HVAC

Why do some rooms in my house never cool down properly?

Nine times out of ten it's the ducts, not the air conditioner. The unit can be pumping out cold air perfectly, but if the ductwork loses it on the way, the rooms at the end of the line barely feel it. The most common culprits are flexible ducts that are too long, too small, kinked or crushed in the roof, often from someone stepping on them or running them in tight bends around trusses. Every bend and sag chokes the airflow, so the rooms furthest from the unit suffer the most.

The roof space makes it worse. On a hot Melbourne day it can get well over 50°C up there, and if the ducts are poorly insulated or have joints leaking air, you're effectively cooling your roof instead of your bedrooms. Leaky joints are especially common in older installs where the tape has dried out and let go.

The other big one is design. A system sized wrong for the house, too few return air grilles, or outlets placed where they just blow cold air at the ceiling will never cool evenly, no matter how hard it runs. Some fixes are cheap, like resealing joints, straightening runs and cleaning filters. Others need a proper redesign of the duct layout, which is where it's worth getting someone to actually calculate it rather than guess.