U-factor is the rate at which a window, door, or skylight transmits non-solar heat flow. For windows, skylights, and glass doors, a U-factor may refer to just the glass or glazing alone. …

Knowing what U-factor is, how it is affected by the energy efficiency of your windows and what type of U-factor to look for when purchasing new windows can help you pick a product that …

Nov 18, 2025 · Our guide breaks down what a window’s U-factor is, how to correctly interpret ratings, and what you should consider when buying new windows for your home. What Is the …

The U-value is expressed in units of watts per square meter per degree Kelvin (W/m²K). Essentially, it tells you how much heat is lost through the window per unit area for every …

Feb 5, 2024 · Expressed in watts per square meter per Kelvin (W/m²K), U-values provide an insightful measure of a window’s capacity to hold heat. Here, the guiding principle is simple – …

Mar 6, 2025 · Learn what U-value means, how it affects window insulation & why lower U-values improve energy efficiency. Get tips on choosing the best windows.

When quantifying the energy efficiency of a window assembly, the rate of loss of non-solar heat can be expressed as its U-factor (or U-value). Understanding the U-factors of windows is …

6 days ago · Discover the most energy efficient windows for 2025. Expert-tested rankings, climate-specific recommendations, and detailed buying guide with ROI analysis.

Oct 27, 2025 · This guide will delve into what U-values are, how they impact your choice of windows, and why understanding these values can lead to significant energy savings and …

A good U-value for windows in your home is 1.4 W/m²K or better for replacement windows. If your budget allows, anything below 1.2 W/m²K is excellent and will keep your home much warmer …