The best Double flow VMC in the UK 2023

To ventilate correctly and economically the house requires a compromise: to renew the air necessary to the well-being and the health of the occupants while evacuating the excess of vapor. For this, controlled mechanical ventilation or CMV is the best solution. It reduces your heating bill by up to 15%. Follow our guide to find the right model for your needs.

Dee fly cube 300 HE 1

Best value for money

Dee fly cube 300 HE

The best dual-flow ventilation unit in 2021

The Dee fly cube 300 HE is our first choice thanks to its ideal features to renew the air in your home and its incredible capacity to reduce consumption.

1 769 £ on Amazon

The Dee Fly cube double flow CMV is very efficient. Moreover, it is of very high output with remote control for any type of individual house from 1 to 6 bathrooms. It is also equipped with the main accessories for its installation. Its maximum flow rate is 300 m3/h. It has a micro-watt motorization and the consumption is from 20 to 54 W-th-C. This VMC is also the quietest of the market because the noise is radiated at 2 m of 30,7 dB (A) and all this only for a T4 housing. It has 4 ventilation speeds. And its thermal efficiency is 92% at 120 m3/h. Moreover its intensity of protection is 2A.

Atlantic 412236 2

Best value for money

Atlantic 412236

The best entry-level dual-flow ventilation unit

The VMC Atlantic 412236 is the affordable VMC that is very practical in your home. With this VMC the consumption of your heating will decrease which is favorable for all.

822 £ on Amazon

The Atlantic 412236 double flow ventilation unit is very high efficiency for houses from T2 to T7 with a maximum of 4 bathrooms. It is available with or without radio remote control. Its efficiency is 90% and thanks to the regulators which are integrated on the tapping, the flows can be regulated room by room. This double flow CMV is equipped with an integrated automatic defrosting system with a manual bypass with a 12-hour timer. The installation of the Atlantic CMV can be done horizontally, and can be done in the attic, and lends itself easily to the renovation or the replacement of existing products.

Atlantic Optimocozy HR plus 3

Best value for money

Atlantic Optimocozy HR plus

The best high-end dual-flow ventilation unit

The VMC Atlantic Optimocozy HR plus is the VMC which adapts to your rhythm of life. It is very quiet which allows you to be always in peace.

1 727 £ on Amazon
Atlantic Duocosy HR 4

The alternative

Atlantic Duocosy HR

A great alternative

This Atlantic Duocosy HR is the excellent choice of double flow ventilation, because it guarantees comfort and air quality in your home, in summer and in winter.

1 173 £ on Amazon

This Atlantic Duocosy HR double flow CMV heats the incoming air in winter and cools it in summer. It is an energy saving VMC, thanks to its low consumption motor with a totally automated use. Its maintenance system is easy, thanks to a direct access to the filters. You don't need any tools to manipulate them. This double flow CMV is also high efficiency. It is suitable for T3 houses with one bathroom and one toilet, but also for T5 houses and more, with up to 3 bathrooms, 4 toilets and a shower room. It is best installed in a utility room, such as a storeroom or a laundry room, and the networks in the heated volume.

Buying guide • November 2023

Best Double flow VMC

Any specific needs?

The best dual-flow ventilation unit in 2021

The best entry-level dual-flow ventilation unit

The best high-end dual-flow ventilation unit

A great alternative

Your guide : Samuel

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Comparison table of the best Double flow VMC

Dee fly cube 300 HE 5
Atlantic 412236 6
Atlantic Optimocozy HR plus 7
Atlantic Duocosy HR 8
Dee fly cube 300 HE
Atlantic 412236
Atlantic Optimocozy HR plus
Atlantic Duocosy HR
The Dee fly cube 300 HE is our first choice thanks to its ideal features to renew the air in your home and its incredible capacity to reduce consumption.
The VMC Atlantic 412236 is the affordable VMC that is very practical in your home. With this VMC the consumption of your heating will decrease which is favorable for all.
The VMC Atlantic Optimocozy HR plus is the VMC which adapts to your rhythm of life. It is very quiet which allows you to be always in peace.
This Atlantic Duocosy HR is the excellent choice of double flow ventilation, because it guarantees comfort and air quality in your home, in summer and in winter.
Very high efficiency unit with remote control
Its efficiency is 90%
22.5 decibels in a room where the box is located
also a very high efficiency VMC
House types
Suitable for any type of house
For houses from T2 to T7 with up to 4 bathrooms
All types of houses
Suitable for T3 and T5 houses
Equipped with 4 ventilation speeds
Available with or without remote control
Equipped with remote automatic ventilation
Easy maintenance system

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Buying guide - Double flow VMC

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How to choose your Double flow VMC

How do you determine which of the many systems available best suits your needs? Consider the following points to be sure.

