Why its a no brainer fitting energy rated replacement double glazing to dwellings

As UK household energy prices are not going to be an cheaper, even one bed flat owners in Britain benefit from having energy rated, thermally efficient double glazed windows installed, especially when done in conjunction with draught proof doors.

Consequently the larger your property, the greater the energy savings you are going to be making by having genuinely thermally efficient double glazing fitted, as obviously it costs exponentially more to heat a dwelling the larger it gets.

Long ago many UK homes were fitted with “first generation” double glazing, which whilst revolutionary then, is now (in today’s terms) rather old hat and not very energy efficient. Many home owners have improved their older larger properties by having cavity wall insulation and loft insulation fitted, but have not yet fitted modern thermally broken double glazing, and are still losing heat through the original single glazing or non-thermally broken first generation double glazing, which although better than single glazing, is a very poor insulator given the technology now available.

Since there are now official BFRC (British Fenestration Rating Council) approved “A+” and “A++” double and triple glazed UPVC windows that are even more thermally efficient than “A” rated windows. It is difficult to explain how much more energy efficient these higher rated energy saving products are when compared to single glazed windows or indeed the first generations of double glazing.

For example, many UK dwellings were years ago fitted with silver anodised aluminium double glazing within hardwood frames, with some home owners subsequently reporting occasional condensation on the inside frames on cold mornings. This condensation can be caused by various factors, firstly often insufficient ventilation within a room and secondly by the fact the product does not have a “thermal break”. Nowadays high quality aluminium windows have a polyamide thermal break between the inner and outer frames which prevents the external cold surface of the outer window pane meeting the warm surface of the inner window pane, hence why today you can purchase “A” rated thermally broken aluminium double glazing as well as thermally broken “A” rated UPVC double glazing (the latter achieving the thermal “break” by a number of UPVC chambers).

Whatever material double glazing frames are made of, the other crucial element of an energy efficient double glazing system is the sealed unit. Most energy saving windows need a sealed unit with a centre-pane U-Value (a measure of thermal efficiency) of about 1.2 W/m2K to enable it to achieve an overall energy rating of “A” or more when combined with the gaskets and window frames.

Consequently the glass sealed unit specification is critical to the overall energy performance of double glazed windows. In between the two panes of glass (usually each 4mm thick) is an air gap of 16mm to 20mm. These two panes are separated by a “Warm-Edge” spacer bar to prevent thermal transference. This vacuum gap is then usually filled with 90% Argon or Krypton which basically helps retain warmth generated by the property’s heating system on cold winter days and helps keep out excess heat on hot summer days.

For example, independent double glazing manufacturers and installers Hazlemere Window Company (whose Head Office and 38,000 square foot factory is in High Wycombe in Bucks) use a high specification of glass as standard in their sealed units for their replacement windows. On the external pane they use a very clear low iron glass with no “green” colouring, which allows more light and heat into a room (Solar Gain). This clear glass reduces the amount of artificial light required, thereby saving on electricity bills. On the internal pane they use a high performance low emissivity glass, a product which has a special “softcoat” coating on the internal side of the inside pane, which helps retains heat that has been generated by the central heating system or by solar gain, or both!

Softcoat glass has a highly neutral appearance with optimal solar heat gain, thermal insulation and light transmission to provide the highest Window Energy Rating (WER) performance. The WER scheme is the UK Government backed method of assessing and ranking the energy efficiency of a complete window. Taking into account its U-Value, solar gain and air infiltration, the scheme allows straight forward comparison of the energy efficiency of different windows, with an “A” or higher rating being the best and “C” rating being the minimum replacement windows must achieve in order to comply with the current Building Regulations.

Those with larger homes that have thermally inefficient windows and doors who want to future proof their homes against rising energy bills therefore need to replace their old draughty windows with modern thermally broken energy rated double glazing. Whatever the size of your dwelling fitting technologically advanced replacement double glazing is therefore an absolute no brainer.


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