- A single-zone (also called a mini-split) ductless Heat Pump system offers heating in the cooler months and air-conditioning in the warmer. Like the cooling only systems, the Heat Pump allows you to control the temperature of one room by connecting an outdoor unit to an indoor unit, with no ductwork needed. An outdoor mini-split unit is placed outside your home and is connected to an indoor mini-split unit by small cables and a refrigerant line through a hole in the wall. Ductless systems deliver efficient cooling and heating with lots of flexibility. They can provide climate control for small additions that aren’t connected to existing duct work.