What is U-Value for Windows?

One of the most irritating parts of a home improvement project is listening to a contractor using industry buzzwords and jargon to “explain” how something works without actually educating you. They may know what they’re talking about, but if you don’t, they’ll bank on being able to upsell you as long as you trust that all those fancy words mean something good for your home. And in the world of replacement windows, there are plenty of terms installers use that will confuse most homeowners.

One such term that is especially important for Arizona homeowners to know is U-value (also called U-factor). Maybe you’ve seen it before if you’ve previously had any windows replaced, but you just glanced at it on the product sheet and promptly forgot about it. We’re not here to judge! But we are here to educate you so you can get the best windows for your home the next time you need to have replacements installed.

What the Term ‘U-Value’ Means

Warm air has a natural tendency to move into cooler areas in order to balance out the temperature between spaces. In warmer months, it wants to get inside your home where it’s nice and cool. In colder months, when you’re heating your home, the warm air wants to escape. This is called heat transfer (or thermal transfer. The main goal of window insulation is to reduce heat transfer, and U-value is simply a calculation that tells you how successful a window will be based on its glass’ insulation.

What Is a Good U-Value?

U-values typically range from 0.1 to 1, but while a window’s number can be lower or higher, we’ll stay within this range for educational purposes. The lower the U-value, the better a window will be at preventing heat loss—and a U-value of 0.1 indicates that a window is exceptionally good at that. Conversely, a U-value closer to or greater than 1 tells us that a window is not good at preventing heat loss, and if you’re going to install a window with such a high U-value at your home, your best move is to put it in an area that rarely (if ever) gets direct sunlight.

Not all areas of the United States get as much sunlight as we do in Tucson, AZ, so there is a much greater need for low U-values in our homes’ windows than in a cloudier, grayer climate.

What Can Affect a Window’s U-Value?

The U-value of any window is determined by the glass. If it’s a multi-pane glazing package with inert gas fills, low-e coatings that protect against UV rays, and warm-edge spacers inside, that is a good window to have in an area of your home that gets a lot of sunlight throughout the day.

On that note, you’ll likely see something called SHGC associated with the U-value. This is short for Solar Heat Gain Coefficient, which measures how much solar heat comes through a window and can be affected by the direction in which the window will face when installed. It is ideal to have a low SHGC number, which ranges in value from 0 to 1, along with a low U-value.

Get Energy-Efficient Windows for Your Home

Looking for high-performing replacement windows with U-values ideal for the Tucson, AZ climate? Open Enclose has you covered. Contact us today to schedule a consultation and learn more about our well-insulated replacement windows.