Nature Optimo XLT

The NATURE OPTIMO XLT window is a special type of window from the Optimo family. It is made of thermally modified spruce and is officially certified as passive window. It is made entirely of wood, boasts an attractive, exotic look and outstanding energy efficiency (thermal transmittance of window (Uw ≥ 0.66 W/m2K), bringing real added value). It is actually the world’s most cost-effective PHI-certified passive timber window. The window is especially attractive due to the aligned frame and casement. * XLT = L (Line), X (Xclusive), T (Thermally modified spruce)


  • made of thermally modified spruce
  • use of Super Spacer
  • aligned casement and frame on inner and outer side of the window
  • thickness of window casement and frame 110 mm
  • hidden hinges
  • produced using the newest computer controlled technology implemented in 2014


  • high thermal efficiency
  • modern design
  • suitable for low-energy and passive buildings
  • warm feeling
  • excellent water- and airtightness
  • very long lifespan oweing to very good resistance of thermally modified spruce
Profile dimensions installation depth 110 mm
visible width 116 mm
Instalation options rectangular
arched, semicircular
Opening options fixed
combined (tilt and turn window)
folding walls
tilt-slide walls
lift-slide walls
opening outwards
two-sided handle
Thermal insulation of the window (Uw) Ug = 1,1  
Ug = 1,0  
Ug = 0,7 0,79 W/m²K
Ug = 0,6 0,72 W/m²K
Ug = 0,5 0,66 W/m²K