This is the heating/cooling system we are using in our project. They are relatively new in the U.S. but millions have been installed in Europe and Asia. It is a completely proven technology that offers substantial advantages over both gas furnaces and standard heat pumps. The name tells a lot of the story:

“Mini” refers to the size of the units which are generally smaller than comparable heat pumps.

“Split” because (like standard heat pumps) there is an outdoor condensing unit that is split apart from the indoor fan coils.

“Ductless” because…they are. This is the big technical difference. In mini-splits, refrigerant is piped directly from the outdoor unit through small-diameter insulated refrigerant lines. It goes to an individual evaporator unit and air handler mounted in the room that you’re cooling or heating. A quiet fan blows the indoor air across the cooled or heated coil and then directly into the room. With a conventional heat pump, the refrigerant lines run from the outdoor condensing unit to a central indoor evaporator coil, where the air is heated or cooled. The conditioned air is then distributed through ductwork branched off to various rooms. Since mini-splits have no ducts, all the hot or cold air they produce stays in the areas where it is wanted. Ducts (used in any type of central forced air system) are almost always run through unconditioned space such as attics and crawlspaces and they are rarely well designed, connected, insulated or sealed. The result is that in a typical house up to 30% of the hot or cool air that goes into the ducts ends up outdoors rather than in the house. There are a lot of better ways to design a heating/cooling system and the mini-split ductless heat pump is one of them.

I’ll talk performance and how they compare to other systems in my next post.