What is a flume vent?

Ventilation, explained simply

What is a flume vent?

Builders use the word every day — but most homeowners have never heard it. In plain English: a flume vent (or roof flume) is a weather-tight outlet through your roof that lets ducted exhaust — from a rangehood or fan — escape safely outside.

When you run your rangehood or bathroom fan, it pushes hot air, steam, grease and cooking smells along a duct. That air has to go somewhere — and you don't want it dumped into your roof cavity, where it causes condensation, mould and rust. A flume vent is the cap that sits on your roof at the end of that duct, sealed against leaks and keeping rain, pests and embers out.

In one line

A flume vent is the weather-proof "chimney" that takes your rangehood or fan's exhaust out through the roof.

OUTSIDE INSIDE THE HOME METAL / TILE ROOF Weather-tight flume cap Low-profile, sealed roof penetration 1.99mm perforations Ember & pest sealed — no mesh One-way valve Stops back-drafts, rain & cold air Flexible ducting Carries exhaust up to the roof Rangehood or fan Kitchen, BBQ or ceiling exhaust Hot air, steam & odours exit outside

Cross-section · how a roof flume vents a rangehood outside

Exhausts appliances

Vents ducted kitchen & BBQ rangehoods and bathroom/laundry exhaust fans straight outside — for every brand.

Clears the roof cavity

A modern

Controls condensation

Moving moist air out helps prevent condensation

Old vs modern

Not all flumes are equal

The flume you picture is probably the tall old "mushroom" or whirlybird. Modern low-profile flumes do the same job — far better, and almost invisibly.

Standard non-conforming builders roof ventStandard non-conforming builders vent
  • Tall storm-cap / mushroom shape — up to ~500mm proud
  • Open gaps plugged with rust-prone retrofit mesh
  • Chokes airflow & adds back-pressure on the motor
  • Lets in flies
  • embers
  • drafts and weather
Modern low-profile Dragon flume ventModern low-profile flume
  • Just 60mm proud — sits flush with the roofline
  • 1.99mm perforations moulded in — no rusting mesh
  • Low-restriction Hi-Flow path — quieter
  • stronger pull
  • One-way valve & sealed flashing keep weather out

Bushfire (BAL)

In bushfire-prone areas

roof vents must be ember-proof to AS3959 — BAL 12.5 up to BAL 40. Dragon vents are CSIRO inspected for bushfire compliance.

Condensation (NCC)

The National Construction Code sets requirements for roof ventilation to manage moisture and prevent condensation damage.

Weather & cyclone

Roof penetrations need custom flashing and cyclone-rated fixings to stay leak-free in heavy rain and high wind.

Need the right flume for your roof?

We make a low-profile, Australian-made flume for every roof type and appliance.

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