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What Are Window Energy Ratings?

The energy efficiency of various window products can be compared if you know the window energy rating of each of them. You can use them to help you select the right windows for installing in your home.

When you select the right windows or if it is secondary glazing it will make a difference to not only the warmth, but also to the security of the home where you live.

Correctly installed energy-efficient windows will reduce any heat loss from the living areas of your home. If your windows have a superior thermal performance you will save money in the long run, as your dependence on fuel for heating or cooling your home will reduce and result in savings on your expenditure on energy costs.

On the other hand, if you have windows that have a low level of energy efficiency, they can become a source of heat loss and require you to spend more on energy.

Every window product is by law required to have a Window Energy Rating label and you should look out for it.

These labels of Window Energy Rating are colourful and make for an easy way to compare the energy efficiency of different window products.

You will find the same ‘rainbow’ design as the energy labels that you find used on refrigerators, washing machines, and other home appliances.

Several schemes are followed for rating window energy ratings, but those that are most widely used are those of British Standard Institute, CERTASS, and British Fenestration Rating Council. However, they all work in the same way.

The energy performance of the entire window allows it to get a letter rating for the window product that includes all its components from frame design, material used in frame, glass type, and others. So if a window is rated A+, it means it is more energy efficient than a window that has a C rating.

These letter ratings are derived from a formula that takes into consideration the overall thermal efficiency of the window product, leakage of air, and how much heat passes through the window because of the sun, also called solar gain.

Energy Savings and Energy-efficient Windows

These ratings, Window Energy Ratings are only an indication of the efficiency level of the window itself.

An actual saving of potential energy after a window is installed can also be influenced by other factors, like other installed insulation, the window location, the orientation of the building, and the efficiency of any installed heating system, as well as other factors.

Frequently Asked Questions About Window Energy Ratings

Which Energy Rating should I Choose?

These ratings allow you to make a comparison of potential savings. These ratings are very accurate, as they use computer model stimulations for their determination. It then becomes almost certain that those that have the highest ratings will be those that will have the most potential for saving.

Any window product can have a superior energy rating compared to another, but the person who buys a product has to consider this efficiency along with a number of other factors.

These can be planning restrictions, preference for materials, design requirements, and budget.

Since 2009, KJM has been offering you a choice between windows that are rated E, C, or A. Regulations have since changed, and now our offer is limited to only C and A rated windows. There is only a small difference in cost between these windows, but we suggest that you always go in for A rated frames.

Window Energy Rating (WER)

It is an objective method that is used to assess a window’s total energy performance. It is determined using the following criteria:

  • Frame material which can be aluminium, PVC, or timber
  • Air Leakage
  • Solar gain