Heating systems make warmth.
Insulation keeps it.
Controls decide how wisely it’s used.

Clear, independent advice for a efficient home.

When installing a fossil-fuel boiler in the UK, a range of regulations must be followed to ensure both safety and compliance. They are designed for consumer protection, property protection, health and safety and some are guidance for warranty validation.

• All gas work must be completed by a suitably qualified and competent person
• Appliances must be installed according to the manufacturer’s instructions.
• Gas pipework must be correctly sized and installed.
• Appliances must be safely commissioned and tested.
• Flues must safely remove combustion gases.

Reference: Gas Safety (Installation and Use) Regulations 1998 – Health and Safety Executive (HSE)

Building Regulations 2010.

Boiler installations must comply with UK Building Regulations.

Approved Document L – Conservation of Fuel and Power
This regulation focuses on improving energy efficiency.

BoilerPlus (Introduced April 2018)

Applies to all new and replacement gas boilers in existing homes.

• Minimum boiler efficiency of 92% ErP (Energy-related Products)
• Time and temperature controls must be installed
• A boiler interlock must stop the boiler firing when no heat is required

For combi boilers, at least one additional efficiency measure must be installed: see controls.

• Weather compensation
• Load compensation
• Flue Gas Heat Recovery System (FGHRS)*
• Smart thermostat with automation and optimisation

*A FGHR device (a heat exchanger) is installed on the boiler exhaust, using the hot flue gases to heat the incoming cold mains water before it hits the burner.

Reference: Domestic Building Services Compliance Guide / Boiler Plus legislation

Approved Document J – Combustion Appliances.

This regulation ensures safe installation of appliances that burn fuel.

• Proper air supply for combustion
• Safe flue installation
• Correct flue terminal positioning
• Protection from carbon monoxide
• Heat protection for surrounding building materials

Reference: Building Regulations Approved Document J

Building Regulations Notification.

Once a boiler is installed:

• The installer must notify Building Control via the Gas Safe Register.
• The homeowner receives a Building Regulations Compliance Certificate.

Heating System Water Treatment.

BS 7593:2019 – Treatment of Heating Systems

This standard protects the heating system from corrosion and sludge.

• The heating system must be flushed before installing a new boiler.
• A chemical inhibitor must be added to the system.
• A magnetic filter is recommended to capture system debris.

Reference: BS 7593:2019 – Code of Practice for Treatment of Water in Domestic Heating Systems

Heating Controls Requirements.

Energy efficiency regulations require proper heating controls.

• Room thermostat
• Programmer or timer
• Thermostatic radiator valves (TRVs)
• Zoning for larger homes (over 150m²)

Reference: Domestic Building Services Compliance Guide

Important British Standards for Boiler Installation.

• BS 6798 – Installation of gas-fired boilers
• BS 6891 – Gas installation pipework
• BS 5440-1 – Flueing requirements
• BS 5440-2 – Ventilation requirements
• BS 7593 – Water treatment for heating systems
• BS EN 12828 – Heating system design
• BS EN 14336 – Heating system commissioning
• BS 7074 – Expansion vessels

Commissioning and Documentation.

After installation, the following documentation should be completed:

• Benchmark commissioning checklist
• Gas Safe notification
• Building Regulations Compliance Certificate
• Manufacturer warranty registration

Installation Requirements and regulations.

Green, Information.

Amber Guidance.

Red Regulation.

Whether the installation is carried out privately or through UK government backed schemes such as the Warm Homes Grant, it must meet the relevant Building Regulations and industry requirements.
This includes fitting a carbon monoxide alarm in the same room as the boiler, complying with “Boiler Plus” standards, and following the manufacturer’s instructions regarding magnetic filters, system flushing, and appropriate heating controls.

For any insulation project, whether funded privately or through a UK grant scheme, the current PAS (Publicly Available Specification), best practices, and relevant building regulations should be strictly adhered to. Once you have engaged an installation company to perform the work. Alway enquire about your consumer rights and guarantees that are going to be supplied.

Always ask pre install if existing ststem will be cleaned? this is a must on older sysems being upgraded. Ask for certificate showing chemicals used, wether it was a hot clean or cold clean, some companies perform a full powerflush and others remove radiators to flush outside. Always ask for inhibitor (internal protection) details and a sticker should be added to benchmark showing chemical used and date added.

If a funded standalone boiler installation is being installed and is not part of a government backed scheme , then this may not fall under the current PAS and will only need to follow gas safe and manufacturers instructions, unless a package that includes insulation has been developed as part of a funded scheme, this may change due to future legislation.

Magnetic filter fitted. Some boiler manufacturers ask for this as part of warranty. The filter should be fitted to the return pipe on the heating. It is designed to trap rust and debris from the system before it goes through the heat exchanger.

