U-factor, solar heat gain, visible transmittance and air leakage explained in plain language, with notes on how to read a window label.
A window label packs a lot of information into small numbers. U-factor tells you how fast heat moves through the window, and a lower number means less heat flow. Solar heat gain coefficient shows how much of the sun heat comes through the glass. Visible transmittance shows how much daylight passes through. Air leakage shows how much air moves through the closed window. Together these numbers describe how a window performs, which makes it easier to compare models side by side.
The right numbers depend on where you live and how the window faces. In Middle Tennessee, with hot summers and cool winters, owners often look for a balanced U-factor and a solar heat gain that suits the exposure. A south or west window may favor lower solar heat gain, while a north window may favor more light. In Nashville, we help read the labels, compare the options and explain why installation matters as much as the numbers on the sticker.
Heat flow, lower is better.
Sun heat through glass.
Daylight through the glass.
Air through the closed window.
Common method for fair comparison.
Where performance is won or lost.
Vinyl Replacement WindowsLow-maintenance vinyl windows with welded frames, good insulation and a wide range of styles and colors.Explore 
Fiberglass Replacement WindowsStrong, stable fiberglass frames that resist expansion, take paint well and suit sun, heat and big windows.Explore 
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Window Trim and Casing InstallationNew interior casing, stools and aprons around windows, cut and fitted for clean lines and a finished room.Explore 
Exterior Capping and WrapAluminum capping or wrap around exterior window trim, for a clean, low-maintenance finish that sheds water.Explore Check problems, pick a style or ballpark a budget.
Window Problem Checker: What Is Wrong?Pick what you see or hear from a window to get likely causes, what to do first and the service page that fits.Try it 
Window Style PickerAnswer a few questions about your home, rooms, ventilation and view to see which window styles usually fit best.Try it 
Window Replacement Budget PlannerPick a window type or repair, set the quantity and add extras to see a ballpark planning range for your project.Try it It depends on your goals. U-factor and solar heat gain matter most for comfort and energy in our climate.
No. They describe the window itself. Installation affects how it performs in the wall.
Not always. Balance the numbers with light, view, budget and the way the window faces.
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