Decoding Window Ratings: How U-Factor, SHGC, and Visible Transmittance Affect Your Home
September 24, 2025
Understanding Window Ratings: U-Factor, SHGC, and Visible Transmittance Explained
When shopping for replacement windows, it’s easy to get lost in the alphabet soup of energy ratings. Terms like U-Factor, SHGC, and Visible Transmittance might sound technical, but they have a huge impact on your home’s comfort, energy efficiency, and monthly bills. At RRSA Windows & Doors, we believe informed homeowners make the best decisions—so here’s a simple breakdown.
U-Factor (Insulation Power):
- Measures how well a window keeps heat inside.
- Lower = better insulation.
- In Missouri’s four-season climate, a low U-Factor means less heat escapes in winter.
SHGC (Solar Heat Gain Coefficient):
- Measures how much heat from the sun passes through your window.
- Lower SHGC = blocks more solar heat (better for hot summers).
- Balanced SHGC helps reduce cooling costs without making your home dark.
Visible Transmittance (Natural Light):
- Indicates how much daylight passes through the glass.
- Higher VT = brighter rooms, less need for artificial lighting.
- A balance of VT + SHGC ensures you enjoy sunlight without overheating.
Why It Matters:
The right balance of these ratings depends on climate and lifestyle. In St. Louis, homeowners benefit most from windows with a low U-Factor, moderate SHGC, and good VT—keeping homes warm in winter, cool in summer, and filled with natural light.
Looking for wndows that maximize efficiency and comfort for Missouri weather? RRSA can help you choose the best options for your home.
Contact us today for a free consultation.
You may not see it, but those tiny drafts sneaking through your old windows could be costing you hundreds of dollars a year. Many St. Louis homeowners underestimate how much air leakage affects comfort and energy efficiency. The truth is, drafty windows don’t just make your home chilly in the winter and stuffy in the summer — they make your HVAC system work harder, driving your utility bills up month after month. Here’s how to spot the signs of drafty windows, understand their real costs, and fix the problem for good.
When it’s time to replace your windows, one of the biggest decisions you’ll face is what material to choose for your window frames. Each type - vinyl, fiberglass, and wood - offers its own mix of looks, performance, and price. For St. Louis homeowners, where summers are humid and winters can be bitterly cold, the right window material makes all the difference in comfort and energy efficiency. Here’s how to decide which is best for your home.
As temperatures drop and the Midwest winter approaches, St. Louis homeowners start preparing for the cold. But while you’re checking your furnace and sealing up doors, don’t overlook one of the biggest sources of heat loss in your home: your windows. Old or inefficient windows can make your heating system work overtime, drive up energy bills, and leave your home feeling drafty. Before winter hits, use this checklist to find out if it’s time to replace your windows.
Your front door is one of the first things people notice about your home. It sets the tone for your curb appeal, influences your home’s value, and plays a big role in keeping your home comfortable and efficient. If your entry or patio doors are old, drafty, or outdated, upgrading them can make a dramatic difference in both appearance and performance. Here’s how new doors can enhance your St. Louis home inside and out.
As summer fades, St. Louis homeowners start thinking about cooler weather—and higher heating bills. Old or failing windows can let in drafts, drive up energy costs, and make your home less comfortable. Here are six signs it’s time to consider replacement windows before winter arrives.
We hope your end-of-summer BBQ was legendary. We hope you enjoyed your pool parties and porch-sitting. But time marches on and autumn is here. Before the cold weather hits, there’s a few things we think you should know about your roof – and steps you can take to make sure it stays functional and damage-free through the harsh winter months. As you might know, it costs an average of $7,200 to replace a roof in Missouri. Unfortunately, homes don’t really come with how-to manuals to protect roofs and avoid repairs, but RRSA has you covered. Let’s take a look at three ways you can prep your roof for fall and winter.
It’s hard to gauge the life expectancy of a roof. The best estimates put the lifespan of the average roof at between 20 and 30 years for standard asphalt shingles. Other materials, like clay and concrete, can last up to 100 years . Aside from materials, lots of factors play a role in aging or preserving a roof: temperature, exposure to elements (like wind and hail), and maintenance history. But no matter what kind of roof you have, it pays to know what the early signs of age and degradation are so that when you see them, you can act before your roof becomes compromised and begins to leak, which can cause thousands of dollars of damage , or otherwise fail. Let’s take a look at three warning signs that your roof is getting up there (pun intended).
Did you know that only 2% of roofers in the U.S. qualify to be recognized as GAF Master Elite™ Contractors? That figure may seem small, but taken together with the fact that the roofing industry has a failure rate more than 50% — and much of that failure attributed to lack of knowledge — it starts to make a little more sense. If you’ve owned a home for more than a few years, you’ve likely heard stories (or had your own experiences) with bad roofers. When trying to avoid the shoddy workmanship, subpar product, and un-warrantied work, three letters are going to change the way you think about roofs and roofers: GAF. Let’s look at three reasons this particular certification ensures you get the most for your money.
How often do you think about your roof? If you’re like most people, the answer is probably not a lot — after all, we’ve got plenty to think about without worrying about the condition of our houses. But a roof is one of those things that you really don’t want to fail on you when you need it most. On top of being a fairly expensive thing to fix, it’s also incredibly stressful to deal with when inclement weather is approaching. To this end, one of the best things you can do for the long-term health of your roof (and of your savings account) is to be proactive and consider roof ventilation. Let’s take a look at three reasons it’s a smart investment.
