Upgrading Windows - As Easy as A, B, C!

Poorly insulated window frames and single glazed windows account for up to 20% of heat loss in the average home. If you upgrade to energy efficient windows, you can help reduce your energy consumption and save money!

In recent years, windows have undergone a technological revolution to bring them up to today's insulating standards. Upgrading single glazed windows with energy efficient ones will not only make the property more secure, warmer and more comfortable to live in, but they will also help reduce your home's energy bills and enhance your property's overall appearance. The wide variety of materials, sizes, and colours for windows has opened a new world of design possibilities, which is limited only by your imagination and budget!

Above: Passive House standards can now be achieved with these Upvc/Alu-clad windows from Internorm (Passion Vetro Design and Thermoj). They are triple glazed as standard and come in a range of shapes and colours. Visit www.ecoglaze.iefor more information.

So what are energy efficient windows?

They are windows that help contain and conserve heat with i n the home, resist condensation and benefit from solar gain. They can be made using any frame material aluminium, uPVC or timber or even a combination of materials. Energy efficient windows are easy to recognise - simply look­ for its energy rating, as classified by the British Fenestration Rating Council (BFRC), where 'A' is the most efficient. The BFRC scheme assesses the total energy performance of a complete window (not just the glass) and allows accurate comparison of the performance of windows under identical conditions. The most energy efficient windows (A being the most efficient) also carry the Energy Saving Recommended logo issued by the Energy Saving Trust. NB. Glass doors are to be included in the BFRC rating scheme in 2009. Conservatories are currently excluded.

How much do energy efficient windows cost?

The cost varies not only between the various ratings but is also dependent on the frame materials, type of glazing used and the size and style of the overall window. A-rated windows will cost more than B, C, 0 and E rated windows, but when offset against the energy savings you will make, this is comparatively low.

How much would I save on my energy bills?

According to the Energy Saving Trust, when you replace single glazed windows with Energy Saving Recommended double glazing, you can cut heat lost through windows by half, as well as saving around £140/€160 a year on your heating bills (which at the time of writing this, was the equivalent of around 400 litres of home heating oil!) It can also save you around 720kg of carbon dioxide (CO2) a year.

How much could I reduce my carbon footprint by?

It is generally recognised that if you live in a single glazed house and install energy efficient windows you could reduce the energy you use by 0.30 tonnes (or 18%) per year. This calculation is based on 'an average, semi-detached house'.

Frame Type

The material used to manufacture a frame not only governs the physical characteristics of the window, such as thickness, weight, and durability, but it also has a major impact on its thermal characteristics. Since the frame represents 10-30% of the total area of the window unit, the frame properties will definitely influence energy performance and looks.

uPVC - A derivative of plastic, this material requires no painting. The choice of colours and textures has grown, from imitation timber to stand alone colours. They can easily be cleaned and aren't subject to attack from woodworm and insects. However, they can warp or discolour over time.

Timber Wood - this is a natural and sustainable material which comes in a variety of colours depending on the type of timber being used. It's warm to touch and can be stained or painted to suit your interior style. Minor maintenance is required to prevent moisture building up and rotting the frame.

Aluminium - This is perhaps the strongest and most durable of materials as it maintains temperature in accordance with the seasons and has an excellent lifespan. However, when it's freezing outside, aluminium can be exceptionally cold to the touch, which is why some window manufacturers have introduced Alu-Clad systems which have aluminium outside and another material inside. The aluminium protects against rain, hail, UV light, dust and air pollution, and comes in a range of colours or even timber effect finishes. On the inside, timber, vinyl or uPVC can be used to provide a warmer and decorative finish.

Above: These vertical sliding sash windows combine the elegance of traditional sash windows with all the benefits of modern uPVC - strong, won't rot, warp or require repainting. Available in cream, white or oak with brass, chrome or white window furniture. BFRC rated 'C and available from Camden Group, www.camdengroup.co.uk


There are three fundamental approaches to improving the energy performance of glazing products (two or more of these approaches may be combined).

