Our system has been tested at a UKAS accredited testing station and passed the PAS23 weather test to extreme weather conditions of over 300 pascals.
Most systems on the market are weather tight, with high performance rubber seals and brush seals. However, there are some systems that have little or no seals at all. One crude but easy test is to close a folding door onto a sheet of paper and try to pull the paper out. If it pulls out easily there is not a water tight compression on the seals.
We use 2 rubber EPDM seals on each side of each panel and high performance seals on the top and bottom of the panel. The system also includes a tongue and groove feature to (1) prevent water infiltration, (2) keep the system stable with one panel interlocking with another and (3) to prevent attack by an intruder.