those? Or forget placement and just tap into an existing duct (all in ceiling)?