The Verplas VKC5660 is a 204×60mm flat rectangular uPVC in-line duct silencer, 600mm long, designed to attenuate fan noise and limit cross-talk between rooms in System 204 flat-channel ventilation installations. Part of the Verplas Noise Solutions range, it fits inline within a 204×60mm flat duct run and is lined with acoustic material to absorb broadband duct-borne noise from MVHR units, dMEV fans, and continuous extract systems. It is SAP Appendix Q compliant and suitable for use on both supply and extract branches.
Range Context: The VKC5660 is the shortest silencer in the Verplas 204×60mm Noise Solutions range. Longer versions are available — VKC5661 (1m) and VKC5662 (1.5m) — for installations requiring greater attenuation. A Hi-Flow variant (VKC5663) is also available for high-airflow systems.
Pressure Drop: Every in-line silencer adds resistance to the duct system. Include the silencer's pressure drop in your system design calculation to confirm your fan or MVHR unit can still achieve the required flow rate. Refer to the VKC5660 datasheet for published pressure drop figures at your design flow.
Key Features
204×60mm Flat Profile
Designed specifically for System 204 flat rectangular ducting — the slim 60mm height makes it suitable for installation within ceiling voids, stud walls, and other space-constrained routes where circular silencers cannot fit.
Acoustic Inner Lining
The uPVC shell is lined with acoustic absorbent material that captures and dissipates broadband duct-borne noise — including the low-to-mid frequency tones characteristic of MVHR and dMEV fan units.
Female Adaptor Connectors
Both ends feature female adaptors for connection outside the System 204 duct — accepting the male spigots of standard 204×60mm duct lengths, bends, and fittings without additional hardware.
Cross-Talk Prevention
Fitted on room branch ducts in MVHR systems, the silencer prevents noise from one room transmitting through the duct network to another — a common issue in open-plan layouts and adjacent bedrooms.
SAP Appendix Q Compliant
Fully compliant with SAP Appendix Q product characteristics database recommendations for ducting used with both extract and MVHR systems — supporting Part F compliance documentation.
Noise Ingress Reduction
Also effective at reducing external noise ingress transmitted through the duct from outside the building — particularly relevant for installations near busy roads or noisy external environments.
White uPVC Construction
Manufactured from white uPVC consistent with all other Verplas System 204 flat channel components — connectors, bends, T-pieces, and plenum boxes.
Range Available in 3 Lengths
Where 600mm attenuation is insufficient, step up to the VKC5661 (1m) or VKC5662 (1.5m) for greater insertion loss within the same duct profile.
Technical Specifications
| Verplas SKU |
VKC5660 |
| Your Reference |
SIL150 |
| Duct Profile |
204×60mm flat rectangular |
| Silencer Body Length |
600 mm |
| Material |
White uPVC with acoustic inner lining |
| Minimum Free Area |
5,264 mm² |
| Colour |
White |
| Connection Type |
Female adaptor both ends — accepts System 204 male spigots |
| Compliance |
SAP Appendix Q — extract and MVHR systems |
| Longer Variants |
VKC5661 (1m), VKC5662 (1.5m) |
| Hi-Flow Variant |
VKC5663 (600mm Hi-Flow) |
| Typical Use |
MVHR branch ducts, dMEV systems, single-fan extract runs, noise ingress control |
Frequently Asked Questions
Where should I fit this silencer in a 204×60mm duct run?
For fan noise attenuation, install the silencer as close as possible to the fan or MVHR unit on the branch duct — this intercepts noise before it travels to the room terminal. For cross-talk prevention between rooms, position the silencer on the branch duct between the room outlet and the main distribution duct.
Will the VKC5660 fit in a standard ceiling void?
Yes. The 204×60mm flat profile is specifically designed for ceiling voids and floor zones where height is restricted. At just 60mm deep, it fits within standard timber joist depths when installed horizontally within the duct run.
What is the difference between VKC5660 and VKC5663 (Hi-Flow)?
Both are 600mm long and 204×60mm profile. The VKC5663 Hi-Flow variant is designed for higher airflow systems where a standard silencer would create excessive pressure drop — it maintains a larger free area at higher flow rates. Use VKC5663 where your system airflow exceeds the rated capacity of the VKC5660.
Do I need a silencer on every room branch in an MVHR system?
Not necessarily — silencers are most beneficial on branches serving bedrooms, living rooms, or any noise-sensitive room adjacent to the MVHR unit or to another occupied room. Supply and extract branches on both sides of a party wall or between bedrooms are the highest-priority locations.
Is this silencer suitable for a tumble dryer exhaust?
No. Tumble dryer exhausts carry hot, moist, lint-laden air that can clog and damage acoustic lining materials. Use only manufacturer-approved tumble dryer ducting for this application.
Can I use this on an MVHR supply branch?
Yes — the VKC5660 is suitable for installation on both supply and extract branches. On supply branches it reduces fan noise reaching the room; on extract branches it prevents cross-talk and reduces noise ingress from outside.
