Balanced Ventilation

Air Exchangers

Air exchangers do exactly what their name implies: they exchange stale indoor air with fresh air from the outside. Although the energy savings derived from using an air exchanger is often minimal, the benefits to occupants are significant. As buildings have become tighter, less air moves through leaks around windows, doors, chimneys, etc. This can lead to an unhealthy build-up of odors, carbon dioxide, or volatile organic compounds (VOC). Opening a window may allow fresh air in, but at a considerable energy loss. Air exchangers provide the fresh air needed for occupants and minimize the energy losses for heating or cooling.

Balanced ventilation
Air exchangers provide fresh air for occupants that used
to be provided by leaky houses—before we insulated and
sealed them properly.
  • Heat recovery ventilation (HRV) is a system that exhausts air from inside of a home and replaces it with outdoor air. During this process the system captures heat from the air being exhausted and uses it to preheat the air entering the home. The air flows (fresh and exhaust) don’t mix.
  • Energy recovery ventilation (ERV) is a system that does everything that an HRV does with the addition of transferring moisture from the exhausted air into the air entering the home (in the winter) and restricting moisture from incoming air (in the summer). This can provide higher comfort for occupants by balancing the humidity levels inside the home.

Maintenance of Ventilation Systems

All ventilation systems require periodic maintenance to ensure safe and efficient operation.

  • HRV and ERV units should have filters cleaned or replaced in the spring and the fall. Vent openings on the exterior of the home should also be checked for blockages from snow, debris, or insects.
  • Exhaust fans should have the fan cleaned once a year, and the dampers on the venting should be inspected once a year to ensure that they are working properly. Kitchen exhaust fans should have the metal filters in the hood washed every few months or when grease builds up.


What are the benefits of using air exchangers in buildings?
Air exchangers provide several benefits to building occupants, including improved indoor air quality, reduced odors, and lower concentrations of carbon dioxide and volatile organic compounds (VOCs). By exchanging stale indoor air with fresh outdoor air, air exchangers help maintain a healthy indoor environment while minimizing energy losses associated with opening windows. Additionally, air exchangers can reduce the risk of moisture-related issues, such as mold growth, by controlling humidity levels.
How do heat recovery ventilation (HRV) systems differ from energy recovery ventilation (ERV) systems?

HRV systems exhaust stale air from a building and replace it with fresh outdoor air, recovering heat energy in the process. ERV systems, on the other hand, not only recover heat energy but also transfer moisture from the exhausted air to the incoming air, reducing the load on the building’s HVAC system. ERV systems also restrict moisture from entering the building, which is particularly important in humid climates. While both systems provide ventilation and heat recovery, ERV systems offer additional moisture management capabilities.

What are the key components of a balanced ventilation system?

A balanced ventilation system typically consists of an air exchanger, supply and exhaust fans, and a network of ducts to distribute fresh air and remove stale air. The air exchanger is the core component, responsible for transferring heat energy and, in the case of ERV systems, moisture between the exhaust and supply air streams. Proper sizing, installation, and maintenance of these components are critical to ensure efficient and effective operation of the ventilation system.

How often should air exchangers be maintained to ensure optimal performance?

Regular maintenance is essential to maintain the performance and efficiency of air exchangers. It is recommended to inspect and clean the air exchanger every 3-6 months, depending on usage and environmental conditions. Additionally, filters should be replaced every 1-3 months, and the system’s fans and motors should be inspected and lubricated annually. Failure to maintain the air exchanger can lead to reduced airflow, increased energy consumption, and decreased indoor air quality.

Can balanced ventilation systems be integrated with existing HVAC systems?

Yes, balanced ventilation systems can be integrated with existing HVAC systems. In fact, many modern HVAC systems are designed to work in conjunction with ventilation systems. The key is to ensure that the ventilation system is properly sized and configured to work in harmony with the HVAC system. This may involve modifying the HVAC system’s controls, ductwork, or equipment to accommodate the ventilation system’s requirements. A qualified HVAC professional should be consulted to ensure a successful integration.