Solar control glass
Sun protection glass is a special flat glass that reduces excessive solar radiation into a building and thus excessive heating of the room air. Sun protection glasses achieve this effect through absorption or reflection : dyes (e.g. iron (II) , iron (III) and copper (II) oxide ) are added to the absorption glass when the glass is melted. The reflective glass can have a reflection in the non-visible range (infrared range, imperceptible to the human eye) and / or the visible range. This glass is coated with metallic, dielectric, semiconducting substances as an adherent film.
functionality
Sun protection glass can either be used as sole protection from the sun or in combination with other shading and cooling systems. The mode of action is different for colored and coated solar control glass. Colored solar control glass absorbs solar radiation and releases the energy to the outside. Coated glass causes the radiant energy to be reflected outwards.
There are different types of coatings. Some coatings are suitable for use on individual panes of glass and for installation on the weather side, while others have to be processed into insulating glass. If the coating is applied to the outside of the outer pane of glass, the degree of light reflection is higher and there is an increased mirror effect. If the sun protection coating is only used on the inside of the outer pane (as is the case with all infrared reflective glasses), there is less or no mirror effect. In some cases, the reflection is even lower than with uncoated glass.
Differentiating features of sun protection glasses
Sun protection efficiency
Basically, the effectiveness of any sun protection depends on the behavior of the user, the way in which the sun protection is attached and how it is ventilated, the distance from the glazing and the type of glazing. Depending on the orientation , construction and use of the building , different requirements are placed on sun protection through glass.
Total energy transmittance
The degree of sun protection on glass is determined by the total energy transmittance , the g-value. The total energy is made up of the solar energy, which reaches the interior of the room directly through the glass, and the energy that is released inwards when the glass is heated. The lower the g-value, the higher the sun protection effect. The g-value of modern sun protection glasses is between 0.18 and 0.48, the values of heat-insulating glazing are between 0.6 and 0.65, with triple glazing it is 0.55.
Light transmission
Sun protection glasses have a light transmission between 50 and 70%, depending on their efficiency (for comparison: heat protection glasses have a light transmission of approx. 80%). Depending on the proportion of windows, these values are completely sufficient to illuminate the interior of the room with daylight. An antiglare not provide sun lenses, it can by additional shading systems such as shutters or blinds to be achieved.
U-value of glazing
The heat transfer coefficient , the so-called U-value, should be as low as possible for glazing so that the heat inside does not escape to the outside in winter. Sun protection glasses that are equipped with thermal insulation as insulating glasses have these low U-values. Both functions, solar and thermal protection, are partially fulfilled by just one coating. The currently most efficient solar control glass has a Ug value of 1.0 W / (m² · K) in double glazing.
selectivity
The selectivity S of a glass indicates the ratio of the light transmittance TL to the total energy transmittance g: S = TL / g. In the case of sun protection glasses, a high level of light transmission with a low g-value is desired; accordingly, a high selectivity index reflects a particularly favorable ratio. The most powerful sun protection glasses now achieve selectivity values of> 2.
Manufacturing
It all starts with classic glass production using the float glass process . In this endlessly continuous process, the glass , which mainly consists of the materials quartz sand , lime and soda , goes through a long production line. The initially liquid glass is solidified by very slow cooling and then cut to tape dimensions of up to 800 × 321 cm and transported to further processing plants.
The sun protection glass gets its properties with tape dimensions of up to 600 × 321 cm by coating and / or coloring the glasses, depending on whether colored or color-neutral sun protection glass is to be produced. There are two coating methods: the pyrolytic and the magnetron method.
Magnetron coating process
The so-called multi-chamber magnetron high vacuum coating process is predominantly used today. This is a so-called off-line process, i.e. H. the coating is not applied during the actual glass production, but in a separate production process. With magnetron technology, the glass is thinly coated with precious metal and, thanks to the very precise control, achieves an exceptional uniformity of the layer thickness.
Pyrolytic coating process
The pyrolytic process is a so-called on-line process. Liquid metal oxides are sprayed onto the hot glass during flat glass production . The metal oxides are literally burned into the still hot glass surface. Pyrolytic layers are characterized by high mechanical resistance and freedom from corrosion.
Selection of sun protection glasses
The sun protection effect, the light transmission and the aesthetics are decisive for the right glass. In most cases, glass with a high level of light transmission and light sun protection (light transmission 70% / g value 40%) is suitable for use in living areas. In the case of roof glazing, on the other hand, you tend to choose a glass with a higher sun protection effect. Furthermore, the Ug value (the lower the better) is important for the choice of sun protection glass.
Effect in practice
Sun protection glasses can block up to 82% of the incident solar energy. In a study by an engineering office in 2007, the effect of sun protection glass was tested in comparison to conventional heat protection glazing in four different rooms (living room, children's room, attic room and winter garden). The average temperatures in the rooms with solar control glazing were noticeably reduced both in a hot period and in the annual average. In the test living room with light solar control glass, temperatures over 26 degrees prevailed for 7% of the time it was used. With conventional thermal insulation glazing , the residents had to withstand temperatures above 26 degrees for 22% of the usage time.
Solar control glass can replace other shading systems and relieve or partially replace cooling devices such as air conditioning systems, which protects the environment and saves energy.
Areas of application
Sun protection glasses are available in different variations: neutral color, colored or reflective, flat or curved and in different sizes. They can be installed vertically or overhead. They are used on glass facades , as point-fixed facade glasses, glued, as double facades and external wall cladding.
The installation of sun protection glasses can be particularly useful in the following situations:
- if the view outside should always be unobstructed or if the unobstructed view is important (e.g. in shop windows) and glare protection plays a subordinate role
- where external sun protection systems are not desired or permitted for aesthetic reasons or for reasons of monument protection
- where low maintenance is required
- if the price for the building area is so high that external protection is too expensive
Additional functions
Modern sun protection glasses are mostly made as insulating glass . This means that they also have a heat-insulating function. Sun protection glass can also be manufactured as toughened single - pane safety glass (ESG) or as laminated safety glass ( VSG) and thus offer protection against the risk of injury and break-ins.
Another useful additional function is self-cleaning . A special coating on the outside of the glass causes the dirt adhering to the glass to decompose, which is then washed away by rain or spray water.
With a special acoustic film in the space between the panes and a slightly different pane structure, the glasses also have a soundproof effect. Sun protection glass in combination with design is also possible, colored or with ornaments.
Adaptive or switchable sun protection glasses are glasses whose light transmission can be changed. This enables them to adapt automatically or user-controlled to changing solar radiation. Switchable sun protection glasses belong to the so-called intelligent glasses . The techniques used for switchable sun protection glasses include electrochromism and thermochromism .
Combination with shading systems
Sun protection glasses offer effective protection against overheating inside, but no glare protection. In order to completely exclude the annoying glare and to avoid heating up even more, additional shading systems are useful. Certain restrictions must also be observed: External shading has the disadvantage of being susceptible to wind and dirt and they have to be serviced regularly. Internal shading systems can also be in need of repair, they are prone to dirt and dust and can fade. Another alternative is thermal insulation glass with an integrated shading system, with lamellas in the space between the multi-pane glass.
Individual evidence
- ↑ MÜLLER-BBM GmbH : Study: Efficiency of sun protection glasses in residential buildings , 2007