What is an MVHR System?

Vent Axia MVHR unit installation

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An MVHR system, which stands for Mechanical Ventilation with Heat Recovery, is an intelligent way to keep the air in your home fresh.
An MVHR unit brings in fresh air from the outside while removing the stuffy air inside your house. As it does this, it saves the heat from the indoor air on its way out and uses it to warm up the new air.
It has three important jobs:

  • It keeps the air inside your home clean, which is excellent for your family’s health.
  • It ensures your home feels comfortable throughout the year, regardless of season.
  • It helps you spend less on heating because it reuses heat that usually disappears.

How Does an MVHR System Work?

How Does an MVHR System Work
Source: Open Learn

The MVHR system works in a way that’s easy to understand. It has four main steps:

  • Step 1: It starts by removing the damp and old air from rooms like your kitchen and bathroom, where there’s usually too much moisture and odour.
  • Step 2: This air goes through a particular part of the MVHR unit called a heat exchanger. Here, it gives up to 95% of its warmth to the new air.
  • Step 3: Simultaneously, clean air from outside is pulled in. It gets cleaned, picks up the heat from the old air, and then moves around your house.
  • Step 4: The system has a unique ‘Summer Bypass Mode’ when it’s hot out. This keeps your house from getting too warm, ensuring it stays comfortable.

Simply put, a heat recovery ventilation system, like an MVHR system, keeps the air moving. It pushes out the air that’s not fresh anymore and brings in fresh air from outside.

How is the MVHR System Controlled?

An MVHR system is always at work, swapping the old air inside your home with fresh air from outside. However, it doesn’t operate the same way all the time. It has two different modes.
The usual mode, called Trickle Speed, keeps a steady but gentle flow of air moving. This mode is made to be quiet and keep the air fresh without too much energy.
When there’s a lot of moisture or strong smells, like when you’re cooking or after a shower, Boost Speed can start. Therefore, the system speeds up to quickly clear out the extra humidity and odours inside your home. You can begin this faster mode or set it to work automatically.

Benefits of an MVHR Unit

  • Energy Efficiency: An MVHR unit is bright. It catches up to 90% of the heat from the air leaving your home and uses it to warm up the new air coming in. This can cut down on how much heat your home needs by about 25%.
  • Cost Savings: Energy prices have increased a lot (56% since 2021), but these heat recovery systems help save money by keeping the heat in. This means you spend less on heating your home.
  • Improved Indoor Environment: The system lowers the amount of pollutants inside, which can be two to five times more than outside. This means your home stays comfortable and safe to live in all year round

MVHR System Cost

Installing an MVHR system usually costs about £7,500. If you add it to a building already standing, you might pay more because of the extra work needed to fit the system inside the existing structure.

Running Costs

Even though setting up an MVHR system can be expensive initially, the cost to keep it running each year is surprisingly low. You’ll spend about £35-45 annually, which breaks down to less than 10p a day.
These systems are intelligent because they save heat that is usually lost and can be used again. This means you won’t have to rely as much on other heating or cooling systems, helping you save even more.

Servicing Cost

Keeping your MVHR system in top shape means you must check on it often. The cost for a yearly check-up range from £50 to £170. This check-up includes changing the filters.
You should change the filters every six months to keep the air moving smoothly. Over time, dust and other airborne particles can get inside the system, making it dirty. Cleaning these parts not only keeps the system working well but also prolongs its life.

MVHR System Servicing & Maintenance

You must take care of your MVHR unit regularly to keep it working well. If you don’t, dust and other small bits can gather inside the system. This can make your home feel less fresh, cause stuffy air, and add extra moisture.

When is an MVHR System Service Recommended?

To ensure your MVHR system works well, it’s best to check it yearly. This keeps it running smoothly.
You should look at and change the filters every six months. However, if your home is in a place with lots of pollution, you might need to change them more often.

What’s Included in an MVHR System Service?

When it’s time to service your ventilation system, here’s what you can expect:

  • A thorough check-up and cleaning of the main parts, like the unit and its motors, to make sure everything works smoothly.
  • A deep clean of the heat exchanger to keep it working well and efficiently.
  • Swapping out old filters for new ones so the air stays fresh and clean.
  • Careful cleaning to ensure the air valves in your rooms are germ-free for a healthier home.
  • Check how much air is moving through the system and make any needed tweaks to keep it running just right.

Common MVHR System Problems

Common MVHR System Problems

Without question, MVHR systems are usually reliable, but sometimes they run into problems that need fixing. Here are some of the common issues they might have:

Duct Leaking

Duct leaks are a common problem in MVHR systems, and they can happen if the system isn’t put together correctly or doesn’t have enough insulation.
When the ducts that carry warm air pass through cold spaces without insulation, water can build up and start to leak. If the parts where the system gets rid of water aren’t sealed well, water can drip out. Also, If the unit isn’t level, water can pool inside and cause leaks.
Therefore, it’s important for the system to be set up straight so that water flows out properly.

Motor Issues

Motor problems, like worn-out bearings, can make your MVHR system noisy. You might hear a loud humming or a rattling noise that worsens over time. To fix this and make your system quiet again, you may need to replace the damaged bearing in the motor.

Failed PCB

The Printed Circuit Board (PCB) is like the system’s brain. If something goes wrong, the whole unit can stop working. Water getting into the ducts can damage the PCB, leading to mistakes in how the system runs and even making it break down.
Usually, the best way to fix this issue is to replace the broken PCB with a new one.


One of the most common issues is blockages. Grease, dust, and dampness can accumulate, blocking parts like valves, motors, or the outside cover. Therefore, it’s important to clean the system regularly.
It’s key to ensure everything is balanced to keep the airflow steady and avoid any backups in the drainage part. For instance, if the fan that removes the stale air is too strong, it could lead to water collecting inside the unit.


In conclusion, an MVHR system is smart for keeping your home’s air fresh and comfortable. It works well to control the airflow and save heat, which can lower your energy bills. This makes it a good option for people who care about the environment and want to save money.
But it’s essential to take good care of your MVHR system. Regular check-ups are needed to keep it running right. If you fix problems like leaks in the ducts, motor troubles, or blockages quickly, your system will last longer and work better.
In the end, choosing an MVHR system means you’re looking out for the well-being of everyone in your house.

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A mechanical ventilation system is an excellent way to keep your home healthy and efficient.
A mechanical ventilation system is an excellent way to keep your home healthy and efficient.

Our Range of Economical Ventilation Systems

We supply and install Heat Recovery Systems (MVHR), PIV units, Bathroom or Kitchen Extractor Fans (MEV), and Single Room MVHR Units (DMVHR)

There is no one-size-fits-all approach when it comes to choosing a ventilation system. The layout of your property, the specific issue and your budget are all important factors to consider before taking steps to address needs.