Balanced ventilation systems can control indoor pollutants and provide good indoor-air-quality (IAQ). They provide fresh air through intake ducts and expel polluted air through exhaust ducts. Balanced ventilation systems have two fans and two air filters. The two fans push air into and out of the building. The air filters keep the heat and moisture recovery units from accumulating dirt. Most balanced systems employ heat recovery ventilators (HRVs) or energy recovery ventilators (ERVs).
What HRVs and ERVs Systems Do
HRVs reclaim heat from the exhaust air stream during the heating season remove incoming heat from air during summer air conditioning. HRVs work well in dry climates.
Energy recovery ventilation exchanges both sensible and latent heat between the outgoing airstream and incoming airstream. This means that ERVs reclaim moisture along with heating or cooling energy, depending on the season. Energy recovery ventilation removes water vapor from the more humid airstream and transfers it to the less humid airstream.
This exchange of water vapor however, rarely if ever has a dehumidifying effect on building. Instead water vapor exchange just reduces the amount of water vapor that the ventilation air adds to the building or reduces the amount of water vapor leaving the building. In comparison to heat recovery ventilator, energy recovery ventilators add less humidity and subtract less humidity.
Benefits of Balanced Ventilation Systems
Exhaust-only and supply-only ventilation systems are unbalanced. Unbalanced ventilation systems can draw pollutants into the home or move moisture around causing condensation. HRV and ERV systems are balanced, but they aren’t trouble-free. When operating properly, balanced systems prevent the IAQ problems and moisture problems related to unbalanced ventilation. However, many homes with “balanced” ventilation systems experience pressure imbalances and poor IAQ due to inadequate design, installation, or maintenance.
In a dry climate, heat recovery ventilation works very well during the winter and also during the summer while air conditioning. In a humid climate, energy recovery ventilation works considerably better than heat recovery ventilation.
Problems and Necessary Improvements
Balanced ventilation systems can provide the IAQ and comfort of home, but they require exemplary installation and maintenance. Installers must test and commission the ventilation system during both the initial installation and periodic service calls. Also, homeowners must clean the two filters inside the balanced ventilator along with grills and termination fittings in the ducts.
Currently, a lack of trained installers and educated consumers contributes to problems with existing balanced ventilation systems. The most common problem is insufficient airflow because of faulty ducts or dirty ducts. Other problems include the following.
- Occupants turn ventilator off
- Operation time is too long or too short