Energy Recovery Ventilators (ERVs) and Heat Recovery Ventilators (HRVs) are balanced ventilation systems that remove stale, stagnant air from inside your house while adding back an equal volume of fresh outdoor air. As homes have become more tightly constructed and air-sealed to conserve energy, air stagnation and unhealthy indoor air quality have become acute. ERVs and HRVs not only ventilate with balanced air volume, but they also transfer heat. The advantages of both ERVs and HRVs depend largely on the status of air infiltration through cracks, gaps and other air leaks. Older, “leaky” houses typically benefit less from ERVs and HRVs than newer, airtight structures.
Inside the core of the central controller, a heat exchanger extracts heat from the warmer air stream and adds it to cooler air stream. In summer, heat taken from incoming fresh air is added to the outgoing cooler air stream to preserve indoor temperatures and avoid burdening the A/C. During winter, heat in the outgoing stream is recovered and added back into the incoming air to prevent heat loss. Approximately 85 percent of heat energy can be transferred between air streams in heat recovery and energy recovery systems.
ERVs exchange heat like HRVs but also add an extra dimension: humidity transfer. The core inside the central controller utilizes an enthalpy transfer process to move water vapor from the more moist air stream into the drier air stream. This reduces the influx of excessive outdoor humidity during summer and in winter helps prevent indoor dryness during cold, low-humidity conditions.
Because water vapor contains latent heat energy, ERVs also have higher total heat recovery efficiency than HRVs due to the extra heat exchange that accompanies humidity transfer. Total heat recovery efficiency of an average ERV can be up to 30 percent higher than heat recovery of an HRV.
For more on the potential benefits of ERVs and HRVs in your home, contact Donald P. Dick Air Conditioning.
Our goal is to help educate our customers in the greater Fresno, California area about energy and home comfort issues (specific to HVAC systems). For more information about ERVs, HRVs, and other HVAC topics, download our free Home Comfort Resource guide.
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