Interesting information in plain English, on windows, glazing and Energy Star. S4 Glazing The difference between a U-Factor of 0.27 and 0.28 is razor thin, but it’s the difference between achieving an Energy Star 6.0 rating, and not. Unfortunately, many window manufacturers have had to resort to S4, or “room-side” Low-e glazing to meet this U-Factor. Learn why Mathews Brothers will never use S4 glazing. S4 Glazing – What You Don’t Know Can Hurt You Everything You Wanted to Know About Window Framing and Glazing, But Were Afraid to Ask Which window frame is the best? What the story on all those numbers on the NFRC label? What do U-Factor, SHGC, VT, Air Infiltration and CRF stand for anyway? Find out here: Everything You Wanted to Know About Window Framing and Glazing, But Were Afraid to Ask Spencer Walcott Catalog Downloadable and printable version of our Spencer Walcott catalog. Spencer Walcott Catalog Spencer Walcott Window Warranty Spencer Walcott Window Warranty Spencer Walcott Door Warranty Spencer Walcott Door Warranty Sanford Hills Catalog Sanford Hills Catalog. Sanford Hills Catalog Spencer Walcott/Sanford Hills Comparator Coming soon, and when it does, it’l be awesome. Sanford Hills Window Warranty Sanford Hills Window Warranty