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Cooling & Heating · Concealed DuctedDucted Mini-Split Installation
Ducted mini-split installation puts a slim concealed air handler above a ceiling or in the attic and feeds two or three rooms through short ducts, so nothing hangs on a wall. It suits a bungalow, an addition or a second floor as long as the duct runs stay short. These units push air at low static pressure, and one slim unit asked to feed more than about four outlets is being asked for too much.
A ducted mini-split is the same inverter heat pump as a wall-mounted ductless unit with a different indoor half. In place of a wall head, a shallow air handler roughly 20 to 25 cm tall hides in a dropped ceiling, a bulkhead, a closet soffit or the attic. It draws room air through one return grille and delivers it through short insulated ducts to a ceiling or high-wall grille in each room. The outdoor unit, refrigerant lines and controls are those of any mini-split.
Three kinds of house in our area suit it. A 1950s–60s bungalow in Aldershot or on the Hamilton Mountain with boiler heat can have three bedrooms cooled from one unit in the attic above the hallway. A rear addition with a flat ceiling takes a unit in a bulkhead. And a two-storey whose basement furnace never quite cools the upstairs can have its bedrooms served from the attic, which is one of the options on our second-floor cooling page.
The limits come from the fan. A furnace blower is built to push air through a whole house of ductwork; a slim-duct fan is rated for a fraction of that pressure, so every metre of duct, every elbow and every extra outlet costs airflow. We keep runs short and straight, size them from the manufacturer's static-pressure tables and stop at the number of outlets the unit can feed, usually two to four. A full floor of six rooms needs a mid-static air handler or two units, not one slim unit stretched thin.
Two details decide whether the system still works well in year ten. The filter has to be reachable, so it goes behind a hinged return grille in the ceiling where it can be changed from a stepladder, not from the attic. Condensate has to leave reliably: a gravity drain where there is slope, the unit's lift pump where there is not, and under any attic unit a secondary pan with a float switch that stops cooling before water reaches the ceiling. For wall-mounted options and their prices, see ductless mini-split installation.
A ducted mini-split is the right choice when
- You want two or three adjacent rooms cooled and heated with no equipment visible on the walls
- An accessible attic, bulkhead or dropped ceiling sits a few metres from every room served
- The rooms are bedrooms with doors closed at night, which a single head in the hall cannot reach
- The house has radiators or baseboards and no existing ductwork
- A wall head has nowhere to go: sloped ceilings, full-height windows or a heritage interior
How it works
A room-by-room load calculation sets the capacity. Then we check attic depth, joist direction and the access hatch, and decide where the return grille, the drain and the outdoor unit go.
The air handler is hung on isolating supports or set on a platform, and ducts are cut to length, sealed with mastic and insulated. Attic ducts are buried in insulation so they neither sweat in July nor lose heat in January. A licensed electrical contractor runs the dedicated circuit under an ESA notification.
After a nitrogen pressure test and a deep vacuum, airflow is measured at every outlet and the fan's static-pressure setting is adjusted to suit the ductwork as built. You are shown the filter grille, the controller and the float switch.
Brands: Mitsubishi, Fujitsu and Daikin all build concealed ducted indoor units for their mini-split outdoor units, and those are the three ductless brands we work on most.
Common questions
Is a ducted mini-split less efficient than a ductless one?
Somewhat. The same outdoor unit paired with a ducted air handler carries a lower efficiency rating than with a wall head, because the fan works harder and ducts lose a little along the way. Short, sealed, well-insulated ducts narrow the gap. For most owners the trade is appearance and even bedroom coverage against a modest efficiency cost, which ducted vs ductless heat pumps compares in detail.
Can one ducted unit do my whole house?
A slim-duct unit cannot. It serves a zone of two to four nearby rooms. A whole house takes several zones on a multi-zone outdoor unit, or a full-size ducted heat pump with a proper air handler and trunk ductwork. If the house already has good ducts, heat pump installation through them is usually the better route.
Will it heat in winter from a cold attic?
Yes, when the outdoor unit is a cold-climate model and the attic work is done properly: unit and ducts sealed, wrapped and buried in insulation, with no gaps left in the ceiling air barrier. Heat lost from an attic duct is gone for good, which is another reason runs stay short. The drain line is sloped to empty completely so no water sits in it to freeze.
How loud is a concealed ducted unit?
Quieter in the room than a wall head, since the fan is above the ceiling and what you hear is air at the grilles. Noise complaints trace back to undersized ducts and grilles forcing the air too fast, or to a unit hung rigidly from the joists over a bedroom. Generous grille sizes and isolating supports deal with both.