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Timber provides one of the best insulation values of any material used in the construction of a window and has been used extensively over the last hundred years. Unfortunately it is not maintenance free, hence the surge in U.P.V.C. windows.


Most timber windows in the past and even recently have been single glazed because of the inability of bulky standard double glazed units with 10mm deep perimeter seals to be glazed into timber windows particularly with astragals and not acceptable by Planning Authorities for Conservation, Listed or Graded buildings.


This new innovative Slimlite Ultra Clear Self Cleaning Double Glazed Units open up many possibilities for the timber manufacturer of windows.

It is no longer necessary to apply adhesive astragals to a standard double glazed unit to effect a ‘Georgian Look’ as Slimlites will fit into the rebates of an astragal which usually has a 7mm rebate depth, which prevents the 5mm overall perimeter seal being visible and a rebate astragal width of around 20mm which can accommodate a Slimlite overall thickness of 12mm with a front putty or bead of around 6mm or more. (Pilkington UK Technical Bulletin Ref M17 Date 13th October 2011)




There is of course enormous potential in the replacement of Slimlite into single glazed windows, as Slimlite will fit into most single glazing rebates.

However in England some single glazed timber windows tend to have smaller rebates than in Scotland and it may be necessary to router 2mm or 3mm from the rebate without detracting from the physical appearance of the windows.


Most timber windows constructed for single glazing would have rebate depths of at least 7mm and glazing width rebate of approximately 20mm (see sketch).


New technology Slimlite Ultra Clear Self Cleaning Double Glazed Units with a 5mm perimeter seal depth and overall thickness of 12mm, can be glazed into most single glazing rebates or new timber windows which are manufactured to maintain the slim astragal appeal.


When Slimlite Ultra Clear Self Cleaning Double Glazed Units are glazed into a timber window, they are undetectable unless from close up examination.

Given the Governments drive to reduce carbon dioxide emissions, Planning and Conservation Authorities should consider the use of Slimlite Ultra Clear Self Cleaning Double Glazed Units in Conservation and Listed or Graded Buildings as there is no change to the physical appearance of a window, but provides serious reduction in energy requirement and therefore reduction in carbon dioxide emissions.