Determining the difference between a drained and back-ventilated rainscreen and a pressure-equalized rainscreen cannot be done by visual inspection alone; test results are essential. Some Arrowhead metal cladding rainscreen systems meet both AAMA 508 Pressure Equalized Rainscreen System criteria and AAMA 509 Drained and Back-Ventilated Rainscreen System criteria, highlighting the challenge of visual identification.
Key differences between these systems can be identified through closer inspection and understanding of their design and installation principles:
    1. Drained and Back-Ventilated Rainscreen System: This system relies on gravity and air pressure differentials for ventilation and drainage behind the cladding. It typically          features a continuous ventilation space and drainage openings at the bottom to allow water to escape.
    2. Pressure-Equalized Rainscreen System: Designed to equalize air pressure behind the cladding, this system reduces the potential for air infiltration and water penetration. It        includes pressure-equalizing chambers or compartments to balance air pressure and prevent water ingress.
To distinguish between these systems, examine specific design and installation details such as the location and size of ventilation and drainage openings, the use of pressure-equalizing chambers, and the sealing and flashing details to prevent water infiltration.
In metal panel rainscreen systems, perimeter extrusions on a Pressure Equalized system might have mitered corners to create compartments. However, this is not always the case, as the Arrowhead Lean rainscreen system achieves both AAMA 508 and AAMA 509 ratings without mitered corners.
In summary, the only definitive way to determine whether a rainscreen system is Pressure Equalized or Drained and Back Ventilated is to review the test data. This ensures a properly tested system, avoiding assumptions about performance.
