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U-Values and WER Window Energy Rating Scheme

A+ Energy Rated Windows

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We would like to tell you about regulations that are currently enforced as part of Building Regulation Part L1b being a FENSA registered company since it all began. In 2002. We would like to educate people about some salesman ploys that they may come across when getting a price for replacement windows.

The new method of complying with this area of the Building Regulations that covers thermal efficiency, energy efficiency and solar gain.

Before these changes, to get windows and doors to comply with building control you needed to achieve a good overall U-value or specify a sealed unit with an outer glass pane having a U-value of 1.2 or less using a low emissivity glass (Pilkington K or Saint-Gobain soft coat glass) coating on one side of the sealed unit and using hollow metal spacer bar to hold desiccant, the spacer bar also helps to maintain a unit structural integrity and gives us different unit thickness ie 24mm or 28mm units. This type of spacer bar is also one of the worst products to use as aluminium is a highly conductive metal and conducts heat at the edge of the sealed unit, reducing the insulation.

This has now been scrapped and replaced with the Window Energy Rating Scheme (WER) The aim was for the WER to simplify for you the consumer, this know includes the frame and air leakage as part of the calculation and not just the glass unit.The rating from a low G to a high A++ only being achieved with triple glazing at the moment with a C rated being the minimum requirement for building regulation requirements.

British Fenestration Ratings Council (BFRC) has created a system that checks all the components to ensure the final product reaches the energy efficient standard claimed.

This includes:

Heat loss through the frame material.
Surface coatings on the glass to reflect or trap energy.
Air leakage between the moving, opening parts of the window.
Solar gain it can expect during the year.
Values for thermal efficiency, solar gain.

Our multi-chambered walled frame with 28mm double glazed units incorporating, soft coat low E glass, warm edge spacer technology and Argon gas designed to achieve a WER value of A+12 Window Energy Ratings with the correct licence number to correspond with the BFRC licence.

Irrespective of what a salesman tells you the only window rating that is relevant for Building regulation compliance is the WER rating the 12 means you will retain an additional 12 kWh each year over a standard A+ 0 rated window in solar gain.

So next time someone offers you a window with U-value 1.2 or lower remember this is only the glass unit, not the whole window as required by the new regulations.

At the moment there is no energy rating scheme for doors, but all doors with more than 50% of their total area glazed must have a glass unit with a U-value of 1.8 or lower.

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