#1 - Technical feasibility

It is a very important step, before buying your double flow CMV, think first to check with a professional that the installation of this type of ventilation system is possible. Indeed, a double flow CMV is more complex to install. Generally speaking, this type of ventilation system is only suitable for houses under construction or for major renovations.

#2 - Performance

This is the most important criterion. The efficiency determines the amount of heat that can be recovered by the CMV via the stale air to heat the fresh air in the heat exchanger. The efficiency depends on the models of the double flow CMV, their brand and the range of the product. For example, entry-level CMVs have a maximum efficiency of 60%, while high-end products can recover up to 90% or more of the heat calories from the stale air. The higher the efficiency, the more heating savings the unit can make, especially in winter. Whenever possible, choose a unit with 90% efficiency for long-term effectiveness.

#3 - The right airflow for your house or apartment

This flow rate will correspond to the volume of air (in cubic meters) that your CMV can renew per hour (m³/h). The most important thing here is to choose a double-flow CMV that offers a sufficient flow rate to meet your needs. For example, for a home with five main rooms, we recommend a CMV with a minimum flow rate of 105 m³/h.

#4 - Energy consumption

Whenever possible,

choose a low-energy dual-flow CMV. This will allow you to comfortably reduce the energy needs of the unit. It will be all the more efficient.

#5 - Noise level

A ventilation system generally generates noise during operation, the VMC is no exception. And this is a criterion that should not be neglected. Especially if you want to place your device in the attic, above bedrooms, or in an adjoining room.

How does a double flow CMV work?

The double flow CMV allows to recover the heat of the extracted air to transfer it towards the supply air via an exchanger. The stale air and the new air do not mix, only the heat is exchanged. A double flow ventilation system is composed of different elements requiring regular maintenance.

These are: a supply fan, an exhaust fan, the heat recovery unit (optional), the by-pass (optional depending on the brand), the filters, the diffusers, the supply and exhaust terminals and the two supply and exhaust networks.

The different types of Double flow VMC

The CMV extracts the stale air. The clean air enters through inlets above the windows. When the clean air is also extracted through ducts, this CMV is called a double flow system (incoming air / outgoing air). There are mainly two types of double flow CMV: the classic double flow CMV and the thermodynamic double flow CMV.

The classic double flow CMV

With the double flow ventilation system, the air is blown in and out by mechanical devices. A major advantage: the supply air is preheated by a heat exchanger which recovers the heat from the extracted air. This leads to savings in heating energy.

The air inlets are installed in the main rooms while the air outlets are located in the sanitary rooms. A solution adapted to major renovations aiming to reach the BBC (low consumption building) performance level.

The main weakness of the classical double flow CMV is that it requires a major renovation to install the double duct system and it may require a technical room.

The thermodynamic double flow CMV

It works like a double flow CMV. Except that a heat pump is added and performs the additional function of preheating the air. The thermodynamic double flow CMV is a technology capable of providing ventilation, heating, cooling and even hot water production.

This type of double flow CMV is equipped with a reversible heat pump, allowing to easily reverse the mechanism according to the season. Thus, the freshness of the interior temperature will be preserved. This compact 2-in-1 product takes care of your domestic hot water and your domestic ventilation.

Benefits of this technology: significant energy savings, hot water is produced at a lower cost thanks to the recovery of heat from the hot air expelled (by the ventilation system). The main disadvantage of this type of device is the choice of location because of the noise generated and the connections.

Ideal ventilation against allergies

Double-flow ventilation systems can be combined with high-efficiency filters. The combination is an ideal solution against allergies caused by pollen, dust and soot.

Double flow or single flow CMV?

Double flow VMC

Contrary to the simple flow CMV, the double flow CMV uses the heat of the extracted air (stale air) to temper the new air. The device controls simultaneously a flow of new air blown in and a flow of stale air extracted. This allows the new air to penetrate at a temperature very close to the indoor temperature.

The installation is more complex than for the simplified CMV. But it is more economical in the long run. This type of CMV is really only suitable for new buildings.

Single-flow CMV

Here, the outside air enters through vents in the main rooms, and is then exhausted to the outside via service areas (bathrooms, kitchens) through a ventilation unit. This type of CMV is easier to install: it can be installed in the attic. You can easily install one, even in a renovation.

The main disadvantage of single-flow ventilation is that it brings in fresh air directly from outside, which systematically causes a temperature imbalance in the house. You will need heating or air conditioning to correct this imbalance.


Single or double flow VMc? The choice is yours, but if you want to save a lot of energy in the long term, we advise you to opt for the double flow. However, you may have no choice but to install a single flow CMV if your home is not new. The installation of a double-flow CMV may require a lot of work, the cost of which may make the investment unattractive.

