Last update: 06.08.2019
Building with glass
7.

Special applications

Glass façades have now established themselves as stylish elements in major offices, hotels and residential buildings. In order to meet requirements on energy efficiency, modern glazing now has high-performance functional coatings that consist of precious metals, which are capable of significantly reducing excessive solar heat gain in summer and the loss of heating warmth in winter.

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Glass elevators

One highlight of today’s architecture is transparent elevators, which gives users the feeling of floating. In these applications, the shafts, lifts and cars are made from glass. These types of constructions must meet a number of safety and mechanical requirements that are regulated in European elevators by directives 95/16 EC 7/99 and EN 81 02/99. 

Additional national requirements may exist, such as building regulations of the respective federal state in Germany. For a glass shaft, proof of stability for an applied force of 300 N on an area of 5 cm2 is required. Depending on the size of the cars, the walls, which are fixed and mounted on all sides, create different demands on the characteristics of the laminated glass to be used. If the glazing stretches from the floor to the ceiling, a crosspiece should be installed in the vicinity of a height of 0.90 - 1.10 m which should not be supported by glass.

      
Doors, on the other hand, need to meet special requirements which should be assessed according to the fixture, mechanism and dimensions. Lifts made from glass are always custom-made products which can only be realised together with everybody involved. All lift glass components should have a permanent and visible identification marking.

Interaction with long-wave radiation

Radar reflection damping glazing

Other interference phenomena arise as a result of major reflection on the exterior of glass building envelopes. The so-called multi-path propagation of radio waves that occurs here can cause major interference in many communication systems. This includes air traffic control radar waves. For example, the authority responsible for German air traffic control, Deutsche Flugsicherung (DFS), uses secondary surveillance radar systems (SSR) in the microwave range (ca. 1,1 GHz) at airports and selected locations to ensure the broadest possible monitoring of the airspace. An interrogation signal from the radar determines the direction of the aircraft here according to its identity, altitude, speed, etc.  The reply from the aircraft can be reflected on large surfaces (e.g. tall buildings), resulting in its duplication from another direction. These phantom targets can lead to the erroneous position determination of aircraft or, in the case of multiplication, even result in transponder overloading.

Air traffic control therefore requires that buildings of a specific size, distance and alignment relative to the radar system are planned and realised with radar reflection attenuation characteristics.

Specific project-related requirements are determined by qualified experts. This generally involves a requirement for reflection attenuation with regards to building components in [dB] relative to the incidence angle of radar waves.

The attenuation or damping properties of glass types depends greatly on their structure. Single glass panes with a normal thickness have only a very minimal damping effect. The improvement is also barely discernible in the case of normal insulating glass. The most problematic situation is, as mentioned above, evident in relation to solar and thermal protection glass with precious metal damping. An undesirable and practically complete reflection of radar waves occurs here. 

Consequently, the most common contemporary solar and thermal protection glass types cannot be used where radar attenuation is demanded without taking further measures!
 

Radar reflection attenuation with SunGuard® RD coated glass 

SunGuard® RD is specially developed for radar beam attenuation to exploit the phase displacement effect. The coating, which is “semi-permeable” for radar waves, is on the outer pane of the insulating glass. The residual beam is reflected completely on the inner pane on a (typically low-E) coating containing silver. Wave superposition occurs as they are reflected on both coatings. As the wavelength of the radar beam is approximately within the range of the insulating glass thicknesses, the degree of superposition and, consequently, the phase displacement can be optimised relative to the incidence angle with exactly corresponding pane interspaces and thicknesses of the individual glass panes.
 

The following applies  d = f(ƛRadar and Radar)

The front coating should be calibrated in its electrical properties so that an exactly measured beam volume is allowed to penetrate and, in conjunction with the back reflection of the second coating, the maximum possible obliteration occurs.

Radar reflection attenuation with SunGuard RD coated glass

Based on the topographic conditions and requirements stipulated in the expert radar appraisal, a special insulating glass structure is determined for each specific case with uniquely determined attenuation properties derived from this.

These reflect a logarithmic function (table to the right).  

Damping reduction

In cooperation with engineering firms and consultants, Guardian provides assistance during preliminary dimensioning of radar reflection attenuation glazing. This involves the mathematical determination of insulating glass structures, which meets the requirements for radar beam attenuation (secondary radar).

This preliminary dimensioning does not replace the final confirmation of glass structures through measurement and appropriate expert radar appraisals which must be compiled for each specific project.

For more information please contact Guardian’s Technical Advisory Centre.

Damping of electro-magnetic high frequency radiation / electrical smog

Only the use of high-frequency pulsed radiation makes the performance of today’s mobile service applications possible. Ultimately, this has led to its widespread use. Many people are now worried about excessive exposure to radiation, particularly near mobile service transmission installations.

The term “electrical smog” originates from the 1970s and refers to the pollution of the environment by electromagnetic radiation.

Electromagnetic radiation is reflected by conductive surfaces or boundary layers. Absorption plays a decisive part where poor electrical conductors are concerned (e.g. thickness of concrete structural elements).
Electromagnetic screening is always relative and depends on the incident signal and its strength (radiation density in μW/m²).

As the electromagnetic screening is mathematically difficult to determine, the damping properties of a whole series of building materials, including double and triple glazing, were examined at the Bundeswehr University in Munich, together with the consultant Dr. Moldan many years ago.

High-frequency radiation is dampened very effectively by thermal insulating coated glass (such as ClimaGuard Premium2 or ClimaGuard 1.0+ and solar protection glass of the types SunGuard HP, SN and SNX) with a surface resistance of the coating of < 5 Ohm.
For triple glazing with 2 ClimaGuard/SunGuard coatings, HF transmission damping of approx. 42 dB was achieved for 900 MHz (GSM900 mobile service) and approx. 48 dB in the 2000 MHz band (GSM 1800 mobile service, DECT, UMTS).
Aside from that, double glazing with a single ClimaGuard coating achieves an HF transmission damping of approx. 32 dB at 900 MHz and approx. 28 dB at 2000 MHz.

The damping is specified as the so-called "damping ratio". It describes the amount by which the incident electromagnetic signal is reduced on passing through a structural element and is specified in the unit dB (Decibel). Since the function is logarithmic, the following relationship results:

Damping ratio

The damping ratio and the related transmission reduction of the electro-magnetic radiation in the considered range, demonstrate that a very low signal level can be received behind energy efficient glazing.

In order to improve the permeability for high-frequency radiation the coatings can be segmented by special treatments (laser, specific ceramic enamels). This segmentation influences the generation of circular currents in the highly-conductive coatings which are responsible for the reflection properties.

In any case, however, it must be noted that only comprehensive considerations can offer solutions. In the specific case, therefore, the complete window and façade elements must be considered along with their corresponding profiles and wall connections.