U-VALUE AND WHAT IT MEANS TO YOUR PROJECT

The following table is set out in Building Regulations Document L1B.

Fitting	(a) Standard for new fittings in extensions	(b) Standard for replacement fittings in an existing dwelling
Window, roof window and roof light	U-Value = 1.8W/m²K or Window Energy Rating = Band D; or Centre-pane U-Value = 1.2W/m²K	U-Value = 2.0W/m²K or Window Energy Rating = Band E; or Centre-pane U-value = 1.2W/m²K
Doors with more than 50% of their internal face area glazed	2.2W/m²K or centre-pane U-value = 1.2W/m²K	2.2W/m²K or centre-pane U-value = 1.2W/m²K
Other doors	3.0W/m²K	3.0W/m²K

The following is general advice given by Jeld Wen:

What does it mean to our customers?

There are now different requirements for Replacement, Extension and New Build frames and doorsets. Understanding that there IS a difference. We have to know the project type to give the best quotation & price compliant product.

Part L 2006 Windows

In simple terms:

Replacement windows; no change from 2002

Maximum U-Value = 2.0 W/m²K or an Energy Rated window E or better (where A is best). A centre pane (glass only) U-Value of 1.0

Extensions (ex. conservatories) to existing buildings

Maximum U-Value = 1.8 W/m²K or an Energy Rated window D or better (where A is best). A centre pane (glass only) U-Value of 1.1.

New build: Determined by Building Design

U-Value (range) = from 1.1 up to 2.2 W/m²K (weighted average).

Summary

Is it a replacement? – Maximum U-Value of 2.0

Is it an extension to an existing building? – Maximum U-Value of 1.8

Is it a new build? – The customer must provide the U-Value

Part L 2006 Doors

Replacements & Doors in extensions (to existing dwellings);

Maximum U-Value = 3.0 W/m²K where glazed area of door & frame is less than 50%

Maximum U-Value = 2.2 W/m²K where glazed area of door & frame is greater than 50%

New build: Determined by Building Design

U-Value (range) = from 1.1 up to 2.2 W/m²K (weighted average)

Summary

Is it a replacement? Has the door & frame a glazed area more than 50% glass?

YES = Maximum U-Value of 2.2

NO = Maximum U-Value of 3.0

Is it an extension to an existing building? – Same as above

Is it a new build? – The customer must provide the U-Value