Frequently Asked Questions

Almost all glass produced in developed countries is created using the “float process”. The glass composition materials, mainly silica sand, soda ash and limestone, are melted in a furnace and then flowed on to a bath of molten tin. The glass is formed and gradually cools as it moves from the tin bath to an annealing lehr, which is a controlled cooling chamber. This annealed glass moves through a process in the form of a continuous ribbon, which is cut to size and packaged at the final stage.

Annealed glass can be further fabricated in many ways. Coatings of various types can be applied to achieve many visual effects and affect the optical properties. In addition, the glass can be heat-treated to increase its strength and give it safety glazing properties. Glass can be put into an insulating glass unit, meaning two or more pieces of glass are separated by a dry air space to improve the insulating properties.

Float glass, also called annealed glass, is the most common type of glass. Float glass can be clear or tinted.

Proper window design in the south must account for solar heat gain in order to help reduce air conditioning. Therefore, glass products should have a low solar heat gain coefficient or low shading coefficient. The U-value, or insulating performance, is of lesser importance. Solarban^® solar control low-e window glasses by Vitro glass are ideal for these warmer climates.

No. Low-e coated glass can work in all climates. Low-e coatings reduce heat loss from the interior through windows, thus reducing the energy used to heat buildings and associated heating costs. Low-e coatings also offer solar control that reduces heat gain due to both the transmitted solar energy and conducted heat caused by indoor – outdoor temperature difference. This reduces cooling loads and consequently, the energy and costs associates with cooling the building.

It's a matter of where the most heat is coming from: in summer it is outside, and in winter it is inside. Low-e glass by Vitro glass keeps the heat where it is needed. In the winter, low-e glass by Vitro glass keeps more heat inside by reducing the amount escaping though the glass and helping to lower heating bills. Some heat (long-wave infrared) is not permitted to enter or exit the home, but this is outweighed by the benefits of the amount of extra heat kept inside (much less heat escapes). Some short-wave infrared is still allowed to enter the home and is converted into long-wave heat. In the summer, low-e glass by Vitro glass reduces the amount of direct heat that enters through the glass, thus reducing the solar heat gain and helping to reduce cooling costs.

Sungate^® low-e coatings work 24 hours a day. In the winter, they reflect the heat (long-wave infrared energy) back into the interior, both day and night. Low-e coatings do not differentiate between furnace heat and heat created by solar energy, as they are both absorbed and re-radiated back to the source side.

First, heat is transferred in three ways: Conduction, convection and radiation. Sungate^® and Solarban^® coatings directly affect only the radiated component of the heat transfer. The coatings incorporate an extremely thin metallic layer that reflects the radiated energy (heat), similar to the way a mirror reflects light.

Many factors need to be considered, some of which include the glass and low-e coating, available solar energy and angle of incidence (season of the year, latitude). Environmental factors such as temperature, relative humidity, potential contaminants and the specific plant type also need to be considered. A horticultural specialist is best suited to address specific issues and plants.

A number of factors may affect the time it takes to recover the up-front purchase cost of low-e glass windows from savings in heating and cooling fuel bills. The cost difference between clear glass windows and the upgrade should be considered. Several payback factors to consider include:

• The quality of installation of the window
• The quality of workmanship of the window
• How warm or cold the seasons are compared to usual, especially winter
• Whether windows are kept open in the winter
• The amount of shading from large trees or blinds
• Geographic location

There is a slight difference in appearance, but this difference is extremely difficult to see between windows in different parts of a home. However, if a pane of low-e glass is installed directly next to a pane of clear glass, there will most likely be a slight difference in appearance.

Initially the homeowner may be aware of a slight reduction in the intensity of light coming into their homes compared to the old windows. When sunlight is coming directly through windows in which clear glass has been replaced with low-e glass, most people say that the low-e is more comfortable because they feel less heat and glare from the sun. An insulating glass unit with Solarban^® 60 solar control low-e glass transmits about 13 percent less visible light than an insulating unit with all uncoated clear glass, and about 48 percent less total solar energy.

Low-e glass by Vitro glass can improve window performance for all exposures all year round. For example:

• In the winter, while low-e glass by Vitro glass retains heat no matter which direction the window is facing, it can be especially useful on north-facing windows because they resist heat loss.
• Vitro low-e glass is useful for east, west, and south facing windows because it helps reduce solar energy transmission.
• Low-e glass by Vitro glass helps prevent heat from escaping regardless of exposure, even at nighttime, helping to reduce heating costs.

Since all Vitro Architectural Glass (formerly PPG glass) Magnetron Sputter Vacuum Deposition (MSVD) low-e coatings must be sealed within an insulating glass unit, no maintenance is required. If Sungate^® 400 low-e glass is used in a single glazing application, or as a storm window, then normal cleaning with a mixture of 50% water and 50% isopropyl alcohol is recommended.

No. For windows that use low-e glass by Vitro glass, the low-e coating is glazed inside a sealed insulating glass unit and is not exposed to the atmosphere. The indoor and outdoor surfaces of the insulating glass in the windows are plain uncoated glass surfaces, and will clean like normal glass.

Argon gas that is inside insulating glass units is not dangerous. Argon gas is an inert gas and it exists in small quantities in the atmosphere around us. It is not toxic nor is it poisonous to humans.

Krypton gas is also a noble gas. Similar to argon gas, krypton gas is three times heavier and provides superior thermal efficiency.

Short-wave infrared energy comes directly from the sun but is not felt as heat. It converts into heat when it strikes something. Long-wave infrared is the heat re-radiated from an object which has received short-wave radiation. Examples include a hot automobile dashboard, or a hot sidewalk or roadway where you can often see heat re-radiating from the surface.

No. Any heat source such as a furnace or engine, that consumes and combusts fossil fuel, releases long-wave energy. Any object, like a sidewalk, road or windowsill, which has been exposed to short-wave solar radiation, will also emit long-wave infrared energy.

The sun’s energy, or solar energy, includes ultraviolet, visible and infrared energy. Ultraviolet light, or UV, is short-wavelength energy with wavelengths from 290 to 380 nanometers. It is invisible and accounts for approximately 3% of the solar energy that reaches the earth. A 1” insulating glass unit with Solarban^® 60 solar control low-e glass allows only about 14% of the UV that reaches the earth’s surface to pass through the insulating glass unit.