Not all glass is the same, and people choose new windows or glass doors for many different reasons, from security and energy saving to noise reduction, appearance, low maintenance, fire resistance and safety. There is a type of glass for each of these needs.
Low-E Glass
With today’s energy bills, keeping the house warm matters more than ever. Low-E glass, which stands for low emissivity, has an invisible metal oxide coating that reflects heat back into the room while still letting light in, improving thermal insulation. Combined with good-quality double or triple glazing, Low-E glass can help cut your heating bills. If you think this is something your home could use, talk to Double Glazing Worcester based company Firmfix about the latest options.
Energy Ratings
Energy-efficient windows are given ratings so you can see what you are getting. Performance is measured by the U-value, which shows how much heat escapes, and the g-value, which shows how much heat from the sun gets through. Window energy ratings in the UK are run by the British Fenestration Rating Council (BFRC).
Acoustic Glass
In towns and cities, traffic noise can reach around 70 decibels. We may get used to it, but long-term exposure to noise has been linked to health problems such as heart disease. For homes near busy roads or under flight paths, acoustic glass can help reduce the noise that gets in.
Safety Glass
Toughened and laminated glass are designed for safety. Toughened glass breaks into small, blunt pieces, while laminated glass holds together when broken, which also makes it harder for intruders to get through.
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Laminated glass and why it matters overhead
Laminated glass is made by bonding two or more sheets of glass to a plastic interlayer, usually PVB or EVA, under heat and pressure. If the glass breaks, the interlayer holds the fragments together and keeps the pane in its frame, which is why it is used wherever security matters or glass sits overhead, as in rooflights and glazed roofs. It also cuts noise better than an ordinary pane.
The interlayer needs care. PVB absorbs moisture, so poor storage or badly sealed edges can make it turn cloudy or begin to separate from the glass, known as delamination; stresses from a poor fit can cause the same problem. For rooflights, heat-strengthened laminated glass is often the preferred specification. It is roughly twice as strong as ordinary annealed glass, resists cracking from thermal stress, and is not prone to the rare spontaneous breakage that tiny nickel sulphide inclusions can cause in toughened glass.
How safety glass is made and where it is needed
Laminated glass is made by bonding two or more sheets of glass to a tough plastic interlayer, usually polyvinyl butyral. If it breaks, the fragments stick to the interlayer, so the pane cracks into a spider-web pattern but stays in its frame. That is why it is used for car windscreens, shopfronts, glass balustrades and overhead glazing, and why it adds security in windows and doors.
Toughened glass is ordinary glass that has been heated and then cooled rapidly. This puts the outer surfaces into compression and the core into tension, making it several times stronger than standard glass. When it does break, it shatters into small, blunt granules rather than sharp shards, so it is used in shower screens, glass doors and fridge shelves. It cannot be cut or drilled after toughening, so it has to be made to size. In homes, safety glass is required in critical places, such as doors and low-level panes, and should carry a permanent mark in one corner.
Choosing frame materials for double glazing
The glass is only half of a window. Frames were once always wood, with steel and aluminium arriving in the first half of the 20th century, but these early frames let heat escape. uPVC was introduced in the 1980s as an energy saving option and is now by far the most popular choice.
Wood is the most expensive material. It insulates well and has a classic look, but it needs more maintenance, although it can be stained or painted. Aluminium is very strong, with thin frames that let in plenty of light, and modern versions achieve almost the same energy ratings as uPVC with very little upkeep.
As a rule, properties built before the 20th century benefit from keeping timber windows for their period character. Homes built from the mid 20th century onwards suit uPVC, while aluminium looks striking on contemporary designs with plenty of glass. Whichever you choose, clean frames with a soft cloth and mild soapy water, avoid abrasive or ammonia-based products and use only light oil on hinges and locks.