500 layers against the heat - BMW introduces new heat-reflecting laminated glass technology

Munich. In a world first, BMW has introduced a pioneering heat-reflecting
laminated glass technology into the new BMW 5 and 7 Series. The rear windscreen
featuring more than 500 ultra-thin plastic embedded layers can be specially
requested as part of the climate comfort laminated glass option. "With more
than 500 layers of plastic, the laminated glass pane reduces heat build-up in
the interior of the car. Each of the layers is only around 0.00001 millimetres
thick, which is some fifty thousand times thinner than a human hair," says BMW
project manager Gerald Buck.
The result: enhanced passenger comfort on hot days thanks to glazing which
reflects the heat-generating infrared component of the sun's rays and thus
noticeably reduces heat build-up in the cabin even at temperatures of over 30
degrees Celsius.

Direct sunlight, especially if the car is stationary, causes a powerful
build-up of heat in the interior. Compared to a car with standard glazing, the
new climate comfort glass affords several advantages:
Firstly, it reduces the internal air temperature by some 5° C in a car standing
in the sun. Secondly, it lowers the surface temperature of seats and storage
areas, for example, by up to 10° C.
The bottom line: automatic air conditioning provides adequate cooling even at
the start of a journey and on less power. It means the blowers can operate at a
lower setting, thus reducing noise levels and improving fuel economy.

Development and technology
This new glass was jointly developed by the BMW Group, 3M and Saint-Gobain
Sekurit, Germany. Manufactured by the partners in an elaborate production
process, this glass has made it possible for the first time to protect the
car's interior from undesirable heat from the sun's rays by the use of glass
and plastic exclusively.

Previously, this "solar protection function" had only been achieved by means of
metal thin-film systems in the glass. These also reflect the infrared component
in the sun's rays and reduce the build-up of heat inside a car, but the
advantage of the non-metallic interlayers is that they do not screen off the
cabin area, ensuring improved reception of communications systems.

Climate comfort laminated glass thus offers several benefits compared with
standard glazing, namely enhanced thermal and acoustic comfort coupled with
some saving in weight but without increased absorption of visible incoming
light.