There are many choices for energy efficient windows. It depends on where you live. If you live in a very cold climate region you may want to get triple-pane windows. For mild climate region, I think double-pane windows are sufficient.
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Wood and fiberglass frames have great insulating properties. Vinyl frame insulating property is good but not as good as wood and fiberglass. Aluminum conducts heat unless it’s thermally broken (insulating layer between inner and outer frames). Wood is the most expensive, vinyl is the least expensive, and the price of fiberglass is in between.
Vinyl windows are more affordable. Avoid vinyl frame windows if you have extreme heat southern exposure. (If you choose, you can use vinyl on other sides of the house. Install fiberglass on the south side of the house. They look similar but insulating property is different). Vinyl tends to warp when exposes to high heat. It warps when outdoor temperature is about 100 degree F in California.
Ask for low-E argon filled double-pane or triple-pane widows, since some window products do not include low-E or argon gas.
For winter and summer comfort is a little tricky, I would suggest
SHGC from 0.25 to 0.37, U-factor of 0.28 to 0.32. For more details
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