Low-E coatings and double glazing


Energy consumption has been a source of growing concern over the past few decades, and limiting heat losses through glazing has become a priority for glassmakers. AGC Glass Europe and its R&D Centre have long worked on improving the insulating properties of glass by applying coatings on it.


This is an advanced glass technology for which AGC Glass Europe claims European leadership. AGC Glass Europe boasts a wide range of super insulating coated glass, also called low-emissivity (low-e) glass and unified under the iplus and Planibel brand names.


Comparison of single glazing versus double glazing and double low-e glazing


Single glazing has a Ug value of 5.8 W/(m²K). In such a case more heat is lost through the window compared with solar gain: the overall balance is a clear loss of energy. This loss of energy must be compensated by extra heating corresponding to emission of 84 kg of CO2 per year per square metre of glass, or 2,000 kg of CO2 per dwelling per year.
The use of ordinary double glazing with a Ug value of 2.8 improves the balance by reducing the amount of heating needed, but it remains still negative with an overall energy loss corresponding to 22 kg of CO2 per square metre of glass, of 500 kg per dwelling per year.


Now if we compare on the one hand the energy used and the CO2 emitted to produce the glass, and on the other the energy and the CO2 saved by using low-e double glazing, the balance is once again positive. To produce 1 square metre of Thermobel Energy, with a Ug value of 1.0, the industry emits around 35 kg of CO2. By contrast, replacing single glazing by low-E double glazing leads to a saving of about 91 kg per year. 

Double glazing AGC glass

CO2 balance comparison between single glazing (lower bar), basic double glazing (middle bar), and low-e double glazing (upper bar).


That means that the CO2 emitted to produce the low-e double glazing is offset by the savings in 3.5 months. If conventional double glazing is replaced by Thermobel Energy low-E double glazing the time needed to cancel out the CO2 emission is 10.5 months. 


AGC follows the communication efforts from Glass for Europe, the trade association of Europe manufacturers of building, automotive and solar-energy glass, on the importance of providing products that can generate energy savings, reduced CO2 emissions and healthier buildings. According to this trade association, today in Europe, over 85% of glazed areas in buildings are still inefficient because of either single glazing or outdated double glazing. A EU window energy label should guide consumers towards more energy efficient windows, by way of an A to G scale to identify products' performance. 

For more information please follow the initiative “Window Energy Label”. For detailed information read the pdf or watch the info video.


With its complete and diverse "iplus" and “Planibel” ranges of low-emissivity products, AGC Glass Europe continues to design solutions that meet all comfort requirements. AGC Glass Europe has also developed and offers a wide range of insulating glazing units commercialized under the brand name Thermobel using the iplus low-e coatings. such as Thermobel Advanced 0.8, Structura Duo, Thermobel VIP (Vacuum Insulation Panel) and Triple Silver Coating.


Energy performing insulating glazing solutions are offered for the façade & building envelop (vision glazing and spandrel glazing) and for point fixed glazing.

Thermobel Advanced 0.8 –Double glazing

Thermobel Advanced 0.8 –Double glazing unit

Thermobel Advanced 0.8 is insulating glazing that is as efficient as a triple insulating glazing and provides the highest levels of thermal insulation available on the market today. Launched in 2011 and improved in 2014, Thermobel Advanced 0.8 combines the exceptional insulation performance of a standard triple insulating glazing (Ug value of 0.8) with the installation benefits of double glazing (compact thickness, lightweight). This is achieved by combining an innovative composition of low-e coatings combined with a thermal gas-filled spacer. Light transmission is maximised (LT= 72%) and the solar factor is optimal for benefitting a maximum a the free solar heat (SF = 50%). Thermobel Advanced 0.8 is the best insulating double glazing currently available on the market. It is the ideal product for anyone looking for a compact, light and high-performance glass solution. 


Thermobel VIP (Vacuum Insulation Panel)

Used as a spandrel, Thermobel VIP is a double insulating glazing unit integrating a vacuum panel element into the cavity which delivers excellent thermal insulation performances of the spandrel area, with Ug values of up to 0.15 W/m²K.  Thermobel VIP can be totally recycled and can also provide sound insulation.


Structura Duo +

AGC Glass Europe produces an insulating glazing systems for the application of point-fixed-glazing, recommended when a high level of thermal and solar performance is required. Solar control coating with low-e performance and characterized with a high light transmission (e.g. Stopray or ipasol) can be build into Structura DUO+. The glazing system released in 2013, is especially suited to facades with insulating glazing, use in the European climate zones.

Connector- Brussels Airport - Architect Chapman Taylor

Stopray Ultra – triple silver-coated products

Based on the latest glass technology, AGC Glass Europe now offers triple silver-coated products for facade applications in commercial buildings. Stopray Ultra-50 on Clearvision and Ultra-60 are part of AGC Glass Europe's new generation of high-performance glazing solutions. The high level of light transmission maximises natural light, yielding all the benefits of large indoor spaces bathed in light year round. The very low solar factor reduces solar gain, resulting in significantly lower air conditioning costs. The selectivity (ratio of light transmission to solar factor) is always higher than 2. The superb thermal insulation (thanks to a Ug value of 1.0 W/m²K) minimises energy losses, resulting in major energy savings.


