What is the generally accepted ratio of return air to supply air?

The generally accepted ratio of return air to supply air is 1 to 1. This ratio is crucial in maintaining balanced airflow within HVAC systems. When the amount of return air matches the supply air, it helps ensure that the system operates efficiently, effectively exchanging the air within a space without creating negative or positive pressure imbalances. Such balance minimizes the risk of issues like drafts, discomfort, or increased energy consumption.

In HVAC design, this 1 to 1 ratio facilitates optimal air mixing and temperature control, vital for occupant comfort and system performance. Keeping the return and supply air balanced also aids in maintaining good indoor air quality, as it promotes better circulation of conditioned air while ensuring adequate ventilation.