Approved Document L1Conservation of fuel and power1L1ContentsPAGECONTENTS1Use of Guidance3Summary guide to the use of this ApprovedDocument5The Requirements7Section 0 : General9Performance 9Introduction to provisions 9Technical risk 9Thermal conductivity and transmittance 9U-value reference tables 10Calculation of U-values 10Roof window 11Basis for calculating areas 11Air permeability 11Standard assessment procedure (SAP) 11Historic buildings 11Section 1 : Design and construction12Alternative methods of showing compliance 12Elemental Method 12U-values for construction elements 12Heating efficiency 12Areas for windows, doors and 13rooflightsExtensions to dwellings 13Summary of provisions in the 13Elemental MethodTarget U-value method for new 13dwellingsOptional allowance for solar gains 14C