The only commercially available, NFRC-certified full frame 0.10 U-factor window in North America. Finally, the R10 window has arrived. Window manufacturers have been working for decades to develop a commercially viable, full-frame R10 window. Now, an industry leader has emerged with the only full frame certified R10 window on the market—Alpen High Performance Products. Alpen’s Zenith Series ZR-10 / 1025 features include: The ZR-10 / 1025 high profile fixed window certified to a 0.10 U-factor Operable windows certified to 0.14 U-factor Super-insulated energy efficient pultruded fiberglass frames Double film, triple chamber insulated glass assemblies featuring four independent low-e surfaces High-performance spacers and high-performance inert gas fill 99.5 % UV protection Extraordinary solar control performance Proudly designed, developed and manufactured in the USA.