When you invest in replacement windows, you expect them to be energy efficient and protect your home from the elements. That protection includes shielding your home from the sun’s harmful rays. To understand how well your windows perform, it’s essential to know about a window’s solar heat gain coefficient.

So, what exactly is solar heat gain coefficient, often called SHGC? If you’ve never heard of it, you might assume it’s not all that important. In reality, SHGC directly affects your home’s temperature, comfort, and even the condition of your furniture and flooring.

We’ll cover everything you need to know about SHGC—what it is, why it matters, and how it impacts your home. That way, when it’s time for replacement windows, you’ll know exactly what to look for.

What is Solar Heat Gain Coefficient?

Simply put, solar heat gain coefficient is the industry term for the amount of solar radiation admitted through a window. In other words, it measures how much of the sun’s heat and ultraviolet (UV) rays pass through the glass.

A lower SHGC means fewer UV rays enter your home. This doesn’t mean you’re blocking out natural light—it means you’re reducing unwanted heat and protecting your home’s interior from sun damage. High SHGC windows, on the other hand, let in more heat, which can fade flooring, discolor walls, and wear down furniture over time.

How Do You Measure It?

SHGC is calculated by multiplying a window’s shading coefficient (SC) by 0.87. The lower the number, the better the window resists solar heat gain.

The shading coefficient was the older metric used before SHGC became the industry standard. It measured the thermal performance of glass compared to a clear, 3mm thick float glass pane. Like SHGC, the lower the SC, the better.

The good news is you don’t have to do the math yourself. Manufacturers now label windows with their SHGC ratings, so you’ll know exactly how much solar radiation each product allows in before you buy.

Why It’s Important to Know Your SHGC

SHGC plays a big role in how your windows perform, especially in regions with unpredictable weather like the Midwest. Choosing windows with the right SHGC can mean the difference between a comfortable, efficient home and one that’s costly to maintain.

Keeps Your Home Cooler

SHGC directly impacts indoor temperature. While it’s not the same as a window’s u-factor, it works hand in hand to regulate comfort. The higher the SHGC, the more solar radiation enters, warming up your home. A lower SHGC keeps excess heat out, making it easier to stay cool without overworking your air conditioner.

Blocks Harmful UV Rays

Many homeowners underestimate the damage UV rays can cause. Even without direct sunlight, UV exposure can fade floors, dull paint, and weaken furniture fabrics.

High-SHGC windows allow more UV rays into your home, increasing the risk of expensive damage. Low-SHGC windows act like built-in sun protection, preserving your interior and helping your home look its best for years to come.

Saves You Money

Energy-efficient windows with a low SHGC don’t just prevent damage—they also cut energy costs. By limiting solar heat gain, your air conditioner doesn’t have to work as hard to maintain a comfortable temperature. That means less electricity use and lower monthly bills.

Look for the Energy Star Sticker

One of the easiest ways to identify energy-efficient windows is to look for the Energy Star label. This blue sticker is awarded to products that meet strict standards for efficiency. You’ve likely seen it on appliances, but windows can earn the designation as well.

Energy Star windows are judged on several factors, including multiple panes, insulation, u-factor, and yes—solar heat gain coefficient. Choosing Energy Star Certified windows ensures you’re getting top-performing products that help you save money year-round.

Why SHGC Matters When Choosing Replacement Windows

Windows that let in too much solar radiation make your home less comfortable, increase wear on your belongings, and drive up energy bills. Understanding SHGC ensures you can choose windows that keep your home cooler, protect your investment, and improve efficiency.

At Feldco, we design windows with a low solar heat gain coefficient—perfect for Midwest homeowners who deal with hot summers and cold winters. With nearly 50 years of experience and over 500,000 satisfied customers, we know how to deliver comfort and value.

Get a free quote today and see why so many homeowners trust Feldco for their replacement window projects. We’ll help you find the right windows with the performance and efficiency your home deserves.