The HX45 is loaded with options to fit many applications while providing an industry leading U-factor. The energy efficient design provides a substantial improvement in the interior frame temperatures as well. Both block and tackle and class 5 balances are available along with the quality auto locking and sweep lock hardware that has been a part of other EFCO products for many years. Designed to meet the increasing demand for thermally superior products needed in schools, government buildings and green construction, EFCO HX45 double hung window sets a new standard. The outstanding U-factor provides demonstrable energy savings when used in a conjunction with building envelope performance software.