Heat Recovery MVHR - Greenwood

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.  

                       Part F Building Regulations 

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.


How do I choose the correct size Heat Recovery Unit?

Choosing or specifying a Heat recovery system is more 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

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.

Read about what we found in our MVHR filters and what we are doing about educating homeowners, installers and developers

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!


Our Heat Recovery MVHR range

  • Vireo HR155WM

    BRAND NEW: Suitable for apartments and small houses up to 110m² this model has been designed to fit into kitchen cupboard for easy installation and access. Includes the latest in Greenwood SMART Technology including commissioning wizard. EST Best Practise Performance to 93% efficiency.
  • Vireo HR155CM

    BRAND NEW - For inline or ceiling mounting and suitable for apartments and small houses up to 110m². Includes the latest in Greenwood SMART technology for easy commissioning and right or left handing at the touch of a button! EST Best Practise Performance at 93% efficient
  • Vireo HR185WM

    BRAND NEW: Suitable for small and medium houses 3-4 bedrooms up to 130m². Can be fitted in airing or tall boy cupboard and also includes the latest in Greenwood SMART Technology like Greenwood HumidiSMART which isn't affected by distance and dilution effects....
  • CAQ350/450/600

    Brand New Innovative Heat Recovery Range offering World Class 96% heat recovery efficiencY, ultra quiet noise performance and innovative on-site commissioning via smartphone app
  • CA160

    Zehnder Comfosystems Passive House accredited unit suitable for apartments up to 150m2. Suitable for installation with ComfoTube Semi Rigid Ducting. Varying control options including luxury touch-screen panel.
  • CA200

    Zehnder Comfosystems Passive House accredited unit suitable for apartments and houses up to 120m2. Provides up to 93% heat recovery efficiency and is available with a variety of controls including a luxury touch-screen panel
  • CA350

    Zehnder ComfoSystems Passive House accredited product suitable for apartments and houses up to 220m2. Designed for comfortable living with low running noise and choice of control options for end user. Outstanding energy performance. Optional Comfort Cooling and Enthalpy Heat Exchanger.
  • CA550

    Zehnder ComfoSystems Passive Haus accredited product suitable for large houses up to 300m2. Designed to ensure low noise, excellent energy performance and heat exchange efficiency. Choice of control options including LCD touch screen display. Can be combine with ComfoCool for optional cooling of up to 5 degrees and humidity reduction by 20%


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