The HX45, part of the XTherm line of architectural grade products from EFCO (a Pella Corp. company), is a high-performance double-hung window. Designed for a variety of applications (such as schools, government buildings, and green construction), it has an energy-efficient design that improves interior frame temperatures (CRF) and U-factor ratings, as well as AAMA structural ratings. Options include block and tackle and class 5 balances and auto-locking and sweep-lock hardware. The window features a 4-1/2" frame depth, a snap-in grid option, fixed mate, and an AW70 standard and AW110 optional rating.