What do this summer’s Building Regs changes mean to you?

What do this summer’s Building Regs changes mean to you?

The changes to the Part L, F and O of the Building Regulations which were announced at the end of 2021 came into effect on 15th June 2022. Heating engineers who install both oil and renewable heating systems, as well as developers, need to be familiar with the changes and the implications they will have.

The Building Regulations which changed in June 2022 are part of the Government’s ongoing strategy to reduce carbon emissions, serving as a stepping stone towards the Future Homes Standard, which is due to be implemented in 2025, which will mandate that homes produce at least 75% less COemissions. The changes to Part L (Conservation of fuel and power), Part F (Ventilation) and Part O (Setting Standards for overheating in new residential buildings) are the biggest set of updates to Building Regulations which will affect the heating sector in over a decade. Therefore, it is important that everyone working in the heating industry is familiar with what these changes mean to their daily workings.

It is important to note that these Regulations only affect new and existing buildings in England. Further information about the regulations changing in Wales from 23rd November 2022 can be found here and further information about the regulations changing in Scotland from 1st December 2022 can be found here.

New Builds (domestic and commercial)
These ambitious changes to Part L1 set out an interim target of a 30% reduction in COemissions relative to the 2013 version of the document. Currently, a building’s performance can vary depending on the occupant’s behaviour (opening windows when too hot or when cooking for example). From 15th June, the thermal performance of a new building will see improvements in external wall U-values (down to 0.18W/m2K). The heating systems for such new builds will also have to be designed with a maximum flow temperature of 55°C or lower, thus favouring low-temperature, low carbon systems (such as air source heat pumps).

Time delays have also been significantly reduced. Whereas the previous iterations of the Building Regulations assisted the developer by allowing them an indefinite period of time to complete the site provided they started developing the site within 5 years of permission being granted, the new Regulations include a transitional arrangement for individual buildings where plans submitted after June 2022 or where construction has not started before June 2023 must comply to these new Regulations.

Similar changes to Part L2 will see a 27% reduction in carbon emissions on properties such as shops and offices.

Approved document O is new to this suite of regulations. This document is aimed at preventing domestic dwellings overheating as a result of solar gains in the summer and provide a means of removing this heat through the use of cross-ventilation – this will be introduced to include domestic dwellings, offices and schools etc.

Approved Document F deals with ventilation and these changes will bring about changes to increase the standard of ventilation in new homes. It is also intended that these changes will also be included for new extensions in existing properties as well as non-residential buildings.

Existing properties
While historical versions of the Building Regulations only applied to new buildings, the 2022 version also tackles some areas relating to existing properties, particularly important when renovating an existing dwelling. For example, when a wet heating system is newly installed or fully replaced in an existing building (including the heating appliance, emitters and associated pipework), it must be designed to allow the space heating system to meet the heating needs of the dwelling at a maximum flow temperature of 55°C or lower. If this is not possible, the space heating system should be designed to the lowest design temperature possible that will still meet the heating needs of the dwelling. It is anticipated that this will have to be justified before electing to use a higher flow temperature.

While this will not be a requirement for simply replacing a boiler, it makes perfect sense to start improving the system efficiency of the existing system by reducing the flow temperature that will still work with the existing heat emitters. However, to do this, the new Regulations now require a full room by room heat loss calculation to be carried out prior to the boiler replacement.

New Heat Loss calculation method
This change will affect installers of all heating system types, both oil, gas and renewable. While a thorough room-by-room heat loss calculation is standard practice for all heat pump installations, it was not previously required for oil boilers. However, from 15th June 2022, all oil heating installations will need a room-by-room heat loss calculation carried out as part of the initial site survey. It is also worthwhile calculating the output of the existing heat emitters to offer advice on energy saving measures that could be introduced while changing the boiler.

Section 5.8 of the new Regulation states that “The specification of space heating systems should be based on both of the following:

a. An appropriate heat loss calculation for the dwelling.
b. A sizing methodology that takes account of the properties of the dwelling, such as the Chartered Institute of Plumbing and Heating Engineering’s Plumbing Engineering Services Design Guide."

This means that a whole house type calculation is no longer allowed. This will obviously have a huge effect on installers who are requested to replace a boiler in a distress situation.

The section goes on to say that “systems should not be significantly oversized” – but what does this mean? I could offer my opinion, but it could be completely different to an assessor or Building Control officer. Is a 36kW boiler satisfying a heat loss of 14kW significantly oversized? The purpose of the Regulation is clear in that the selected boiler should match as closely as possible the calculated heat loss. But what about combination boilers where the output has been historically sized for DHW performance and not space heating requirements.

While only gas combination boilers are directly referred to in the Regulation, I think we should be cautious in assuming that oil combination boilers are exempt. For example, if the same property has a 14kW heat loss, should you install a 36kW combination boiler? Or should you discuss this ‘oversize’ element with the homeowner with a view to installing a traditional boiler/cylinder system, thus being able to select a smaller boiler while maintaining (or improving in most cases) the DHW production?

Oil Heat Loss Calculator
To coincide with this new requirement to carry out room by room heat loss calculations as part of an oil boiler installation, Grant UK have developed an Oil Heat Loss Calculator which is available to G1 Installers via the online G1 Portal. G1 members simply need to log into their Portal account via and then visit the ‘Downloads’ page where they will find the calculator available. To read more about how to use this oil heat loss calculator tool, please read our blog here.

To download the new Part L, F and O documents, please follow the links below:

Conservation of fuel and power: Approved Document L
Ventilation: Approved Document F
Overheating: Approved Document O

Neil Sawers
Commercial Technical Manager at Grant UK
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