So call it 400 liters/min at 30C delta with air's heat capacity about 1kJ/kg/C and 800 liters/kg. You're at 15kJ/min or 250W just for that airflow. Figure there

So call it 400 liters/min at 30C delta with air's heat capacity about 1kJ/kg/C and 800 liters/kg. You're at 15kJ/min or 250W just for that airflow. Figure there are 40 rooms and you're at 10kW of heating just for that fresh air flow. An ERV can cut that by 90%. You just saved 9kW of continuous power for the building during the winter with an ERV.