What is the UK’s Most Thermally Efficient Window

By on 23rd December in Home Inspiration

We wanted to find out what the most thermally efficient window in the UK was, but to do this we have to understand how efficiency is measured and who the governing body behind verifying Window Energy Ratings are.

Who are the BFRC & What Do They Do?

The BFRC are the British Fenestration Rating Council and they are responsible for independently verifying the ratings of energy efficient windows and doors. Windows and doors are typically registered with the BFRC by manufacturers to demonstrate that they achieve the appropriate performance levels. By having these energy labels attached to each product, you can easily compare them to similar products and see which performs best.

Windows are measured on their thermal transmittance (U value), solar gain (G factor) and air leakage (L factor) to give them their BFRC Window Energy Rating. A small minority of companies don’t register their windows with the BFRC, but these windows only need to demonstrate that a window’s U value reaches appropriately low levels, ignoring the impact of solar gain and air leakage.

Three performance factors of a window

Related: What are Window Energy Ratings

With this in mind, many products which aren’t BFRC registered are designed to minimise the U value, but with this disregard for air leakage and solar gain, you won’t be maximising the potential of your windows. This also means these windows can’t be easily compared to BFRC registered windows.

The BFRC offer 2 licences:

Detailed Energy Licence, which displays the energy index, U, G and L value of a single product, reflecting the information taken from the simulation report of a single specification.

Simplified Energy Licence¬†only displays the energy banding. The licence can cover multiple specifications and simulation reports grouped under the same profile and energy banding. This means the energy index, U, G and L values can’t be displayed as they may vary from product to product.

This means that you could buy A++ windows that are under a simplified licence achieving a plus 20 rating or higher, but you won’t know for sure what the exact rating is. Whereas if you buy windows with a Detailed Energy Licence, you can be sure of the energy rating you will receive.

The Most Thermally Efficient Window

As it stands today, December 22nd 2015, the most efficient window registered with the BFRC’s Detailed Energy Licence is Anglian Home Improvement’s A++ plus 32 white casement window.

Anglian's A++ Rated Triple glazed window energy rating


It is possible that there is a higher rated window, but as they don’t have a Detailed Energy Licence, it is hard to confirm that an A++ product will definitely be providing you with +32 energy index.

The Anglian A++ triple glazed window is a new product added to their range recently. The new technology has helped them boost the performance of not just their triple glazing to an A++, but also their A and A+ rated windows, so when you mix and match your products, you can maximise the performance. They also offer top notch security features and are Secured By Design.

If you’re in the market for new windows and you want the most efficient window you can get, you will struggle to find a more efficient window than Anglian’s as it stands. Visit the Anglian Home Improvements website for more information about Anglian triple glazed windows.

big discounts on Anglian conservatories, click here to find out more