Window Energy Ratings Explained

Nowadays, homeowners are looking for every possible way to save money on their home improvement projects. One of the most popular projects that people partake in is replacing their windows with energy efficient windows. Everyone wants the highest window energy ratings

window energy ratings

How do you know if the windows you have or the windows you’re getting have good energy ratings? There’s much to know about what makes a window energy efficient and it’s important to learn so you don’t get a product that isn’t rated well.

We’ll go over everything you need to know about window energy ratings so you can get the best replacement windows for your home.

What Labels to Look For on Your Windows

Before you can even consider any windows as energy efficient, you need to make sure they have the proper labels on them. Anyone can say their windows are amazing and will save you money, but none of that matters if they don’t have the appropriate labels.

The first, and probably the most important, label you need to look for is the Energy Star seal. The Energy Star label will specify which climate zones the windows are certified for.

This is especially important for Midwest homeowners because the climate changes and experiences many extremes throughout the year. If you have windows that aren’t certified for where you live, they’ll become damaged and broken very quickly.

The next label you need to look for is the National Fenestration Rating Council or NFRC for short. The NFRC is a non-profit organization recognized by the window and door industry that reports energy efficiency stats for products that’ll help you decide which ones are more efficient. You’ll learn more about those later.

It’s important that your replacement windows have both labels so you know you’re getting the best possible product. When you choose Feldco, you have the assurance of knowing that our windows have all the proper characteristics of energy efficiency.

What are Window Energy Ratings?


There are many factors that go into window energy ratings and all of them are equally important. U-factor, solar heat gain coefficient, visible transmittance and air leakage are the four main categories that contribute to window energy ratings.

We’ll go over what each factor means and why they’re important to look for on your replacement windows.


U-factor refers to the window’s ability to keep heat from escaping from the inside a room. It’s measured in a range from 0.20-1.20 and the lower the number, the better the window is at keeping heat inside your home.

Having a low u-factor is extremely important for homeowners in the Midwest. Winters get brutally cold and you need your windows to be able to keep the heat inside. It’ll help you save money on your heating bills as well.

Solar Heat Gain Coefficient

Solar heat gain coefficient, or SHGC, is the measure of how well your windows can keep heat from entering your home. The SHGC is measured on a scale of 0-1 and the lower the number, the better your windows can keep heat out.

It’s important to make sure your windows have a low SHGC because it’ll help you save money in the summer. If your windows are very effective at keeping heat out, then you won’t have to crank the air conditioner as much to keep your home comfortable.

Visible Transmittance

Visible transmittance is measured by how much natural light is let into your home through your windows. This is one of the most important window energy ratings to consider because it can help you lower your electric bill by not relying so heavily on artificial light.

Rated on a scale of 0-1, the higher the number, the more natural light your windows will let in. Since window and glass technology has increased, a higher amount of light let in does not mean that the room will get hotter as well.

Window glass has evolved to be able to let sunlight in, but block out the rays that cause heat gain. You can rely less on having to turn the lights on during the day with windows that feature a high visible transmittance.

Air Leakage

One of the biggest problems homeowners face with their windows is that they become drafty. Drafty windows will cause you to lose money because the outside air is entering your home and forcing you to put more stress on your furnace and air conditioner.

When deciding to replace your windows, look for a low number in terms of air leakage. In order for a window to become Energy Star Certified, it must have an air leakage value lower than .30.

This number indicates how much air will enter a room through the windows.

In compliance with a low air leakage rating, your windows must be professionally installed to ensure that there are no cracks or leaks between the frames and sashes.

The Best Window Energy Ratings are Found at Feldco

replacement window energy ratings

If you’re looking for window replacement in the Midwest, your search has ended with Feldco. All Feldco products are Energy Star Certified and designed to withstand the unpredictability of every season.

We pair our outstanding window energy ratings with excellent service to make the entire replacement process as easy and smooth as possible. With over 500,000 homeowners served, it’s no wonder why we’re named America’s #1 window and door company.

If you want your home to be energy efficient and look great, Feldco has you covered. Our vinyl windows come in many different styles and colors including wood grain finishes. Our windows are custom made to fit your existing openings to ensure a secure and proper fit.

Get started today on your window replacement project with a free quote online.

Share this article:


Get started with

*View our privacy policy

Or call us at 1-866-4FELDCO®
or visit one of our locations.


Is Window Trim Necessary?

Is Window Trim Necessary?

What Is Window Trim and Why Is It Necessary? Window ...
exterior window shutters

Painting Vinyl Shutters

Painting Vinyl Shutters: Expert Tips and Techniques Updating the appearance ...
Protecting your roof

5 Steps to Protect Your Roof on July 4th

5 Steps to Protect Your Roof on July 4th In ...
entry door sidelights

Painting Doors vs. Staining Doors

Should You Stain or Paint Your New Front Door? Deciding ...
how to fix a bent gutter

How to Fix a Bent Gutter

How to Fix a Bent Gutter: A Step-by-Step Guide Understanding ...

Book Today and Save!

Over 500,000 homeowners have trusted Feldco with their windows, siding and doors. Click the button below and we’ll get started on your quote!