If the walls are framed with 2x4s there s often not enough space even for a little bit of duct insulation.
Ac ducting inside room without attic.
An hvac return air duct should be in every room except a bathroom and kitchen.
The remaining 2 tons of capacity is at least 1 5x oversized for the actual 1 load.
However it absolutely must be an unused chimney in an unused fireplace.
When you decide to trade in your room air conditioner for central air you ll have decisions to make including where.
Good luck getting better cooling in the upstairs in an old home using a basement hvac system than one in an attic.
You can pipe the hot air out through a chimney.
Can you put your air conditioning unit in the attic with blown in insulation.
Never try to vent a portable ac unit through a functional working chimney or fireplace that s a huge safety risk.
In more cases than not a 3 ton ac with the ducts in the attic has a ton or so of load that s just from the location of the ducts in the attic and the associated duct gains leakage etc.
Sure if you can find enough space and afford the large cost to have someone poorly carve up the inside of your house to get the proper sized ductwork through the house.
Most homes have wall insulation in the cavities not outside the framing.
Duct losses to outdoors.
Quit writing papers and go try a seat of your pants experiment.