Heat pumps absolutely do not need to connect indoors and outdoors, every fridge and freezer is just a heat pump connected to a box.
Ive had a ventless heat pump clothes dryer, about 5 years ago, maybe 6. Technically it made the room it was in slightly colder while it ran, but that heat from my house was just concentrated inside the box and then allowed to escape back into my house.
I also think there have been advances in heat pump technology either with the refrigerant used to transfer the heat or with cascading systems that run multiple loops with different heat capacity so that one loop takes room temp water to “warm” temps and a secondary loop takes the “warm” water to hot.
Heat pumps absolutely do not need to connect indoors and outdoors, every fridge and freezer is just a heat pump connected to a box.
Ive had a ventless heat pump clothes dryer, about 5 years ago, maybe 6. Technically it made the room it was in slightly colder while it ran, but that heat from my house was just concentrated inside the box and then allowed to escape back into my house.
I also think there have been advances in heat pump technology either with the refrigerant used to transfer the heat or with cascading systems that run multiple loops with different heat capacity so that one loop takes room temp water to “warm” temps and a secondary loop takes the “warm” water to hot.