Any suggestions and recommendations appreciated for info on heat & a/c units for single room use. I am adding two small rooms from attic space and find the current HVAC inadequate. The original design of the unit on 2nd floor will not supply adequate volume and efficiency. Upgrading the current system is not an option.

Are small units available to place in an unused area of the new room to which I would connect ductwork to supply heat & a/c?

Thanks for any information.

I think that the smallest split A/C system availiable is 1,5 ton, or a ton and a half. Depending on how much you need, you may want to go with window A/C. Oh,...almost forgot, there is a unit that is called a "Mini-Split" which uses a small air handler, usually mounted on wall in conditioned room. The only draw back is that their is a line-set connecting to the outdoor unit. If your addition is on the second floor, this can be unsightly.
Hope this was helpful to you.