		Double Glazed Sealed Units


	CN Glass manufacture Double Glazed Units by hand to British Standards BS EN1279 Parts 2 & 3.

	A skilled workforce in traditional glass and glazing techniques working with the most up to date machinery providing high quality hand finished products for our customers. Unlike larger companies who have a production line of robotic machines that are supervised by a person and produce hundreds or even thousands of units per day we are limited to producing an average of 150 per day. We believe manufacture by hand produces a superior quality unit because each glass unit is constantly being monitored as it goes through manufacture and we are proud to put a 10 year guarantee on all our double and triple glazed units subject to the glazing of the units also being carried out to British Standards BS 6262.


	Double Glazed Sealed Units

Double Glazed Sealed Units are manufactured by us using either Aluminium Spacer Bar or Warm Edge Spacer Bar to provide the air gap between the two panes of glass.

The thickness of a normal double glazed sealed unit can vary in size depending on the frame. Below is a list of the thicknesses available:

Glass is a good insulator but it would need to be very thick as a single pane in a window to have much effect.

So rather than have thick glass in your windows it is better to have two panes of glass with an air or gas space between them.

The bigger the air space, the less heat is lost, up to an optimum of 20mm.

All well designed and well fitted double glazed units significantly reduce the intrusion of unwanted noise.

By specifying glasses whose thickness differ by at least 30%, resonance effects are suppressed and the acoustic benefits are, therefore, maximized.

What are the benefits of having Double Glazed Units?

Heat loss through single glazing will be at least halved with double glazed units

Draughts through windows caused by sinking cooled air will be less with double glazed units

Rooms will be warmer with double glazed units

Outside noise can be reduced with double glazed units

Condensation can be reduced with double glazed units

Increases the saleability of the property with double glazed units

Savings on fuel bills with double glazed units

Overall Depth

• 14mm

• 16mm

• 18mm

• 20mm

• 22mm

• 24mm

• 28mm

Glass x Spacer Bar x Glass

(4-6-4)

(4-8-4)

(4-10-4)

(4-12-4)

(4-14-4)

(4-16-4)

(4-20-4)

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A 20mm spacer is the widest available, so using 4mm glass the widest unit will be 28mm which is used as standard in all our PVCu and Aluminium windows and doors, with thinner units more commonly used in timber frames.

Most of the older timber frames tend to accommadate 14mm or 16mm units, with the newer timber frames (complying with the building regulations part L) typically being 20mm - 24mm.

Most sealed units we make now have 'Low E' glass to meet current building regulations and are 20mm or thicker.

	Critical locations

Since 1992 there has been a requirement in the England & Wales Building Regulations for robust or protected glazing in certain critical locations. This means the glass must either break safely, resist impact or be protected from impact by permanent guarding. Where Doubled Glazed Units are provided both sheets of glass will need to conform if people are likely to come into contact with the glass from either side (e.g. patio doors).

All tempered (i.e. toughened) or laminated glass must (with minor exceptions) be marked in accordance with BS6206.

Homeowners are becoming increasingly aware about safety in their homes and visible etched markings on all panes is the only evidence of complying with British Standards BS6206.

The diagram below shows the dark shaded areas as those requiring safety glass.

Small panes of 6mm annealed glass are suitable in critical locations if the area of the single pane is no more than 0.5m2 and the width of each pane is no more than 250mm.

Double Glazing Glass Options

Ordinary glass – called Annealed or Float glass

Safety Glass – This can be either Toughened, Laminated, Safety Wired Glass or Annealed glass with safety film applied to it.
Safety glazing is mandatory for new installations within 800mm of the floor in windows and partitions, and within 1500mm of the floor in doors and side panels. Glazing is marked in the corner with BS6206.

Security Glass - Laminated glass or Annealed glass with film applied to it.
When security glass is installed you must ensure there is an emergency escape route in case of fire.

Low Emissivity glass or Low E glass - The glass must be used in a double glazed window so that the special reflective coating, which is always placed inside the cavity, is protected from any damage

Decorative glass - This can be Opaque, patterned, Stained, Sandblasted or Etched.

