What This Requirement Covers
Replacing a boiler is one of the most common types of building work in the UK. It is classified as a controlled building service under Part L and must comply with minimum efficiency standards. The work must be carried out by a registered competent person or notified to Building Control.
Key Requirements
Minimum Efficiency
- All replacement gas boilers must be condensing with a minimum seasonal efficiency of 92% ErP
- All replacement oil boilers must be condensing with a minimum efficiency of 93% ErP
- Non-condensing boilers can only be installed where a condensing boiler is not technically feasible (e.g., no suitable condensate disposal route); the installer must record the reason on the notification
Heating Controls
When replacing a boiler, the minimum heating control package must be provided
- Programmer or time switch
- Room thermostat (or programmable room thermostat)
- Thermostatic radiator valves (TRVs) on all radiators except the reference room
- Boiler interlock
- Where the boiler supports it, weather compensation or load compensation controls
Competent Person Schemes
- Gas boilers: Gas Safe registered engineers can self-certify compliance
- Oil boilers: OFTEC registered technicians can self-certify compliance
- If the installer is not registered with a competent person scheme, a Building Control application is required
Documentation
- The installer must provide: Benchmark certificate (in the boiler manual, signed and dated), Building Regulations compliance notification (via the competent person scheme), and operating instructions to the householder
Practical Compliance Tips
- Always use a Gas Safe (gas) or OFTEC (oil) registered installer
- Request the Benchmark certificate; it is proof of correct installation and commissioning and is required for most manufacturer warranties
- Upgrade heating controls at the same time as the boiler; the cost is minimal and the energy savings are significant
- Route the condensate pipe internally where possible to avoid freezing
- Consider whether a heat pump would be more appropriate than a like-for-like boiler replacement, particularly with the Boiler Upgrade Scheme grant available
- Keep all certificates and documentation for property sales
- Register the boiler warranty with the manufacturer