Good information on double glazed windows and insulation.

Myth - Planning permission is needed to replace windows

Fact –Planning permission for replacing windows is needed only for listed buildings, for homes in conservation areas, and for flats.

Myth – Condensation on windows is something you have to live with

Fact - By installing well insulated (or Low E) double glazing, condensation problems on the room-side of the window can be greatly reduced. If the double glazed unit incorporates warm edge (or thermal break) spacers, condensation can be reduced still further. In a properly sealed double glazed unit there should be relatively little condensation in the window’s inner cavity as dehydrated air and desiccants are used.

Myth - Secondary glazing is just as energy efficient as double glazing

Fact – The insulation properties of secondary glazing are far lower than those offered by true double glazing – and especially those offered by Low E double glazing. Houses with secondary glazing will be score a poor energy rating on the new compulsory Energy Performance Certificate – which is now required for the sale of any home.

Myth - All Low E glasses offer the same levels of energy saving

Fact – The U (or energy saving) value of Low E glasses can vary by up to 25%. The most efficient Low E glasses have a special coating applied online using a process known as magnetron sputtering. This coating stops indoor heat from escaping but allows natural heat energy from the sun to pass into the room (Solar Heat Gain). Only double glazed units which combine high performance Low E glass with warm edge spacers and argon gas fillings are capable of achieving an ‘A’ grade on the official Window Energy Ratings scale.

Myth - Offline coatings are fragile and easily damaged

Fact - Offline coatings, which are applied after the basic sheet glass has been manufactured and cut, were previously considered less resistant than online coatings. However, the latest magnetron coating technologies mean than offline coatings are now far more durable and can even be heat treated for toughening. The new magnetron coatings also give glass superior clarity and transparency.

Myth - If argon gas is used to fill double glazed units, it can leak into the room

Fact - Argon gas fillings should last the lifetime of a double glazing unit and should not leak by more than 5% over a period of 25 years.






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