Safety and Security
Safety and security
Though mostly considered a key element of building design for daylighting and views, glass is also a important component for design consideration regarding safety and security. Whether human related safety considerations, mitigation strategies for natural disasters, or minimizing the impact on wildlife and the surrounding environment, glass provides transformative solutions that can achieve the desired project appearances while providing improved protection within a design. The inception of general safety glazing as we know it today was created with human safety in mind.
However, through advancements in technology, design, and building codes, glass design can now also be synonymous with building resiliency, human safety, and animal welfare.
Safety glazing can be defined as glass that will break "safely" to reduce risk of cutting or piercing injuries caused by human impact. Typically, safety glass options are comprised of laminated or tempered glass with each providing different safety benefits.
Wire glass: Though no longer considered a safety rated product, "safety glass" started off out of necessity to deal with the risk of broken glass and the potential for falling hazards. During the World's Columbian Fair in Chicago in 1893 for example, chicken wire was installed underneath glass overhangs to prevent dangerous falling chards of glass from injuring fair attendees. This eventually evolved into the wire being manufactured inside the glass, but then led to other more significant and effective safety products. (Note – in most countries, wire glass is not considered a safety rated product as the large, sharp pieces are still possible when broken and don't reduce injury as effectively as other methods.
Laminated glass: Laminated glass is composed of 2 or more pieces of glass held together by an interlayer. When impacted, the interlayer holds the glass in place preventing fragments from falling or potentially piercing anyone upon impact. Laminated glass performance can be enhanced to become a semi-structural element as well with the inclusion of stiffer type interlayers, now common on frameless glass railings.
Tempered glass: Tempered glass is glass that has been subjected to a thermal treatment process to produce high levels of compressive surface stress. The increased internal stresses created from the heat treatment process present two significant safety benefits. 1) Tempered glass is approximately four times stronger than standard annealed glass, and 2) Tempered glass fractures into small, rounded fragments rather than sharp jagged pieces.
Fire rated glass: Glass and glazing components that slow the transmission of fire and heat through a glazed area. Most times this is rated through a time constraint (20-minute protection) as well as other elements of failure, such as fire hose durability. These glass products are either typically a ceramic glass designed to withstand the heat or they are a complex unit involving multiple layers of glass and heat absorbing liquid/gels.
First introduced in the 1920's automotive industry via optional laminated windshield, safety glass is now a standard requirement in all automobiles and in buildings locations where there is high risk of impact or injury from fallout such as doors, atriums, and skylights.
Today, glass standards surrounding safety and security of building occupants have expanded to cover forced-entry resistance, bullet resistance, blast resistance, and multi-threat resistance. While a glass configuration might meet more than one of these requirements, there are specific test procedures for each dependent on the intended use/function.
Building Resiliency and specialty codes
While glass can be designed to provide protection against human impact, glazing design also provides beneficial properties to building resiliency from natural disasters. Windstorms, hurricanes, and earthquakes can directly cause glass breakage putting both occupants and building interior at risk.
The laminated configuration of hurricane resistant glass not only prevents glass debris from flying and injuring building occupants but also prevents glazing fallout. Glazing fallout during a windstorm or hurricane not only exposes interior property to the elements but can create high levels of internal pressure in the building and result in added damage to the structure members and ultimately structural failure. Most hurricane and similar codes are focused on minimizing structural damage and the results of these storms and though they do improve human safety, the key element of design has more to do with structural integrity for debris impact. Some types of these products are known as hurricane ratings, earthquake resistant, forced-entry resistant ratings, or multi-threat ratings.
Even further, some specialty glass products are designed to minimize human injury through very specific ratings and design. Bullet-resistant is designed through multiple layers of glass and plastics, these products are designed to minimize or stop the penetration of medium to small-powered arms. Blast-resistant glass on the other hand is designed to reduce human threat by minimizing the spall from glass to prevent injuries from flying debris.
As we continue to build and develop cities, we also should take into consideration the impact design can have on wildlife. Research continues to develop on how buildings impact animal welfare and legislation has been introduced for bird-friendly and turtle-friendly glazing.
Bird-friendly glass: Birds do not see building elements, such as window frames, as visual markers to identify glass as a physical barrier. Instead, birds see a clear line of sight to what is on the other side of the glass, or an uninterrupted reflected image of natural surroundings on the glass surface. As a result, birds perceive an unobstructed flight path to vegetation or open skies leading to collisions with windows. There are several ways to prevent birds from flying into windows. Through application of ultraviolet coatings, patterned frits, etching and specialized interlayers, birds are able to perceive these markers and recognize glass as visible barrier.
Turtle-friendly glass: Sea turtle hatchlings migrate to the water at night following the moon. Lights coming from beachside buildings can disorient hatchlings and lead them away from the ocean, prolonging their exposure to predators. To protect turtles during nesting season, turtle friendly glass reduces visible light transmittance. This reduces the amount of artificial light that reaches the beach and allows hatchlings to migrate towards the brighter illuminance of the moon.
So as you can see, glass provides a wide array of safety and security options. Glass is an extremely versatile material and can be molded to meet the form and function of the demands of a space and most times is done in a way where the occupant is unaware of the change. Whether personal safety or building resiliency, we expect the use of glass and the functions we provide to continue to expand to meet the future needs of design.