The National Fenestration Rating Council label provides standardized ratings for the complete window. U-factor addresses heat transfer; solar heat gain coefficient addresses admitted solar heat; visible transmittance addresses daylight; and air leakage reports tested air movement. Compare the exact configured product.
Get the details in writing
A trustworthy proposal should identify the exact product and installation scope. If a term is important to your decision, ask that it be included in the agreement rather than relying on a verbal statement.