MVHR Ventilation Diffusers

MVHR ventilation diffusers are the only part of a heat recovery system you ever see — so they should look as good as the system performs. Ventmann UK manufactures architectural supply and extract diffusers for MVHR, machined from a unique gypsum composite that plasters directly into the ceiling or wall for a completely frameless, paintable finish. No plastic rims, no visible fixings — just clean air and clean lines.

Every diffuser on this page works with standard UK duct sizes, ships with next-day UK delivery, and is backed by a 5-year warranty. Our team also provides free airflow calculations, so you can specify the right diffuser for every room before you order. Call 01283 240025 or email sales@ventmann.co.uk.

What are MVHR ventilation diffusers?

An MVHR diffuser (also called an air valve, ceiling vent or room terminal) is the grille that delivers fresh supply air into habitable rooms — bedrooms, living rooms, offices — and extracts stale, moist air from wet rooms such as kitchens, bathrooms and utility rooms. In a Mechanical Ventilation with Heat Recovery (MVHR) system, the diffuser is the final connection between the ductwork and the room, and it directly affects three things: how evenly air is distributed, how much noise you hear, and how the ceiling looks.

Most MVHR installations are finished with basic plastic ceiling valves. They work, but they sit proud of the plasterboard, yellow over time and interrupt an otherwise clean ceiling. Ventmann diffusers take the opposite approach: a gypsum, plaster-in diffuser body is skimmed flush into the ceiling, leaving only a crisp slot, circle or square opening. The result is ventilation that architects, interior designers and self-builders can actually design around.

Supply and extract — one diffuser family for the whole system

Ventmann MVHR diffusers are suitable for both supply and extract air, so the same design language runs through the entire property. Supply diffusers in living spaces deliver pre-warmed, filtered air at low velocity to avoid draughts; extract diffusers in wet rooms pull humid air back to the heat exchanger. Paired with an acoustic plenum box, airflow is equalised across the full face of the diffuser, keeping air velocity even and noise levels low — essential for bedrooms and open-plan living.

The Ventmann MVHR diffuser range

Every model below is manufactured for both supply and extract duty, integrates with our plenum boxes, and arrives ready to plaster in, sand and paint to match any interior.

Which duct size do you need?

MVHR diffusers connect to standard UK duct diameters. As a rule of thumb, choose the size that keeps air velocity low at the design flow rate — low velocity means low noise and no draughts. The ranges below are typical comfortable duties; for an exact specification, send us your room-by-room flow rates and we will size every terminal for you, free of charge.

Linear diffusers are also sized by length and slot count — Ventmann Line and Performance Line diffusers are available in 1, 2 or 3 slots and multiple lengths, fed by acoustic plenum boxes with 75 mm, 125 mm or 160 mm connections.

Plaster-in gypsum diffusers vs plastic ceiling valves

Standard plastic poppet valves are cheap and adjustable — and that is where their advantages end. Here is how an architectural plaster-in diffuser compares on the things that matter over the life of a building:

Plenums, ducting and accessories

A diffuser is only as quiet and balanced as what sits behind it. We manufacture and stock the complete chain from duct to room:

Also available: insulated flexible ducting, pre-drilled connection flanges, reducers, couplers and aluminium foil tape for airtight joints.

Installing MVHR diffusers: the plaster-in process

Fitting a Ventmann diffuser is a straightforward first-fix / second-fix job that any competent installer or dryliner can complete:

1. Fix the plenum box above the ceiling line and connect it to the duct run with the correct spigot (75–160 mm on linear plenums; 100–200 mm on round and square diffusers). Seal joints with foil tape.
2. Cut the aperture in the plasterboard and offer the gypsum diffuser body up to the plenum. The diffuser sits flush with the board.
3. Tape and skim the gypsum flange into the ceiling exactly as you would a plasterboard joint. Our gypsum composite absorbs water well, so joint plaster keys in and will not crack later.
4. Sand and paint with the rest of the ceiling. The diffuser disappears — only the slot or aperture remains visible.
5. Clip in the grille — internal metal grilles mount on industrial-grade magnets, so they remove in seconds for cleaning or commissioning with no visible fixings.

Balancing and commissioning your MVHR system

Every MVHR system must be balanced so each room receives its designed flow rate. With Ventmann diffusers, commissioning engineers adjust flow at the plenum or with in-slot magnetic airflow regulators, which can also steer air left or right along a linear slot. Because the grille lifts off magnetically, access for anemometer readings and future filter-season checks takes seconds — without disturbing the plastered finish. If you are designing a new system, send us your plans: we will produce the airflow calculations free of charge and recommend a diffuser schedule room by room.

Why specify Ventmann MVHR diffusers?

• First-of-its-kind gypsum composite — plasters in seamlessly, sands smooth, takes paint, and will not crack at the joint.
• Truly frameless — magnetic grilles mean no screws, rims or visible locks anywhere on the ceiling.
• Supply and extract — one design language across every room of the property.
• Complete system — diffusers, acoustic and thermo plenums, ducting and fittings from one UK supplier.
• 5-year warranty on our diffuser range, with next-day delivery across the UK.
• Specification support — free airflow calculations and physical samples for architects, M&E consultants and self-builders.

MVHR ventilation diffusers — FAQs

What is the difference between an MVHR diffuser and an air valve?

They do the same job — terminating a duct in a room — but an air valve is a basic adjustable plastic or metal disc, while an architectural diffuser is designed into the ceiling itself. Ventmann diffusers plaster in flush, distribute air across a slot or aperture via a plenum, and can be painted to match the interior.

Can I use the same diffuser for supply and extract air?

Yes. All Ventmann MVHR diffusers are suitable for both supply and extract duties, so bedrooms, living areas, kitchens and bathrooms can share the same clean design.

What duct sizes do MVHR diffusers connect to?

Standard UK sizes: 100 mm, 125 mm, 150 mm, 160 mm and 200 mm round duct, plus 75 mm connections on linear acoustic plenums. Flanges and reducers are available to adapt between sizes.

Are plaster-in diffusers difficult to install?

No — they install like a piece of plasterboard. Fix the plenum, cut the aperture, skim the gypsum flange, sand and paint. The magnetic grille then clips in with no visible fixings. Any dryliner or MVHR installer can fit them.

How do I balance airflow through the diffusers?

Flow is set at the plenum or with magnetic in-slot airflow regulators on linear diffusers, which can also direct air left or right. Grilles remove magnetically in seconds, so commissioning and future adjustment never disturb the plastered finish.

Can the diffusers be painted to match my ceiling?

Yes. The gypsum body is skimmed into the ceiling, sanded and painted with it — any colour, any finish. Art grilles can also be produced in custom designs and colours on request.

How quickly can you deliver, and what warranty do I get?

Orders ship with next-day delivery across the UK, and Ventmann diffusers are covered by a 5-year warranty. Need help first? Call 01283 240025 or email sales@ventmann.co.uk for free airflow calculations.