220mm x 90mm Rectangular Ducting

Frequently asked questions

What is 220mm x 90mm ducting?

220mm x 90mm is a standard UK size of rigid rectangular PVC ducting, part of the Domus Megaduct System 150 range. The "System 150" name reflects that it's airflow-equivalent to 150mm round ducting, the standard diameter for large kitchen cooker hoods and MVHR trunk lines. The flat rectangular cross-section, 220mm wide by 90mm deep, routes through ceiling voids, service risers and floor zones where a 150mm round duct wouldn't fit without dropping the ceiling.

What is 220mm x 90mm ducting used for?

The main uses are MVHR trunk lines carrying combined supply or extract flow from multiple rooms back to the unit, large kitchen cooker hoods with 150mm spigots (typically wider island or high-output range hoods), tumble dryer extract on commercial laundry installations, and domestic-scale commercial extract where the airflow volume exceeds 204x60 capacity. On MVHR systems, 220x90 typically forms the trunk from the unit with branches stepping down to 204x60 before each room terminal.

Is 220mm x 90mm ducting the same as 150mm round?

Airflow-equivalent, yes. The 220x90 cross-sectional area matches 150mm round ducting, so a 150mm extract fan, cooker hood or MVHR unit performs similarly to a 150mm round run. They are physically different shapes, so a round-to-rectangular adapter (Domus 970, 220x90 to 150mm, in stock) is needed to transition, typically at the fan, MVHR unit, or external cowl. The rectangular duct itself is 220mm wide by 90mm deep externally.

What's in the Domus Megaduct 220x90 range?

The full Megaduct range in 220x90: 2m (D4-2000), 1.5m (915) and 1m (910) straight lengths, 90° and 45° bends in both horizontal and vertical orientations, elbow bends with 100mm, 125mm and 150mm rotating spigots (941, 951, 961), T-pieces for branched runs, straight connectors (DD920, 920 and 981) and the 927 connector with backdraught damper, 3m and 500mm flexible hose, Thermal insulation shells, round-to-rectangular adapters (220x90 to 150mm), in-line step-down adapters (220x90 to 204x60) for transitioning trunk-to-branch on MVHR systems, 922 duct clips for fixing, and DFS220 fire sleeves.

How do I step down from 220x90 to 204x60?

The Domus 958 in-line rectangular adapter (220x90 to 204x60, in stock) is a direct push-fit transition piece. It's the standard component for MVHR installs where the trunk line runs in 220x90 from the unit and branches step down to 204x60 before reaching each room's supply or extract terminal. Fit the adapter at the point where the trunk splits into branches, usually above a ceiling void or service riser. On the 220x90 side, push-fit into a Megaduct connector or T-piece; on the 204x60 side, continue in Supertube range parts.

Can I use 220x90 ducting for a cooker hood?

Yes, for cooker hoods with a 150mm spigot, typically larger island hoods, high-output range hoods, and some professional-grade domestic hoods with extraction rates above 600 m³/h. Use the Domus 970 round-to-rectangular adapter at the hood to transition from 150mm round spigot to 220x90 rectangular. For standard domestic hoods with 125mm spigots, use 204x60; for 100mm spigots, use 110x54. Always check the hood's installation spec, as using a smaller duct than specified will restrict airflow and can void the hood warranty.

How do I join 220x90 Megaduct sections?

Megaduct uses push-fit joints. Straight connectors (DD920, 920 or 981) join two lengths end-to-end, and the 927 connector adds a backdraught damper. Bends and T-pieces have integral sockets. For airtight joints, essential on MVHR and Building Regs extract, apply duct sealant inside the socket before pushing home, then foil-tape over the joint. Fix horizontal runs every 600 to 800mm with the Domus 922 duct clip to prevent sag.

Do I need a fire sleeve on 220x90 ducting?

Yes, wherever the duct penetrates a fire-rated wall, floor or compartment boundary. Building Regulations require sealed penetrations to maintain the fire rating. The Domus DFS220 fire sleeve fits the 220x90 profile and contains intumescent material that expands during a fire to close the opening. This is particularly relevant on MVHR trunk lines in apartments, HMOs and multi-storey housing where the trunk typically crosses multiple compartments between unit and terminals.

Should I insulate 220x90 ducting in a cold loft?

Yes. MVHR trunks carrying warm extract air through unheated lofts condense internally when the duct surface drops below dewpoint, and the resulting moisture pools, drips, and over time damages the MVHR unit and ceilings. Domus Thermal insulation shells clip over Megaduct in cold spaces: the TS910 for 1m of straight duct, the TS950 for 90° bends and the TS961 for the 961 elbow. Where no shell fits, wrap the duct with foil-backed mineral wool or proprietary duct insulation (25mm minimum) so the run is insulated continuously through any unheated space.