The guidance gives three alternative approaches to the design of the insulation envelope of dwellings. These are:

. Elemental method
. Heat loss method
. Carbon Emissions calculation method

Domestic
To use the Elemental method, individual exposed building elements and other elements forming the insulation envelope of a dwelling or a building consisting of dwellings should have a U value which do not exceed the value given in the table below.

There are two levels of U value; Column A and column B. Column selection depends on the type of heating system to be installed in a dwelling and whether or not it has a central heating boiler with a SEDBUK of at least the percentages given in the table below.

Maximum U values for building elements using the Elemental method

Exposed element	With boiler min. SEDBUK % ( see table below) W/m2K	Other heating system W/m2K
Pitched Roof               ins. between rafters               ins. between joists	0.20 0.16	0.18 0.16
Flat roof or roof (including pitched) with integral insulation	0.25	0.22
Exposed wall, external wall	0.30	0.27
Exposed floor or floor	0.25	0.22
Windows, doors and rooflights                           metal frames (area weighted average)                wood on PVC frames (area weighted average)	2.20 2.00	2.00 1.80

Minimum boiler SEDBUK which allows U values in Column A
of the above table to be used

Central heating system fuel and boiler type	Minimum SEDBUK (%)
Mains natural gas (all boiler types)	78
LPG (all boiler types)	80
Oil (combination boilers)	82
Oil (all other types of boilers)	85

Non domestic
To use the Elemental method, individual exposed building elements and other elements forming the insulation envelope of a dwelling or a building consisting of dwellings should have a U value which do not exceed the value given in the table below.

Maximum U values for building elements usind the Elemental Method

Exposed element	W/m2K
Pitched roof               ins. between rafters               ins. between joists	0.20 0.16
Flat roof or roof (including pitched) with integral insulation	0.25
Exposed wall, external wall or wall	0.30
Exposed floor or floor	0.25
Windows, doors and rooflights                           metal frames (area weighted average)                wood on PVC frames (area weighted average)	2.20 2.00
Vehicle access and similar large doors (including doors located in walls)	0.70