When replacing windows and doors, you need more than unsubstantiated claims about energy efficiency; you need complete and impartial proof.
By asking for a BFRC rated product, you are making sure the energy efficiency of the
whole window or door system you are buying has been independently tested to determine how well it keeps heat in (U-value), the amount of energy available from the sun (G-value), and the amount of air leakage (L-value).
Only when you know all three values can you be sure about its complete balance of energy performance. Find BFRC rated products