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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. This 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. As an added bonus, this system can make your home more energy efficient when installed correctly.

Envirovent provides a wide range of MVHR products that offer 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 the unique needs of the property. 

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, the 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 throughout the building. Therefore it is important to prioritise the heat supply to the rooms that should be warmer. If the building is of sufficiently high standard then it might only be necessary to put heat directly into certain rooms. Of course, no matter the design the ventilation system must adhere to building regulations.

Building Regulations and Ventilation 

When building a new property, or making changes to an existing 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 provides guidance on how to meet these building regulations.

Approved Document F: Means of Ventilation 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 that air properly flows through the property maintaining good levels of indoor air quality. 

Each new room in a house should have adequate ventilation for general health reasons - with the type of room determining how much ventilation is required.

Mechanical Ventilation with Heat Recovery (MVHR) is listed as a key method of ventilating a property in 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 Table 1.3 of Approved Document F. A minimum rate of 0/3l/s per m2 of floor area should be calculated and compared with the number of bedrooms and information provided in Table 1.3. The higher figure is then chosen. Table 1.2 provides calculations for single room ventilation rates, but should be used in conjunction with Table 1.3 if necessary.

Background ventilators or trickle vents as commonly known, are not required with MVHR systems. 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. As per Approved Document F of Building Regulations, MVHR is suitable for properties of all air tightness rates, though there is the potential that for an older, leaky dwelling, the efficiency returns may not be as high as that of a newer build. Air tightness targets should always be set for new built and refurbishment properties, this is usually completed by an architect or consultant at the start of the project.

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