Approved Document L1A For Wales

By Administrator

Knauf Insulation

15th Aug 2014

As of 31 July 2014, the Welsh Approved Document L1A (Conservation of fuel and power in new dwellings) came into effect – the first version of its kind for use solely in Wales. 

Previously Welsh and English Regulations have been combined. However the publication of this document brings notable differences that housebuilders and developers will need to be aware of.  Knauf Insulation is in a position to not only recommend practical guidance to specifiers, but also offer high performing, quality product solutions that comply as part of a more flexible and commercial approach.

Approved Document L1A 2013 for Wales targets an approximate 8% reduction in the carbon dioxide emissions from the mix of new dwellings relative to Approved Document L1A 2010, rather than the 6% reduction in the English 2013 version.  As a result, the below comparison table sets out the minimum acceptable fabric performances:  



ADL1A Wales

ADL1A England

External walls

0.21 W/m2K

0.30 W/m2K

Party walls

0.20 W/m2K

0.20 W/m2K


0.18 W/m2K

0.25 W/m2K


0.15 W/m2K

0.20 W/m2K

Windows, roof windows, glazed roof lights, curtain walling and doors

1.60 W/m2K

2.00 W/m2K

Air permeability

10 m3/h.m2@ 50 Pa

10 m3/h.m2@ 50 Pa

Similarly with the new L1A for England, the Welsh revisions also include compliance criteria: Target Fabric Energy Efficiency (TFEE) which recognises the importance of a Fabric First approach to meeting the ultimate ambition: Zero Carbon Homes.  This is calculated using actual dwelling dimensions and the performance values in the current notional dwelling specification. 

Ultimately, if the actual dwelling is constructed entirely to the notional dwelling specifications it will meet the carbon dioxide and TFEE and the limiting values for individual fabric elements and building services.  What’s important though, is the degree of design flexibility afforded by the L1A version.  Developers are free to vary the specification across certain building elements, provided the same overall level of carbon dioxide emissions and fabric energy efficiency performance is achieved or exceeded.

Stephen Smith Market Development Manager at Knauf Insulation Northern Europe comments:As with the English Approved Document L1A, the Welsh version includes some U-values in the elemental recipe that may not be beneficial to all housebuilders and developers, in terms of the practical and commercial elements.

“However, by using the design flexibility which has been included within ADL1A 2013 and adopting a more practical approach that improves on some elements, we can make sure housebuilders and developers achieve compliance across all house types - that best suits their needs and not just a compliance exercise.”

For cost-effective, practical solutions that meet Part L1A England and Wales housebuilders should speak to Knauf Insulation’s Business Development team for full guidance and for technical support please contact 01744 766666 and or use the company’s comprehensive Part L 2013 guide.

For more information please visit

Tags on this post: conformance, insulation