U-values webpage last updated: November 2023
The Building Regulations stepped forward with changes that came into force on 15 June 2022 – intended as a stepping stone toward the government’s new Future Homes Standard (due to be introduced in 2025).
This provides an intermediate uplift to existing energy efficiency standards including fabric insulation standards, improved u-values and increased insulation thickness within home extensions.
Hertfordshire Building Control has been pleased to work with prominent manufacturers in the insulation and concrete block industries to collate this useful guidance on the specification of floor, roof and wall elements in domestic extensions. The listed solutions can achieve the maximum U-Values listed in Table 4.2 of Approved Document L Volume 1 covering development in England. They are supported by calculations with appropriate third-party accreditation under the BBA Competency Scheme for U-Values or an equivalent standard.
It is important to note that the listed specifications should always be constructed in strict accordance with the respective manufacturer’s technical guidance. For the potential performance to be achieved there must be due regard for the need for continuity of insulation and a reasonable standard of airtightness.
The indicative U-Values and insulation specifications in the following tables are derived using various assumptions and input factors incorporated within manufacturers’ software. Thermal performance can be affected by many factors including the method of construction and installation of the product and the end-use application. When specifying products, you need to satisfy yourself that use of the system meets all relevant national Building Regulations such as those relating to fire safety and condensation risk.
Should I use the old or new values?
Based on regulation updates to new Part L which came into force on 15 June 2022, the following applies:
- Works which commenced and had an application deposited before the 15 June 2022 are allowed to use the previous U-Values
- Works which have had an application deposited before 15 June 2022 and have NOT yet commenced can only use the old U-Values if work commences prior to 15 June 2023
- Works commencing after 15 June 2023 MUST use new U-Values
- Works which had an application deposited after 15 June 2022 MUST use new U-Values.
