U Values

All new windows and doors must comply with the new building regulations for England & Wales and have a U value of 2.0 or less (see table below). There are two ways of ensuring that this is verifiable:

The installer must be FENSA Registered and so police themselves.

After installation the local authority building control officer is invited to inspect the work and verifies that it complies with Document L .

Summary: Anyone can install new windows and doors. So long as the U value of the installed windows and doors must be 2.0 or below and that after installation the glass unit/s must be certificated. We can arrange for this to be done by the local Building Control Officer (LABC) on completion of the installation. (Listed buildings need not apply to Document L.)

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Hot Box tests conducted on a wide range of standard PVC-U and Timber windows
incorporating
PILKINGTON K GLASS
in a 4/16/4 air filled double glazed unit,
show U-values of the order 1.8 - 1.9 can be achieved

comfortably enabling the required elemental value to be satisfied.
Standard U-values for vertalinsulating glass units [Pilkington Glass Guide]
Double Glazing
Cavity Width [mm]
4mm Clear Glass has a U-Value of 6.0
6
8
10
12
14
16
18
20
Traditional Units
Glass /Air/Glass
3.3
3.1
3.0
2.9
2.8
2.7
2.7
2.8
Glass/Argon Gas/Glass
3.1
2.9
2.8
2.6
2.6
2.6
2.6
2.6
Glass/Air/Pilkington K Glass
2.7
2.3
2.1
1.8
1.7
1.7
1.7
1.7
Glass/Argon Gas/Pilkington K Glass
2.3
2.0
1.8
1.5
1.5
1.5
1.5
1.6

Note: U values based on 4mm glass thickness and determined in accordance with BSEN 673.
For Argon gas-filled units, a gas mix of 90% argon /10% air has been assumed.
The lower the U-value the more efficient the glass is.
Only the highlighted figures comply to the new regulations.