Coated Architectural Glass

[M II A II R II K]

Coated Architectural Glass


Michael Elstner, state certified Engineer & Master Glazier



Read More: http://www.glassonweb.com/articles/article/638/

Glass is the dominant building material in modern architecture. It creates visual accents and offers multiple technical features like glass for thermal insulation, solar protection, and sound proofing, as well as a design component, safety glass, or as a part of solar plants. The industry nowadays offers glass with customised technical data for every application possible. In architecture, a special emphasis is often placed on energy-saving building methods, particularly in view of the rising energy and raw material costs which are the greatest challenge of our times. Due to the wide diversification of the technical features, tailor-made technical glass consulting is becoming an increasingly important service in architectural glazing. This paper describes the historical context as well as the evolution of glass as a material and its applications in windows and facades, with a description of its most important building-physics values.

- Flat glass has been used for around 2000 years as a space-enclosing component and is, therefore, one of the oldest artificial building materials. Due to ongoing developments concerning manufacturing and finishing methods, it is now also one of the most advanced building materials and it characterises modern architecture today. Since it can now fulfil nearly any requirement of modern building envelopes, the conflict between the fundamental human need for protection from the outside world, on the one hand, and the openness to light, on the other hand, has now been overcome.

- Single glazing, which was standard until the middle of the 1970, is responsible for large thermal losses (Ug Ø ≈ 5.8 W/m2 K). Double glazing then became more common, with its improved Ug value of about 3.0 W/m²K. It was not until double glazing technology was combined with modern thin film technology to create transparent coatings on glass that the specific energy losses could be halved yet again. In contrast to metals, which re-radiate about 2 to 10 percent of the absorbed energy, i.e. which have a low emissivity value, ε, glass does not possess this favourable property. More than 80 percent of absorbed heat is emitted via the glass surface (ε ≈ 0.85). In order to combine the transparency of glass with the excellent emission properties of precious metals, thin metal films are deposited onto the glass. These are transparent to sunlight but simultaneously reduce the emissivity of the glass surface very effectively. Extremely thin silver films with a thickness of about 1/100,000 mm (= 10 nm) are optimal. Colour-neutral, coated insulating glazing was first introduced by INTERPANE to the market at the beginning of the 1980. A vigorous market campaign, including the distribution of basic coated glass as a semi-finished product, ensured that iplus was soon widely disseminated. Today, thermally insulating glazing (low-e glazing) with a Ug value of ø 1.1 W/m²K is accepted as the state of the art. With triple glazing, Ug values down to even 0.5 W/m²K can be achieved. This means thermal losses that are only a tenth of those for single glazing!

- Different coating materials are deposited onto glass to produce functional coatings. These provide adhesion, thermal functions, cover and protection, forming a complex system. The optical properties are achieved by applying the interference principle, which is familiar from antireflective coatings on camera and spectacle lenses. The ipasol solar-control coatings are similar to the others in principle, but have a significantly more complex coating structure. The desired properties regarding solar and thermal radiation are obtained with additional absorbing and/or reflecting components.

Structure of a simple Low- E coating on glass






Schematic diagram of the continuous operating coating line with high-performance sputtering (in-line method).






Schematic cross- section of a cathode chamber to deposite thin films by the magnetron sputtering procedure






Surface processes during sputtering






Heat flow through insulating glass

[Busy Bee]

Interesting.