Helpful Insights to Right-Sizing ERV/HRVs

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Comfort

July 31

In residential and light commercial construction, achieving superior air quality depends on precise sizing and balancing of ventilation equipment. This equipment (also known as an energy recovery ventilator, or ERV) is responsible for bringing in outdoor air, filtering and distributing it throughout the building envelope, while also extracting an equal amount on contaminated air.

These systems play an important role in ensuring that the specific needs of the building are met.

For builders, contractors, and engineers, understanding the principles of right-sizing ensures optimal system performance, reduced operational costs, and enhanced occupant comfort.

The Importance of Right-Sizing ERV/HRV Systems

Right-sizing ERV systems involves a detailed analysis of factors including building layout, occupancy, insulation levels, local climate, and specific ventilation needs. Oversized systems can lead to inefficient energy recovery and increased costs, while undersized systems struggle to maintain proper ventilation, leading to poor indoor air quality.

Best Practices for Right-Sizing HVAC Systems

To achieve optimal performance, right-sizing ventilation systems requires a thorough approach. Here are some best practices:

Detailed Load Calculations

Room-by-Room Analysis

Perform load calculations on a room-by-room basis to ensure each space receives the appropriate amount of ventilation, avoiding oversizing or under sizing equipment.

Considering Ventilation Needs

Tailoring Ventilation to Building Use

Customize ventilation solutions based on the specific use of the building to ensure adequate air changes per hour (ACH) and compliance with indoor air quality standards. This ensures that the system is neither under- nor overperforming, maintaining energy efficiency and optimal air quality.

Balancing Supply and Exhaust Air

Ensure that the amount of air supplied to and exhausted from the building is balanced to avoid pressure imbalances, which can lead to drafts, moisture problems, and infiltration of outdoor pollutants.

CFM Calculations

Accurate CFM Calculations

Ensuring accurate cfm calculations for the fresh air appliance helps maintain energy efficiency and optimal air quality. Accurate cfm calculations ensure that the system is sized correctly, avoiding underperformance or excessive energy use.

Determining Correct CFM

The correct cfm per square footage is vital for the effective operation of ERVs and HRVs. The recommended ventilation rate typically falls between 0.35 to 0.70 air changes per hour, which translates to approximately 15-20 cfm per person or 0.01 cfm per square foot.

Adhering to Local Codes and Standards

Building Codes

Understand and adhere to local building codes, which often dictate minimum requirements for ERV/HRV system design, installation, and performance.

Industry Standards

Follow industry standards such as those set by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), including guidelines for ventilation and indoor air quality in residential and commercial buildings.

Achieving Optimal ERV/HRV Performance

Achieving optimal ERV/HRV performance requires careful consideration of every aspect of system design. This involves accurately calculating loads, performing a thorough balancing procedure, and adhering to industry standards. The balancing process ensures that the airflow rates for both supply and exhaust are equal, which prevents pressure imbalances in the building. By achieving balanced ventilation, builders, contractors, and engineers can ensure their ERV/HRV designs meet and exceed expectations for energy efficiency, comfort, and indoor air quality, ultimately enhancing the overall performance and reliability of the system.

References

Home Ventilating Institute (HVI). "Performance Ratings."

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). "ASHRAE Standards and Guidelines."

Environmental Protection Agency (EPA). "Indoor Air Quality (IAQ)."