Breakage of glass windows by explosions

This problem can occur with windows that have horizontal or vertical separators in the middle of the window i. Research has shown that as long as the horizontal or vertical separator member has an internal reinforcement bar, the deformation will not take place Quarles and Beall For most vinyl window manufacturers, inclusion of the reinforcement bar has always been standard practice because of the need to meet other performance requirements e.

McArthur tested wood- and aluminum-framed windows and reported that the glass was the most vulnerable component. These results generally agree with unpublished research conducted at the University of California Fire Research Laboratory. In these studies a variety of frame and glass types were studied. During one test the beading material that holds the glass to the frame failed, allowing the glass to fall out prior to breaking, but otherwise these results support the recommendation to use the more resistant tempered glass, and select frame material based on other factors aesthetics, cost, etc.

Therefore, to improve the performance of their windows under wildfire exposures, homeowners should upgrade to a multipaned unit two or three panes , using tempered glass the California building code requires that at least one pane in a multipaned unit be tempered.

Tempered glass is about four times stronger, and also much more resistant to thermal exposures, than the normal annealed glass commonly found in most windows. Research conducted in Australia has shown that a reflective film on the exterior surface of the outside glass provides effective protection against radiant exposures Bowditch et al. These coatings are most often used to reduce energy costs of a building and there are a number of commercially available products. If you are considering use of a reflective coating to improve the performance of your windows during a wildfire, consult with an energy professional to evaluate other impacts of the coating.

Bowditch et al. Low-E coatings have sometimes been discussed as a means of enhancing the wildfire performance of windows. Low-E coatings are always on one of the inner surfaces of a dual-pane unit.

Mathematical modeling has predicted that a low-E coating placed on the inner surface of the outside glass would improve the performance of a window exposed to a wildfire Cuzzillo and Pagni This has not been confirmed by laboratory testing, but agrees with reports that manufacturers will place low-E coatings on this surface in order to minimize the potential for thermal stress Carmody et al.

Ignition of window curtains from a radiant exposure, prior to glass breakage, is unlikely as long as annealed or tempered glass is used.

Babrauskas summarized research investigating glass breakage and ignition of materials under radiant heat. He reported that glass breakage occurred at radiant exposures between 10 kilowatts per square meter for single-pane annealed glass approximately 25 kilowatts per square meter for double pane and 45 kilowatts per square meter for tempered glass.

Cotton and polyester materials which curtains might be made of were igniting at about 40 kilowatts per square meter, but he also reported that glass reduces the amount of radiation transmission by half. With these types of glass, breakage is far more likely to occur before curtains ignite. It is still a good idea to remove easily ignitable things away from the window in case of glass breakage and ember entry. If you have more expensive types of glass e.

However, windows with any of these kinds of glass are very expensive and beyond the budget of most homeowners. Automatic shutters would be more affordable and would provide comparable protection from radiant exposures.

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All content is available under the Open Government Licence v3. Free digital downloads While there is limited access to our Kew site, signed-in users can download digital records for free. Read about our fair use policy and why we are doing this. Like fire resistance and manual attack the glass has to form part of a complete system and will not perform as required in isolation. Glass can be tested to the North American and European standards below. ASTM F Test method for glass and glazing subjected to air blast loadings EN : : 'Glass in building - Security glazing - Testing and classification of resistance against explosion pressure' Subject to blast waves generated using shock tube Simulation of high explosive detonation 4 classifications ER1, ER2, ER3 and ER4 S Splinters or NS No splinters The selection and application of blast resistant glass needs specialist advice and there are consultants who offer advice in this area.

Like most threats it can be hard to determine the size of the explosion and the proximity to your location. The channeling effect of other buildings and street architecture can change the way the pressure wave effects buildings. Post examination of explosions can reveal some odd results.