Published
Most 4 bedroom homes on the Sunshine Coast need a ducted system of about 12.5 to 14 kW, with five or six zones. The exact size comes from the rooms you want cooled, not the total floor area of the house. Here is how we size a ducted air conditioner for a 4 bedroom Queensland home.
What size ducted air conditioner does a 4 bedroom home need?
A 4 bedroom Queensland home usually needs a ducted system between 12.5 kW and 14 kW. A 12.5 kW system suits five zones and a 14 kW system suits six zones. The final size depends on the floor area of the zoned rooms, ceiling height, insulation and how much sun the house takes.
Those figures are a starting point, not a quote. Two 4 bedroom houses can land on different sizes. A single storey with a low ceiling and good insulation behaves very differently to a two storey with a west facing living room and a high void.
That is why we measure on site before we put a number on it.
How do you work out the size of a ducted system?
We allow about 150 watts per square metre for each room that gets a zone, add them up, then size the system at about 70 percent of that total. Ducted systems are sized below the full load because the zones are almost never all running flat out at once.
As an example, say the zoned rooms add up to 120 square metres. At 150 watts each that is 18 kW. Seventy percent of 18 kW is about 12.6 kW, so a 12.5 kW system is the match. Four bedrooms, a living area and a dining or kitchen zone is five or six zones in practice.
Only the rooms that get an outlet and a zone count toward the total. A laundry or garage you are not cooling does not add to it.
Why not just fit the biggest unit available?
Oversizing wastes money and makes the house less comfortable. A system that is too big cools the air quickly, switches off, and leaves the room damp and clammy. On the Sunshine Coast, where humidity is high, a system that runs steadily at the right size dries the air properly.
Bigger units also cost more to buy and install, and larger ducting takes more roof space. There is a limit to what your roof can hold. A correct size also usually runs quieter, because the fan is not pushed hard.
Undersizing is the other trap. A system that is too small runs flat out on a 34 degree afternoon and still cannot keep up. The 70 percent rule is a balance of the two, and it is why we check the house first.
How many zones should a 4 bedroom house have?
Most 4 bedroom homes suit five or six zones. A common layout is one zone each for the master suite, the living area and the kitchen and dining, and one or two more for the remaining bedrooms. Zone count and system size move together, so a 12.5 kW system fits five zones.
Zoning is where a ducted system saves you money. You can close the bedrooms during the day and run only the living area, then swap at night. We fit AirTouch 5 zone control with a wall touchscreen and phone control.
If you are still deciding between systems, read ducted vs split system for a Queensland home. For a shorter answer, see what size ducted system is right for your home.
What affects ducted sizing apart from floor area?
Ceiling height, insulation, window size and direction, roof colour, and how the house is used all change the load. A west facing glass wall or a dark roof with thin insulation adds load. Good insulation and shading reduce it. A site inspection picks these up where a floor plan does not.
The roof space matters too. The indoor unit and ducting need clear room to be hung and run properly, and the layout of the trusses can limit where the ducts go. We check that on the same visit.
After the free site inspection, we give a fixed quote. The number you get is the number you pay for the job we described.
Why choose Delta Temp for a ducted install?
Delta Temp Climate Solutions has installed more than 1,000 systems across the Sunshine Coast, from Caboolture to Noosa. We are a Fujitsu Dealer and a Hisense Pro Dealer, our licensed team does the work with no subcontractors, and every installation carries a 10 year workmanship warranty.
Manufacturer warranty is 5 years on Fujitsu and 7 years parts and labour on Hisense. We hold QBCC licence 15415739, ARCtick AU 59733 and electrical contractor licence 1505107. The details are on our business facts page.
Finance is available through humm, subject to approval by humm.
