Ventmann UK · Architectural Ventilation · Made from Gypsum
The frameless, plaster-in ceiling diffuser your MVHR system deserves.
Standard plastic MVHR valves interrupt a ceiling. A Ventmann frameless plaster-in ceiling diffuser disappears into it — skimmed flush, painted with the ceiling, and engineered for heat recovery ventilation, supply and extract air, from 100 mm to 200 mm duct connections.
Shop Performance Circle Shop Line Diffusers Free Quotation
The Basics
What is a frameless plaster-in ceiling diffuser?
A frameless plaster-in ceiling diffuser (also called a plastered-in air valve or flush MVHR ceiling vent) is a supply or extract air terminal that is set into the plasterboard, skimmed over at its edges and painted — leaving no visible frame, trim ring or plastic grille. Only a clean shadow-gap slot remains in the ceiling or wall.
Ventmann diffusers are manufactured from natural gypsum — the same material as the ceiling around them — so the finish is seamless, crack-free and accepts any paint colour. They are purpose-designed for MVHR (mechanical ventilation with heat recovery), mechanical extract and air-conditioning systems in high-end residential, Passivhaus and commercial projects.
- Truly frameless: plastered in and painted — virtually invisible once decorated
- Gypsum, not plastic: no yellowing trim, no visible fixings, lower embodied carbon than aluminium or plastic valves
- Supply & extract: one architectural language for every room on the MVHR system
- Ceiling or wall mounting, in plasterboard and suspended ceilings
Architectural Detail
Anatomy of a plaster-in MVHR diffuser
A section through a finished ceiling: duct, plenum and diffuser sit entirely above the plasterboard line. All that reads from below is the slot.
How the airflow works: Ventmann diffusers use the Coandă effect so conditioned air clings to the ceiling plane and mixes evenly across the room — higher comfort, no cold dumping, quieter heat recovery ventilation.
Circular · Supply & Extract
Performance Circle — the circular frameless MVHR ceiling vent
From £86.65 excl. VATThe flagship round plaster-in diffuser: a gypsum-composite disc with one or two slots that plasters flush into the ceiling and connects straight onto standard MVHR ducting.
- Spigot sizes 100, 125, 160 & 200 mm — matches common MVHR duct runs
- Airflow up to 300 m³/h (200 mm, 1-slot) — one diffuser can serve a large room
- Supply and extract in the same frameless design
- Click mounting system for fast, secure fitting and easy access
- Paintable gypsum-composite — any RAL colour, lower embodied carbon than plastic or aluminium valves
- BIM object (.rfa), 3D models and technical data included
Linear · Slot Diffusers
Line Diffusers — linear slot diffusers, plastered in
From £125.00 excl. VATFor continuous shadow-gap lines across ceilings and walls, the Ventmann Line diffuser is a gypsum linear slot diffuser that installs with a plenum box and finishes with jointing compound, sanding and paint — a single crisp line instead of a grille.
- 1, 2 or 3 slots · lengths 625, 1000 & 1250 mm · slot gaps 12 or 18 mm
- Pairs with acoustic plenum boxes (GTG) for top-entry and insulated thermo boxes (VTBOX) for side-entry ductwork
- Runs can be butted end-to-end for full-width architectural ventilation details
- Six BIM objects (.rfa), Sketchfab 3D models and a full installation guide
The Full Frameless Range
One frameless language, every shape
Performance Line
High-flow linear diffuser with the Coandă profile. From £148.11.
Explore →Square Diffuser
Plaster-in square ceiling vent for a crisp, minimal grid. £67.74.
Explore →Side Round
Round diffuser for wall and side-entry positions. From £122.37.
Explore →All Products
Diffusers, plenum boxes, fittings and flexible ducting.
