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  • Writer's pictureCliff L'Aimable _Chartered Surveyor & Building Engineer

New gas central heating installations

Updated: Nov 27, 2022

Blog entry by Cliff L'Aimable - Principle Surveyor at Building Control Surveyors - Private Building Regulation service provider.

My company and team offers private Building Regulation Approvals, technical design checking and site inspections of all building projects. Tel 01992 710 763 EmaIL

If a central heating or hot water system needs to be updated, an application might not be necessary, and even if it is, it might not need to be submitted in advance of the work being done.

Air source heat pumps_Building Control Surveyors Ltd
Team carrying out electrical and heating installs

There is no restriction on performing repairs right away if emergency work is required (for example, a hot water cylinder springs a leak), but the repairs must meet the standards, and it is essential to apply for retrospective approval and a completion certificate after the fact.

If a new system needs to be installed, the installer should approach the job as if it were being done in a brand-new structure.

The person who last worked on an existing system is responsible for ensuring its safe operation and should give a certificate to demonstrate that the appropriate checks have been made. This is true if the system has been modified or replaced.

Even though the installations will primarily be signed off by registered competent persons (installers), we are required (as Surveyors / Building Engineers) to be up to date with advice given and on assessing compliance due to new Part L Building Regulations changes that went into effect in June 2022.

If you are project managing then checking that installers are aware of all the new legal requirements whilst specifying and carrying out their work on both new and existing heating systems when the heat source is replaced.

Here is a brief summary and items to highlight in these new regulations.

Fabric first

A "fabric first approach" entails using techniques to maximise the performance of the materials, including insulation and glazing, that make up the building fabric of a home. This strategy sets a target of a 31% reduction in carbon emissions aligning with the governments intention and forthcoming "Future Homes Standard" target of a 75–80% reduction by 2025.

Calculations of Heat Loss

The installation of a replacement boiler will now need heat loss assessments for each room in a home rather than just the dwelling overall, which is a significant change from the previous Building Regulations. In order to prevent an enormous heat source, do this.

Mitsubishi Air to Water Heat Pumps
Air to Water Heat pump kit

For all types of heating systems, including oil, gas, and renewable ones, an installation must determine heat loss.


The new rules say that these systems must have a maximum flow temperature of 55 degrees, down from the previous standard of 80 degrees, in order to further the push toward low carbon heating systems.

The new standards indicate that the space heating system should be made to allow the use of the lowest flow temperature while still satisfying the needs of the home if this is not achievable for an existing installation.

Gas Boilers

The minimum standards for Part L will be met by high efficiency condensing gas boilers, but only in conjunction with secondary energy efficiency measures like:

· PV solar panels

· flooring heating

· Heat recovery from waste water

· Heat recovery from flue gases

As part of the new regulations, the minimum energy efficiency for heating systems has been set at 92% ErP for gas boilers and a SCOP of 3.0 for heat pumps.

HEAT PUMPS - Seasonal coefficient of performance (SCOP) for heat pumps has been set at 3.0 – This is a measure of the efficiency of a heat pump over the designated heating season, measured using the procedures in BS EN 14825.

Mitsubishi Air to Water heat pump
Mitsubishi Air to Water heat pump

Mitshubishi Air Source Heat Pump

The Boiler Plus Scheme

The "Boiler Plus" scheme was established in 2018 and is still in use at the time of this blog. According to the applicable requirements, a gas combination boiler (whether it is placed in a brand-new or existing system) must have one of the following components:

• Flue gas heat recovery

• Load compensation; and

• Weather compensation

• Intelligent control with automated and optimising features

Heating Controls

Every room will need thermostatic room controls when a replacement heat source is installed under the new Part L regulations.

The thermostatic room controls must be able to be utilised to separately adapt the heating output in each room that the heating appliance services.

The heat controls may be thermostatic radiator valves (TRVs), thermostats, programmers, boiler interlocks, cylinder thermostats, or independent HW time controls.

The least intrusive way to comply with this regulation is to add a TRV to each radiator as most modern heating systems already have one installed.

TRV’s prevent overheating in those areas, which would be an energy waste, by making sure each space is kept at a reasonable temperature. This will entail turning down the heat output of a radiator during periods of rising outdoor temperatures, intense sunlight, or when people or electrical devices in the room are producing more heat than usual.

The boiler will detect when the TRVs are shutting and, depending on the situation, either turn off or lower the quantity of heat it produces.

Water Treatment

Referencing BS 7593: 2019, for information on mandatory water treatment for every heating system. The BS describes the ideal procedures for setting up the main wet central heating systems.

Each heating system ought to be constructed so that water treatment chemicals can be added, flushed, and cleaned effectively. As part of good installation procedures, installation debris such millscale, metal swarf, soldering flux, jointing compounds, and grease should be kept to a minimum and flushed out during commissioning.

The new Approved Document Part L and the cited BS contained in Appendix E ensures that possible issues are identified and that steps are taken to maintain the effectiveness and extend the life of heating and cooling systems by aligning with this British Standard.

Balancing the installation

Every time a heating system is installed, the goal is to supply the right amount of heat transfer, exactly when and where a building requires it.

That objective is nearly never accomplished without proper system installation balancing and fine tuning.

The most noticeable effects of an unbalanced system are discomfort and energy waste due to room air temperatures that are either too high, too low, or both.

It should be a standard procedure to balance a system in order to get around this and guarantee that it continues to comply with the new Part L rules.

This can be accomplished with the help of balancing devices. The system's designer will determine the flow rate necessary to each terminal unit and will choose the type and size of the balancing valve to manage the flow based on the type of pumping system used (constant speed or variable speed).

Regulations for Buildings in the Future

In 2025, with the Future Homes Standard and Building Standards in place, building standards will undergo a comprehensive redesign. These will be a further step in achieving the UK's NetZero goal in 2050.

To guarantee that the new standards are met and optimum efficiency is attained, it is crucial for all installers to take into account both best practice and the new Part L building regulations as published in 2022


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