Survey of Window Retrofit Solutions for Blast Mitigation

Abstract

Explosive attacks on buildings create a rapid release of energy in the form of a shock wave. Window glass is often the weakest part of a building, breaking at low pressures compared to other building components. Explosion-related injuries caused by glass breakage include eardrum damage, lung collapse, and penetration- or laceration-type injuries from airborne glass fragments which may lead to fatalities. As glass breakage may extend for miles for a large external explosion, reducing glass hazard is an important aspect of blast-mitigation for buildings. Blast-mitigating window products are in their infancy in the United States. Categories of available window retrofit solutions include: window film technologies, mullion and frame upgrades, catch systems, window replacement systems, installation of secondary windows, and/or a combination of these technologies. Installation of daylight film is the least costly but provides the lowest level of protection, while replacing windows is the most costly with the greatest gain in blast protection. Selection of the best window retrofit solution is usually based on a number of design constraints including blast criteria, building constraints—which can be broken down into type of building, maintenance and operability requirements, interior finishes, energy conservation requirements, lifecycle—and finally the retrofit cost.