Follow the gas line from your meter if its in basement and see which furnace it goes to could go to both but its doubtful.I have ran across ductwork that a clown didn't install right and someone was getting free heat and air in a bedroom and bath.

I would imagine, given the building's age, that it would need to have the duct work put in to accomplish this, which would have a steep price tag.  

On another note, as FYI, the coffered ceiling is likely a capitalized consequence of creating the open floor plan and adding central HVAC... concealing a dropped beam(s) perhaps, to create the openness, and at least in the Kitchen area, it is concealing ductwork.  

If you have duct work, make sure the ducts are clean and the air registers are not blocked.

Is there already ductwork through-out?

I want to keep the duct-work in case I need it later. 

They have to have a water source , cut into the ductwork .Its not a DIY project .

I assume this price does not include replacing duct work.

This is what causes the motors to break - they are just over worked.Furthermore, the electricity that it takes to run the fan exceeds the energy that you save from cooling the attic - again, regional differences may occur, but this is at least true in the south - see this study done in Florida:http://www.fsec.ucf.edu/en/publications/html/FSEC-GP-171-00/You do get benefit of reducing strain on the HVAC system and ductwork if it is in the attic, so even though you are spending more on electricity, reducing the temperature in your attic is important because this will increase the longevity of your HVAC system (if it is in the attic).So, the conclusion is that for energy savings, solar powered attic fans are superior.

You can also hire someone to clean the ductwork because a lot of hair can get stuck in there depending on how long the dog occupied the home.Another option is an ozone generator.