Why buy a double flow CMV?

To enjoy healthy air

Breathing clean air is good for your health. Precisely, the double flow CMV provides you with an irreproachable air quality. It eliminates the humidified air in your home and replaces it with air from outside, which it filters before diffusing it. You thus obtain a completely healthy indoor air, a real plus if you are prone to allergies.

To enjoy the same comfort at all times

When the temperature drops, the dual-flow CMV quickly warms the indoor air. And when summer arrives, it gives you the benefit of fresh air free of unpleasant odours. This is because the device is equipped with high-performance filters that prevent the spread of pests and other elements that can pollute the air inside your home.

For its discretion

The operation of a double flow CMV does not produce any noise pollution. You can use it without it disturbing your peace and quiet. It prevents the air from entering through the windows and filters at the same time the noises coming from outside. In addition, it does not make a mess of your decor because of its pure design.

To save money

A double-flow CMV consumes little energy. During the winter season, it heats the air, giving you the possibility of saving up to 20% of energy. In addition, consumption decreases as the air enters the house, since it is warmer and does not require any additional heating. Note that you can further reduce your energy consumption by combining the double-flow CMV with Canadian wells.

For a healthy home

With double-flow CMV, your living spaces benefit from better ventilation. This way, you will avoid the formation of mould on the walls; the same goes for the windows, which are protected from humidity. It is also an excellent device to eliminate other impurities such as pollens, bacteria, spores and fine particles.


Dust and clean your double flow ventilation system every quarter.

Clean the extract units, they tend to get dirty faster than the other parts of your dual-flow CMV. Dismantle them and simply use a cleaning solution based on hot water and washing-up liquid, before fixing them back to the wall. For more efficiency, we advise you to clean the outside air inlets at the same time with a medium power vacuum cleaner.

Check the heat exchanger at least once a year.


efficiency of your CMV depends on the heat exchanger, whose filters facilitate the transmission of energy between warm and cold air. You need to clean the filters in this exchanger regularly (every six months or every year) to keep the CMV working properly. Keep in mind that if the filters are in poor condition, the CMV will run at full capacity and become energy intensive.

Call in a professional.


you're installing your CMV or checking that it's working properly, we recommend that you always call a professional. He will be able to carry out an exhaustive check of your installation: the state of the motor block, the state of the various draft and vacuum parts, etc.


What is the best double flow ventilation system?

The best double flow ventilation system depends on your needs and your budget. Read our buying guide to find out which products are the best at the moment.

How do I choose the ventilation rate for my project?

The extraction flow rate is determined according to the type and number of water rooms, as well as the number of living rooms. It is a volumetric flow rate. It is fixed for metropolitan France by a decree of 24 March 1982, modified on 28 October 1983.

How to build the double flow ventilation network?

In new construction, we advise you to favour a solution with a dedicated technical room (if possible a room not off-centre giving onto an external wall), anticipated from the design of the house which will house the ventilation box and the distributors. As soon as possible, you should adapt a 15 cm false ceiling to easily distribute the ventilation ducts to the rooms. For a successful installation in a renovation or in a house that does not have a false ceiling, you should have a corridor serving as many rooms as possible. Lowering a false ceiling in the corridor is not uncomfortable. The double flow CMV exist in flat box with a height of 20-30 cm, which allow to make everything pass in the warm volume.

Do you heat a house with a double flow ventilation system?

Yes and no. It depends. It depends, the main function of the double flow CMVs (static) is to ventilate, and not to heat the house. Thermodynamic double flow CMVs, or multi-energy systems can have this function either of pre-heating or heating, but their good functioning will require a very well insulated envelope, and a limitation of the effects of stratification. In short: aim for a passive envelope performance if you wish to heat by this means.

Do double flow CMVs make noise?

If the double flow CMV produces noise, it is a sign of bad installation (it is the same with the single flow CMVs). Three main elements are involved: the radiated noise, the suction noise and the telephony noise, which is the perception of sounds from one room to another, through the ventilation network. In all cases, it is necessary to require a control of the acoustic levels at the reception of the installation, and to make this reception of the installation conditional to the obtaining of the acoustic levels.


Note: Below are some of the sources we have consulted in writing this article. Links to other sites are not continuously updated. It is therefore possible that a link may not be found. Please use a search engine to find the desired information.
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March 2022 : Translation of this buying guide from our partner

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Our selection
Dee fly cube 300 HE 9
Dee fly cube 300 HE
Atlantic 412236 10
Atlantic 412236
Atlantic Optimocozy HR plus 11
Atlantic Optimocozy HR plus
Atlantic Duocosy HR 12
Atlantic Duocosy HR


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