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Energy Efficient Glass

We only fit energy efficient glass which is rated at least ‘C’ and we offer the exceptional value of higher rated ‘A’ glass. All our units are Argon filled, which acts as an insulator to further improve the efficiency of your new glass.
Low-E (Low Emissivity) Glass And Thermal Efficiency
What Is Low-E Glass?
Low emissivity glass is glass that has an invisible microscopic coating applied to it in order to improve its thermal efficiency.

How Does Low-E Glass Improve Thermal Efficiency?

Low emissivity glass is an essential part of most energy efficient windows and doors. It has a surface coating that operates as follows:

  • It allows short wavelength heat from the sun to enter your home through the glazing.

  • This solar energy works with your domestic heating system to warm up your room, which then gives off long wavelength heat radiation.

  • A large proportion of that long wave heat would vanish back out through windows made of ordinary glass. However, the Low-e coating reflects that heat back into your room so the heating system does not have to work as hard to maintain a comfortable room temperature.

Will Low-E Glass Meet The Building Regulations?

Better than merely meeting the Building Regulations, Low-e glass will enable you to both achieve and surpass the new targets for windows and doors.

What Other Characteristics Should I Be Aware Of?

Whilst there are significant advantages to selecting thermally efficient Low-e glass for your home, there can be some side effects under certain conditions.


Recent innovations in creating neutral Low-e coatings minimise the phenomenon of light coloured materials (such as net curtains) appearing slightly darker when viewed through the glass.


This phenomenon may occur at times of the day when the sun is at a particular angle or under some lighting conditions. It can also be influenced by the type of Low-e coating used.

External condensation

Thermally efficient windows are so good at keeping the heat in that the outer pane can get cold, as it is no longer being warmed by wasted heat.

Under some weather conditions and at certain times of the year, this can result in the formation of condensation on the outside surface of the glass. This is a positive indication of a thermally efficient window.


Depending on coating type, glass substrate and glass thickness, some slight colour or hue differences may be noticeable on Low-e glass.

This may be more evident when one double or triple glazed window unit is replaced in a home, as the Low-e coating will likely be slightly different (i.e. from a different batch) from those on the other window units.


Certain Low-e glass is good at solar heat gain, harvesting free heat energy from the sun, helping to reduce heating demands. In some situations, this can cause overheating resulting in an uncomfortable environment.

It is recommended that a combination of Low-e and solar control glazing be considered for large glazed areas, particularly south-facing conservatories.

    Other considerations

    The glass is important but it is only part of the overall efficiency of your windows. At ReSealed we can advise you on the state of your draught seals, hinges and handles, as well as the glass. Some older sealed units were made with thinner spacer bars (the bit separating the panes of glass), modern sealed units have a spacer bar of a minimum of 12mm. We only fit this type of modern efficient units.