While basic LowE glass is standard and in many cases REQUIRED in California Residential Window Replacement these days, there are Many different variations and upgrade options. All are going to give you an energy savings, but it's up to you to determine which one is right for your home, and your budget.
The first thing to keep in mind is the energy efficiency of the walls supporting and surrounding the window to be replaced, as it would not be cost effective to put in the highest grade of LowE and Argon currently available, if you have low quality or lack of insulation as is often found in many older homes.
Over the Years, as technology has improved, the cost of these varied options has come down, and the efficiency and durability has increased. As an example, Dual pane windows of the highest quality even just 25 years ago are now considered lacking in energy efficiency by today's standards, and those installed with the early wave of Dual pane technology are often not up to minimum efficiency standards currently REQUIRED for replacement in rental residences.
Window Glass has evolved ::: Single Pane -> 1/2" Dual Pane -> 7/8" Dual Pane -> Triple Pane ...... ???
The materials to make the frame have evolved ::: Simple Wood --> steel --> Aluminum --> Vinyl --> Fiberglass --> ???
and the additives have evolved ::: Clear float (no additives) --> Low E Coating --> Gas FIll --> ???
A home with original construction in the 50's would most likely be single pane float glass in wood with no additives - and little to no wall or ceiling insulation.
while an average home built in the late 90's would most likely be 7/8" Dual pane, Vinyl frame and LowE2 additive, with significant wall AND ceiling insulation.
Low-E Glass
Low-emissive (Low-E) glass is window glass that has been treated with an invisible metal or metallic oxide coating, creating a surface that reflects heat, while allowing light to pass through. Windows treated with Low-E coatings are proven to reduce energy consumption, decrease fading of fabrics, such as window treatments, and increase overall comfort in your home.
How Low-E Glass Works
The heat that passes through your window glass is measured by the U-factor or ultraviolet light. The lower the U-factor the more energy-efficient your glass is. This type of light is produced by the sun and generates heat in your home. Too much of this heat, especially during summer, can cause your air conditioning bill to go up in an effort to keep your house cool. Low-E glass reduces the amount of ultraviolet light that enters your home, without blocking visible light.
Conversely, in winter, Low-E glass reduces the amount of heat lost through your windows from the inside of your home, keeping heating costs down. Depending on your home's heating and cooling needs, various types of Low-E glass have been developed to allow for high, medium or low solar gain.
Benefits of Argon Gas Windows
Argon is the gas most often used between panes in a double- or triple-glazed window. The gas is colorless and odorless, says Bill Lingnell, head of Lingnell Consulting Services in Rockwall, Texas, an independent consultant who works with the Insulating Glass Manufacturers Alliance (IGMA). Argon is denser than the atmosphere, providing more thermal efficiency than having air between the panes, he explains.
Other Types of Gases
Krypton gas is denser than argon, and xenon gas is denser than krypton, providing somewhat more thermal efficiency. Some manufacturers also may offer a mixture of two gases. But the incremental benefit of these higher densities doesn’t necessarily justify their prices, says Carroll Bogard, manager of Trade Segment Marketing for Pella Windows in Pella, Iowa. “Dollar for dollar, argon gas does the best job,” he says.
What Do Filled Windows Offer?
Added energy efficiency is the key benefit to having gas-filled windows, Bogard says. The gas acts as an insulator, working in both summer and winter to keep interiors protected from outside temperatures. Typically, gas infusion is provided in conjunction with applying a low-emissivity (low-E) coating film to the glass panes, he notes.
The other key advantage is making people’s homes more comfortable, Bogard says. The low-E coating and gas keep the interior pane of glass closer to the temperatures of the interior air, minimizing air currents that are created when different temperatures come into contact. This reduces drafts and cold spots. He stresses that proper installation is absolutely essential, and contractors should be trained in proper installation techniques and/or use experienced installers.
Is the Gas Harmful if It Leaks?
No. The gases are inert (nonreactive) and occur naturally in the Earth’s atmosphere. Argon, the most common, comprises about 2 percent of the air we breathe, Lingnell says. “It can’t hurt you or make you ill if it leaks,” he says. - See more at: http://www.lowesforpros.com/Construction-and-Contractors/The-FAQs-on-Gas-Filled-Windows#sthash.hemdUWGK.dpuf