What You Need To Know About Window Energy Ratings

Window Energy Ratings allow consumers to compare energy efficiency relating to various window products. Here is more information on how these ratings can assist you when it comes to choosing window products for your house.


The windows that you choose can have a positive impact when it comes to the security and warmth of your home.

When installed correctly, energy-efficient and soundproof windows can decrease heat loss around your home. The windows that feature premium thermal performance can also help you to lower your electric and heating bills over time.

Windows that are not energy efficient are often the main reason why your home loses heat, which results in spending more money on energy bills.

To determine the energy efficiency of window products, you need to refer to the Window Energy Rating label.

Colour-coded Window Energy Rating labels offer a simple way to compare window products in relation to how energy efficient they are.

These rating labels feature similar “rainbow” designs to the energy labels that are used on a home appliance such as a washing machine or refrigerator.

There are various energy-rating schemes used for windows. The most common include the BFRC- British Fenestration Rating Council (above left), the CERTASS (above right), and the BSI – British Standards Institute (above centre). Each of these schemes works in a similar way.

Letter ratings are assigned to different window products according to the “energy performance” of the entire window. This includes the glass type, frame design, frame material, and any other component. The A+ rated windows are more energy-efficient when compared to the C-rated windows.

Letter ratings are worked out according to a formula. This formula accounts for the window’s overall solar gain (how much heat is derived from sunlight passing through the window), air leakage, and thermal efficiency.

Energy Savings and Energy-efficient Windows

Window Energy Ratings will only offer a suggestion of the type of efficiency that the window provides.

The potential energy levels saved once these windows are installed in homes also depend on various factors such as the orientation of the building, the window location, heating system efficiency, other types of insulation used, and more.

Window Energy Ratings – FAQ’s

What Type Of Window Energy Rating Should I Be Choosing For My Windows?

Window Energy Ratings provide an easy way to make comparisons when it comes to potential savings. The ratings are calculated by precise computer-model simulations which are generally highly accurate. For this reason, it makes sense to assume that windows that have the higher ratings will offer the highest potential saving.

Some window products might have better energy ratings when compared to others, but it still falls on you as the buyer to factor in the energy efficiency of the product alongside all the other important considerations.

Some of these considerations include design requirements, planning restrictions, material preferences, and your budget.

KJM offers the option of either A, C, or E-rated windows, and has been in business since 2009. To adhere to regulations, our product range now only includes A-rated or C-rated windows. The difference in costs is relatively small which is why we recommend that A-rated frames are the standard choice.

What Is WER (Window Energy Rating)?

The Window Energy Rating is an objective method used for assessing the overall energy performance of a window. To calculate this type of energy rating, this is the criteria used:

  • Glass used
  • Solar gain
  • Air leakage
  • Frame material (Timber, aluminium, or PVC)