Designed as a direct replacement for steel windows, Smart’s Alitherm Heritage provides the ideal solution for heritage applications such as listed building renovations and large scale replica-refurbishment projects where planning constraints are to be considered.

Designed to be built as a series of horizontal modules the window can be stacked using horizontal couplers to form a multi-part window featuring a specially designed drip bar between modules.

Utilising Smart’s innovative polyamide thermal break technology which creates a barrier between the cold air outside and the warm air inside. Significantly reducing thermal transmittance and enhancing the overall U-Value of a product and is designed to meet the exacting requirements of Document L 2010.


  • Fixed windows
  • Single or double sash, side hung open out casements
  • Top hung open out casements
  • Tilt & turn windows
  • Single or double doors


Technical Performance:

  • WER Rating – B
  • U Value of 1.5 W/m²K (using sealed unit 1.0 W/m²K
  • Air – Class 4, 600Pa
  • Water – Class 9A, 600Pa
  • Document L compliant
  • Typical sightlines of 59mm
  • Glass: 24mm – 36mm


Recommended Design Limits:

  • Side Hung Vent Max o/a width 700mm
  • Side Hung Vent Min o/a width 300mm
  • Side Hung Vent Max o/a height 1400mm
  • Maximum Vent weight 40kg
  • Top Hung Vent Max o/a width 1400mm
  • Top Hung Vent Max o/a height 1300mm
  • Top Hung Vent Min o/a height 275mm
  • Maximum Vent weight 40kg
  • Max Door Sash Width 900mm
  • Max Door Sash Height 2100mm

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