You cannot place a new order from your country (United States).

Back Draft Shutter

Backdraft shutters for extractor fans: odour control and thermal stability

The moment your extractor fan stops — between cycles, at night on a timer, or under wind pressure — airflow in your ducting reverses. Cold outside air enters and odours escape before reaching your carbon filter. A backdraft shutter prevents this with a simple gravity-driven mechanism: internal aluminium flaps open under outgoing airflow pressure and fall shut the moment the fan stops. No electricity, no maintenance.

Available in five diameters from 100 to 200 mm, compatible with every standard extractor fan. Essential for intermittent extraction, CO2-enriched setups, and ducts venting directly outside. Mount vertically for optimal sealing and secure with duct clamps. Fast delivery throughout Belgium.

There are 5 products.

Sort by:

Back Draft Shutter Metal 100mm air tube connector | Back Draft Shutter

Back Draft Shutter 100 mm Metal

See details

Back Draft Shutter Metal 125mm air tube extraction | Back Draft Shutter

Back Draft Shutter 125 mm Metal

See details

Back Draft Shutter 150 mm Metal

See details

Out-of-Stock

Back Draft Shutter Metal 160mm duct connector ventilation | Back Draft Shutter

Back Draft Shutter 160 mm Metal

See details

Out-of-Stock

Back Draft Shutter 200 mm Metal

See details

Backdraft shutters for your ventilation system: full range

The backdraft shutter (also called a backdraft damper or flapper valve) is the component installed between your extractor fan and the exhaust point to block unwanted reverse airflow. When your system is running, you would not notice it: the flaps sit open and air passes unrestricted. The moment your fan stops — via timer, speed controller or power cut — the flaps close automatically within a second. No reverse airflow, no odour leakage, no cold air intake through the exhaust.

How a backdraft shutter works

The mechanism is elegantly simple. Inside a rigid aluminium housing, three to five rectangular flaps pivot on a horizontal axle, slightly angled so gravity returns them to a sealing edge at rest. When the extractor runs, airflow pushes the flaps upward to the vertical position, letting air pass unrestricted. When the fan stops, each flap falls back onto its sealing edge and closes the passage. With no spring or electronics involved, there is virtually nothing that can fail — a properly mounted shutter operates for ten years or more without maintenance. The only real wear point is the axles, which withstand hundreds of thousands of cycles in quality units.

Five diameters for every system

Pick a backdraft shutter matching the exact diameter of your extractor outlet and ventilation ducting:

Backdraft shutter 100 mm — for small fans and compact setups
Backdraft shutter 125 mm — the most common size for standard grow tents
Backdraft shutter 150 mm — for mid-sized installations
Backdraft shutter 160 mm — for 120×120 cm tents with 400-550 m³/h fans
Backdraft shutter 200 mm — for large spaces and powerful extractors

Three scenarios where a shutter becomes essential

A backdraft shutter earns its place in three specific contexts. First: intermittent extraction. If your fan runs on cycles via thermostat, timer or speed controller, draft reverses within seconds between active and idle phases. Every idle phase becomes a small leakage event: unfiltered odour out, cold air in. Second: direct outdoor venting. If your exhaust duct vents straight outside and the wind is blowing against it, pressure can force air back into your system even when stopped. Third: CO2 enrichment. Growers supplementing their grow room with CO2 lose this expensive gas through every idle duct. A shutter keeps CO2 concentration high and makes your distribution investment worthwhile.

Correct installation for optimal performance

A backdraft shutter only works well when mounted correctly. First: install it on the outlet side of your extractor, not the intake side. The arrow engraved on the aluminium housing shows the permitted airflow direction — follow it strictly. Second critical point: mount the shutter so the flaps hang vertically. This means the housing must be positioned with the pivot axles horizontal. In this configuration, each flap falls back onto its sealing edge by its own weight when the fan stops. Horizontal or inverted mounting leaves the flaps partially open and drastically reduces sealing force. Secure with duct clamps on both sides for an airtight connection. A backdraft shutter remains effective after five or ten years, as long as the flaps never get blocked by dust. Clean them annually with a soft brush or compressed air.

FAQ - Frequently asked questions about backdraft shutters

Does a backdraft shutter reduce my extractor's airflow?

The flaps create slight resistance when opening, but airflow loss is negligible — typically under 5% with a properly sized system. Always pick a shutter matching your ducting diameter exactly to avoid unnecessary restriction. A 125 mm shutter on 125 mm ducting causes virtually no measurable loss.

Can I mount a backdraft shutter horizontally?

Technically possible, but strongly discouraged. The flaps close by gravity: in vertical position they fall shut naturally. Horizontally they stay partially open unless there is back-pressure, allowing small amounts of reverse flow to creep through. Always install vertically or with a slight downward tilt for reliable sealing.

What is the difference between a backdraft shutter and a bushing?

A bushing is a wall pass-through whose only job is to guide the duct through a partition — it blocks nothing. A backdraft shutter has active flaps that block reverse flow. You can combine both: bushing through the wall, shutter mounted just inside for double protection.

Do I need a shutter if my fan runs continuously?

With continuous operation, the added value is limited: there is no stop period during which reverse draft can develop. Still useful for wind-exposed exhausts (roof outlets for instance) and during brief maintenance shutdowns. For growers running timer-based systems, a shutter is essential.

How long does a backdraft shutter last?

Under normal use, ten years or more. No electronics, no spring, no moving part under constant tension. The only real wear point is the axles on which the flaps pivot, which withstand hundreds of thousands of cycles. Annual dust removal keeps the shutter in top condition.

Order your backdraft shutter today at Plant & Flower. Fast, discreet delivery anywhere in Belgium.