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MVHR Ducting – Why it Really Matters

21st May 2024

New Build
Self Build

Installing a Mechanical Ventilation with Heat Recovery (MVHR) system in your home is an investment in your personal health and the quality of air in your home.

If you want to achieve the maximum benefits of a MVHR System, it’s critical the system is installed correctly using best practice materials and procedures.

A Mechanical Ventilation with Heat Recovery system consists of 3 elements: 

  • the ventilation unit usually located in the loft or cupboard/hot-press/utility room
  • a network of ductwork
  • supply and extraction ceiling valves in each habitable room

The ducting of a MVHR system plays a crucial role in the efficiency of the overall system performance. In this article, we consider important aspects of MVHR Ducting and what the recommended solutions and procedures are.

Mechanical Ventilation with Heat Recovery (MVHR) – Best Practice

A 'Branch' type of ducting system is widely recognised as being the industry standard. This type of system involves a supply duct and an extract duct coming from the MVHR unit, which goes through the property with a separate duct branching off into each room or area where a supply or extract valve is required.

This type of ducting system allows for excellent airflow rates which will contribute to the overall performance of the system.

Counterflow mvhr unit installed with insulated ducting

The Optimal Size of Ducting Used

The size of ducting used for the installation of a MVHR system will depend on factors such as the required airflow. Ducts connected to the unit will usually come in industry standard diameters of either 5, 6, 8 or 10 inches, the size dependent on the unit being used. In general, the larger and more powerful the unit, the larger the ducting to allow for adequate airflow throughout the system.

As the ducts branch off towards each vent the size of ducting will decrease. For example, where the initial duct is servicing all valves it may have a 10” diameter, which may then reduce to 6” where it branches off to service a single valve.

In some cases, rectangular shaped ducting can be used, known as flat channel ducting. This may be used in areas where space may be an issue, such as within the ceiling void.

What Materials should your Ducting be made from?

The materials used for your ducting is critical for the performance of the MVHR. BRE recommends using smooth flow rigid ducting – pipework made from solid plastic or metal with a smooth inner surface. Solid smooth flow ducting can offer the following benefits:

  • Provides a higher heat efficiency
  • Low-pressure loss resulting in low energy use
  • Efficient low velocity producing less noise
  • Resistant to crush damage
  • Easily cleaned and maintained

The overall performance of any MVHR system can depend on the type and size of the ducting used. At BEAM, we offer the highest standards of installation, using only precision engineered metal and plastic solid smooth flow rigid ducting where possible, which is properly insulated in all cold spaces to avoid condensation forming within the pipework. All ducts are triple sealed (glued, screwed and taped) to ensure no loss of air.

Round plastic ducting for MVHR system installed

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