Last edited 07 Nov 2016

Limiting fabric parameters

Contents

[edit] Introduction

The building regulations require that reasonable provision be made to limit heat gains and losses through the fabric of new buildings and works to existing buildings. The approved documents to the buildings regulations set out the limiting standards for the properties of the fabric elements of the building.

[edit] L1A, new dwellings, 2013 edition

Roof 0.2 W/(m^2K)
Wall 0.3 W/(m^2K)
Floor 0.25 W/(m^2K)
Party wall 0.2 W/(m^2K)
Swimming pool basin 0.25 W/(m^2K)
Windows, roof windows, glazed roof-lights, curtain walling and pedestrian doors 2.0 W/(m^2K)
Air permeability 10.0 m^3/(h.m^2) at 50 Pa

[edit] L2A, new buildings other than dwellings, 2013 edition

Roof 0.25 W/(m^2K)
Wall 0.35 W/(m^2K)
Floor 0.25 W/(m^2K)
Swimming pool basin 0.25 W/(m^2K)
Windows, roof windows, roof-lights, curtain walling and pedestrian doors 2.2 W/(m^2K)
Vehicle access and similar large doors 1.5 W/(m^2K)
High-usage entrance doors 3.5 W/(m^2K)
Roof ventilators (inc. smoke vents) 3.5 W/(m^2K)
Air permeability 10.0 m^3/(h.m^2) at 50 Pa

[edit] L1B and L2B, existing dwellings and existing buildings other than dwellings, 2010 editions

New thermal elements Retained thermal elements
Wall 0.28 W/(m^2K)
Pitched roof – insulation at ceiling level 0.16 W/(m^2K) 0.16 W/(m^2K)
Pitched roof – insulation at rafter level 0.18 W/(m^2K) 0.18 W/(m^2K)
Flat roof or roof with integral insulation 0.18 W/(m^2K) 0.18 W/(m^2K)
Floors 0.22 W/(m^2K) 0.25 W/(m^2K)
Swimming Pool basin 0.25 W/(m^2K)
Wall – cavity insulation 0.55 W/(m^2K)
Wall – external or internal insulation 0.30 W/(m^2K)

NB Approved Document C gives limiting values for individual elements to minimise the risk of condensation.

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