In accordance with EN 673, the Government specify a maximum u-value for double glazed windows of 2.0 W/m²K. At Weatherproof Windows we can achieve 1.15 W/m²K with a combination of products and techniques, an improvement on the legal requirement of approximately 45%!

Laminated Glass

Capable of withstanding an attack.

Sheets of glass are bonded - or laminated - together with a layer of polymer film (PVB) in between. By using heat and pressure, air bubbles are eliminated from the laminate (in equipment called an Autoclave) so that it appears optically as a single sheet. Laminated comes in several different thicknesses and can be used as a form of security. Standard thickness is around 4.5mm, we would advise a minimum of 6.4mm for household security.

Toughened Glass

Used for areas in need of extra safety, glazed doors and glazing adjacent to doors as standard. Float glass is heated to about 650C in a furnace, then quenced with air jets so that the surfaces are cooled quickly and the inside core more slowly with the surfaces going into 'compression' and the core going into 'tension'.
(Toughened Glass is NOT for security but purely for safety)

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‘Low-E’ Glass

‘Low-E’ glass which usually forms the inner pane of a double glazing unit, allows less heat to escape through your windows than ordinary glass. Thanks to a special energy saving coating which lets the sun’s rays through, but reflects heat from fires and radiators back into your home. Also available as laminated, toughened and patterned.

There are several versions of ‘Low-E’ glass:

• ‘K’Glass - made by Pilkingtons
  will achieve an energy rating of ‘E’ which is 1.7.
  This is the base of UK Regulations but does not meet EU regulations which is a minimum of 1.5
• Soft Coat Glass - made by Saint Gobain
  and has an energy rating of 1.4 which is ‘C’ rated.

‘Low-E’ glass benefits:-

Heat Efficient Windows

• Radiant heat originating from indoors is reflected back inside, thus keeping heat inside in the winter.
• Infrared radiation from the sun is reflected away, keeping it cooler inside in the summer.

Hard / Soft Coated Glass
Hard coated ‘Low-E’ products, such as Pilkington K, have been used predominantly in the UK. They are easier to process but have a slight champagne tint which can make white net curtains look discoloured. A better U Value can be achieved with a soft coated glass such as Saint Gobain's Planitherm, which reduces heat loss further. The product is also much clearer with no visible tint.

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Gas Filling

Insulation glass without ‘Low-E’ coating uses air between the panes as a primary source of insulation. As air itself is a good insulator, filling the gap between the glass panes with a low-conductivity gas such as argon reduces conductive and convective heat transfers. This is because the density of the gas is greater than the density of the air.

Argon is the most commonly used fill gas, due to its excellent thermal performance and cost-efficiency in comparison to other gas fills. Argon gas reduces heat loss in sealed units by slowing down convection inside the air space. It is extremely cost-efficient, and works well with ‘Low-E’ coated glazing. Argon and Krypton are colourless, odourless, non-flammable and non-reactive inert gases.

Several techniques are used to fill the IG cavity and all techniques result in a mixture of fill gas and air. It is generally accepted that the IG unit should achieve a 90% fill gas concentration. Over time this concentration will gradually evaporate, at an estimated rate of 0.5 to 1% per year. IG units filled with argon do not degrade significantly until they reach 75% concentration, which means up to 20 years of durability.

A major benefit of IGU is that it is passive, so it does not require a switching-on process to work. Argon gas is a relatively inexpensive option, and quickly produces heat cost-savings that justify its cost.

Krypton is more effective at reducing heat loss, but is roughly 200 times more expensive than argon per unit volume. Because Krypton works best at smaller pane spacings (8 mm), it is often used in triple and quadruple-glazed windows to minimize the overall thickness of the unit.

Other types of gases are used (for example, sulphur hexafluoride, carbon dioxide) to reduce sound transmission, but these gases do not offer the improved thermal performance of the inert gases.

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Self Cleaning Glass

Recent innovations in glass technology have given us "Self Cleaning Glass" which has been heavily promoted as Pilkington "Activ" or Saint Gobain "Bioclean". These are predominantly used for conservatory roofs or any areas that can be hard to reach for cleaning purposes. The chemical reaction reacts to organic substances which adhere to the glass and activates when rain falls, which helps release the dirt particles. Other glass cleaning chemicals should not be used on this type of glass for cleaning purposes.
We must point out that Self Cleaning Glass is not the same as having a window cleaner.

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Warm Edge Spacer

Did you know that almost half of all the UK's carbon dioxide emissions come from our buildings and homes?

Windows play a huge role in this. According to the Energy Saving Trust, around 20% of the heat lost from an average home occurs through the windows. The heat lost contributes half a tonne of CO2 per home to the atmosphere and increases fuel bills.

Reduce Heat Loss Through Your Windows
Warm Edge Spacer is approximately 950 times less conductive than aluminium and, as most of the heat loss through a window occurs at the edge of the unit, standard metal spacer bars act as a thermal energy drain allowing heat to escape from your home. Warm Edge Spacer blocks the escape route.

Warm Edge Spacer, is new energy saving technology. Windows with Warm Edge Spacer reduce heat lost through your windows, helping to keep your home warm. Less heat lost also means lower fuel bills and lower carbon emissions.

Reduce Noise & Condensation
There are many other benefits of installing windows with Warm Edge Spacer. It reduces condensation by up to 65%, virtually eliminating the potential breeding ground for bacteria, mould and dust mites that can be harmful to people with respiratory diseases. Warm Edge Spacer also reduces noise transmission by up to 2dB which helps you keep your home an oasis of calm, away from the noise of the outside world.

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Window Energy Ratings - W.E.R's

Many Window companies will be trying to achieve high energy ratings to add to the quality of their overall product range and to offer consumers greater informed choices about the products they offer.

Window profiles are part of the story but as glass makes up most of the area in a window and the components used in its construction are critical to achieving good levels of insulation.

Instead of just Centre pane U value the W.E.R is concerned with the heat loss of the whole window.

Therefore a combination of Coated Glass, Low Iron Glass, Warm Edge Technology and gas filling is critical to achieve a good rating.

Energy Saving Recommended Windows:
Just like washing machines and freezers, windows are energy rated by the British Fenestration Ratings Council on a scale of A-G. Windows achieving a rating of C and above are endorsed by the Energy Saving Trust’s Energy Saving Recommended (ESR) scheme and carry the EST’s swing tag logo.

Make sure you ask for windows with the Energy Saving Recommended logo and Warm Edge Spacer inside to ensure the best energy efficiency.

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Technical Information:- However you use glass it is essential for safety and performance reasons that it is correctly specified and installed. Common areas of impact risk, where it is recommended that impact safety glass to BS 6206 is installed, include: Glazed doors, Glazing adjacent to doors, Low level glazing, Bathroom areas, Protective barriers, Furniture and cabinets.