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What is MVHR - Heat Recovery Ventilation?

What is MVHR - Heat Recovery Ventilation?

MVHR (Mechanical Ventilation with Heat Recovery) provides fresh filtered air into a building whilst retaining most of the energy that has already been used in heating the building. Heat Recovery Ventilation is the solution to the ventilation needs of energy efficient buildings.

Mechanical Ventilation with Heat Recovery (MVHR) is a whole house ventilation system that both supplies and extracts air throughout a property. Heat recovery is a domestic heat recovery system, which is increasingly used to reduce the heating and cooling demands of buildings.

A heat recovery ventilation system works by extracting moist and stale air from wet rooms in your home, it recovers the usually lost heat from the extracted air. It also supplies clean, filtered fresh air that is heated from the recovered warmth of the extracted heat.

Heat recovery ventilation, also known as mechanical ventilation heat recovery, is an energy recovery ventilation system which works between two sources at different temperatures. Heat recovery is a method which is increasingly used to reduce the heating and cooling demands of buildings.

A MVHR unit can make your home more energy efficient when installed correctly, extracting moisture caused by condensation which can be especially prevalent in wet rooms like bathrooms and kitchens. All of our MVHR products are manufactured here in the UK and offer a wide range of innovative benefits in addition to exceptional performance and low maintenance. 

The Importance of Good MVHR Design

If you are intending to fit MVHR heat recovery ventilation into a new build or refurbishment then it should be considered from early in the planning stage. For any MVHR heat recovery ventilation system to give its best performance the devil is in the detail. Luckily EnviroVent have a dedicated design team that will ensure the most optimum system is designed, in order to suit your homes unique needs. 

MVHR systems require ducts to be run through the building and the routing is important both from the point of view of the building and the efficiency of the ventilation system. Indeed, layout of rooms can be influenced by ventilation needs.

The installation of MVHR in a building will also affect the heating system design. One of the effects of heat recovery ventilation is to equalise the temperature through out the building. Therefore it is important prioritise the heat supply to the rooms that should be warmer. If the building is of sufficiently high standard then it might be only necessary put heat directly into certain rooms. Of course, no matter the design the ventilation system must adhere to building regulations.

Building Regulations and Ventilation 

Approved Document F provides guidance on meeting building regulations that specifically apply to ventilation. It states that adequate ventilation needs to be provided to prevent excess condensation buildup which could damage the structure of the property. It also ensures then, that air properly flows through the property maintaining good levels of indoor air quality. 

When building a new property it is important to comply with requirements in building regulations for installation, inspection, testing, commissioning and provision of information when installing fixed ventilations systems in your new and existing property. Approved Documents provide guidance on how to meet these building regulations. Each new room in a house should have adequate ventilation for general health reasons. The type of room will determine how much ventilation is required.

Mechanical Ventilation with Heat Recovery (MVHR) is a key ventilation method (previously under system 4 - pre June 2022) of the Building Regulations, Approved Document F. Heat Recovery ventilation provides fresh, filtered air, energy efficiency and a comfortable all year round climate. Stale, moist air is extracted out of the wet rooms of a home.

These include the kitchen, bathrooms, utility and en-suite rooms. MVHR systems should always provide the minimum whole building ventilation rate, which can be calculated using the same steps as System 3 above. The required airflow rates are as follows:

Background ventilators are not required with MVHR. For more information on building regulations and ventilation, click here.

Confused about the changes to the Building Regulations that came into effect as of June 2022? Don't worry, we have created a hub that includes our building regulations bitesize webinar recordings, our next upcoming webinars and free resources to easily understand the changes: click here.

At what level of airtightness is MVHR recommended? 

MVHR Systems provide controlled ventilation with slow but constant air movements. In contrast, natural ventilation through background ventilators (trickle vents) is a form of uncontrolled ventilation, which fluctuates with wind speeds, temperatures, internal obstructions, such as the opening or closure of internal doors, trickle vents, blinds and curtains. Therefore it is recommended to install such systems only in properties with relatively good air tightness. We recommend an airtightness of at least 5 m3/(m2*h) at the pressure test (q50), ideally below 3 m3/(m2*h). Air tightness targets should always be set for new built and refurbishment properties.

Besides the drive to make houses more efficient, there are other reasons, which lead towards the installation of MVHR systems:

Unsure if MVHR is Right For You?

It can be difficult to know which ventilation system is right for you, read our blog, Whole House Heat Recovery Systems For Self-Builders, to learn the different types of units, and understand the benefits of a Whole House Heat Recovery System.

Click here to browse our range of MVHR products