Building Regulations
For any new build and refurbishment projects, there are set standards for the thermal insulation which need to be met according to Building Regulations. They are developed by the government and approved by Parliament. The Building Regulations are dependent on location, building type, the application and can be presented as a U-value which needs to be achieved.
England
PART L 2013
U-values are part of wider assessment criteria to meet the requirements of Part L as a whole. Other factors taken into account include: airtightness, door and window U-values, the heating system, and thermal bridging.
‘Limiting U-values’ are the worst acceptable level of performance, but designing to these values is unlikely to result in compliance. The ‘notional building specification’ is a recipe approach that will ensure compliance if all standards are met. Regulatory compliance should be assessed through the appropriate Standard Assessment Procedure (SAP) – for domestic or Simplified Building Energy Model (SBEM) – for non domestic, calculation software.
NEW BUILD: L1A – new dwellings; L2A – new buildings other than dwellings
EXISTING PROPERTIES: L1B – existing dwellings; L2B – existing buildings other than dwellings
U-value requirements for existing buildings are unchanged from Part L 2010.
WALES
PART L 2014
U-values are part of wider assessment criteria to meet the requirements of Part L as a whole. Other factors taken into account include: airtightness, door and window U-values, the heating system, and thermal bridging.
‘Limiting U-values’ are the worst acceptable level of performance, but designing to these values is unlikely to result in compliance. The ‘notional building specification’ is a recipe approach that will ensure compliance if all standards are met. Regulatory compliance should be assessed through the appropriate SAP (for domestic) or SBEM (for non-domestic) calculation software.
NEW BUILD: L1A – new dwellings; L2A – new buildings other than dwellings
EXISTING PROPERTIES: L1B – existing dwellings; L2B – existing buildings other than dwellings
SCOTLAND
SECTION 6 2015
U-values are part of wider assessment criteria to meet the requirements of Section 6 as a whole. The ‘notional building specification’ is a recipe approach that will ensure compliance if all standards are met. Regulatory compliance should be assessed through the appropriate SAP (for domestic) or SBEM (for non-domestic) calculation software.
DOMESTIC NEW BUILD
As well as U-values, the notional dwelling specifications for gas, LPG and oil fuel packages take into account: airtightness, door and window U-values, the heating system, and thermal bridging. They also include photovoltaics and waste water heat recovery. Specifying U-values therefore needs to be done in careful consideration with the entire dwelling package.
Existing Domestic Properties
For extensions to existing dwellings, the required U-values for the new elements depend on the performance of the existing building:
- The higher standards in ‘A’ apply where the walls of the existing building have a U-value poorer than 0.70 and the roof is poorer than 0.25.
- ‘B’ applies where the walls of the existing building have a U-value better than 0.70 and the roof better than 0.25, or will be upgraded to those levels as part of the works.
Where existing domestic elements are to be altered or refurbished, the standards in ‘B’ apply.
NON-DOMESTIC BUILDINGS – NEWAND EXISTING
For all building types, early consultation with Local Authority Building Standards is advised.
Non-domestic new build standards are based on heating/ventilation specification (natural or mechanical) and have different limiting values depending on type of building (e.g. shell construction where future occupancy/use is uncertain).
For existing buildings, a degree of flexibility is available depending on the feasibility of achieving U-value targets (e.g. in listed buildings). Again, early discussion Local Authority Building Standards is recommended.