running HVAC ducts for newly finished basement room

denemante

Hey all,

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)?

beenthere

If you have an 80%. The venting code will be the same as it is for your current unit.

Best to have the supply air near the outside walls. And generally preferable at or near the windows or doors.

Will work better, it you tap into the plenum, instead of the trunk line.

denemante

Thanks Beenthere. What's 80%? And you're suggesting any pro would just run 2 new supply vents from the plenum? I assume maybe also a new return run to a return plenum, with the return vent lower on a wall?

beenthere

80% efficient furnace. Vents into a chimney.

Many will cut corners, and run it from your trunk line. Which in turn robs air from other supplies.

I'd rumn the return tot he return plenum or drop.