In addition to the above standard glazing options there are a number of further choices to be considered
Low E Energy Saving Glass
Low-E Energy Saving Glass can only be used for glazing as part of a Double Glazed Unit. Low E Energy Saving Glass is designed to help insulate your home by keeping as much heat inside as possible. The glass has a transparent metallic coating on one side that reflects heat back into the room rather than allowing it to escape through the window. It also allows optimum amounts of sunlight to pass through the window. There are two choices of Low E Energy Saving Glass, these are called Hard Coat and Soft Coat. They both perform the same job but the soft coat has better thermal insulation, therefore reducing heat loss even further. The inner surface of the glass stays warmer thereby reducing the likelihood of condensation. And there is less of a yellowish tint or dusty appearance to the glass.
Self-Cleaning, low maintenance glass	Solar Control Glass
A transparent metallic coating applied onto the outside surface of the glass harnesses the power of both the sun and rain to efficiently remove dirt and grime such as dried water marks, dust, resin and insect residues. It will always be easier to clean and it will stay cleaner for longer. It is an excellent choice for areas of glazing that are hard to reach like roof areas.	Annealed, Toughened or Laminated glass can have a metallic coating applied to provide a high performance Solar Control glass. It has a slightly bluish tint that enhances visual comfort by filtering light and offers good solar control performance, therefore keeping rooms cool during sunny periods. Particularly useful on conservatory roofs, and large windows and doors.
Glass can also have a combination of all three of these metallic coatings.

	Accoustic Insulation

	All well designed and well fitted double glazed units significantly reduce the intrusion of unwanted noise. The greatest change in sound insulation occurs for cavity widths between 50-150mm.		By specifying glasses whose thickness differ by at least 30%, resonance effects are suppressed and the acoustic benefits are, therefore, maximized. Laminated glass is used as part of a double glazed unit to achieve a significant reduction in the intrusion of outside noise.

Gas Filling of Double Glazed Units. Argon - Krypton - Xenon

The introduction of gas into the cavity of a double glazed unit reduces the heat conductance between the panes, helping to keep more heat in during the winter and out in the summer. As a result living and working conditions become more comfortable the whole year round. The combination of Argon Gas and Low E energy saving glass can achieve an improvement in thermal performance in the region of 50% over and above that of a standard sealed unit.

Argon, which has 34% lower thermal conductivity than air, is the most commonly used. Apart from its heat insulation properties, Argon is non-toxic, sunlight stable, non corrosive, colourless and odourless.

Although argon-filled units cost around 5% more than air-filled units, they can improve a double glazing window’s U value or energy rating by over 30%. Argon fillings should last the lifetime of a double glazing window and over a period of 25 years should not lose more than 5%.

Krypton and Xenon are even more energy efficient than Argon but are seldom used in double glazing windows as they are more expensive.

It is important to note that sometimes you do have to use Krypton/Xenon when limited width is available. i.e.: in old buildings for example.

	Spacer Bar


			Aluminium Spacer Bar
			A spacer bar, sometimes known as a profile, is the continuous hollow Aluminium frame that separates the two glass panes in a double glazing window. The spacer bar is bonded to the glass panes via a primary and secondary seal, creating an airtight cavity which is filled with air or gas. The spacer bar itself is filled with a desiccant to absorb any residual moisture within the cavity and thus prevent condensation within the double glazing window. Spacer bars are an important contributor to a double glazing window’s energy ratings. Aluminium spacer bars are currently the most commonly used in double glazing windows. Light but strong, their flexibility means that they can be formed into a wide variety of shapes and sizes. Less expensive than warm edge spacers they are, however, less effective in insulating against heat loss than warm edge spacer bars.


