Low Emissivity (Low-E) Glass
This is something to definitely look for when you choosing your window contractor. Some manufacturing companies use cheaper materials to save money on glass coating supplies. In the picture below, you can see vinyl windows installed as retrofit with aluminum capping at the perimeter. Even though the installation was performed correctly and the window will not leak, its low emissivity layer is already peeling off. With a trained eye, you can spot this issue.
Now, imagine this happening to your windows just three-to-five years after installation. It’s a very unpleasant experience—this will definitely reduce the value of your home. Unfortunately, customers with this type of problem will not be able to claim it through warranty or insurance. For most of Canada, low-e glass is now a standard practice for all new development and window replacement projects. It became available at a lower price due to technological progress; nearly all homeowners can afford low-e glass upgrades to their home windows.
Ivory windows provide 25 years all inclusive warranty to protect you from Sealed unit or Low E layer failure.
A low-e coating is an almost-invisible layer of metal that is applied to one side of the glass by the glass manufacturer. The effect of a low-e coating is to lower the U-factor of the glazing and lower energy bills Low-e coatings don't just reflect heat in one direction; they work in both directions. Since the addition of a low-emissivity coating adjacent to an air space has the effect of lowering the U-factor (that is, raising the R-value) of the air space, a low-e coating helps slow heat transfer from the interior to the exterior during the winter, and also helps slow heat transfer from the exterior to the interior during the summer. Knowing that a window has low-e glazing tells you almost nothing about its solar heat-gain coefficient (SHGC). A low-e window might have a low SHGC, making it a good choice for a house in Florida, or a high SHGC, making it a good choice for a house in Minnesota. Just because a window is low-e, doesn’t mean it’s good at reducing solar gain. If you live in a sunny climate, low solar-gain double glazing makes sense. Popular options include:
LoĒ²-272 from Cardinal
ClimaGuard 55/27 from Guardian
Solarban R100 from PPG
If you want to buy a high-SHGC window, you'll need to do some research before placing your order. Many window reps are ignorant about glazing options, so be prepared to educate the sales staff (or go over their heads) to get what you want.Several glass manufacturers make high-SHGC double glazing. Good bets include:
LOE Energy Advantage from Pilkington
LoE-180 from Cardinal
Sungate[IS1] 500 from PPG
ClimaGuard 75/68 from Guardian
Low-E 180 With a glass U-Factor of just 0.26 and an SHGC of 0.69, Low-E 180 Glass is an excellent basic product for passive solar applications. By blocking heat loss to the outside of the glass, the high solar gain glass keeps homes warm in winter and cool in summer. Low-E 272 Glass delivers year-round comfort, reflecting an intermediate level of heat back into the room in winter and rejecting the sun’s heat and UV rays in summer. This product’s patented coating provides clarity and high-performance, low-solar control, reducing window heat gain by 50% compared to ordinary glass. Low-E 366 Is the ultimate performance glass. Low-E 366 provides the highest levels of year-round comfort and the greatest energy savings. Its patented coating offers an ideal balance of solar control and high visibility. Blocking up to 95% of the sun’s damaging rays, Low-E 366 glass sets a new standard in energy performance. Most low-e windows have double-pane IGU’s with a low-e coating on one side of one pane. In almost all cases, the low-e coating faces the air space between the panes, so that the coating is protected from abuse. (It should be noted, however, that hard-coat or pyrolytic low-e coatings are tough enough to be used on single-pane storm windows.) Low-e triple glazing can have either one or two low-e coatings. (If a triple-glazed IGU has two low-e coatings, it's sometimes referred to as “double-low-e” glass.) It's also possible to order triple glazing without any low-e coatings. Such windows may allow more solar heat gain on sunny days, but they will lose more heat at night than a triple-glazed window with a low-e coating. In you are in a hot climate, you probably want a double-glazed low-solar-gain window. Look for these specs:
A whole-window SHGC of 0.25 or lower. Lower is better than higher.
A center-of-glass SHGC of 0.20 to 0.27. Lower is better than higher.
A whole-window U-factor of 0.30 or less. Lower is better than higher.
A center-of-glass U-factor of 0.24 or 0.25. Lower is better than higher.
If you are in a cold climate, you probably want a double or triple-glazed high solar-gain window. If you settle for a double-glazed window, look for these specs:
A whole-window SHGC of 0.42 to 0.55. Higher is better than lower.
A center-of-glass SHGC of 0.59 to 0.76. Higher is better than lower.
A whole-window U-factor of 0.30 to 0.39. Lower is better than higher.
A center-of-glass U-factor of 0.27 to 0.29. Lower is better than higher
If you can spring for a triple-glazed window, look for these specs:
A whole-window SHGC of 0.33 to 0.47. Higher is better than lower
A center-of-glass SHGC of 0.50 to 0.63. Higher is better than lower
A whole-window U-factor of 0.19 to 0.26. Lower is better than higher
A center-of-glass U-factor of 0.16 to 0.22. Lower is better than higher
Read more: http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-glazing-options#ixzz4c4hzmkNE Argon and Krypton Gas Filling the space between the panes of an IGU with argon gas instead of air improves the performance of the glazing by lowering the unit's U-factor. Most low-e glazing units are filled with argon gas. The optimal thickness of the space between panes of argon-filled glazing units is 1/2 inch. Increasing or decreasing the thickness of this space degrades performance. For krypton, the optimal space is thinner — only 3/8 inch — so krypton—a much more expensive gas than argon—is usually reserved for applications where the total glazing unit thickness must be minimized. Don't be tempted to buy glazing without argon or krypton gas. Like a low-e coating, argon gas is a cost-effective upgrade. In almost any location in Canada, argon gas and low-e coatings will quickly yield energy savings, exceeding their cost. These will pay for themselves. Visible Transmittance Although I’ve focused my attention on glazing U-factor and SHGC, there’s another number that matters: visible transmittance, or VT.
A high VT is better than a low VT, unless there is reason to believe that glare will be a problem
Windows with a low VT are less likely to cause glare than windows with a high VT
Every time you add another layer of glazing to a window, the VT goes down.
When the VT drops below 0.40, everything seen through the window begins to look a little grey.