What a Wellington house means for a ducted job
Steady heating more than frost
Wellington Aero averages 1,625 heating degree-days a year, while the airport averages no days below 0 degrees. A ducted system here is about long, steady winter heating, so small duct losses add up over a season.
Older homes are retrofits
Character precincts make Wellington's pre-1930s homes hard to demolish, and the Miramar state houses of 1937 were weatherboard with tiled roofs. Ducting these houses means working around the framing, wiring and insulation already in the roof space.
Flats and townhouses
The 2023 Census counted 30,390 Wellington City households in joined dwellings. An apartment with another floor above has no roof space for a ducted unit, and a body corporate may need to agree before an outdoor unit goes on common property.
Damp needs its own fix
In 2023, 22.6% of people in the Capital, Coast and Hutt Valley health district lived in a damp home (EHINZ). BRANZ says ducted heat pumps usually recirculate the air inside with no fresh air supply, so ventilation has to be handled separately.
Wind and salt outside
The outdoor unit still faces airport gusts over 96 km/h on 24 days a year, and within 500 m of the harbour or coast BRANZ's Level guidance calls for extra anti-corrosive coatings.
Why the ducts matter more than the brand
BRANZ warns that ducted systems can lose more than 30% of their heating energy when ducts are overlong, have many bends or run through uninsulated space. In a villa with a low or patchily insulated roof space, that's the first thing to check.
The best spot for the indoor unit is the ceiling space, BRANZ says, with the supply and return air ducts as far apart as possible. Consumer NZ notes the unit can also sit under the floor, which is worth raising if your roof is tight but the subfloor is roomy.
In a two-storey hillside home, ask how each level gets its share. BRANZ says each room's supply is controlled by its air flow rate, and Mitsubishi Electric NZ says excessive pipe lengths and bends reduce output.
What makes a Wellington ducted job bigger or smaller
It grows with more rooms, a sprawling floor plan, a roof space that's awkward to reach or move around in, and any switchboard work, which the EWRB says may also need a licensed electrical inspector. It shrinks with a single-level house, an open, well-insulated roof space, short runs and an outdoor unit close to the indoor one. In a unit title, allow time for the body corporate.
Questions for a ducted heat pump specialist
- Have you been into my roof space, and where will the indoor unit sit?
- Will any duct cross uninsulated space, and how is each duct insulated?
- How many vents, and where's the return air grille?
- What are the heating capacities at 7 and 2 degrees, and how did you size the system?
- How will the outdoor unit be fixed on this wall, and does it need corrosion protection here?
- Does the body corporate need to approve anything first?
Before the site visit
You can
- Clear a path to the roof space hatch, and leave the climbing to the installer.
- Find out whether the house is a unit title, and get the body corporate rules.
- List the rooms you want warm, and the times you use them.
Leave to a licensed installer
- The heat load calculation and the duct layout.
- All work in the roof space or under the floor.
- Refrigerant work, commissioning and the electrical connection.
- Corrosion coatings on the outdoor unit.
What we'd do
If it were our Wellington house
We'd only go ducted after a specialist has been up in the roof space and shown us how every run stays short and inside the insulation. In an apartment, or a townhouse with no usable roof space, we'd look at a multi-room system instead. And because ducts don't ventilate, we'd plan for the damp at the same time.