The add ons are not heat pumps,,, they add a heat strip to some of the units. If you have a unit that is all metal flashing on the lower unit, I think you can purchase and add a heat strip. If the unit is one that has plastic in the mounting area you cannot add a heat strip. I think I am correct on this,,, hopefully someone that has done this will jump in soon.
Jim M
I see the factory offers an a/c, heat pump unit for the living area if ordered as an option. But do not list heat pump for bedroom or garage area.