The term ‘Eco Glazing’ refers to glass with a high level of thermal insulation. All external glazing on insulated and heated areas should be double glazed as minimum to reduce heat loss through any large expanses of glass but higher performing glass units can be used where extra thermal performance is required.
The use of Low E coatings to insulated glass units has gone a long way to improving thermal performances of glass, these clear invisible coating reflect radiant heat back onto the internal of a space, reducing heat loss. Gas fillings within the insulated cavity such as Argon or Krypton will also improve the thermal performance of an individual glass pane.
The British Building regulations state the minimum thermal performance to any glazing installed on a new build or existing build anywhere in the UK. These thermal performance criteria change depending on the use of the building, ie a residential or commercial building.
Current building regulations state that the thermal performance of any glazing on a new build home has a maximum U value of 2.0W/m2K whereas replacement glazing on a home has a maximum U value of 1.5 W/m2K. When looking at a non-residential building the maximum U value for any glazing on a new build is 2.2W/m2K and an existing building is 1.8W/m2K. It must be noted that these are overall thermal performances of the glass and frame.
These are the minimum requirements for the thermal performance of glazing and in most cases a double glazed unit will suffice but if further Codes for sustainability want to be reached a higher thermally performing glass unit should be used.
Triple glazed units can achieve a Ug value, or centre pane thermal performance, of as little as 0.5W/m2K. These highly performing glass units must be used on projects where a Passiv Haus standard is being aimed for or other similar high performance standards.