Triple glazing


At a time when reducing energy consumption is taking centre stage and design housing and building for minimal fossil fuels demand over the life span – both for financial and for environmental reasons – triple glazing (with three glass 


components with optimized g-value and having the latest generation of low-e coatings) is increasingly being used for new constructions, major renovation, PH and nZEB projects in residential-, utility- and commercial segments.


AGC's triple glazing, Thermobel TG has excellent light- and energy- properties and as a result minimises heat loss: approximately four times less loss than normal double glazing and makes maximum use of the free solar heat.
Thermobel TG LS is a triple glazing unit specially developed by AGC Glass Europe. The objective was a transparent building product with high environmental performance (low Ug-value combined with high g-value) while letting as much natural light as possible for best visual comfort and wellbeing.


Thermobel TG LS products offer a higher level of light transmission since making use of the Planibel Clearlite glass component. Thanks to the unique properties of the iplus low-e coatings and Planibel Clearlite, the Thermobel TG LS range  meets the criteria for PH and nZEB houses and buildings and is recommend in renovation projects for private home owners and building projects.

Triple glazing AGC
thermobeltri triple glazing AGC



Three important studies*, commissioned either by AGC Glass Europe and/or Glass for Europe, have shown the energy efficiency of the predecessor of iplus LS coating, namely the Planibel TRI coating. The results of these three studies confirm the added value of the Planibel TRI coating. With even better values compared to Planibel TRI (higher solar factor and light transmission), the conclusions of these studies are even more relevant for the new iplus LS (see more on http://webcast.yourglass.com/tri/).

Moreover, installing triple glazing with iplus LS not only cuts energy consumption but also adds value to the building, bearing in mind the new legal requirements for energy certification of residential buildings.


(*) Study 1: IFT (Institut für Fenstertechnik) – Institute for Window Technology. “Study of energy conservation and thermal insulation of high-performance triple insulating glass units with optimised solar energy transmittance. Calculation for residential buildings.”
Study 2: TRIBU – French Institute in Environment for the building and town planning sectors in France. “Study on the impact of glass in an environment statement for an individual house in France.”
Study 3: TNO – Institute for market research and scientific research in the Netherlands.



IRIS® coating for automotive glass


CO2 emissions are directly correlated with fuel consumption of the car, and there are basically two ways to reduce this by using glass. The first is to decrease the weight of the glass. The thinner the glass the lower the energy consumption of the car. The second way is to improve the thermal properties of the glazing. Given that air conditioning can increase fuel consumption by 10%, improving the thermal isolation will reduce the fuel consumption.

The sun’s spectrum is made up of three kinds of radiation: ultraviolet, visible and infrared. In an ordinary windshield, the ultraviolet is absorbed by the polyvinyl butyral interlayer but the visible and infrared radiation is mainly transmitted through the glass.


The visible and infrared ranges are responsible for 54% and 43% respectively of the energy transferred into the car. One of the major functions of the windshield is of course to provide high visibility for the driver, and therefore regulations impose a minimum visible light transmission of 70%. The problem is as follows: how to significantly reduce the energy transmission through the windshield while maintaining sufficient transmission of visible light? The IRIS® coating developed by AGC provides an answer to this question.


The IRIS® coating is a complex stack of different thin metallic coatings, deposited directly on clear glass by the magnetron sputtering process. It is important to note that magnetron sputtering only generates wastes that can be recycled. Furthermore it is a dry process and consequently environmental friendly. After coating, the glass can be curved and laminated in conventional windshield production lines.


The IRIS® windshield provides high visible light transmission (more than 70%) and high infrared reflection. These unique properties permit energy reflection of about 35% compared with 5% for a conventional windshield. 


The total energy entering the car is decreased by 10% compared with the best absorption technologies in which part of the energy absorbed inside the windshield is re-emitted into the car. This technology decreases the thermal load inside the vehicle and consequently the need to use air conditioning for cooling the interior.

AutomoviteIRIS glazing AGC

Based on simulations by AGC and our customers, the IRIS® windshield is estimated to decrease CO2 emissions by 1 g/km.

Comfort is also improved for the driver and passengers. Our simulations show that the temperature of the dashboard and seats can be lowered by 9°C, making them less hot to the touch. This further reduces the use of airco.
Given the total amount of CO2 emissions in Europe generated by transport (following EIA, www.eia.doe.gov), reducing the CO2 emissions for each vehicle by 1.5 g/km would cut annual CO2 emissions in Europe by 6 million tonnes!

Beyond this impressive statement, AGC considers that this kind of product has a bright future, especially for the new electric vehicles for which the challenge will no longer be CO2 emissions but the power savings necessary to achieve a sufficient driving range.


Thin Automotive Windshield


In a bid to reduce the carbon footprint of vehicles, AGC Glass Europe is the first company to have overcome industrial and technical challenges to offer a thin windshield with a thickness of just 3.9 mm (as opposed to the usual 4.5 mm for a standard windshield). In practical terms, this means that the thin windshield is some 1.4 kg/m² lighter than its standard counterparts.


This translates into a saving of approximately 0.2 g of CO2 per km travelled whilst accommodating manufacturers' requirements in terms of safety (strength and optical quality), aesthetics (shape and colour) and adaptability to the customer’s process.