Welsh Building Regulations

Welsh building regulations

Today marks a major change for the construction industry in Wales with the launch of the Approved Documents L to the Building Regulations for Wales (ADL 2014). The headline 20% uplift for new non-domestic properties is markedly tougher than that for the new English Approved Documents, and is just one of a number of key differences between the two.


ADL1A 2014

For new domestic properties in Wales, the aggregate uplift is 8%. Whilst marginally above the level set in England, this still falls well short of the 40% originally suggested by the Welsh Government and will leave considerable ground to be made up for the 2016 zero carbon regulations.

As in ADL1A 2010, the Dwelling Emission Rate (DER) must not exceed the Target Emission Rate (TER). The TER is now directly defined by an Elemental Specification for fabric and building services and following this to the letter will typically lead to compliance. 

Rather than using a Target Fabric Energy Efficiency (TFEE) Standard to encourage improved fabric performance, ADL1A 2014 tightens the limiting backstop U–values for several of the fabric elements. These amendments, which can be seen in Figure 1 set a much stronger baseline for the thermal performance of the building envelope.


  ADL1A 2010 ADL1A 2014
Roof (W/m²K) 0.20 0.15
External Wall (W/m²K) 0.30 0.21
Floors (W/m²K) 0.25 0.18
Air Permeability(m³/m²/hr @ 50 Pa) 10 10

Figure 1:  Limiting Backstop Fabric Parameters


As with the English Approved Documents, the Elemental Specification contains stricter airtightness and thermal bridging requirements than those in ADL1A 2010. These can be extremely challenging to achieve using traditional construction approaches – running the risk of non-compliance. A simpler alternative is to raise the U-value performance of the main fabric elements beyond the level within the Elemental Specification. This allows the airtightness and thermal bridging targets to be relaxed as shown in Figure 2.



Elemental Specification

Recommended Best Starting Point

Roof (W/m²K)



External Wall (W/m²K)



Floors (W/m²K)



Air Permeability

(m³/m²/hr @ 50 Pa)



Thermal Bridging

Tougher psi-values than 2010 ADL1A with no Accredited Construction Details provided

2010 Accredited Construction Details

Figure 2: Example specification comparison


ADL1B 2014

Several aspects of the domestic refurbishment regulations have also been tightened. Where new fabric elements are required for refurbishments such as extensions, the minimum U-value performance for these elements is now set at the level of the Elemental Specification from ADL1A 2014. If new or replacement doors are installed on cavity walled properties, insulated cavity closers should also be fitted around the openings.

Consequential improvements have also been introduced for properties which do not meet the required level of performance, these improvements are triggered by any extensions or conversions which increase the habitable area by over 10m2, extension of the heating system or introduction of a fixed heating appliance in previously unheated area.  


ADL2A 2014

More significant changes are incorporated within the regulations for new non-domestic properties. In addition to the 20% aggregate improvement over ADL2A 2010, a new Primary Energy Consumption (PEC) target has also been introduced.

PEC is the measure of energy delivered to the building plus the energy used to produce the energy delivered to the building. The main purpose of this target is to ensure a high level of fabric and building service performance as, in addition to the BER not exceeding the TER, the new Building Primary Energy Consumption (BPEC) must also not surpass the Target Primary Energy Consumption (TPEC). This prevents excessive reliance on renewable technologies as a route to compliance.

Both TER and TPEC are defined directly by a new Notional Building Specification (NBS) and compliance can be confirmed if this is followed to the word. However, the strict air-permeability requirements laid out in the NBS are again challenging to achieve with a traditional construction and may lead to further cost if the building fails to comply when pressure tested.  Improved fabric performance offers a simpler approach to compliance, and a recommended starting point specification for buildings not heavily reliant on cooling is provided in Figure 3.


  Notional Building Specification Recommended Best Starting Point

Roof (W/m²K)

0.18 0.14

External Wall (W/m²K)

0.26 0.22

Floors (W/m²K)

0.22 0.18

Air Permeability

(m³/m²/hr @ 50 Pa)

3-7 dependent on Gross Internal Area and lighting. 10

Figure 3: Example specification comparison


ADL2B 2014

Non-domestic refurbishments which include new fabric elements must now meet the U-values in the Notional Building Specification from ADL2A. Additionally a new category has been created for buildings which are essentially residential in character such as care homes. New fabric elements on these properties must meet the tougher U-values laid out in the Elemental Specification within ADL1A 2014.

As with ADL1B, Consequential Improvements have also been included for non-domestic properties. These are triggered where the building is extended or converted to increase the conditioned area, or for properties with a useful floor area over 1000m2, the installation or expansion of any fixed building service. Where economically feasible, Consequential Improvements should be made up to at least 10% of the cost of the principal works.


Additional Changes

A number of other changes have also been introduced mirroring those within the English Regulations. Evidence must now be provided to show that the building design meets the targets, and that the building itself meets or exceeds the designed performance. The evidence must not only show that the required targets are met, but also explain how this was undertaken, an EPC alone will not suffice. Design stage submissions are needed 1 day before work starts and evidence of as built compliance is needed within 5 days of the work ending.

Alongside the new regulations coming into force, the Welsh Government has withdrawn Technical Advice Note 22 (TAN 22), which required Code for Sustainable Homes assessment for new dwellings and issued amended policy on good design, in a new-look Technical Advice Note 12 (TAN 12) which includes material on the energy hierarchy, allowable solutions and sustainable building policies on strategic sites in local development plans and is available from http://wales.gov.uk/topics/planning/policy/tans/tan12/?lang=en

Also Planning Policy Wales has a new edition published alongside the regulations changes, available from http://wales.gov.uk/topics/planning/policy/ppw/?lang=en and amongst it’s requirements and recommendations it suggests that:

“Development proposals should mitigate the causes of climate change by minimising carbon and other greenhouse gas emissions associated with their design, construction, use and eventual demolition. The overall aspiration is to secure zero carbon buildings while continuing to promote a range of low and zero carbon (LZC) technologies as a means to achieve this.”

Step in the right direction

Whilst falling some way short of the original target for domestic CO2 reduction, the new Welsh Regulations still offer many positives for the insulation industry. The Regulations provide a more stringent test of new and refurbished building performance than their English counterpart and once again emphasise the central role the building fabric must play in any long term strategy to reduce carbon dioxide emissions from buildings.

There’s more information on the Welsh Government website and our guide to the regulations can be found on the Building Regulations page of our website knowledge base.

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Kingspan Insulation is a market leading manufacturer of optimum, premium and high performance rigid insulation products and insulated systems for building fabric and building services applications.

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