Double Glazing: Applied and coupled sashes
Applied-sash or coupled-sash units are popular forms of double glazing. These come in a variety of kits or you can evolve your own system. An applied sash is fitted to the rebate of the “window or other window surround, while the coupled sash is fitted to the window frame.
It is possible to have coupled sash sliding units. Sliding-sash units usually consist of a head track, side member and sill track. The fixing position of the head track decides the final position of the window.
In deciding the position of the track, make sure there is room for any projecting window furniture between the existing window and the track. Some kits include a sealing strip to stop.
For sliding windows to slide easily it is essential to have a true frame. The lack of this does not preclude this form of double glazing.
Most firms supply packing pieces which can be used to ensure a ‘true’ frame, allowing windows to slide easily. As the distance between the sashes is normally 100mm, it provides some acoustical advantage.
This is simple to install and involves the fixing of a removable glazed panel, to the existing window frame. In summer this panel can be taken down and stored.
When making up a coupled-sash unit, the frame of the glazing unit should normally be 19mm less than the dimensions of the window opening and the glass 8mm less than the dimensions of the frame.
Cut the main frame channel to size and fit the glazing strips round the glass. This should be first laid flat. The basic components of the majority of systems are usually four main channels and four corner hinges, locking nuts andand neoprene sealing strips.
To assemble, the four main channels and corner hinges are placed roughly in position. The locking nuts and screws are fixed loosely to the corners.
Cut the neoprene sealing strips to the correct length, mitre the corners (some kits include a mitre block) and then insert the strips into the channels. After fitting the corner hinges to the main frame, the glass is fitted into the frame.
Usually, a sliding foot is provided for the window stay. This is fitted into the groove of the bottom channel. The unit is then tightened and offered up to the window frame. Mark the position of the hinges and set these so that the frame hinges accurately into place.
In detail, coupled sash units may vary but this is the method used to fix most units. For further insulation, a neoprene strip can be fixed to seal the joint between the unit and the window frame.
Before positioning any made-up double-glazing unit, remember to clean both sheets of glass thoroughly on both sides. Condensation between the sheets may prove a problem.
There are two methods of combating this. One is to drill a series of small holes upwards in the base of the frame to provide ventilation. The other is to use silica-gell crystals. These are placed along the bottom of the unit where they act as blotting paper to absorb the moisture. These may become saturated in time and need to be removed and dried out. Coupled-sash glazing frames can also be applied externally to window frames.
Kits, consisting of plastic framing, into which you fit your own glass, are available. Some types consist of a coupled sash which unclips completely, while others have an-fixed plastic head, into which the glass is fitted when needed.
The frames for applied or coupled sash units can be made of plastic, wood or aluminium.
Moisture is drawn through the fibre of timbers, even when painted. A strip of aluminium foil – which is available in an-backed form – can be used to seal the reveal between the glass to keep out moisture.
When using applied or coupled – sash units, it is important to realise that provision should be made for adequate ventilation without draughts. A completely sealed atmosphere with no air changes is neither healthy nor desirable.
An adequate form of double glazing can be provided by using double-sided tape and acetate sheeting. The double-sided tape is placed round the window surround to hold the acetate sheeting in place.
10. November 2011 by admin
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