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What’s the allowable aspect ratio of fixed impact glass in the HVHZ?

Often times a glazing product is approved for large missile impact, but requires a field modification for size.  While the tested span cannot be exceeded and still meet the building code’s large missile impact requirements, the aspect ratio (the length to width ratio) can be altered so long as the glass area does not exceed the tested size.

The maximum aspect ratio of the length to width in glazing within the HVHZ  is 5:1.

See the below link to the Miami Dade website explaining the Aspect ratio requirements. Keep all of the Larger dim/Smaller dim below 5 so the comparative analysis will fall within the ASTM E1300 requirements. If the aspect ratio exceeds 5 and the client wants to include it in a Florida Product Approval, then additional glass units should be tested using the requested Glass unit size.

Bounding Box Understanding

Sometimes glazing units are not rectangular or square. 

Use the below image as a guide to understanding the general theory of measuring glass unit sizes and aspect ratios for your comparative analysis.

Always seek the advice of a design professional prior to installing any shape outside of Miami Dade or Florida Product Approval specifications.

window analysis binding box shape examples
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