High performance or ‘low emissivity’ glass is designed to reduce energy consumption and heat loss. It is measured in W/m²k and expressed in U-values (the lower the better).

Performance levels for heat loss as stated in Document L regulations are:

• 2.0 U-value with pvcU and timber
• 2.2 U-value with metal

For Energy Related Windows, both soft and hard coat glasses can be used and are supplied by CET.

Soft Coat

Also known as Magnetron coating. Very thin almost invisible multiple layers of metal oxide applied online.

Advantages

• Can be used to achieve WER
• High levels of light transmission
• Very low U-values possible, better compliance with Document L
• Superior clarity/neutrality

Hard coat

Also known as Pyrolitic 'hard' coating. Thin coating applied to the glass as it is being manufactured.
 

Advantages

• Can be used to achieve WER
• Good light transmission
• Low U-values
• Good visual clarity