Save money by selecting energy efficient windows which reduce your heating bills.
The windows that we select for our homes bring light, warmth, and beauty into them. Poorly selected windows are a major source of heat loss in the winter and can reduce comfort and the amount of effective living space. Energy efficient windows, when correctly selected and installed, will help to minimise the heating and lighting costs and will also increase comfort and the amount of useable living space. In the past, selecting energy efficient windows has been difficult for consumers and there is a need for a method of selecting energy efficient windows that is both easy to understand and independent.
The British Fenestration Rating Council Limited (BFRC) window rating system meets this need and allows consumers to rapidly compare the efficiency of different products
Windows are rated using a familiar A to G scale on the basis of their total energy efficiency, where an A-rated window is more energy efficient than a G-rated window. Consumers can quickly and easily choose the most suitable window for their needs.
The BFRC is an independent body that controls energy rating of windows as part of a European scheme.
A BFRC rating simply and effectively assesses the energy performance of the whole window. This rating covers the frame material, the frame design, the glass type and all other components that make up the window. For the first time it is possible to compare the energy performances of different complete windows simply and quickly.
Energy efficient windows may cost more initially but will not only improve comfort but will save energy and money for the life of the window. Over the life of a window, the cost of heat lost is greater than the purchase cost. Choosing the most energy efficient window will save money.
The BFRC rating makes selecting windows for energy efficiency easy, it allows windows to be easily compared to find the most energy efficient product. If windows are not BFRC rated, selecting windows for energy efficiency is more difficult and the following information should be considered.
Uncontrolled air flow through a window loses heat and creates uncomfortable draughts .
Windows with compression seals reduce uncontrolled air flow, provide good ventilation when opened and have better resistance to uncontrolled air flow than the sliding seals on vertical sliding windows.
Installation workmanship also affects the air flow through a window. Reputable installers should always be chosen to reduce air flow and heat loss.
An important factor in the energy efficiency of a whole window is the U-value. A window with a low U-Value less heat than one with a high U-value.
The following factors affect the whole window U-value:
Note: Always ensure that a quoted U-value is for the whole window and not just for the glass.
Clear float glass has previously been the major material used for windows in houses. Advances in glazing technology means that special glass is now available to control heat loss through the window. This lowemissivity (low-e) glass has special surface coating to reflect heat back through the window. The low-e coatings reflect between 40% to 70% of the heat that is normally transmitted through clear glass, while allowing the full amount of light to pass through. This type of glass is now standard under most Building Regulations for most homes in the UK.
The traditional approach to improving the energy efficiency of a window has been to increase the number of layers of glass and air. Double or tripple glazed units have insulating air or gas filled spaces between each pane. Each layer of glass and the air spaces resist heat flow. The width of the air spaces that are too wide have higher U-values and allow too much heat to transfer. Highly energy efficient windows are manufactured with insert gases (argon or krypton) in the spaces between because these gases transfer less heat than air.
For further details on the BFRC, visit the British Fenestration Rating Council website at www.bfrc.org.
This article was produced by the BFRC and supported by the Housing Energy Efficiency Best Practice programme.