Choosing the right windows for your home isn’t only about design and aesthetics but also about making smart, energy-efficient choices. One term you might come across in your window-shopping journey is solar heat gain coefficient (SHGC). This blog from Window World of Boston will break it down for you so you can choose the best replacement windows for your home. 

What Is the SHGC Rating?

In the simplest terms, the SHGC rating of a window measures how much heat from the sun it allows into your home. A high SHGC rating means more solar heat is allowed through, while a low SHGC rating means less heat passes through. So, as much as you’re picking a window for its looks and longevity, you’re also choosing how it will manage sun-heated air. 

Why Use SHGC Ratings?

SHGC ratings are a great way to gauge a window’s effectiveness in helping you manage energy costs. By choosing the right replacement windows, you can ensure your home is comfortable and energy-efficient all year round. With the right SHGC rating, you can rest assured that your home will be kept cool in the summer and warm in the winter without breaking the bank.

What Influences SHGC Ratings?

The SHGC rating of your windows can be influenced by a few key elements. First and foremost is the type of window glass. Double-glazed windows, for instance, tend to have lower SHGC ratings than single-glazed windows.

Additionally, the type of window coating can significantly influence the SHGC. Low-E (low emissivity) coatings are particularly effective at reducing solar heat gain. Geographical location also plays a crucial role. The ideal SHGC can be quite different if your home is in a warm, sunny climate compared to a cooler, less sunny one. 

What Are the Best SHGC Ratings Based on Climate?

SHGC Rating for Cold Climates

The ideal SHGC rating for cold climates is typically higher than in hot climates, as this helps keep the home warm in the winter months. The higher the rating, the more heat is allowed through, which can help the home stay warm without resorting to more costly heating solutions. Keep in mind that the best SHGC rating for your home depends on your geographical location, climate and installation details. 

SHGC Rating for Hot Climates 

The ideal SHGC rating for hot climates is typically lower than in cool climates, as this helps keep the home cool in the summer months. The lower the rating, the less heat is allowed through, which can help the home stay cool without resorting to more costly air conditioning solutions. However, the best SHGC rating a home window repair expert can install for you could vary depending on your location, climate, and other installation details.  

How Are SHGC Ratings Determined? 

The SHGC rating of a window is based on computer simulations and tests. It is measured in a laboratory with all possible heat sources taken into consideration—including solar radiation, conduction, convection and air leakage. The resulting SHGC rating is expressed as a number between 0 and 1. A higher number indicates a window with higher solar heat gain, while a lower number suggests a window with lower solar heat gain.  

What Other Window Ratings Should I Take Into Consideration?

Home window repair and replacement experts may have mentioned other window ratings, including the U-Factor and R-Value. U-Factor, also known as U-Value, measures the rate of heat loss or gain through a window or door and is expressed as a number between 0 and 1. The lower the U-Factor, the better the window’s insulation. The R-value, on the other hand, is the measure of resistance to heat transfer and is the inverse of the U-factor. So, the higher the R-value, the better the window’s insulation.

When shopping for windows or doors, knowing the SHGC, U-Factor and R-Value can help you determine the energy efficiency of the products. That way, you can make an informed choice about what’s best for your home! 

Do You Know the SHGC Ratings of Various Windows?

Single-Glazed Windows  

Single-glazed windows feature a single layer of glass, as opposed to double- or triple-glazed windows. They tend to have higher SHGC ratings than their double- or triple-glazed counterparts, meaning they allow more solar heat to pass through. While this may be desirable in colder climates, it could be problematic in sunnier and hotter locales. It’s usually better to opt for double- or triple-glazed windows with low SHGC ratings in those areas. 

Double-Glazed Windows 

Double-glazed windows feature two layers of glass separated by a gas-filled gap or spacer. This helps insulate the window from outside temperatures, resulting in lower SHGC ratings compared to single-glazed windows. Due to their low SHGC ratings, double-glazed windows are particularly well-suited to warmer climates, where reducing heat gain is a priority. 

Triple-Glazed Windows  

Triple-glazed windows feature three layers of glass separated by a gas-filled gap or spacer. The extra layer of glass provides additional insulation, resulting in even lower SHGC ratings compared to single- and double-glazed windows. These windows are ideal for areas with hot climates, as they can keep the heat out. 

Window Coatings and Their Effect on SHGC Rating 

Window coatings can also influence the SHGC rating, as some types of coatings can reduce solar heat gain. The most common type of window coating is Low-E (low emissivity) glass, designed to reflect infrared light, helping reduce the window’s SHGC rating. This type of window coating is great for keeping the home cool in the summer. 

How Does SHGC Affect Window Performance?  

Most window and door installation experts will tell you that windows with good SHGC ratings reduce the need for additional energy sources to maintain a comfortable temperature in your home. A window with a high SHGC rating allows more solar heat to pass through, keeping your home warm in the winter without resorting to costly heating solutions.

Conversely, a window with a low SHGC rating keeps solar heat out, maintaining a cool temperature in the summer without resorting to expensive air conditioning solutions. However, cracks, leaks or faulty seals can let more heat pass through, decreasing the window’s effectiveness at managing solar heat gain. Prompt home window repair can rectify these issues, restore the intended SHGC rating and maintain your home’s energy performance.

Ready to make your home more energy-efficient? Trust the window and door installation experts at Window World of Boston. Call us at (781) 262-3925 for our Woburn location, (781) 343-7129 for Pembroke, or (508) 845-6676 for Shrewsbury. You can also fill out this contact form to reach us. Let us help you make the best choice for your home.