If I install a balanced ventilation system, sometimes referred to as a Heat Recovery Ventilation (HRV) or Energy Recovery Ventilation (ERV), may I add the exhaust airflow and supply airflow together for compliance with the ASHRAE 62.2 Standard?

No, the exhaust and supply airflows are not added together. For example, if the minimum dwelling-unit ventilation requirement if 100 CFM (50 L/s), the balanced ventilation system must supply 100 CFM (50 L/s) and exhaust 100 CFM (50 L/s).