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How Efficient Are MVHR Systems?

How Efficient Are MVHR Systems?

How Efficient Are MVHR Systems?

How efficient are Mechanical Ventilation with Heat Recovery (MVHR) systems? It is a question that seems easy to answer but has many caveats. This article should leave you with a better understanding of the relationship between airtightness and ventilation, and how improving airtightness increases the efficiency of MVHR.

How Efficient Are MVHR Systems?
How MVHR works!

What is MVHR?

MVHR is a whole home ventilation system. It works by extracting the stale, moist, and polluted air from the inside of your home or other property. It then resupplies it with fresh, filtered air. 

At the same time, the air travels through a heat exchanger. This transfers a large percentage of the heat energy from the extracted air to the incoming air, resulting in a more energy-efficient building when installed correctly.

This creates a more comfortable, condensation and mould-free environment year-round.

Read more about this in our previous article! What is MVHR?

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How airtight does a home need to be for MVHR?

The more airtight a property starts before MVHR, the better. However, this does not mean that MVHR does not benefit “leakier” properties. 

MVHR will still improve indoor air quality in a leakier property for example.

The efficiency however is much greater with an actual airtightness level of 3 m3/(hr.m2) or lower.

Generally speaking, newer, building regulation-meeting properties will be more airtight, and older buildings will be “leakier”. Renovated buildings have their own level of regulations to meet, and will generally be quite airtight.

How Efficient Are MVHR Systems?
MVHR systems can help save energy

Lowering Your Heating Bills with MVHR systems

In a previous article, we spoke about whether or not MVHR systems are worth it. In that article, we spoke a little about cost-effectiveness.

Using an MVHR heat recovery system can recover up to 90%+ of otherwise wasted heat energy. This recovered energy can reduce your heating requirements by up to ~25% with a well-installed system. 

Depending on where you buy, your initial investment could pay for itself within 5 years. Factors like air tightness do however come into the equation, causing this efficiency to drop. The leakier the property the less efficient. 

An office building using a heat exchanger above 80% efficiency can save around 30% on heating bills. The cost of running a heat recovery system is usually less than 10p per day.

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Installing MVHR in Older Buildings

Older buildings are often quite leaky, but ventilation in old buildings is still important. This may seem odd as usually, we try to make older buildings more airtight, sealing holes and gaps. While this is important to stop cold air from getting in, airtight buildings have no air circulation which can create condensation and mould. This is why mechanical ventilation is important.

It is often said that older buildings do not benefit from MVHR, however, this is not the case. It may not be as efficient as it is in newer buildings but there are still benefits, such as:

  • Improved indoor air quality (IAQ)
  • Lower humidity
  • No need for bathroom fans or window vents
  • Reduced noise and dust

Read more about this, and installing MVHR in new builds in a previous article!

How Efficient Are MVHR Systems?
Design and Install the MVHR system early

Design and Install Early for the Best Efficiency

Whether renovating or building anew, the answer is almost always: As early as possible.

Ideally, as soon as the project receives planning permission is the best time to design the MVHR system.

Once built, a new energy-efficient build can be difficult to modify with an MVHR system. It is important to work closely with your engineer/architects to overcome issues during the design stage.

In a renovation project, always plan the renovation around the MVHR system to avoid problems with installation later.

Planning right from the start can ensure:

  • You won't find problems during the build
  • You correctly plan your ducting
  • Little to no noise ingress
  • Correct condensate drainage
  • No freezing of MVHR unit

Read more about this in a previous article!

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Does MVHR require much maintenance?

Generally, MVHR requires little maintenance. It spends most of its life running unnoticed in the background! You won’t even touch the control very often unless you take a lot of showers, and even then you will just briefly boost the fan speed. 

The only maintenance you will need to do on most MVHR systems is a little bit of upkeep. Changing filters once a year may be required, though often you can vacuum these, and reuse them for quite some time. 

It can also be worth checking the heat exchanger for damage, which on most units will simply slide out for inspection.

So, How Efficient Are MVHR Systems?

MVHR systems are highly efficient systems, that recycle thermal energy used in your home, reducing your carbon footprint and saving money on your bills. 

How much depends on your property and how airtight it is, the more airtight the more efficient your system will be.

If you find yourself in need of a bit more guidance regarding how this applies to your property, please feel free to call and speak to one of our experts at 01636639900!

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