			Warm Edge Spacer Bar
			Low E windows with the highest performing double glazing window energy ratings use a combination of Low E glass, warm edge spacers and argon gas-filled cavity. Warm edge (or thermal break) spacers reduce the heat lost around the perimeter of a double glazed window by replacing conventional aluminium with a low heat-conductive material. As with aluminium, thermal break spacer bars are filled with a silicone desiccant to absorb any moisture within the double glazing window and can contain dry air or gas-filled cavities. Thermal break spacer bars further reduce condensation on the room-facing surface of the double glazing window as they transmit less of a temperature difference to the interior pane. Warm edge spacer bars have the same geometrical form as a metal spacer bar, but are usually made from a fibre-glass reinforced insulation material. An ultra-thin foil lining acts as a barrier to the gas or air trapped within the cavity. Some warm edge spacers are available in an array of different colours.


			Edgetec Super Spacer
			Super Spacer introduces no-metal, pre-desiccated, structural foam spacer system that is a warm edge technology to suit all sealed glass unit applications helping to deliver windows of the highest standards. It offers a complete solution for Georgian Bars, simulated divided lights and astragal bar windows. Super Spacer is a flexible material that does not have to be cut and jointed by keys (elbo joints) to form shapes. Its award winning, patented Thermal Set Spacer (TSS) technology gives the ultimate in high performance spacer systems. Super Spacer has 100% memory and allows for expansion and contraction, a major cause of fractures in conventional sealed units. Most PVC-U and traditional timber windows include low line glazing beads and gaskets. This creates problems for standard aluminium spacer bars which protrude into the sightline of the window. Super Spacer has a lower sightline (equivalent to only 9.8mm from the edge of the glass) which eradicates the problem. Super Spacer also takes on the appearance of the colour of the profile into which it is glazed. For example, if Super Spacer is glazed into white profile the spacer reflects back white. Super Spacer is produced down to a minimum depth of 4mm allowing us to produce the VERY THIN Double Glazed Units suitable for glazing in conservation areas and listed buildings (subject to planning permission). It is important to note that sometimes you do have to use Krypton/Xenon when limited width is available. i.e.: in old buildings for example.

	Leaded and Georgian Styles

Leaded Designs	Aluminium Georgian Bar	Astragal Georgian Bar
The most common lead light designs are rectangular/square and diamond shaped designs. Other alternatives such as Tudor and Elizabethan designs are available. The lead is applied to both sides of the outside piece of glass in a double glazed unit prior to assembly. Please note the lead is only ever applied to one of the two pieces of glass making a double glazed unit. The inside is usually left as clear glass in order to make internal cleaning easier. Coloured film may be used between the lead to create patterns and pictures often used for a glazed panel in entrance doors.	Aluminium Georgian bars are flat shaped bars that are painted the same colour as the window frame and are made up into a grid with cross centres that join the bars together. The grid is then integrated inside the double glazed unit during make up, therefore looking like a Georgian style but unlike a traditional Georgian window there is only one pane of glass to clean.	Designed to replicate the traditional Georgian Bars found on timber windows. Use of an Astragal Bar system gives you the true effect of a Georgian window. Although the sealed unit remains in one piece the internal divide effect gives the impression of multiple units. Astragal Georgian bars are made up using the same Aluminium or Warm Edge spacer bar to create the Georgian style inside the double glazed unit. When the unit is glazed into the window frame the astragal bars are then placed over the spacer bars.

Triple Glazed Sealed Units

Expertly designed assembled and installed triple glazed windows will significantly reduce energy usage in a new dwelling.

At its most basic a Double-Glazed Unit will consist of two pieces of glass seperated by a spacer bar which denotes the thickness of the cavity. By using three panes of glass and two spacers we can make a Triple-Glazed unit.But to put things in

context, a single-glazed window will have a U-value of 5.0W/m2, double-glazed will be between 2.2 and 1.2W/m2 and triple-glazed 1.0 to 0.6W/m2.
In a new build, installing double glazed windows is a must, but there is little point in triple-glazing unless you have super-insulated the rest of the house. Triple-glazing will cost about 20 per cent more than double-glazing and reduce the overall heat loss by about 5 per cent.

Our Terms and Conditions

CNGlass services clients in Chipping Norton, Banbury, Oxford, Cheltenham,and the surrounding counties of Oxfordshire, Gloucestershire,
Warwickshire and South Northamptonshire. Double Glazing and Conservatories.