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Heat Recovery Ventilation: Fresh Air and Energy Savings

Heat recovery ventilation: Fresh Air and Energy Savings

Heat recovery ventilation (HRV) is a system that provides fresh air while also saving energy. It is an effective solution for improving indoor air quality and reducing heating and cooling costs. In this comprehensive guide, we will explore the benefits of heat recovery ventilation, how it works, its components, installation process, and maintenance requirements. We will also discuss the different types of HRV systems available and provide examples of their applications. By the end of this guide, you will have a thorough understanding of heat recovery ventilation and its potential to enhance your home or building’s comfort and energy efficiency.

1. Understanding Heat Recovery Ventilation

Heat recovery ventilation, also known as mechanical ventilation with heat recovery (MVHR), is a system that exchanges stale indoor air with fresh outdoor air while recovering the heat from the outgoing air. This process helps maintain a constant supply of fresh air while minimizing energy loss. HRV systems are particularly beneficial in tightly sealed buildings or homes with limited natural ventilation.

The core principle of heat recovery ventilation is to transfer heat from the outgoing air to the incoming air. This is achieved through a heat exchanger, which is the heart of the HRV system. The heat exchanger allows the warm air from inside the building to transfer its heat energy to the cooler incoming air, without the two air streams mixing. This heat exchange process significantly reduces the amount of energy required to heat or cool the incoming air, resulting in energy savings.

2. How Does Heat Recovery Ventilation Work?

Heat recovery ventilation systems consist of several key components that work together to provide fresh air and energy savings. Let’s take a closer look at each of these components and their functions:

2.1 Heat Exchanger

The heat exchanger is the central component of an HRV system. It is responsible for transferring heat from the outgoing air to the incoming air. The heat exchanger consists of a series of plates or tubes that separate the two air streams while allowing heat transfer to occur. The design of the heat exchanger determines its efficiency in recovering heat.

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2.2 Air Supply and Exhaust Fans

The air supply and exhaust fans are responsible for moving the air through the HRV system. The supply fan draws fresh outdoor air into the system, while the exhaust fan expels stale indoor air. These fans ensure a continuous flow of air and maintain the desired ventilation rate.

2.3 Filters

Filters are essential components of an HRV system as they help remove pollutants, allergens, and dust particles from the incoming air. These filters ensure that the air entering the building is clean and healthy. Regular filter maintenance is necessary to maintain the system’s efficiency and prevent clogging.

2.4 Ductwork

Ductwork is used to distribute the fresh air throughout the building and extract the stale air. Properly designed and installed ductwork ensures efficient airflow and balanced ventilation. It is important to consider the layout and size of the ducts to minimize pressure drops and maximize energy efficiency.

2.5 Controls and Sensors

Controls and sensors play a crucial role in regulating the HRV system’s operation. They monitor indoor air quality, humidity levels, and temperature to adjust the ventilation rate accordingly. Advanced HRV systems may also include smart controls that allow users to customize settings and monitor the system remotely.

3. Benefits of Heat Recovery Ventilation

Heat recovery ventilation offers numerous benefits for both residential and commercial buildings. Let’s explore some of the key advantages of installing an HRV system:

3.1 Improved Indoor Air Quality

One of the primary benefits of heat recovery ventilation is the improvement of indoor air quality. HRV systems continuously supply fresh outdoor air while expelling stale indoor air, reducing the buildup of pollutants, odors, and excess moisture. This helps create a healthier and more comfortable living or working environment.

3.2 Energy Savings

By recovering heat from the outgoing air, HRV systems significantly reduce the amount of energy required to heat or cool the incoming air. This leads to substantial energy savings and lower heating and cooling costs. Studies have shown that HRV systems can reduce energy consumption by up to 50% compared to traditional ventilation methods.

3.3 Enhanced Comfort

Heat recovery ventilation helps maintain a consistent indoor temperature by preheating or precooling the incoming air. This eliminates drafts and temperature fluctuations, providing a more comfortable living or working environment. HRV systems also help reduce condensation and moisture-related issues, such as mold growth.

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3.4 Noise Reduction

HRV systems are designed to operate quietly, ensuring minimal noise disturbance. The fans and motors are typically insulated to reduce noise levels, allowing for peaceful indoor environments. This is particularly beneficial in residential settings where noise can be a significant concern.

