The highest energy rating a window can receive is A++, ranging down to G. Ratings are primarily calculated based on the U, G and L values that the window achieve. This covers the thermal performance, solar gain and air leakage performance of the window. All of these are considered when calculating the overall WER rating. We manufacture quality windows that consider all of these performance elements ahead of testing.

WER takes the following factors into account when ranking on a scale from A++ – G:

Glazing: The number of glass layers (single, double, or triple glazing) and any coatings applied to the glass can affect the window’s energy performance.

U-Value: This measures the rate of heat transfer through the window. The lower the U-value, the better the insulation and amount heat is lost through the double glazing

Solar Heat Gain: This measures how well the window holds solar energy. A higher solar heat gain value indicates better solar heat retention, which can be better in colder conditions.

Air Leakage: This assesses how much air can pass through the window.

Warm Edge Spacers: These are insulating components that separate the glass panes in double or triple-glazed windows. The type of spacer used can impact the overall energy efficiency of the window. See how we build super spacer technology into our casement windows at Sternfenster.

Frame Material: The material used for the window frame affects its insulative properties- we use energy efficient uPVC and aluminium at Sternfenster with our manufacturing.

Window Size: Larger windows generally have a larger impact on energy efficiency due to their greater surface area for heat transfer.

We offer exceptionally fast lead times as low as five days, without compromising on quality. Contact us today to find out more on our glass enhancements.

We offer competitive warranties, lead times as fast as five days and outstanding aftercare.