ENERGY STAR Windows Requirements for Loudoun County Homeowners
The Ratings That Matter Before You Replace Windows For most Loudoun County homeowners, ENERGY STAR is less about a logo and more about whether a window is built for the climate you actually live in. The local climate matters. In zone 4A, the right window has to reduce cooling load in July and limit drafts in January, not just look good on a brochure. The two numbers homeowners should learn first are U-factor and SHGC. U-factor measures how well the window resist