There may be concerns about the mechanical stresses set up within the double glazing units, where dummy frame members restrict the normal movement of both panes of the unit under environmental temperature and pressure changes. There are three situations which would be considered acceptable, irrespective of the type of glass specified. They are:

1. If they are ‘adhered’ to the outside of the unit, the dummy frame members should be ‘flimsy’ enough and the adhesive flexible enough so that the dummy frame members move with both panes of glass and do not restrict the normal movement of these panes under temperature and pressure fluctuations.

   Adhesive/sealant manufacturers should be asked for the most appropriate products to adhere the dummy frame members to the glass.



2. If dummy frame members are not adhered directly to the unit, then sufficient clearance, say 6mm, should be allowed between them and the unit. This is so no contact is made between the unit and dummy frame members during the normal movement of the unit under temperature and pressure fluctuations. The dummy frame members, in this case, are attached to the main mullion and transom by the frame maker, using methods of their own choosing.


3. If neither of the above conditions can be met then both panes should be supplied in toughened glass.