I am in the process of preparing my basement for a bathroom, kitchen and laundry/furnace utility room. I am trying to reclaim as much living space as possible. Is it possible to move the furnace off center (yellow line) and create a L shape with the duct work (green line) in order to reclaim usable living space (red line)? Or will this effect the efficiency of the unit?

Hello All, I am hoping someone can help me. I am building a Home theater in my basement, and there will be no outside windows/doors, only a door from the inside. The room will be pretty 'air tight', as I am caulking around all the borders of the room to help with sound Transmission. Most of the time, we'll likely only have 4-6 people in the room, but there will be seating for up to 16. The room is 22.5' x 17.5 feet, and an average height of 8' - so, around 3,100 cubic feet. To 'condition' the room, I had a Mitsubishi Mr. Slim installed. This will provide cool &/or Hot air, but not 'Fresh Air'. My 'air supply' plan, is to use a 6" round Flex Duct, and a Duct Fan pulling in air from the rest of my basement. The 'rest of basement' area is quite large, so, I think that air should be 'okay'. I was tentatively thinking of putting in a "Return", through one of my vertical walls into the existing house return. The area would only be about 12" x 3.5" where it goes into the house return duct. I could put a large return vent in the wall, but was worried if the intersection between vertical wall & horizontal return, was only that 12" x 3.5", I might not have sufficient 'air withdrawl' from the room. I was thinking that 12" x 3.5" would be the bottle neck and it didn't matter if my return on the wall was twice that size, since that is the bottleneck. The house return duct is simply using ductboard on the bottom of the floor joists, so it is about 9.5" x 20" wide. My other option, is trying to extend the existing return air into the room, and making a larger return air penetration also in the Floor joists, directly into the return air. The slight issue for me, is that the ceiling height will be 2 3/4" lower than the floor joist, so, not sure how I make the right penetration/ seal it up. So, first question.. is do I need a larger return than the 12"x3.5" area? If so, what size do I need? And what is the best way to make a small duct box that extends the 2 3/4" down to the bottom surface of the ceiling? Thanks, Kevin