Mikron. Featuring tri-extruded frames and an air-cell insulating core, EnergyCore vinyl replacement windows offer nearly 15% improved full-window U-factors over hollow vinyl, the company says, while blocking thermal conductivity six times better than fiberglass, four times better than rigid PVC, and three times better than wood. When combined with high-performance triple-glazing systems, the windows provide a 0.15 U-factor and a 6.5 R-value, exceeding Energy Star standards by 50%. Double-hung, casement, picture, and double-slider units are available. 800.456.8020. www.mikronvinyl.com.