Browse →Why Plaster-In
Standard MVHR valve vs. frameless plaster-in diffuser
Typical plastic ceiling valve
- Visible plastic ring and dome in every room
- Trim discolours; fixings and gaps collect dust shadows
- Fights the interior design on high-end projects
Ventmann frameless gypsum diffuser
- Invisible once painted — only a clean slot in the ceiling
- Same gypsum as the ceiling: no cracking lines, no plastic edge, any colour
- Engineered airflow — Coandă-driven supply and quiet extract, with published technical data for every size
MVHR & Passivhaus
Designed around heat recovery ventilation
Every Ventmann diffuser is sized for MVHR supply and extract terminals: spigot connections from 100 mm to 200 mm, acoustic plenum boxes to kill cross-talk and duct noise, and published airflow & pressure-drop data so your ventilation designer can balance the system properly. That makes them a natural fit for Passivhaus, EnerPHit and low-energy new builds — without compromising the architecture.
Not sure which size or how many terminals a room needs? Use the Product Selector — filter by airflow, noise level and pressure drop — or send us your plans for free airflow calculations.
Installation
Plastered in, in six steps
No specialist trade needed beyond a competent drylining and plastering crew. Full step-by-step guides, videos and drawings are on our installation pages.
- Position the ductwork and fix the plenum or mounting frame at the planned terminal location.
- Set the height so the diffuser face will sit just below the finished plasterboard line.
- Cut the opening in the plasterboard (~1 cm oversize) and fix the sheet as normal.
- Click the diffuser in and connect the spigot to the MVHR duct run.
- Fill and skim the perimeter with jointing compound, then sand flush.
- Paint with the ceiling. The vent disappears; the slot stays.
Circle installation guide Line installation guide Plenum box installation
For Architects & Specifiers
Specify it in one afternoon
BIM objects (.rfa)
Revit families for Circle and all six Line configurations, downloadable from each product page.
Download →Technical catalogue
Dimensions, airflow and pressure-drop data for the whole frameless diffuser range.
Open →Architect CPD
A CPD course on frameless architectural ventilation design for your practice.
Book →Design showcase
Real projects where the ventilation vanished into the architecture.
View →Frameless explained
Deep-dive into how frameless plaster-in diffusers are built and finished.
Read →Trade accounts
Exclusive trade pricing for installers, M&E contractors and MVHR specialists.
Apply →FAQ
Frameless plaster-in MVHR diffusers — your questions
Can you plaster over an MVHR ceiling vent?
Yes — if the vent is designed for it. Ventmann diffusers are made from natural gypsum specifically so the perimeter can be filled, skimmed and painted as part of the ceiling. Standard plastic valves cannot be plastered in; a purpose-made plaster-in diffuser is the correct product.
What duct sizes do frameless MVHR ceiling diffusers connect to?
The Performance Circle offers 100, 125, 160 and 200 mm spigots, covering typical MVHR branch sizes. Line diffusers connect via a plenum box, with the spigot matched to your duct run (reducers available).
Can one diffuser handle both supply and extract air?
Each terminal is set up as either supply or extract, but the same frameless design is used for both — so kitchens, bathrooms and living spaces all share one consistent ceiling detail across the whole heat recovery system.
Are plaster-in diffusers suitable for Passivhaus projects?
Yes. With published airflow and pressure-drop data, 100–200 mm connections and acoustic plenum boxes, Ventmann diffusers are regularly specified on Passivhaus and low-energy MVHR systems. We provide free airflow calculations so each terminal is correctly sized and balanced.
Can the diffusers be painted any colour?
Yes — the gypsum face takes standard emulsion and spray finishes, so the diffuser can match a white ceiling, a dark feature wall or any RAL colour your designer specifies.
How quickly can you deliver in the UK?
Next-day UK delivery on orders placed before 11am, with a 5-year manufacturer's warranty and 14-day returns. Trade customers get exclusive pricing via a trade account.
Start Your Project
Make the ventilation disappear.
Send us your plans and we'll size every frameless plaster-in diffuser on your MVHR system — airflow calculations free, delivery next-day across the UK.
Request a Free Quotation Shop the Range
Call 01283 240025 · Email sales@ventmann.co.uk