Double Glazing & Windows
What are
Energy Efficient Windows & Double Glazing
Double glazing is a method of making a window with two layers of glass and a space between each layer.
It comprises of a sealed double glazed unit which is made up of two panes of glass separated by a space which is filled with an insulating gas (typically Argon) or turned into a vacuum before being sealed up.
This sealed unit (also known as and insulated glass unit (IGU) then sits within a frame which can be made in a variety of styles and materials to suit your property and requirements.
Obviously the main benefit of double glazing is energy efficiency and thermal insulation – preventing drafts, retaining heat and stopping colder outside air getting inside.
It goes without saying that it’s always worth upgrading from single glazing but, with advances in window technology and innovative use of new materials upgrading from old existing double glazing to new A++ units could also result in significant benefits
Double Glazing Example
What are the main benefits of double glazing?
Replacing old single glazed units with double glazing is going to give you the greatest impact. That said, upgrading existing double glazing will also deliver the same benefits as advances in technology means that new windows can be far more energy efficient and secure when compared with dated units. Obviously the impact of the benefits will be reduced to a certain degree.
Significant reduction in energy usage and cost: Estimates from the Energy Saving Trust indicate that you can save as much as £14 a month if you install double glazed windows. That’s about £170 per year for the average semi detached home.
Reduces Your Carbon Footprint: Lower energy consumption can only be good for the environment! Replacing single glazing with top rated energy efficient double glazing on an average semi could reduce CO2 emissions by over 400kg.
Reduced condensation: Keeping the temperature of the inner glass pane closer to the outside temperature reduces internal condensation.
Quieter living: Noise travels through solid particles such as air, solids and liquids. Your window insulates you against outside noise by providing a space between layers of glass that noise cannot travel through. This means that your home will be quieter.
Keeping heat in or out: Heat travels through the same particles as noise. This means that double-glazing your windows prevents heat from moving out of your home. This is especially important during winter. Likewise, double glazed windows prevent heat from moving into your home during hot seasons such as summer.
Enhanced security: Security is critical in any home. Double-glazing your windows provides an additional security barrier to any would be intruder because such windows have two layers of glass. This makes your home a bit safer than conventional windows.
Is all double glazing the same?
Absolutely not – different materials, different types, different styles and different energy ratings.
Energy Ratings
These are explained in more detail below but double glazing is rated for energy efficiency from a least efficient E right up to the best A++ rating
Glass
Different types for different requirements / environments.
- Annealed or float glass – the most common standard glass used
- Tempered or toughened glass – safer and more durable
- Laminated glass – higher security and reduced noise
- Low-emissivity (Low E) glass – improved energy efficiency and UV protection
- Self-cleaning glass – coated to keep clean
- Noise reduction glass – to reduce noise even further
Cavity
The space between the two panes of glass can be filled with different gasses – typically:
- Dehydrated air – heat and noise does not travel through it as easily as standard air
Inert gasses are also used – the main ones being:
- Argon – cheap and denser than air.
- Krypton – denser than argon and particularly effective when used in smaller cavities
Xenon – densest and highly insulating.
Frame Materials
The sealed unit sits in a frame which can be made in a variety of materials and coloured to your requirements. The most popular three are:
- uPVC (unplasticised polyvinyl chloride) – the most versatile and popular option
- Timber – natural product
- Aluminium – modern and stylish
Window Types / Styles
There are a number of types of windows and double glazing can be made in any of these:
- Casement – the standard style where windows can be side or bottom opened
- Tilt and Turn – can be fully opened for increased ventilation
- Sash – two panels one of which is fixed, the other can side up or down
- Sliding – frame slides to the side
- Bay – window protrudes out from the wall with brickwork below
- Bow – as above window protrudes out from the wall but without any brickwork support
- Skylight – window in roof
- Transom / Fanlight – window above a doorway
And you thought that windows were just windows!
Double glazing energy ratings explained.
Double glazed windows are rated from a poor energy rating of E right up to the very best rating which is A++. This makes it very easy for a consumer to assess the windows for energy efficiency.
The double glazing rating system was developed the British Fenestration Rating Council (BFRC) who describe themselves as “the UK’s most trusted rating council for verifying the energy performance of windows and doors, with the most widely-used energy rating system”. They rate the combined energy efficiency of a window by taking into account each component, from the casement to the frame.
Building regs also stipulate the minimum U-value of windows should be 1.6W/m²K or less … the lower the better.
The U-value represents the rate of transfer of heat through the window, divided by the difference in temperature across it. It is quoted in W/m²K.
How much does double glazing cost?
Completely depends on the property you live in, the size and number of windows you’re replacing and the style and quality of windows you go for.
Take an average house with eight windows and include two uPVC doors – in this case the cost of fairly standard casement double glazing is likely to be in the range of £8,000 to £12,000.
Sash windows, bay windows, tilt and turn windows etc are all going to cost more.
Are double glazing grants available?
Double glazing is classed as a grant approved energy efficiency measure within many of the Government schemes and so double glazing grants are available … but usually only if you meet the criteria and you’re replacing single glazing.
Unfortunately the advances in technology and improvements in energy efficiency of modern double glazed windows are yet to be recognised through grant support.