Insulation ratings are essential when it comes to selecting the best insulated double hung windows for your home. It is important to understand the different rating systems and how they apply to window selection. U-factor ratings measure a window’s ability to keep heat in, while R-value ratings measure a window’s ability to keep heat out. Both of these rating systems are important when choosing the right windows for your home. By understanding these insulation ratings, you can select the best insulated double hung windows for your needs and budget.