Energy Recovery Ventilator (ERV) Calculator

Airflow Rates

ASHRAE 62.1: 5-10 L/s per person
Keep within ±15% of supply

Outdoor Air Condition

Design outdoor temp (coldest/hottest day)
Winter: 70-90%, Summer: 40-70%

Indoor Air Condition

Offices: 20-22°C
Comfort range: 40-60%

Recovery & Fan Settings

Total ERV recovers heat + moisture
Plate: 50-75%, Rotary: 70-85%
EC fans: 75-85%, Standard: 55-65%

Estimation & Operation Parameters

Office: 2500-4380h, Continuous: 8760h
Cold climate heating: 25-35%
Thermal energy cost (heating fuel)
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Energy Recovery Ventilation

Energy Recovery Ventilators (ERVs) transfer heat and moisture between exhaust and supply air streams, dramatically reducing HVAC energy consumption. In winter, they pre-heat and humidify incoming fresh air using warm, moist exhaust air. In summer, they pre-cool and dehumidify incoming air. ERVs are mandatory in many energy codes for buildings with high fresh air requirements (offices, schools, healthcare). Key metrics are recovery efficiency (sensible/latent), Specific Fan Power, and economic payback (typically 3-7 years).

Key Points:
  • Recovery efficiency: Plate 50-75%, Rotary wheel 70-85%, Enthalpy membrane 60-80%
  • Sensible recovery: transfers temperature only (HRV). Total recovery: transfers heat + moisture (ERV)
  • Latent recovery is critical in humid climates (summer dehumidification, winter humidification)
  • Supply/Exhaust airflow imbalance should be <15% to avoid pressurization problems
  • Frost protection required when outdoor temp < -5°C with high efficiency units
  • Typical pressure drop: 150-300 Pa. SFP target: <0.42 W/(m³/h) (~1.5 W/(L/s)) for energy codes
  • Payback: 3-5 years for commercial, 5-8 years for residential (depends on climate & energy prices)
  • CO₂ reduction: ~0.20 kg CO₂/kWh saved (natural gas heating). 2000 m³/h ERV saves 3-8 tonnes/year
Calculation Steps:
  1. Enter all required parameters
  2. Click "Update Calculation"
  3. Review results and analysis
Formula Variables:
V̇_supply Supply Airflow (m³/h)
V̇_exhaust Exhaust Airflow (m³/h)
ṁ Air Mass Flow (kg/s)
T_out Outdoor Temperature (°C)
T_in Indoor Temperature (°C)
RH_out Outdoor Relative Humidity (%)
RH_in Indoor Relative Humidity (%)
ε Recovery Efficiency (-)
W Humidity Ratio (kg/kg)
Q_s Sensible Heat Recovered (kW)
Q_l Latent Heat Recovered (kW)
Q_t Total Heat Recovered (kW)
P_fan Fan Power (kW)
LF Load Factor (%)
h_eff Effective Operating Hours (h/year)
c_e Energy Cost (€/kWh)