The Pros and Cons of Mechanical Ventilation with Heat Recovery (MVHR)

Mechanical ventilation with heat recovery (MVHR) systems have become increasingly popular in recent years as an energy efficient way to ventilate homes and buildings. 

While there are certainly many advantages to using MVHR, there are also several disadvantages that should be taken into consideration. But before we delve into its main pros and cons, let's have a quick look at what this heating and ventilation technology actually is.

What is Mechanical Ventilation with Heat Recovery (MVHR)?

MVHR is a ventilation system that uses a heat exchanger to transfer heat from the stale indoor air to the fresh outdoor air.

The system works by extracting stale air from bathrooms, kitchens, and other humid areas and passing it through a heat exchanger to recover the heat before expelling it outside. At the same time, fresh outdoor air is drawn in and passed through the heat exchanger, where it is preheated before being distributed to living areas.

The heat exchanger is designed to allow the transfer of heat while preventing the mixing of the two air streams.

The concept of heat recovery ventilation has been around for many years, with the first systems dating back to the 1970s. However, it wasn't until the 1990s that MVHR technology became more widely used in properties across the UK, particularly in high-performance, low-energy buildings.

Since then, the technology has continued to evolve and improve, with more efficient and effective systems being developed to meet the changing needs of building owners and occupants. 

So, now we know what it is, what are its benefits and what are its drawbacks?

MVHR Advantages

Improved indoor air quality: MVHR systems work by continuously extracting stale air from your home or building and replacing it with fresh, filtered air. This helps to improve indoor air quality by removing pollutants, allergens, and other harmful particles that can lead to health problems.

Energy efficiency: MVHR systems recover heat from the stale air being extracted and transfer it to the incoming fresh air. This means that the system is able to maintain a constant temperature in your home or building while using less energy. As a result, MVHR systems can help to lower your energy bills and reduce your carbon footprint.

Enhanced comfort: with an MVHR system, you can maintain a consistent temperature throughout your property. This means that you won't experience cold spots or drafts in certain areas of the building. Additionally, MVHR systems can help to reduce humidity levels, which can help to prevent mould growth and improve overall comfort.

Reduced noise pollution: MVHR systems are designed to operate quietly, which means that you won't be disturbed by loud fans or other noise pollution you might encounter from natural ventilation (like open windows). This is particularly important for buildings located in urban areas where outside noise can be a problem.

MVHR Disadvantages

Upfront cost: MVHR systems require specialised equipment and installation, which can be expensive. The cost of an MVHR system can vary depending on the size of the building, the complexity of the system, and the quality of the components used. In some cases, the cost of an MVHR system may be prohibitively expensive.

Maintenance: MVHR systems require regular maintenance to ensure they’re functioning correctly. This maintenance can include cleaning filters, checking ductwork for leaks, and inspecting the heat exchanger. Failure to perform regular maintenance can result in reduced efficiency, higher energy bills, and potentially even health problems if the system becomes contaminated with mould or other harmful substances.

Reduced flexibility: MVHR systems are designed to operate continuously, which means they may not be suitable for buildings with irregular occupancy patterns or where there are significant variations in internal heat loads. For example, in a building with high internal heat loads (such as a commercial kitchen), an MVHR system may struggle to keep up with the demand for fresh air.

Complex installation: installing an MVHR system can be complex, particularly in older buildings where retrofitting may require significant modifications to the existing structure. This complexity can increase the cost and duration of installation, making it less attractive for some building owners.

There are also other considerations for MVHR installation that must be taken into account such as the airtightness of the building for which it’s intended. If a building isn’t particularly airtight it will significantly compromise MVHR performance, since heat energy will escape before it can be recovered.

Is a Heat Recovery Ventilation System Worth It?

While MVHR systems may have some cons, the benefits often outweigh the drawbacks, and these systems can be a great investment if you’re looking to improve indoor air quality, reduce energy consumption, and lower carbon emissions. 

However, it's important to consider the individual circumstances and priorities before making a decision. It’s also important to consult an experienced HVAC contractor to help you determine the best solution for your needs. 

At Loughborough Air Conditioning we have years of experience designing, installing and maintaining both domestic and commercial HVAC systems, including MVHR.

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