DOCUMENT L

When Document L comes into force the installation of double glazed units manufactured with standard float glass will not be acceptable in most situations.
In the case of replacements, all windows have to be double-glazed with a low-E glass, and meet a certain U-value. By windows we mean the frame and double-glazed unit combined. If only the double-glazed unit is to be changed this can be done on a like for like basis.

Questions and answers

What is Document L ?

Document L is the part of the Building Regulations for England & Wales that sets the standards of energy efficiency in buildings.

Why are the changes being introduced ?

As part of the Koyto agreement, the UK Government has made commitments to reduce emissions of greenhouse gasses,such as carbon dioxide, which are harmful to the environment.

Do the changes apply to all buildings ?

The previous version of Document L covered construction of new dwellings (houses) and non domestic buildings, such as offices and public buildings. The new Document L still covers these but goes much further by addressing work on existing buildings, such as replacement windows installed as a home improvement.

Do the requirements extend to repair work on existing windows ?

The new Document L only applies when the whole window is to be replaced. Replacement of just the glass or part of a damaged frame is exempt from the regulations and the replacement can be carried out on a like for like basis.

Are there any exceptions ?

Listed properties and buildings in conservation areas may be exempt as are display windows and shop entrance doors. Also replacement doors that have a glazed area of less than 50% are not required to meet the new u-values.

Do the new requirements apply to conservatories ?

As long as a conservatory is unheated and seperated from a house, it does not have to comply with Document L

Why should I bother to comply ?

Complying with Building Regulations is a legal requirement.

When will the new Document L take effect ?

The new Document L will come into force from 1st April 2002. In the case of home improvement work, all windows replaced after this date will have to comply with the new standards.

For new build, all buildings that have had their plans approved before this date may be constructed to the previous standards although a time limit on constructing may be enforced.

What is a U-value ?

The U-value measures the rate at which heat is lost through a material. The lower the U-value, the lower the amount of heat lost and the lower the amount of energy wasted through the window. U-values are measured in Watts per square metre per degree of temprature difference (W/M2k).

What U-values should my windows be ?

PVC-U and Timber

2.0 W/m2K

Aluminium and Steel

2.2 W/m2K

What is Low-E glass ?

Low-E stands for low-emissivity. The double glazed unit has one of its inside faces lined with a special coating that lets heat and sunlight filter through but reflects any heat trying to escape back into the room.

The Benefits of Low-E glazing are :- Reduced heat loss, eliminates cold spots & reduced condensation.
Low-E glass is available in Normal float, Toughened & Laminated glass.

To find out more on Low-E glass Click Here to go to our information page.

Cavity width of the double glazed unit.

6mm    12mm  16mm

6mm    12mm  16mm

6mm    12mm  16mm

en refers to the emissivity of the low-E glass (w/mk).

U-values for wood and PVC-U frames.

U-values for metal frames (4mm thermal break).

U-values for metal frames (16mm thermal break).

Single glazing.
 

4.8

5.7

5.5

Double glazing - air filled.
 

3.1

2.8

2.7

3.7

3.4

3.3

3.5

3.2

3.1

Double glazing - hard coat low-E en = 0.2 air filled.

2.7

2.3

2.1

3.3

2.8

2.6

3.1

2.6

2.4

Double glazing - hard coat low-E en = 0.15 air filled.

2.7

2.2

2.0

n/a

n/a

n/a

n/a

n/a

n/a

Double glazing - soft coat low-E en = 0.1 air filled.

2.6

2.1

1.9

3.2

2.6

2.5

3.0

2.4

2.3

Double glazing - soft coat loe-E en = 0.05 air filled.

2.6

2.0

1.8

3.1

2.5

2.3

2.9

2.3

2.1

Double glazing - argon filled.
 

-

2.7

2.6

-

3.3

3.2

-

3.1

3.0

Double glazing - hard coat low-E en = 0.2 argon filled.

-

2.1

2.0

-

2.6

2.5

-

2.4

2.3

Double glazing - soft coat low-E en = 0.1 argon filled.

-

1.9

1.8

-

2.4

2.3

-

2.2

2.1

Double glazing - soft coat low-E en = 0.05 argon filled.

-

1.8

1.7

-

2.3

2.1

-

2.1

1.9

How will Document L be enforced ?

New build will be monitered in the existing way, through building control approval.
In the case of replacement windows as a home improvement, approval could be sought through building control but this is likely to be very time consuming and expensive. The preferred method is via the self - certification scheme Fensa.

 The FENSA Scheme

over one million installations of replacement glazing happen every year. It would be impractical for all of these to go through the Building Regulations application process. Fensa has been set up to allow installation companies that meet certain criteria to self-certify that their work complies with the Building Regulations.  The scheme is known as FENSA which stands for the Fenestration Self-Assessment Scheme.

A sample of the work of every installer will be checked by FENSA appointed inspectors to ensure standards are maintained.  FENSA will also inform local authorities of all completed installations and issue certificates to householders confirming compliance. 

Click here for a pre-registration form or to find out more on Fensa.

Or contact Fensa direct on 020 7207 5874. 

The following documents can be downloaded and viewed using Adobe Acrobat. If you do not have Acrobat a free copy can be downloaded here.

Document L1 - Conservation of fuel & power in dwellings (2002 edition).

Document L2 - Conservation of fuel & power in buildings other than dwellings (2002 edition).

© Cristal Glass & Glazing (Leics) Ltd. 2000©

[information] [products] [glass patterns] [contact us]

[home] [about us] [double glazing] [glazing] [stained glass]

Site design & construction by 'carl mac' If you have any problems or queries regarding this site, please E-mail me