Low e coating which surface

The reverse happens during the summer. To use a simple analogy, low-e glass works the same way as a thermos. A thermos has a silver lining, which reflects the temperature of the drink it contains. The temperature is maintained because of the constant reflection that occurs, as well as the insulating benefits that the air space provides between the inner and outer shells of the thermos, similar to an insulating glass unit.

Since low-e glass is comprised of extremely thin layers of silver or other low emissivity materials, the same theory applies. The silver low-e coating reflects the interior temperatures back inside, keeping the room warm or cold. There are actually two different types of low-e coatings: passive low-e coatings and solar control low-e coatings.

Solar control low-e coatings are designed to limit the amount of solar heat that passes into a home or building for the purpose of keeping buildings cooler and reducing energy consumption related to air conditioning.

Finally, the glass is cut into stock sheets of various sizes for shipment to fabricators. Because of the historic evolution of these coating technologies, passive low-e coatings are sometimes associated with the pyrolytic process and solar control low-e coatings with MSVD, however, this is no longer entirely accurate. General advice is that the preferred location of the coating is on surface 2 of the unit, but if the glass types used in the unit make it difficult to assemble the unit than surface 3 can be selected.

There is no loss of insulation performance by using it on surface 3 however SHGC performances will vary. Since the coating is covalently bonded to the glass, pyrolytic low-E is extremely durable and can be handled, transported and stored just like clear glass.

Furthermore, pyrolytic low-E is suitable for monolithic use, making it a cost effective replacement for single-lite glazing. In addition, the passive solar properties of hard-coat low-E, as noted in the solar heat gain coefficient SHGC rating, allow enough solar energy to enter during the winter months to noticeably reduce heating costs.

Despite its merits, pyrolytic low-E is chiefly a niche product. Although the energy savings and performance benefits of low emissivity coatings have been known for years, acceptance on a global scale remains limited, with low-E accounting for just 11 percent of worldwide flat glass consumption in Market penetration in regions outside North America and western Europe has been particularly slow.

In the reverse, a 3 coating will be best at preventing internally radiated heat from being absorbed by the window and emitted outwards, and so is best in cold climates.

In cold climates, high SHGC values should be chosen with care, and potentially with further analysis of individual window orientations or external shading.

If a high SHGC window is in a position where eaves are not large enough to shade the summer sun, then what is a welcome source of heat in the winter can quickly become an inescapable heat load in summer.

Using two low-e coatings in a double-glazed assembly is generally unnecessary, unless very high performance is desired. A standard low-e coating might have an emissivity rating of about 0.

Adding another coating could take this to about An exception to this is where a very low SHGC coating could be applied to surface 2 in addition to a purely thermal coating on surface 3 to create a very high-performance unit for hot climates.

For triple-glazed units, two low-e coatings are the standard, as these reduce radiative heat transfer through both insulation cavities and hence optimise the assemblies total U-value. Using additional coatings suffers the same kind of performance cost-trade off that was discussed for the double-glazed unit.

The position of the standard two coatings can vary, where 2 and 4 might be used for hot climates and 3 and 5 for cold. A good all-round approach is to coat surface 2 and 5 as this way the emission through the assembly is kept low from either direction.

Another consideration is the visible light transmittance or VLT value. This is the percentage of the visible spectrum that the window transmits through it.

Lower VLT values might mean a slight discolouration or dimming of light through it, but this is a lot less noticeable if the same VLT value coatings are chosen for all the windows in any single room or house, so as to prevent direct comparison.

The final parameter worth mentioning that might play a role in choosing a low-e coating is the manufactured type of coating. The two main choices here are hard and soft coatings.

Hard coatings are applied to the glass either early on in the manufacturing process while the glass is still hot so that the coating gets welded to the surface or via chemical vapour deposition CVD , where a catalyst is used to generate a tough, bonded metallic film.

These coatings are resistant to handling but tend to have lower VLT values and do not perform as well as the soft coat. Soft low-e coatings are generally applied after a glass pane has been fully hardened. Here, a sputtering process is used whereby under a vacuum metal is evaporated and deposited directly onto the pane.