What impact approval actually tests
An impact-rated assembly is fired at twice: a Large Missile test drives a nine-pound piece of lumber at the glass at approximately 34 miles per hour, and a Small Missile test throws steel ball bearings at it to represent roof gravel carried by wind. The unit then goes through 9,000 cycles of positive and negative pressure to confirm the glass stays in the frame after it has been broken.
Passing means the interlayer holds the broken glass in the opening and the building envelope is not breached. That is the whole point: once wind enters a house, internal pressure does the structural damage.
Large and Small Missile, HVHZ
All nine Fortwell systems are approved for both Large and Small Missile Impact in the HVHZ. There is no separate non-impact line to specify around and no zone where part of the collection drops out of approval.
Design pressures run from ±65 psf on the residential window range to ±90 psf on the 150 Series outswing French door.
Reading a Notice of Acceptance
Each NOA names the tested glass make-up, the maximum tested size, the design pressure, and an expiry date. A system used outside those limits is not covered by the approval, so the tested size on each product page is the number to design to, not a marketing maximum.
