Hi all, I am working on finishing my basement and have arrived at the point I need to do a little HVAC work and am looking to the board for a "sanity check" and a little advice. For now I am going to be finishing three rooms: a walk-in storage closet, a rec room and a "theater room". I am not going to do anything HVAC related in the closet so that one is easy. Now the rec room is about 34 X 16 with 8 foot ceilings and three windows. My plan of attack is to install three registers in this room, one over each window. I'm thinking for cold air return that I will make a 32" wide return by "thermopanning" the space of three studs. Now is it common practice to connect a cold air return to the main return ductwork with pipe (like 6 of 7 inch)? Where I need to put the return I have no direct access to the main trunk and about the only way to get it connected is to use some pipe (ie. I can't thermopan it the whole way). Is this okay? And if so, any recommendations on the size of pipe to use (does it really even matter)? Finally for the theater room (11X14 again with 8 foot ceilings) the main trunk of the outgoing (conditioned) air runs through the ceiling of this room so I am planning on just cutting 2 holes in it and screwing a couple registers into the eventual drywall to get heat to the room. As far as return goes from this room I can put a return in pretty easy as long as it is okay that it will be within a couple feet of the actual furnace in the unfinished part of the basement. (I heard someone mention that returns can't be placed too close to the furnace, but I'm not sure why, it's pulling it's air from a completely different room).

Anybody see any issues with my plan? I would appreciate it greatly if anyone sees any oversights, please point them out. Thanks!

-Corey

One obvious issue is that apparently you will be stealing air from rooms above, and this will more than likely completely upset the balance of your heating system. I think dealing with your new rooms is a job for a professional, who can determine the exact air delivery requirements and how best to satisfy them. A good heating contractor is your best bet.

Size does matter for return air ductwork. If the duct is too small, velocity will be too high, and that part of the system will be noisy.

Consult a pro before you mess up your system.

Yeah, I understand that fact, I forgot to mention I built the house (not all by myself) but I had the HVAC installed with the knowledge that the basement was going to be finished so the system was sized appropriately. So I should be okay that way, I really just need to know about the mechanics of installing the system. Thanks again!

Even so, the balance of your system is going to be affected. If it was right before, it won't be right after you supply the basement, especially if you guess at return air grille and duct sizes and don't calculate them properly. The capacity may be there, but the balance will change, and probably not for the better. Have your supply registers and return grilles and ducts sized properly by a professional and save yourself much "do-over" work.