Window frames made from vinyl instead of wood or aluminum are increasingly popular for use in both new homes and as window replacements. They are easily available and can be custom-ordered because most manufacturers of vinyl windows are regional. Also, ordering windows to custom fit the window space you already have makes the work and expense of replacing windows much less. The advantages to vinyl windows are, they're generally less expensive than other kinds of windows, they're virtually maintenance-free, they can be custom-made easily, vinyl windows are energy-efficient, they come in many styles and sizes, and often don't need to be pained.
If you're feeling drafts, excessive condensation, excessive frost, appearances of aging (cracks, or weather damage), or you are having trouble fully closing the window, it may be time to replace it. Look for the government's EnergyStar label. These windows are, on average, twice as efficient as windows manufactured a decade ago and can reduce your utility bills by as much as 15%. The Office of Energy Efficiency and Renewable Energy recommends these certifications on vinyl windows to help ensure that both the glass and the vinyl are of good quality manufacturing.
-Look for the National Fenestration Rating Council (NFRC) label; it means the window's performance is certified.
-Remember, the lower the U-value (a measure of heat flow), the sport ter the insulation. In colder climates, a U-value of 0.35 or below is recommended. These windows have at least double glazing and low-e coating.