When buying new windows, here are some things to think about:
Window glazing material
Technology is increasing, even for windows, and it may be confusing if you don't know what's going on. See if the window is performance certified with an NFRC label or an Energy Star label.
The U-value of a window refers to its insulation properties, the lower the number the more insulated it is. Low-E glass, used to lower this U-value, is glass coated with an extremely thin layer of metal or metallic oxide. You can't see this layer since it appears transparent, but it blocks radiant heat flow by preventing heat from being transferred from one pane of glass to the other in a double-pane window.
Depending on your climate, you'll need a different window technology to allow the best possible energy conservation. For example, if you live in a cold climate, get a U-value of 0.35 or lower. This window will have double glazing and low-solar-gain low-e coating.
Actual window measurements
Older houses don't always have standard-sized windows and should be measured by the contractor before you order. If your windows aren't standard, you can sometimes get a custom size.
Window air leakage rates
A good window will have a leakage rate of 0.3 cubic feet per minute or less.
Window company reputation
You should be able to obtain references from the company or contractor you'll be buying from. It always helps to get an unbiased opinion, so make sure you actually contact the references you're given.
Look at several companies before you make your choice and make sure you understand the contract.
When someone is installing windows in your house, they should also have proper insurance.
Vinyl and aluminum window frames are low-maintenance, but something else may be more to your taste, so be informed concerning your options.
We had recently moved to this area and didn't have the ‘built in network’ of friends and family to suggest a good contractor. Knowing you pre-screen the contractors you work with took a lot of pressure off the entire hiring process.