Windows

As with the glass itself, the frame material used in energy-efficient windows and doors is also important.

There are several options here:

• PVC-U has many benefits including performance longevity (usually 20 years or more) and is recyclable.

• Wooden frames are environmentally friendly and are often specified for properties where the use of original materials is necessary, such as those within a conservation area.

• Aluminium frames are an eco-friendly, modern choice because the creation of the material is low impact, recyclable and the slim look of the frames is desirable.

• Composite frames are composed of a combination of wood and aluminium or plastic.

For ease of purchase, certain window manufacturers label the energy efficiency of their windows with an energy rating ranging from A++ to C, A++ being the most efficient. This rating system has been developed by the British Fenestration Rating Council (BFRC) and it takes into consideration the entire window.

When this energy rating is given, a whole window u-value is also calculated. The u-value refers to how easily heat can pass through the unit. The u-value scale works in the opposite way to an energy rating, in that the higher the u-value, the more easily heat can pass through the window and the window is less efficient.

There are many benefits of EEG, which are increasing all the time as technology and building techniques advance, and our eco-awareness increases.

Key benefits include:

• Improved energy efficiency: Energy-efficient glazing may form part of a wider range of energy-saving measures. If your home also contains cavity wall insulation, loft insulation and an energy-efficient heating system, these can all work together to reduce the amount of energy needed to heat your home. As a consequence, you can enjoy lower energy bills and a reduced carbon footprint.

• Reduced noise pollution: Sealed double and triple glazing can be effective at reducing medium to high-frequency noise, creating a more comfortable, private and peaceful home environment.

See more: Glazing and noise reduction in homes

• Improved thermal insulation: Energy efficient glazing can help to keep your home warmer in winter and cooler in summer. The air or gas gap between the panes of glass in a sealed unit provides an extra layer of insulation. This increased thermal resistance reduces the amount of heat that can escape the home during the colder months. In summer the reverse occurs, and the windows help keep the heat outside, keeping the home cooler.

• Reduced condensation: Energy efficient windows and doors help reduce the risk of condensation which occurs when a cold surface and moist air meet. The resulting moisture can potentially damage the window frame and if it is particularly bad, may even affect other areas of the room.

See more: How double or triple glazing helps reduce condensation

• Safety and security: As there are two or more panes instead of one, energy-efficient glazed windows offer a more secure barrier against unwanted entry than a single glazed window. The level of security can be enhanced further when laminated glass is used.

• Cost savings: Assuming all other measures have been taken, Installing energy-efficient windows can save you money over the long term by reducing the amount of energy required to heat your home.The savings you gain from energy-efficient glazing will depend on a number of factors, including the size of the home, the type of windows you purchase and your energy supplier. For an indication of the potential savings, you could enjoy based on your home and windows.

• A more comfortable living environment: Lower heat loss, plus reduced noise, helps toward a feeling of a much more comfortable home.

• Increased home value: Making energy-saving improvements to your home has the potential to boost its value. Potential homebuyers are increasingly aware of the eco-credentials of any house they consider purchasing. According to a report conducted by the Government based on property sales made between 1995 and 2011, a homeowner making energy-saving improvements to their home could see a 14-38% increase in value as a result.

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 longwave 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 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.

Tint
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.

Haze
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.

Hue
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.

Overheating
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. Guidance should be sought from the manufacturer or supplier.