Heat recovery ventilator

Savings = m³/h × 1.2 kg/m³ × 1.005 kJ/kg·K × Δt × efficiency / 3600. Typical efficiencies: plate 60–70%, rotary 75–85%, enthalpy (with moisture) 65–75%. In winter at −10°C and 100 m³/h a plate unit returns ~1 kWh/hour — up to 30% of a house's heat loss. Without recovery, ventilation = heating the frost.