New Building Regulation Part L1B
The Requirements for Existing Dwellings – Part L1B applies to Provision, extension, alteration or renovation of thermal elements, controlled fittings and controlled services to existing dwellings
Part L1B introduces a new concept of Thermal elements.
Definition - A wall, floor or roof that separates the internal conditioned space from the external environment.
Thermal elements – there is now a reasonable provision to improve energy efficiency.
- On provision of new thermal elements
- On replacement of existing thermal elements
- On retention of existing thermal elements
- On material change of use or material alteration
- On renovation of existing thermal elements -If more than 25% of surface area is treated
Standards for thermal elements W/m2K.
| Element | Standard for new thermal elements in an extension | Standard for replacement of thermal elements in an existing dwelling |
| Walls | 0.30 | 0.35 |
| Roofs (insulation at ceiling level) | 0.16 | 0.16 |
| Roofs (insulation at pitched plane) | 0.20 | 0.20 |
| Roofs (flat) | 0.20 | 0.25 |
| Floors | 0.22 | 0.25 |
Controlled fittings.
- Scope windows, roof window and external doors
- Requirement on provision (extension) or replacement
- Use draught-proof fittings that achieve minimum standards (maximum area-weighted average U value)
- Consider ventilation requirements
- Especially where there are open-fluid appliances
Controlled services.
- Heating and hot water systems -On full or partial replacement
- Insulation of pipes and ducts – On provision of heating and hot water systems
- Commissioning of heating and hot water systems – Provide a commissioning certificate
Please note these brief guidance notes are not a substitute for reading the regulations and the Approved Documents (ADs).
For a more authoritative guide you are advised to use the link below to go to the Regulation of Ads.