1. Alter the glazing material by changing its chemical composition or physical characteristics, ego tinted glazing.

2. Apply a coating to the glazing surface.

Reflective coatings and films were developed to reduce heat gain and glare, while low-E coatings improve both heating and cooling performance. There are even coatings available for the exterior to break down dirt!

3. Add multiple layers of glazing with low conductance gas to the spaces between the layers; and use thermally improved edge spacers between the panes.­

Upgrading your glazing to include specialist coatings will help you save money controlling solar gain. www.pilkington.com

Understanding the Jargon ...

Double Glazed - Two panes of glazing with air spaces in between.

Triple Glazed - Three panes of glazing with air spaces between each.

Low-E (emittance) Coating - The coating is a microscopically thin, virtually invisible, metal or metaIIic oxide layer deposited on the inside of glazing primarily to reduce its Uvalue. The effect is reduced heat loss and better solar gain.­

Argon &. Krypton Gas - Originally, the space between panes was filled with air or flushed with dry nitrogen just prior to sealing. However, if the space is filled with a less conductive or slow-moving gas like Argon or Krypton, it minimises the convection currents within the space and the overall transfer of heat between the inside and outside is reduced. Argon is inexpensive, nontoxic, nonreactive, clear, and odourless, while Krypton has a higher thermal performance but more expensive to produce.

Tinted/Obscured Glass - Tinted glass is usefuI in controlling glare but solar heat gain and visible light transmission may be reduced, which is a benefit in summer but not in winter. The tint has no effect on the U-value. Obscured glass is used to protect privacy, but it can also reduce solar light.

Spacers - Higher quaIity spacers between panes can reduce 'fogging' and condensation, while some can incorporate a thermal/warm-edge for better insulation. This is particularly effective if you have aluminium or uPVC frames.

Safety Glass - Glass can be toughened (via repetitive heating and cooling processes) or laminated, both of which are difficult to break and ensure injury is reduced if they are. Laminated glass is a sandwich of two layers of glass with a plastic sheet 'filling'.

Top Tips

  • Windows and roof lights should be positioned where they will maximise solar gain.
  • The minimum standard for an 'energy-efficient' house is Low E, Argon filled cavity double glazing.
  • Ensure draught proofing seals and spacer bars on windows are working effectively - move a candle along the edge to see if it flickers. This may indicate air is leaking
  • Replacement windows & doors must comply with current building legislation on thermal performance, fire safety and ventilation. Ask your supplier to certify this before installation.
  • Decorate & Improve Your Home.

Operating System

When you select a window, there are numerous operating profiles to consider. Traditional profiles include projected or hinged types like casement and French windows; or sliding types like double/singlehung and sash windows. In addition, the current window market includes storm windows, sliding/folding and swinging glass doors, skylights and roof-mounted windows, and window systems that can be added to a house to create a bay or bow. The choice is vast' Modern profiles may also offer additional benefits of 'tilt-in' or 'tilt and turn', which make cleaning exterior panes possible from inside the house.­

Heat loss is a major concern for today's home owners and one of the key reasons we opt for multiple glazed units with gas infill. However, if your period property has traditional timber sash or casement windows, you won't want to replace them. Frank Clissmann from sashwindows.ie says the best way to make traditional timber sash windows more energy efficient is to draught proof the frame. He adds, "replacing single glazing with double glazing can reduce a room's heat loss by around 6%. However research from Glasgow Caledonian University found draught proofing an old sash window can reduce heat loss by around 86% without replacing the single glazing. This method is also more environmentally friendly because there is no waste."

 Other Considerations

  • Acoustic Performance - Noise is an environmental problem and makes life very difficult for some people. One way to reduce noise in your home is to use thicker glass or more of it and improve the seals around the window.
  • Security Performance - Window locks and thicker glass or multiple panes can improve safety.
  • Warranty – Lifespan and installation warranty will vary between manufacturers.

Did You Know...?

  • Trickle vents on windows will provide sufficient ventilation to reduce the build up of condensation and odours, and also control heat loss in your home. Shutters and thermal blinds or lined curtains and can help minimise heat loss at night.
  • Replacing single glazed windows with energy efficient windows can help increase the resale value of your property.
  • Shutters and thermal blinds or lined curtains can help minimise heat loss at night.