Energy Recovery Ventilator (ERV) Calculator
Airflow Rates
Operation Settings
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: <1.5 W/(m³/h) 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:
- Enter all required parameters
- Click "Update Calculation"
- 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)