Choosing a window is three separate decisions that get sold to you as one: the frame material, the glazing inside it, and the style of opening. This section separates them, because they trade off against different things and you can change one without changing the others.
A sales appointment tends to present one product and one price. Underneath that there are three independent choices, and knowing they are independent is what lets you move a quote without simply accepting or rejecting it whole.
The three decisions
The frame material is what the window is built from. It sets most of the price, the maintenance you will be doing, and how the window looks from the street.
The glazing is the glass package inside the frame: how many panes, what is in the gap between them, and what coatings are on the surfaces. This is what the performance ratings describe, and it can usually be specified up or down independently of the frame.
The style is how the window opens, or whether it opens at all. This is partly taste and partly constrained: egress requirements, what the opening will physically take, and whether the window is over a sink, a walkway or a driveway.
How to read a performance label
Windows sold in the US carry a rating label from the National Fenestration Rating Council, and ENERGY STAR requirements vary by climate zone. Two numbers do most of the work on it:
- U-factor describes how much heat passes through the whole assembly. Lower is less heat transfer.
- Solar heat gain coefficient (SHGC) describes how much of the sun's heat gets in. Which direction you want this to go depends on your climate, which is why there is no single best number.
The rating bodies publish the criteria themselves, and both are linked from the sources on our home page. Where the pages below quote a specific threshold, it is cited to one of them with the date it was checked.
What this section covers
The pages underneath compare specific materials, glazing packages and styles against each other. Where a comparison involves a price, the figure is sourced and dated, and the fuller cost picture lives in What It Costs.
Common questions
Which frame material is best?
There isn't one, which is why the pages below compare them on separate axes - up-front cost, expected service life, upkeep, and appearance - rather than ranking them. The right answer changes with your budget, your climate and how long you intend to own the house.
Do I have to keep the same style of window I have now?
Not necessarily, but the opening, the structure around it and your local code all constrain it, and bedrooms have egress requirements. That is a question for whoever measures the opening.
Do you recommend particular brands?
No. This site publishes no reviews, ratings or star scores of its own, because we have not inspected anyone's work or tested any product. Where a brand has a page here, it is because people search for it by name.