The rise in energy prices and the growing awareness concerning sustainability encourage us to create well-insulated buildings. A huge part of our facades is made up of doors and windows consisting of insulating glasses up to 90%. We should pay attention to details in order to own well-insulating glasses in our buildings and to cut our costs up to 30-50%.
Heat conduction
Heat conduction happens when the temperature differs between two given points of a solid structure. In this case, heat moves from the warmer structure towards the colder one. If the difference in temperature maintains, constant heat conduction can be observed. Heat conduction is marked with λ; its unit of measurement: W/mK.
Heat transmission
When a liquid media or a gas form comes into contact with a solid structure, the heat exchange developing on the verge of the two structures is called heat transmission. For instance, the air traveling in front of our windows draws or transfers heat to them.
Heat radiation
Each structure with T>0 K emits electromagnetic waves. This phenomenon is called heat radiation. The most common example is the radiation of the Sun, the intensity of which is 1,4kW/m2. In case of an insulating glass, 2/3 of the energy gets through by heat radiation. Consequently, the application of glasses with low emission (Low-e) has a great importance since they remarkably improve the heat insulating ability of the glass.
Ug (g=glass), thermal transmission value of glass
Unit of measurement: W/m2K
It shows the amount of energy traveling through the glass between indoors and outdoors (on a given surface, at a given difference in temperatures).
The lower value we receive, the better glass we have.
The Ug value can be improved by:
The evolution of Ug value (EN 673)
4 mm thick single-layer glass 5,8 W/m2K
4-16 spacer-4 2,7 W/m2K
4-16 spacer -4-16 spacer -4 1,8 W/m2K
4-16 spacer -4 Planibel G (hard coating) 1,7 W/m2K
4-16 spacer -4 Low-e (soft coating) 1,4 W/m2K
4-16 argon (90%)-4 Low-e 1,1 W/m2K
4-16 argon (90%)-4 Super Low-e 1,0 W/m2K
4 Low-e-16 spacer -4-16 spacer -4 Low-e 0,8 W/m2K
4 Low-e-16 argon (90%)-4-16 argon (90%)-4 Low-e 0,6 W/m2K
4 Low-e-18 argon (90%)-4-18 argon (90%)-4 Low-e 0,5 W/m2K
4 Super Low-e-16 argon (90%)-4-16 argon (90%)-4 Super Low-e 0,5 W/m2K
4 Super Low-e-16 krypton (90%)-4-16 krypton (90%)-4 Super Low-e 0,4 W/m2K
Lately, we are able to construct quadruple-layer insulating glasses as well. These glasses can achieve a 0.3 Ug value if they are filled with argon, and even a 0.27 Ug value if we fill them with krypton.
Although, the price of a 4-layered glass is quite high:
The technology of CE Glass is modern enough to produce such quadruple-layer glasses, what is more, even the production of 100mm thick insulating glasses is possible.
The information above clearly shows that gas filling is able to reduce the Ug value by 0.2 – 0.3; consequently the insulating ability of the glass improves. In many cases, this small amount is needed to reach the standard value or the value specified by the designer. Gas filling is realized on modern machines insulating glass production lines at the moment of pressing together the glass unit. Manufacturers providing high-quality –including CE Glass –constantly monitor their machines as well as the adequate amount of gas in insulating glasses. With our declaration of performance, we guarantee that the gas concentration filled in the structure is at least 90% and it conforms to the regulation. The gas concentration may reduce after 20-30 years, yet it causes only a 0.1-0.2 increase in the Ug value.
The better insulating glass we have, the more possibility there is to observe vapor on the exterior surface of the glass in autumn or spring. This a completely ordinary phenomenon. Humidity, airflow and other environmental factors affect the duration and the extent of this phenomenon.
Today, coated glasses are available; by applying them, we can minimize the number of those days when this phenomenon occurs. In order to find the best solution, please contact our colleagues.
There is a standard for determining the U value by calculation and there is a separate standard for the methods of measuring these values.
EN 673 – calculation
EN 674 –measuring
The value we receive by calculation is not necessarily equal to the value we get by measuring. In most cases, measuring does not result in worse values than calculation. As a consequence, the calculation method is more widespread and it is available for everybody (for free).
The measurement is appropriate only if it is carried out in an accredited laboratory. Such laboratories are hard to find in most countries since the requirements are very strict, what is more, the equipment and the technology needed are also very expensive. In Hungary, ÉMI is authorized to carry out such examinations and to issue such certifications. As a result, the examination of a glass unit and the acquisition of this certification is quite costly.
It is interesting that in case of some structures, measurement shows better values than the calculation method does. For instance, CE Glass has a certification that ensures better Ug value in case of the following glasses (based on EN 674):
4-16 argon (90%)-4 Low-e 1,0 W/m2K
4-16 argon (90%)-4 Super Low-e 0,9 W/m2K
Uw (=window), the heat transmission value of doors and windows
The Uw value is influenced by the heat transmission ability of the frame of doors and windows, the so-called the Uf (=frame) value, by the Ug value of the insulating glass, and also by the quality of spacers placed between the glasses. Taking into consideration these factors, we can simply determine the Uw value of insulating glasses of different sizes with the following formula:
We can conclude from the diagram that the psi-value is not only influenced by the quality of the spacer, but is also affected by the number of air gaps and the quality of the frame of doors and windows.
The use of traditional aluminum spacers is still prevalent nowadays, however, the demand for warm edge is increasing. The use of warm edge enables the improvement of the Uw value of the structure by 0.15.
The title warm edge includes all spacers that provide more favorable characteristics than aluminum spacers do. Warm edge spacers include stainless steels (inox), plastic spacers with a steel coat and plastic spacers as well.
The principle is that materials with lower heat conduction ability insulate better. Our informative diagram considering heat conduction values:
For more details, for psi-values and for their effects influencing the Uw value, contact our colleagues.
Besides improving the Uw value, the use of warm edge spacers enables the mitigation of condensation forming along the periphery on the internal glass. As a result, not only does this increase our sense of comfort, but our state of health will be better as well (positive effects can be perceived by people suffering from allergy and asthma).
CE Glass provides a wide range of colors concerning warm edges that can increase the aesthetic value of our glass structures. Please, contact our colleagues for more information about the available warm edges.
The most significant European glass manufacturers have configuration softwares that are available for free. These softwares can be used online, or you can download and install them as well. With these programs, you can model different glass units from different glass types from the given manufacturer’s range of products. Moreover, you can determine parameters concerning energy, light transmission, sound-proof ability and safety rating.
For e.g.:.: https://www.yourglass.com