Shock arrestor fitted, if boiler close to incoming water meter. 
To prevent water hammer, which can damage pipework and be annoying and loud.

Loft walkways should be introduced if boilers are being situated into a loft area and adequate lighting is a must.

The homeowner should provide measures as a minimum for their own safety and so that gas engineers can work in a safe environment.

A means to control each heat emitter (radiator thermostats, TRV’s). Regulation to allow each room to be individually controlled. Smart radiator thermostats are becoming popular. Some low temperature systems like heat pumps may not need thermostats on the radiators.

Section 5 (specifically paragraph 5.20) of the Approved Document L, Volume 1: Dwellings, 2021 edition (incorporating 2023 amendments.

The rear safety pipe safely positioned. If outside should be away from above doorways and walkways and pointed into the wall, if inside then should discharge to current regulations and should be visible.

The Gas Safety (Installation and Use) Regulations 1998 (GSIUR), specifically regarding safe installation and discharge. These must also comply with the Pressure Systems Safety Regulations 2000 (PSSR)

External condensate pipework to be insulated with a class 0 insulation and off ground. Condensate pipes can freeze in the winter. Protection using a class 0 insulation (usually black) prevents the insulation soaking up water and becoming a block of ice! Ideally the manufacturer will state size of condensate pipe to be used, if outside keep off ground and best practice is to terminate indoors. Some class 0 insulation comes with UV protection and some does not.

Condensate pipework is primarily regulated by BS 6798:2014 (Specification for installation and maintenance of gas-fired boilers), alongside UK Building Regulations and manufacturer instructions

A means of programming (timer). Able to set on/off holidays and timed presets. Saves fuel as we have the system on and off as required.

The primary regulation for boiler programmers in the UK is Part L of the Building Regulations (Conservation of fuel and power), which was significantly updated in 2018 (Boiler Plus) and again in 2022 to improve energy efficiency

A means of interlocking to be present (a room thermostat can introduce interlocking on the boiler).

Boiler interlock, which ensures the boiler and pump turn off when there is no demand for heating or hot water, is required under Part L of the Building Regulations in England and Wales, specifically enforced through the Boiler Plus standards introduced in April 2018. It is mandatory for all new gas and oil boiler installations in existing homes to have this control functionality to improve energy efficiency.

Pipework to be insulated unheated spaces (lofts, garages etc). To prevent freezing and damage in the cold months.

Boiler pipework insulation in the UK is governed by Building Regulations Approved Document L (Conservation of Fuel and Power), specifically requiring compliance with BS 5422:2023. All primary circulation pipes for heating and hot water, including those in voids, must be insulated to reduce energy loss.

Installation to be carried out by a competent person. Gas Safe, Oftec, etc.
Boiler to be installed in a safe and accessible area. This is for maintenance and electrical safety, especially in areas that contain bathing facilities (bathrooms).

Gas boiler installation is governed primarily by the Gas Safety (Installation and Use) Regulations 1998 (GSIUR), which legally mandate that only a Gas Safe registered engineer can install, repair, or maintain gas appliances.

Flue to be accessible via removable boxing in or hatches. This is a regulation called flues in voids. The entire length of the flue should be able to be inspected.

Flues in voids must allow for inspection along their entire length to comply with the Gas Safety (Installation and Use) Regulations 1998 (GSIUR 26(9)) and Technical Bulletin 008.

A means of safely removing condensation from the boiler (soak away, drain etc). Condensate is acidic but not really dangerous (like lemon juice) but it can damage cement etc over time so it should be away from property walls.

Boiler condensate removal is primarily regulated by BS 6798:2014 (Specification for installation of gas-fired boilers) in the UK, which dictates that condensate must be discharged to an internal foul water system to prevent freezing. If external termination is required, pipes must be at least 30mm diameter and insulated.

Benchmark to be competed by installer. This is in the manufacturer’s supplied service book. It needs to be filled in so the installers address, contact number, name, and business can all be clearly read. It’s a tick box exercise to show the installer has signed off the installation.

While the “Benchmark Scheme” itself is an industry-led code of practice, it is recognized by the government as a means of demonstrating compliance with mandatory Building Regulations. Unfilled benchmarks can void warranty and class the installation as Uncommissioned and unsafe.

Flues should be at least 300 mm from openings into property (windows, doors etc). This is to stop products of combustion entering the property. A high level flue kit can be used in some circumstances to mitigate distance. Flues should be over 2m from ground. If not, then a flue guard is needed to protect from damage

Gas flue regulations in the UK (Building Regulations Approved Document J, BS 5440) require terminals to be at least 300mm–600mm away from doors/windows and 2m below roof levels to prevent exhaust reentry. Concealed flues in voids must have inspection hatches for safety checks.