Rangehood Ducting And Why It Matters

Most complaints about a rangehood are that it does not work. In an apartment, the usual reason is that it was never connected to anything.

Two completely different products

Ducted. The air is pulled out of the kitchen and discharged outside the building. Grease, moisture and smell all leave with it.

Recirculating. The air passes through a carbon filter and comes straight back into the room. It removes some smell and nothing else. The moisture stays, the fine grease largely stays, and the filter loses effectiveness within months if nobody changes it.

Both look identical from underneath. In an apartment, recirculating is often what got installed because ducting to outside was difficult, and the owner was never told the difference.

What it costs you

Grease deposits on the ceiling above and around the cooktop, then on the cabinetry, then everywhere in the kitchen. It builds slowly, it is difficult to clean once it has set, and it eventually needs the surfaces repainted.

Moisture stays in the apartment, which contributes to condensation and to mould in the same way an unvented bathroom does.

Smell lingers, particularly overnight.

In a rental or a short-stay property the complaint is usually about the smell, and the underlying cause is the ducting.

Why apartments end up recirculating

Getting a duct from a kitchen to the outside of the building is genuinely hard in some layouts.

The cooktop is on an internal wall. There is no ceiling cavity. The run is long enough that the fan cannot push the air through it. Or the external wall is common property and a new penetration needs approval nobody chased.

Those are real constraints. They are also frequently solvable if someone looks properly rather than defaulting to a carbon filter.

What makes a ducted install actually work

Duct diameter. A run reduced to a smaller diameter than the hood outlet chokes it. This is the single most common installation fault, and the hood then performs far below what it is rated for.

Length and bends. Every bend costs performance. A long run with several tight bends can reduce a powerful hood to something ineffective. Fewer, gentler bends beat a shorter run with sharp ones.

Rigid rather than flexible. Flexible ducting has a corrugated internal surface that resists airflow and traps grease. Rigid duct moves more air and stays cleaner.

A proper external termination. A weatherproof cowl or vent that lets air out and keeps water and vermin out. A duct terminating in a ceiling space or a wall cavity is the same as not ducting at all, and it deposits grease inside the building instead.

Make-up air

A kitchen with a powerful hood and a well sealed apartment cannot extract, because no air can get in to replace what is leaving.

The symptom is a hood that sounds like it is working and moves nothing. Opening a window changes it noticeably, which is the test.

In a strata building

A new external penetration is work on common property and needs approval. The position matters to neighbours, because a kitchen exhaust discharging next to someone's window generates complaints.

Some buildings have a shared exhaust riser, and where one exists, connecting into it is usually the answer rather than making a new hole.

What to check in a property you manage

Is it ducted or recirculating. Where does the duct actually terminate. What diameter is it and how many bends. When were the filters last changed.

Four questions, and they explain almost every rangehood complaint.

We handle the hood, the ducting, the penetration and the make-good as one job across climate and air, electrical and building. Tell us the kitchen and we will tell you what is possible.