What is required if the final CFM50 is less than 70% of BAS?

When the final CFM50 (Cubic Feet per Minute at 50 Pascals) is less than 70% of the Building Airflow Standard (BAS), it indicates that the building has inadequate mechanical ventilation capability. According to guidelines for maintaining indoor air quality and comfort, sufficient ventilation is necessary to ensure that the air inside a building is fresh and conducive for occupants.

In this scenario, mechanical ventilation becomes essential to compensate for the shortfall in airflow. This can involve the installation or adjustment of systems such as HVAC units, exhaust fans, or energy recovery ventilators to enhance air exchange rates. The requirement for mechanical ventilation addresses potential risks like elevated carbon dioxide levels, indoor pollutants, and overall poor air quality that may arise from insufficient air movement due to the low CFM50 reading.

Increasing natural ventilation might not be feasible or sufficient, especially if outdoor conditions (like weather or pollution levels) are not suitable. Conducting another blower door test may help confirm the initial findings, but it does not remediate the ventilation issue. Thus, implementing mechanical ventilation is a key corrective step when airflow metrics suggest a significant deficiency.