When choosing new windows and doors, the coloring and overall aesthetics are important, but the feature to pay attention to the most is the Energy Star rating.

Your windows are the gatekeepers between your home and the outside climate. The rating you choose makes a big difference to temperatures, insulation, and even humidity levels inside the home.

In this article, we’ll provide a simple overview of window insulation ratings to help with understanding U-factor windows, SHGC vs U-factor, and how to choose the best windows for your climate.

Every window and door has an energy rating in line with the new Energy Star standards 2025 (developed by the US Department of Energy).

You’ll typically come across the terms U-factor, SGHC (solar heat gain coefficient), and R-value, followed by a number or letter that determines the rating.

Or you’ll see the terms Energy Star® Rated Windows, or Low E glazing, which means the windows are exceptionally energy efficient.

In summary, the window insulation ratings mean:

• U factor: Measures how well a window insulates (i.e., how well it keeps heat in and cold out). The lower the U-factor number, the better the window’s insulation.
• SGHC: Indicates how much solar heat passes through a window (i.e., how warm a room gets with the sun coming through). The lower the number, the less heat from the sun comes through.
• R-Value: Mostly used to describe door energy ratings and measures how well it insulates. The higher the number, the better the insulation.

A good U-factor for a window is around 0.25 and 0.30 for residential homes. However, it depends on the climate you live in.
Choosing a low U-factor is generally considered good, but in some climates, you may be better off focusing on the SHGC rating instead of the U-factor rating.

Both the U-factor vs SHGC are important when choosing new windows.

Since the U-factor determines how insulated the windows are, while the SHGC determines how well the windows deflect heat rays, you have to consider the climate you live in and the direction your windows face.

In some regions, focusing on insulating the windows is more important than keeping out the sun’s rays. In other areas, the SHGC rating may only be important in rooms with long periods of direct sunlight.

Review the guide below (provided by the US Department of Energy) for a better understanding of U-factor vs SHGC for your home:

R-values on windows typically range between 1 and 5, with some higher values available. The higher the R-value, the more thermal resistance there is (meaning the windows are more insulated).

But that doesn’t mean the highest R-value (around 5-6) is always the best choice for residential homes. A rating between 2-3 can be just as good at insulating a home.

As a guide to R values, the ratings can refer to:

Up to and around 1: Typically means single-glazed windows
Between 2-3: Typically refers to double-glazed windows, Energy Star® Rated Windows, or Low E glazing
Around 5-6, and over: Usually refers to triple-glazed windows, Energy Star® Rated Windows, or Low E glazing

When comparing R-value doors vs windows, exterior doors are generally good when the R-value is 3-5, or higher. The less glass in the door, the better the R-value is likely to be.

When deciding on your new windows, it’s important to consider three main things: the local climate, your municipality requirements, and your preferred style or colorings. Here’s more detail to help you decide.

Climate considerations

While a lower U-factor and SHGC are considered good, the most energy-efficient windows for your home depends on your climate. For example, the best windows for a cold climate, like Chicago, would be a low U-factor to ensure maximum insulation.

Here’s a guide on the best window rating for your climate (source: Department of US Energy):

• Northern: U-factor between 0.30-0.32 and SHGC between 0.35-0.40
• North-Central: U-factor of 0.32 and SHGC of 0.40
• South-Central: U-factor of 0.35 and SHGC of 0.30
• Southern: U-factor of 0.60 and SHGC of 0.27

Municipality requirements

It’s also important to pay attention to your local municipality’s requirements when installing new windows and doors.

For new homes and renovations, homeowners and developers often have to adhere to certain standards. For example, in Chicago, the U-factor is the most important for Energy Star or local village requirements.

Make sure to check with your municipality or speak to a local window professional for advice on adhering to the right standards.

Aesthetics/coloring
Windows and doors come in various styles and window materials (like aluminum, wood, vinyl, fiberglass, etc.). Our collections include single-hung, double-hung, casement, slider, awning, and special shape windows.

Provided you adhere to your local village requirements, it’s always important to choose a color and design that suits your décor as a priority.

What are the Best Windows For Cold Climates?

The best windows for cold climates are those that prioritize energy efficiency and insulation, particularly if the area receives little sunlight. Try to choose a window with a low U-factor rating, or Energy Star® Rated Windows and Low E glazing.

What are the Most Energy Efficient Windows For Chicago or Illinois?

The most energy-efficient windows for Chicago are Energy Star® Rated Windows, or Low E glazing types. These ensure that heat loss is minimized in cold weather (potentially helping to reduce energy bills) and prevents cold air from seeping inside the home.

Are you considering upgrading the windows and doors in your home? Our team of experts is here to make the process as easy as possible.

Find your new dream windows today using our walkthrough (choosing the style, color, and Energy Star rating that suits your home best), and get a price for your new windows.

Or get in touch with our team of professionals for help and advice on choosing the right windows for you.