Genuine UK industry technological advances in double glazing over the last decade mean that the first and second generations of replacement double glazing (which at the time were a significant improvement on single glazing) have long since been overtaken by “thermally broken” energy saving efficient windows, that achieve far better and higher energy ratings than their predecessors could manage.
WER’s (Window Energy Ratings) were introduced by the UK Government many years ago to help property owners know how thermally efficient any particular combination of frame, gaskets and double glazed glass sealed units were. On 1st October 2010, the Building Regulations in England and Wales changed so that from that point on, double glazing installers, suppliers and home owners had a legal responsibility if and when replacing windows, to replace them with either an independently tested “C” energy rated, “B” energy rated or “A” energy rated window, with until fairly recent times an “A” being the highest rating available, and “C” being the minimum standard permitted under these regulations.
The legislation brought about major changes throughout the double glazing industry, whereby it had to suddenly assign to the scrap heap any outdated non-thermally broken window products (i.e. any combinations that were unable to achieve the minimum “C” rating) and in their place introduce more expensive, more technologically advanced, higher quality, better designed thermally broken products, be the window frames made out of aluminium, wood or PVCU (unplasticized polyvinyl chloride).
The subsequent improved living environment, both domestically and commercially, combined with the resultant financial savings on energy bills for property owners, has led to much of the UK housing stock and commercial properties being better insulated, so much so that domestic home owners looking to sell their properties with older outdated double or single glazing are now severely disadvantaged in today’s highly competitive marketplace, with them not being able to achieve the sale price they had hoped for, as savvy buyers get quotes to replace all the outdated windows and doors, which they then use to drive down the selling price.
For UK double glazing manufacturers to achieve even a “C” window energy rating (which in itself is a real decent level) they need a window outer frame and opening window sash vent that is thermally broken (i.e. where the outer pane and inner pane are separated, so that the cold on the outside cannot interfere with the heat generated and gained internally) and a high specification double glazed sealed unit with a warm edge spacer bar separating the inner and outer glass panes which is filled with an inert gas like Argon, which not only acts as an insulator, it helps with sound reduction.
More recent technological advances enable certain PVCU window and door products to obtain an even greater energy ratings than “A”. Some double glazing companies use triple glazing to achieve better than an “A” rating, whereas others have opted to improve their double glazed frames and sealed units, making them more robust as well as more thermally efficient at the same time.
Triple glazed sealed units costs more than double glazed sealed units to manufacture and buy, simply because there are 2 warm edge spacer bars, rather than 1 warm edge spacer bar, and 3 panes of glass rather than 2. This obviously means triple glazed sealed units cost more to replace if they break down or crack than double glazed units, a factor worth noting if choosing between the two glazing options.
Independent double glazing suppliers and installers Hazlemere Window Company Ltd have been replacing windows in the South of England for over 34 years. Several years ago they switched all their PVCU casement windows with side hung and top hung opening vents to be A+ window energy rated as standard. The outer window sash on the higher quality bespoke PVCU energy rated windows they supply and install now has 6 chambers, which increases the thermal break between the internal and external, as well as the overall robustness of each PVCU window. They also offer a PVCU triple glazed window with a slimmer outer frame that has an A++ window energy rating.
Given it is now possible to have professionally fitted bespoke A+ energy rated double glazed windows installed for far less than A++ triple glazing, it makes more financial sense to invest in double glazed A+ energy rated windows rather than triple glazed. Finally, be warned that even if the most thermally efficient windows available are not well fitted, they won’t perform to the standard they were designed for, so it is important to select an experienced installer you can trust to do a professional project.
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