3.5 Environmental Sustainability

By reducing energy consumption and improving energy efficiency, heat recovery ventilation contributes to environmental sustainability. Lower energy usage means reduced greenhouse gas emissions and a smaller carbon footprint. Installing an HRV system demonstrates a commitment to sustainable living and responsible resource management.

4. Types of Heat Recovery Ventilation Systems

There are several types of heat recovery ventilation systems available, each with its own unique features and applications. Let’s explore some of the most common types:

4.1 Plate Heat exchangers

Plate heat exchangers are the most common type of heat exchanger used in HRV systems. They consist of multiple thin metal plates with small channels for the air to flow through. The plates are stacked together, creating a large surface area for efficient heat transfer. Plate heat exchangers are compact, lightweight, and offer high heat recovery efficiency.

4.2 Rotary Heat Exchangers

Rotary heat exchangers, also known as wheel heat exchangers, are another popular choice for HRV systems. They consist of a rotating wheel with a honeycomb structure made of a heat-absorbing material. As the wheel rotates, the outgoing and incoming air streams pass through separate channels, allowing for heat transfer. Rotary heat exchangers are known for their high efficiency and ability to recover both sensible and latent heat.

4.3 Run-Around Coils

Run-around coil systems use separate coils for the outgoing and incoming air streams. A heat transfer fluid, such as water or refrigerant, circulates between the two coils, transferring heat from one air stream to the other. Run-around coil systems are often used in situations where the two air streams cannot physically come into contact, such as in hospitals or laboratories.

4.4 Heat Pipes

Heat pipe systems utilize sealed pipes filled with a heat transfer fluid, typically a refrigerant. The heat pipes are installed in the HRV system’s heat exchanger, allowing heat to transfer from the outgoing air to the incoming air. Heat pipes are efficient and require minimal maintenance, making them a reliable choice for heat recovery ventilation.

4.5 Thermosiphon Systems

Thermosiphon systems rely on natural convection to transfer heat between the outgoing and incoming air streams. The warm air rises, creating a pressure difference that drives the airflow through the system. Thermosiphon systems are simple and cost-effective, making them suitable for smaller residential applications.

5. Installation and Maintenance of Heat Recovery Ventilation Systems

Proper installation and regular maintenance are essential for the optimal performance and longevity of heat recovery ventilation systems. Here are some key considerations for installation and maintenance:

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5.1 Professional Installation

It is recommended to hire a professional HVAC contractor with experience in heat recovery ventilation systems for installation. Proper sizing, ductwork design, and system integration are crucial for optimal performance. A professional installer will ensure that the system is correctly installed and meets all safety and building code requirements.

5.2 Regular Filter Maintenance

Filters in HRV systems should be checked and cleaned or replaced regularly to maintain efficient airflow and prevent the buildup of pollutants. The frequency of filter maintenance depends on factors such as indoor air quality, outdoor air conditions, and the type of filters used. Refer to the manufacturer’s guidelines for specific maintenance instructions.

5.3 Balancing Airflow

Balancing airflow is important to ensure that the HRV system provides adequate ventilation to all areas of the building. Properly balanced airflow prevents pressure imbalances, reduces noise, and maximizes energy efficiency. A professional HVAC technician can perform airflow balancing by adjusting dampers and registers throughout the ductwork.

5.4 Monitoring and Adjusting Controls

Regularly monitor the HRV system’s controls and sensors to ensure they are functioning correctly. Adjust the settings as needed to maintain optimal indoor air quality and energy efficiency. Some advanced HRV systems may have automated controls that adjust ventilation rates based on occupancy or outdoor air conditions.

5.5 Seasonal maintenance

Perform seasonal maintenance on the HRV system to keep it in optimal condition. This may include cleaning the heat exchanger, inspecting the fans and motors, lubricating moving parts, and checking electrical connections. Consult the manufacturer’s guidelines or hire a professional technician for comprehensive seasonal maintenance.


Heat recovery ventilation is a valuable solution for achieving fresh air and energy savings in residential and commercial buildings. By understanding the principles of heat recovery ventilation, the different types of systems available, and the installation and maintenance requirements, you can make informed decisions about implementing an HRV system. The benefits of improved indoor air quality, energy savings, enhanced comfort, noise reduction, and environmental sustainability make heat recovery ventilation a worthwhile investment. Consult with HVAC professionals to determine the most suitable HRV system for your specific needs and enjoy the advantages of fresh air and energy efficiency in your home or building.

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