How to do Double Glazing and Secondary Glazing

Note: At the moment we can only support the double glazing of wood frames. We have limited solutions for aluminium frames but they are not ideal. If you have aluminium windows and are interested in working with us, please contact us.

The first thing is that you must have the confidence to do the installation yourself. Most people are not experienced at working with glass, but it is not rocket science! A standard wooden window has a 10 mm piece of wood on the outside to hold the glass in place. This can be easily removed. Then, by sliding a knife around the inside of the frame, the silicone seal is broken and the glass can be removed. Inserting the new double glazed unit is also quite easy. You need to clean up the frame, then insert the double glazed unit, checking it fits flat and snugly within the frame. Once you are confident the window sits properly, remove the window, apply silicon to the frame, insert the new double glazed unit, apply silicon around the window then fix a wooden beading to hold the window in place.

   Details on removing glass

   Details on adding a double glazed unit

A cheaper option is to do secondary glazing. You need a second sheet of glass and fix it to the outside of the existing window. You must add a plastic moisture barrier between the panes of glass to stop condensation. We recommend that the second beading is screwed in place, making it easy to remove and fix any problems that arise. This is only recommended if you have access to cheap glass. Buying the second sheet is normally not worth the effort. There is the option to buy double glazed units for half of the windows in the house and then use the glass that is removed for secondary glazing on other windows in the house. This is feasible if the glass is 4 mm thick. 3 mm glass is very difficult to remove without cracking.

   Details on adding secondary glazing

And as they say “the proof is in the eating”. Normally you will not detect any degradation in viewing through a double glazed glazed window. For secondary glazing, it is important that the internal glass surfaces are properly cleaned to maximise transparency. The reduction in transparency is much less for windows on the south side. This is because direct sunlight on the window highlights any dirt or scratches. Also, windows in bedrooms generally do not require the same quality of transparency and are better suited for secondary glazing.

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