What is an MVHR System?

An MVHR system, which stands for Mechanical Ventilation with Heat Recovery, is a system used in modern, energy-efficient buildings to provide fresh air and improved climate control. The system also saves energy by reducing heating and cooling requirements.

How MVHR Works

The MVHR system works by extracting stale air from certain areas of the home (like bathrooms and kitchens) and supplying fresh air to living spaces (like bedrooms and living rooms). The key feature of MVHR is the heat recovery process. The process captures heat from the extracted air and uses it to preheat incoming fresh air.

In the winter, the heat from the outgoing stale air is transferred to the incoming cold fresh air. In the summer, the process is reversed, so the cooler outgoing air cools down the incoming warm fresh air. This heat exchange process significantly reduces the energy required to heat or cool the incoming air to a comfortable temperature, saving energy and reducing carbon emissions.

Components of an MVHR System

The main components of an MVHR system include:

1. Air Supply and Extraction Units – Responsible for the extraction of stale air from the building and the supply of fresh air into the building.
2. Heat Exchanger – The core of an MVHR system. The heat exchanger recovers the heat from the extracted air and uses it to warm the incoming fresh air.
3. Ductwork – A network of pipes that carry the stale air out of the building and the fresh air into the building.
4. Filters – Used to clean the incoming air of any pollutants or allergens.
5. Fans – Used to move the air through the system.
6. Controls and Sensors – Allow you to control the MVHR system and adjust the ventilation rates depending on the needs of the occupants and the conditions inside the building.

MVHR and Passive Houses

In a Passive House, an MVHR system is often an essential component. A Passive House is specifically designed to be airtight for energy efficiency. Without adequate ventilation, indoor air quality could become poor, leading to health problems and discomfort for the occupants. Therefore, the efficiency of the system is crucial.

By continuously exchanging stale indoor air with fresh outdoor air, an MVHR system ensures a steady supply of fresh air. As such, the need for additional heating or cooling is lower. This aligns with the Passive House principle of using less energy while still providing a comfortable living environment.

It’s worth noting that to function effectively in a Passive House, the MVHR system needs to be properly designed and installed. This includes ensuring the system is correctly sized for the building and the ductwork is well sealed. Regular maintenance, including cleaning and replacing filters, is crucial for keeping the MVHR system operating efficiently.

Other uses

MVHR systems aren’t just for residential use in passive houses. They can be beneficial in a variety of settings where ventilation is essential and energy efficiency is desired.

1. Commercial Buildings – In office buildings, retail spaces, and other commercial facilities, an MVHR system can help maintain good indoor air quality. This is important for the comfort and productivity of workers and visitors. These systems can also help businesses save on energy costs.
2. Schools and Universities – Maintaining a healthy learning environment is crucial in educational settings. MVHR systems can provide fresh air, remove excess moisture, and also help keep classrooms comfortable.
3. Healthcare Facilities – Hospitals and healthcare facilities have strict requirements for indoor air quality. An MVHR system can help maintain a safe and comfortable environment for patients and staff, while also reducing energy consumption. Crucially, the system will remove pollutants from stale air. The filters in the system will also trap these pollutants which allows proper disposal.
4. Public Buildings – Libraries, museums, community centres, and other public buildings can benefit from the improved air quality and energy savings provided by an MVHR system.
5. Industrial Facilities – In factories and industrial facilities, MVHR systems can help manage indoor air quality by removing pollutants and providing fresh air. The energy savings can also be substantial in these settings, which often have high heating and cooling requirements.
6. Hotels and Hospitality – In the hospitality sector, MVHR systems can help keep guest rooms comfortable and well-ventilated while reducing energy costs. The system is also useful in the kitchen environment as moisture levels tend to be higher.

In all of these settings, it’s important to properly size, install, and maintain the system. This ensures that it functions effectively and also efficiently. The benefits of these systems can be significant, but they depend on correct design and implementation.

Why is air quality important?

Simply put, better indoor air quality will result in fewer pollutants. Therefore, the overall health of the tenants is far better. When the system is paired with an EWI thermal envelope, dampness becomes a non-existent issue. This is particularly beneficial as penetrating damp can lead to mould growth, which can consequently lead to lung and breathing system issues. Health problems such as allergies and asthma can be grossly exaggerated if dampness and humidity are present throughout a property.