SHGC Vs. U-Value: What’s the Difference?

If you’ve been comparing window replacement options, you’ve probably come across the terms “SHGC” and “U-value”. In today’s post, Renewal by Andersen® of Central Pennsylvania shares a quick guide to the differences between these two and why you need them when buying energy-efficient replacement windows.

Energy Ratings

Replacement windows come with an energy performance label provided by the National Fenestration Rating Council® (NFRC). The NFRC certifies fenestrations – skylights, entry doors and replacement windows – after a series of energy performance tests. The energy ratings, published on labels affixed to fenestrations, inform buyers on how well a product performs in terms of insulation, light transmittance, heat gain and air leakage. The organization ENERGY STAR® uses these energy ratings as reference for identifying energy-efficient products.

SHGC and U-Value

Solar Heat Gain Coefficient (SHGC) and U-Value are two of the main energy performance ratings stated on NFRC’s labels.

• SHGC measures how well a window (or other types of fenestrations) can resist unwanted heat gain from the sun. It is represented as a value between 0.0 and 1.0. Windows with low SHGC means they’re ideal for parts of your home that receive direct sunlight.

• U-value measures insulation. More specifically, it measures how well a product can keep radiant heat from passing through it. U-value is represented as a value between 0.20 to 1.20. Low U-value is ideal because it can help keep the house retain heat during cold months and keep heat from getting into the house during hot months. Some energy performance labels may indicate R-Value instead of U-value. While R-value is also a measure of insulation, it measures thermal resistance. This means a window with a low U-value will have a correspondingly high R-value.

Why Do These Ratings Matter?

It’s important to note that there is no one-size-fits-all solution when it comes to choosing replacement windows. Factors like local climate and window orientation must be considered along with your home’s style and your own preferences. As described above, a window with low U-value can help keep your home comfortable during seasonal extremes. If you need windows that will let you get the most natural light, but without the heat that comes with it, windows with low SHGC are what you need.

You can find these features on our High Performance™ Low-E4® glass, a standard feature of Renewal by Andersen replacement windows. Find out more by calling Renewal by Andersen of Central Pennsylvania at (717) 591-4900, or fill out our contact form to schedule an appointment. We serve customers in Lancaster, PA, and the surrounding communities.