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Acoustic, heat soaked toughened secondary glazing for offices


Treat Of The Month


acoustic secondary glazing, fixing methods, curtain wall and ribbon windows, scheduling, low level glazing

This treatment required specific performance from the glass in the secondary glazing. Firstly the client wanted very good acoustic performance and secondly they wanted to reduce any risk for the building users from this floor to ceiling glass treatment. To meet the requirements, 12mm heat soaked toughened glass was specified for all the secondary glazing. 12mm glazing with a 200mm cavity or greater provides a sound reduction in the order of 49dB in combination with the primary glazing and 12mm toughened glass provides an excellent barrier at low levels. toughened glass building images Furthermore, heat soaked toughened glass reduces the risk of spontaneous breakage by removing the nickel sulphide impurities. These are removed by elevating the temperature of the glass to around 280° and holding it there for several hours. Spontaneous breakage is very rare but can occur in toughened glass without any warning. To mimic the original sightlines and to blend seamlessly with the original primary glazing, a mixture of 2 and 3 pane horizontal sliding sash units were specified and manufactured. Each of the 28 units was made individually to fit its designated opening. Typical pane sizes were 2700mm high and 1500mm wide weighing in at over 120kg each. To cope with such heavy panes Series 80 units were used throughout the project. These frames are unique to Selectaglaze and have been designed to provide both uninterrupted sightlines combined with profiles that provide sufficient strength to safely support sizeable, heavy panes of glass. As with all large scale projects careful planning and a detailed work schedule was drawn up between Selectaglaze and the client to ensure that manufacture, delivery and installation could be achieved safely, smoothly and on time. The fixing of the units was staged, due to the scale of the project spanning four floors. Care had to be taken to ensure that the materials were transportable to all the required locations, without breakages or causing harm or injury. The Series 80 units were installed with cavities greater than 200mm to create a sound deadening air gap between the secondary and primary glazing, as well as allowing for maintenance. Removable clip beads were added to the track to make the sashes static keeping them fixed in the fully closed position. When access is required for maintenance or cleaning, the clip beads can be removed. Once the secondary was fitted, head and footer trims were added to the whole installation, to give the impression of a curtain wall to match the primary glazing. Selectaglaze successfully achieved a safe and long lasting installation for the client. Noise ingress was reduced by 49dB and the thermal efficiency was improved too. Secondary glazing provides a highly effective thermal envelope which can reduce heat loss by up to 60%. Given that the buildings external walls are almost exclusively constructed of glass, it is predicted that significant energy savings will be made for many years to come with the introduction of the secondary glazing.