Document L – Building Regulations - Conservation of fuel and power

 

From 1 April 2002 it will be a legal requirement to ensure that glazing complies with the minimum standards set.  This applies to the installation of all new windows and replacement windows (where the whole window frame and glass is replaced).  Conservatories that are separated from the house (for example by a lockable door) and unheated are exempt.

Indicative U values (W/m2 K) of double glazed units

4mm glass thickness

6mm air gap

12mm air gap

16mm air gap

Single glazing

4.8

4.8

4.8

Standard double glazing

3.1

2.8

2.7

Low ‘E’ double glazing (e.g. Pilkington ‘K’ glass)

2.7

2.2

2.0

Low ‘E’ double glazing (‘K’ glass - Argon gas filled)

2.4

2.0

1.9
Low ‘E’ 'soft coat' double glazing 2.3 1.8 1.5
Low ‘E’ 'soft coat' double glazing (Argon gas fill) 2.2 1.4 1.3
Low ‘E’ 'advanced soft coat' double glazing (Argon gas fill)

 

1.3

1.1
       
       

Alternative materials:

 

 

 

25mm Five wall polycarbonate

  

 

1.8

 

 

 

 

Comparative insulation values:

 

 

 

Solid wooden door

3.0

 

 

Un-insulated cavity brick wall

1.0

 

 

 

The maximum permissible ‘U’ value for new windows and doors fitted after 1 April 2002 (combined glass unit and its frame) is 2.0 for wood & PVCu and 2.2 for metal.  (Only the materials in the shaded areas will comply for glazing)

 

Compliance

New building work will be monitored through existing building control approval.  Consent for replacement of windows could be sought through building control, though the preferred method is through the FENSA self certification scheme  Listed properties and buildings in conservation areas may be exempt, as are display windows and shop entrance doors.