FLX-REKU Alnor MVHR: Semi-Rigid Air Distribution System
FLX-REKU household ventilation
FLX-REKU and FLX-REKU-OVAL: Expert Air Distribution System for MVHR
The FLX-REKU air distribution ductwork by Alnor is a complete, semi-rigid solution for Mechanical Ventilation with Heat Recovery (MVHR). It integrates semi-rigid ducts, distribution and plenum boxes, dampers, and other essential elements. This system is engineered for superior durability and flexibility, making it the ideal choice for installations requiring ducts to be concealed within floor slabs, ceiling insulation, or directly buried in structural concrete.
Architectural and Investor Value – Durability and Hygiene
The FLX-REKU system provides key long-term benefits, addressing critical requirements at the design and operational stages of a building.
Concealment in Concrete: The strong circumferential rigidity of the ducts allows them to withstand the pressure of cast concrete, making the system perfect for burying in separating floor slabs and cast-in-place flooring systems.
Low-Profile Design: The FLX-REKU-OVAL duct is a low-profile, trapezoid-like shape (52mm high by 132mm wide). This design allows for easy installation within the restricted depth of floor and ceiling insulation layers, saving valuable space.
Antimicrobial Performance: The FLX-HDPE-A flexible ducts feature an antimicrobial lining with silver ions. This bactericidal and fungicidal performance is independently certified, ensuring a cleaner and healthier air distribution system for the building’s occupants.
Technical Specifications for Installers – Dimensions and Compliance
Compliance with European standards and precise dimensions simplify selection and installation, guaranteeing a high-quality, efficient system.
Round Ducting (FLX-REKU): Radial, semi-rigid ducts are available in outer diameters of 50mm, 63mm, 75mm, or 90mm. Supplied in convenient 50m coils to minimise the need for unnecessary connections.
Oval Ducting (FLX-REKU-OVAL): Dimensions are 52mm by 132mm, supplied in 20m coils.
European Standard: All FLX-HDPE-A ducts comply with EN 17192:2018, which defines critical performance characteristics including:
Airtightness and Pressure Drop
Reaction to Fire
Resistance to External Pressure and Microbial Resistance
Airflow Optimisation: The system is designed to maintain an optimal internal air speed of 2 to 2.5 m/s, crucial for system efficiency and noise reduction.
Installation and System Connection Guide
The system is designed for quick, airtight assembly without complex sealing solutions, relying on precision-fit male and female connectors.
Duct Connection Standards for Distribution Boxes
Component Type
Duct Connection Type
Spigot Designation
FLX-PLO Plenum Box
Fits the inner dimension of the duct
Male connection with gasket
FLX-PRO Distribution Box
Fits the outer dimension of the duct
Male connection (for female duct spigot)
FLX-HDPE ducts are pushed onto male connectors with a gasket (for FLX-PLO) or inserted into female connectors with internal gaskets (for FLX-PRO). For the main air distribution lines, such as from the air intake/exhaust to the Air Handling Unit (AHU) and from the AHU to the manifolds, technicians should utilise SPIRAL system elements (e.g., galvanised ducts, elbows, and fittings).
