Peerless Products Inc.
EnergSave G-500 Window Series has a U-value of 0.15. It incorporates aluminum bars within the thermal break to slow heat flow, low-E foil on each side of the thermal break to reflect heat back out, and neoprene foam above and below the thermal break to absorb and isolate cold air transfer.
Kimball International: Shore
Protimeter: Aquant
Sensaphone: Sentinel PRO
KI: Passel
Sielox: AnyWare