MVHR

The heart of the home

Saving heat that would have otherwise been lost - energy efficient ventilation for the whole house, especially air tight designs.

What is Heat Recovery?
Mechanical Ventilation with Heat Recovery (MVHR) is a whole house ventilation system that both supplies and extracts air throughout a property. It offers a balanced low energy ventilation solution for new dwellings and re-uses up to 95% of the heat that would have otherwise have been lost. It is a recognised ventilation methodology (System 4) in ADF:2010 and a proven low energy and highly efficient way of ventilating.
How does Heat Recovery Ventilation work?
  • Heat Recovery Ventilation is a system which comprises a Heat Recovery Unit and a network of ducting which is connected to each room
  • From a single unit, located ideally in the heated building envelope, it works by continuously extracting air from the wet rooms of the property and at the same drawing in fresh supply air from outside
  • The heat from the extracted stale air is recovered via a heat exchanger inside the heat recovery unit which is then reused to temper the filtered supply air for the habitable rooms such as living rooms and bedrooms
  • Up to 95% of the heat can be recovered. The Heat Recovery Unit runs continuously on trickle and can and is boosted when higher rates of ventilation are required e.g. bathing, cooking.
  • In warmer months a summer by-pass function helps ensure comfort levels are maintained in the home. When summer by-pass is activated, the dwelling continues to be ventilaated and recieve fresh filtered air, however the heat recovery process is intermittently switched off (heat recovery is by-passed)
Heat Recovery How it Works Summer By Pass Heat Recovey
What are the benefits of using Heat Recovery Ventilation?

Heat Recovery Ventilation and its application in new homes as significantly grown over the last few years as the focus and improvements in airtightness are increased through Building Regulations e.g. ADL: Conservation of Fuel and Power.

With 100% of ventilation needing to be provided through purposely installed systems, heat recovery offers major benefits to the building and occupants including;

heat recovery airflow rates

    Key Benefits;

    • Year round removal of condensation and indoor pollutants
    • A direct impact on the Dwelling Emission Rate required in SAP, helping reduce the carbon footprint of the property
    • Fresh filtered air supplied to dwelling, ideal for allergy sufferers and those with conditions such as asthma
    • A balanced ventilation system for the whole house and recovering of heat that would have otherwise have been lost
    • Low noise, non-intrusive ventilation system – located away from the room, however consideration should be given to duct runs to ensure cross-talk contamination doesn’t happen AND the unit is sized correctly so it is not running a high rate all of the time.
    What are the airflow rates for Heat Recovery Ventilation?

    ADF:2010 Means of Ventilation sets out the whole house requirements for Heat Recovery Ventilation (see table below)

    In order to calculate airflow rates and find a suitable unit, you will need to know;

    dwelling type number of bedrooms, floor area and number of occupants.


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    How do I choose the correct size Heat Recovery Unit?

    Choosing or specifying a Heat recovery system ismore than simply choosing the best SFP (Specific Fan Power Performance) and Heat Efficiency (e.g. 93%)

    Considerations must be given to application in order that Guaranteed Installed Performance can be achieved effectively onsite - and it all starts with DESIGN.

    Following these three rules will ensure you choose the correct SIZE Heat recovery unit for your dwelling. An incorrectly sized unit will introduce noise to a property as it will have to work harder to deliver the Building Regulations requirements.


    1. Determine airflow requirements set out in ADF:2010

    Part F Building Regulations

    2. Size the unit based on Dwelling Design
    • Sizing the unit depends on total system pressure
    • A MVHR system may easily provide the correct airflow at 0 pascals, however adding ducting causes resistance and this will reduce airflow
    • Use the pressure curve provided with the product to determine whether it can perform in the location it is intended for
    • Best Practice Guidelines not that a heat recovery unit should not run at above 60% of airflow capacity on trickle speed.

    Heat Recovery Pressure Curve

    3. Choose the right ducting

    There are a few options for MVHR ducting and all can impact performance, particularly noise performance. Your ducting selection may impact the size of the MVHR Heat Recovery Unit you need for your project.

    Look at the benefits of Semi Rigid Ducting, a new type of ducting ideal for heat recovery ventilation installations.

    4. Use the Zehnder Product Selector

    Simply input the desired pressure and flow rate data; you will receive detailed information ensuring that solutions meet your needs.

    Click here

    Filter Replacement for MVHR a Heat Recovery Unit

    Heat Recovery Systems like any other building service require maintenance and servicing throughout their lifetime to ensure consistent energy efficient ventilation is provided to the home.

    We recommend;
    Filters being replaced every 6-12 months
    (depending on your location).

    Filters are fundamental to Guaranteed Installed Performance.
    If they are clogged airflow performance and efficiency will be affected.
    Filters are also important to maintain good Indoor Air Quality - something crucial for those suffering with allergies and conditions such as asthma.

    Cleaning of the grilles in the room by either vacuuming around, or removing and wiping with a damp cloth


    The heat exchanger should be cleaned during the lifetime of the unit and replaced every 10 years.

    Free Filter Reminder Service for Homeowners:

    On every Heat Recovery Unit that goes out of the door you will see a Homeowner Registration Label. Once registered we can send reminders for filter replacements throughout the lifetime of the unit. Filters are crucial for longterm performance and comfort in the home and we practise what we preach so are making it easy for people to change their filters when needed!

    Click here to register yours!

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      World class 96% Heat Recovery efficiency.