When does a heat transfer system make sense?
BRANZ says these systems are most useful where at least one room is heated by a log burner or pellet burner, and the air at ceiling height in that room reaches around 30 degrees or more. Picture a winter evening with the lounge roasting and the bedrooms down the hall sitting cold. That's the house they were made for.
BRANZ is just as clear about where they don't suit: rooms where the heat source runs on a thermostat, or where there's little heat stratification (warm air layering up near the ceiling). Heat pumps run to a thermostat, so a kit fed from a heat pump room deserves a hard look first.
There also has to be heat to spare. In BRANZ's words, these systems 'aren't actually heaters', they just move warm air to where it's needed. If the burner only just keeps the lounge comfortable, spreading that warmth around leaves every room lukewarm.
It moves heat; it doesn't ventilate
Consumer NZ says heat transfer systems aren't ventilation systems: they simply haul warm air from one room to another. Unless a kit has an outdoor air intake (BRANZ says some have one under the eaves, for fresh air in summer), it only circulates air that's already inside, so it won't take damp air out of the house. If condensation is your real problem, start with home ventilation instead.
How the warm air gets from room to room
Through the wall
BRANZ says the simplest units are mounted high on a wall and push warm air straight through to the room next door.
Through the roof space
Bigger systems pull warm air from a grille on the far side of the room from the heat source, then carry it through 150 mm or 200 mm insulated ducts in the roof space to ceiling outlets in other rooms, BRANZ says.
Switched by a thermostat
Some systems have a thermostat, BRANZ notes, so the fan only runs while the source room is above a set temperature. That stops the kit pushing cool air around once the fire dies down.
Moved by a small fan
BRANZ says the fans typically use 40 to 120 W of power. To work out what yours uses, multiply its input power in kW by the hours it runs and your own power rate.
What makes the job bigger or smaller?
A through-the-wall unit between two rooms is a small job. A ducted kit serving three or four bedrooms is a bigger one: more outlets, longer duct runs, and more time in the roof space.
Where the ducts run matters for how well it works, too. BRANZ says the system should ideally sit inside the thermal envelope (the insulated part of the house), and where it can't, the insulated duct runs should be as short as possible with R values (insulation ratings) as high as possible. A long run through a cold roof space loses warmth before it arrives.
A heat transfer specialist will want to know how hot your burner room gets near the ceiling, and where the ducts can go, before they quote. A thermostat, a summer outdoor intake and the number of outlets all change the job.
Who can do which part?
If the fan or thermostat is wired in rather than plugged in, that's prescribed electrical work. A registered and licensed electrical worker must do or supervise it, and leave you a Certificate of Compliance within 20 days.
Ducts and ceiling outlets are building work. Schedule 1 of the Building Act 2004 lets holes of up to 300 mm across for ducts go through an existing house without a building consent, and BRANZ's duct sizes sit well inside that. The finished work still has to meet the Building Code.
A new burner to feed it is another matter. Tenancy Services says wood and pellet burners need a building consent to install or modify, and EECA's Warmer Kiwi Homes programme stopped taking new wood burner applications on 9 January 2026.
Your side, and the installer's
You can
- On a cold evening, compare how warm the burner room feels near the ceiling and near the floor.
- Keep furniture and curtains clear of the intake grille and the outlets.
- Dust any grilles you can reach from the floor, as the manual describes.
Leave to a licensed installer
- Fitting the fan, ducts and outlets, and all roof space work.
- Any fixed wiring, and the Certificate of Compliance.
- Sealing and insulating the duct runs, and setting the thermostat.
- Telling you straight if your burner room doesn't have heat to spare.
What a good quote spells out
- Through-the-wall or ducted, and which rooms get outlets.
- The duct size, length and insulation rating for each run.
- Whether there's a thermostat, and the temperature it switches on at.
- Whether the fan plugs in or is wired in, and who does any wiring.
- Whether an outdoor air intake for summer is included.
- Whether it's a quote or an estimate. Consumer Protection says an accepted quote can only rise if you agree to extra work or the scope changes.
What we'd do
If it were our house
We'd only fit one where a burner room genuinely overheats at the ceiling on winter nights. Then a ducted kit with a thermostat and short, well-insulated runs earns its place. If the far rooms are cold and there's no hot room to borrow from, there's nothing to move, so we'd heat those rooms directly, often with a high-wall heat pump, and deal with any damp separately.