Sealed Units FAQ

How is a sealed unit made?

1. The two glass panes that will be used to make the sealed unit are measured and cut. Cutting The Glass

2. The aluminium spacer bar is then cut to the correct length. The width of the spacer bar determines the cavity depth within the sealed unit. The spacer bars can be different colours, eg black, silver. The completed frame is filled with desiccant which aborbs any moisture that may build up between the two panes of glass. Cutting The Spacer

3. The glass panes are then fed through the automatic washer/dryer using demineralised water. After being washed they are thoroughly inspected by the operator. For leaded units, the leading is applied to the glass which is then fed through the washer a second time. Washing And Inspecting The Glass

4. If bevels have been applied to the glass they are now 'cured' using a UV light unit. This takes approximately 10 seconds to cure the bevels, instead of the 12 hours it would take without it. 'Curing' the bevels

5. The glass is then transfered to the assembly machine where the hot melt insulating glass sealant is applied at 175ºc into the cavity around the edges of the glass. This forms an air tight seal between the panes. At this stage the unit can be filled with Argon if required.

6. The completed unit is then taped around the edges in order to facilitate safe handling by the fitters, and stored on a glass rack ready for delivery/collection.

Properties of Pilkington 'K' Glass

Christie Glass uses Pilkington 'K' glass.

Pilkington 'K' glass varies from normal clear glass in that one side of the glass has a special metal coating known as a low emissitivity coating.

This very fine metal coating allows shortwave radiation through, such as sunlight, but reflects longwave radiation such as heat from fires and radiators.

This coating also makes the surface warmer to the touch and condensation is also reduced.

The Pilkington 'K' glass is said to be up to 30% more efficient in its insulation than other types of double glazing.

This of course results in reducing your fuel bills and makes your home much more comfortable.

The value of Argon filling

When gas is introduced into the cavity of a double glazed unit, it reduces the heat conductance between the panes. This helps to keep heat in during the winter and out in the summer. When used in conjunction with Pilkington 'K' glass on the inside of the sealed unit the thermal insulation is greatly improved.

The pairing of Argon gas and Pilkington 'K' glass can achieve an improvement in thermal performance of approximately 50% over a standard sealed unit.

In addition to its excellent heat insulation properties, Argon gas is sunlight stable, colourless and odourless, non corosive, and is non-toxic.

When is toughened/safety glass required?

The shaded areas in below diagram shows the areas in which safety glass must be used. Glass used in these areas must comply with BS 6206.

Where only part of a unit contains a shaded location the whole of that unit must comply with BS 6206.

Safety glass is 5 times stronger than normal glass, and is ideal for vulnerable ground and first floor installations, and also most importantly for conservatories.

On impact safety glass disintigrates into small granular pieces which are not sharp, thus reducing the risk of injury.