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Understanding Window Ratings: U-Factor, SHGC, and VT Explained

In modern households, energy-efficient windows are a necessity. If you’re unsure how to determine the energy efficiency of your windows, you’re in luck! This blog will discuss specific window ratings that are designed to measure their energy-efficiency performance. Key window ratings include U-Factor, SHGC, and VT. By using these window ratings, you can choose the right windows for your home, improve your home’s comfort, and save money on energy bills.

What Are Window Ratings?

Understanding window ratings is important because it helps homeowners make informed decisions about the energy efficiency, durability, and overall quality of windows. Window ratings provide valuable information about factors such as U-factor, solar heat gain coefficient, visible transmittance, air leakage, and condensation resistance, all of which can impact a home’s comfort, energy costs, and environmental impact. The most common window ratings are U-Factor, SHGC and VT.

Understanding U-Factor

U-Factor is used to express the insulation of windows, including the glazing, spacer and framing. U-Factor is calculated by using the following formula: Btu/h·ft²·°F. Breaking down that formula, BTU stands for British Thermal Units, and you are measuring the rate of heat loss in BTUs. You then divide that by the area times the temperature difference. Windows with the best heat flow resistance, or insulation, have a lower U-Factor. Determine whether you have a low or high U-Factor based on location. For example, for northern climates, your U-Factor should be ≤ 0.30. North Central ≤ 0.32, South Central ≤ 0.35, and Southern ≤ 0.60.

Understanding SHGC (Solar Heat Gain Coefficient)

SHGC, or Solar Heat Gain Coefficient, is the amount of solar radiation that passes through your window. SHGC is measured on a range from 0 to 1, 1 being the maximum amount of solar heat that could pass through, and 0 being the least amount that could pass through. A SHGC rating of 0.40 means that 40% of the possible heat passes through the window. The National Fenestration Rating council determines the SHGC of a window. They add labels to windows that include both the SHGC and U-Factor to help homeowners determine the right windows for them. Lower values are preferred in hot climates and should stay under 0.30. In mixed climates such as the North and Midwest, SHGC is best under 0.40, and for colder climates, the SHGC is not much of a concern, but having it in the range of 0.30-0.60 is helpful to improve energy efficiency.

Understanding VT (Visible Transmittance)

VT, or visible transmittance, is the amount of light that passes through the window. VT is measured on a range from 0 to 1, 1 being the maximum amount of light that could pass through, and 0 being the least amount that could pass through. Though it is usually preferred to maximize the amount of light that passes through your windows, there is often solar heat gain. Also, too much light transmittance can create glare. It is important to find a balanced VT to have natural light without glare issues. Triple-pane windows usually have lower VT than single or double-pane windows.

How to Choose the Right Windows

When choosing your windows, make sure you evaluate the window ratings to ensure you have the most energy-efficient windows possible. Based on your climate, make sure you have the proper U-Factor. For SHGC, consider having a lower rating if you live in a warmer area. There are also many other factors to consider when choosing windows for your home, including style, thickness, and material. Some of the most popular window styles include casement, double-hung, bay windows, bow windows, and garden windows. Consider your budget and home’s aesthetic when choosing a style of window. When it comes to choosing a material, consider your budget, your home’s aesthetic, maintenance, durability, and energy efficiency. The most common windows are made of wood, fiberglass, and vinyl.

Choose APCO for your Energy-Efficient Window Installation

Due to the variety of factors to consider, including window ratings, choosing the right windows can be overwhelming. Luckily, APCO is your window design and installation partner, making the process smooth and stress-free. Our team of experts is committed to helping you find the perfect windows for your home. From the initial consultation to the final installation, we will guide you every step of the way to ensure that your new windows look great and offer maximum energy efficiency for your home. With our extensive knowledge and experience, we can help you choose from a wide range of window options to find the perfect fit for your style and budget. Trust APCO for all your window installation and replacement needs. Contact us today for a FREE assessment and to explore energy-efficient, secure, and stylish options for your home.

For more information about our window installations or to get started on a new project, call us at 614-224-2345 or contact us online to get in touch with our specialists!



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