Slender Fit

stately home

Slender Fit Double Glazed Units are a new concept in the construction of double glazed sash windows and slimline double glazed units which with a 7mm perimeter seal depth and can be glazed into most single glazed windows.

By using and maximising the latest technology it is possible to construct a double glazed unit with very small cavities or space between the glasses with a 7mm perimeter seal depth and selected insulating inert gas cavity to obtain U-Values to comply with Building Regulations and comparable or better than U-Values obtained by standard units with much wider cavities.

Slender Fit Slimline Double Glazed Units are constructed with a 4mm clear outer pane with a selected cavity of 4mm, 5mm or 6.5mm, the wider cavity, increases the insulation, with selected cavity insulating inert gas, argon and krypton which only performs in smaller cavities, and inner pane of 4mm Low Emissivity glass.

The emissivity coating is on the inside face into the cavity and reflects the long wave radiation or heat back into the room. The warm edge technology perimeter spacer incorporated, ensures insignificant differential insulation value between edge and centre of glass.

Today it is necessary for double glazed units to comply with Building Regulations (noted below) in respect of U-Values which are slightly different between Scotland and England. Slender Fit double glazed sash window units can comply with both these regulations as noted.
Building Regulations – Required U-Values
4mm Low E/ Cavity, gas/ 3 or 4mm clear float or
reproduction crown sheet
Slender Fit plus (Low Emissivity)

Single Glazing 5.4 U-Value
3.8mm cavity U-Value 1.9
5.0mm cavity U-Value 1.8
6.0mm cavity U-Value 1.6


New 9mm double glazed sash window unit


Introducing our latest product a 9mm Overall thickness

3mm Opti White/3mm Spacer/3mm Opti White

The warm edge spacer is available in Black, White or Premium Grey

  • New 9mm double glazed sash window unit
  • Eco Friendly
  • Accepted in conservation areas
  • Retains Character