In late 2021, the Department for Levelling Up, Housing and Communities announced a number of changes to various building regulations and the introduction of new ones, which came into effect in June 2022. 

These changes only affect England, but they do not affect any buildings that were already part built, or approved to be built before June of 2022, as long as they are finished before June 2023. 

More recently, further changes to Part R were announced in October 2022, but these do not look like they will affect plumbing and heating at all.

Indeed, while many other changes were made, notably to Part F (ventilation), the majority of the changes that affect plumbing and heating, fall under Part L and G of the Building Regulations, which is what we will focus on in this feature.

What is new?

One of the biggest changes to part L set to affect heating engineers, concerns flow temperatures. 

Put simply, flow temperatures for heating systems should no longer exceed 55°C and, in fact, they should be below this temperature if possible. This is likely a response to condensing boilers, which are inefficient if working with flow temperatures above 55°C. 

One of the problems this change causes, which should become an additional consideration when installing a new boiler system, is the risk of Legionella bacteria forming in hot water that is unvented.

Changes to Part L

In addition to this major change, there are a number of further additions and alterations set to affect the industry. 

Insulation and how to prove it

Regulation 4.24, which refers to newbuild properties, states that all primary circulation pipes, including those in voids, such as underfloor or in ducts between walls, will need to be insulated. In fact, the only area to escape this requirement is the one metre off every pipe from storage systems of hot water, whether this be boilers or unvented hot water cylinders, or where it terminates into a wall or floor. 

Equally, regulation 4.25, which applies to existing properties, states that if a boiler or cylinder is upgraded, any exposed pipe will require insulation. 

The regulations also state that you must submit photographs of the insulated pipework to building control, to prove that they have in fact been insulated.

All about heating

Regulation 5.10, which concerns new systems in new or existing properties, states that all pipework and emitters, including underfloor heating (UFH), be sized appropriately to allow space heating systems to operate in a manner that meets the needs of the property, while staying at or below the aforementioned flow temperature of 55°C. 

While not an out and out rule, the most efficient way to achieve this in newbuilds is through the installation of UFH. It ensures that the property is heated most effectively, despite the drop in temperature setting. 

The regulations do, however, mention, that if, when installing a new boiler for example, if you can’t adequately heat the home at a temperature 55°C or below, it should instead be set to the lowest temperature setting possible. 

According to regulation 5.14, wet heating systems in newbuilds with a floor size of 150m2 or more should have a minimum of two independently controlled heating circuits.

Regulation 5.15 states that system controls should be wired so that when space heaters or hot water are not in use, the appliance and pump are turned off too, while regulation 5.16 determines that domestic hot water circuits supplied from a hot water store, should feature:

  • A time control that is independent of other space heating circuits;
  • An electronic temperature control.

Hot water circuits and boiler upgrades

When it comes to primary hot water circuits for domestic hot water or heating, the system should have a fully pumped circulation when it is compatible with the heat generator, according to 5.17.

Regulation 5.20 states that, when upgrading a boiler, you have to fit a thermostatic radiator valve on every radiator, unless they are installed into areas controlled by individual room thermostats. This used to just be a recommendation; however, it has now been changed to a regulation and must be carried out.

The one for all installers

The final change to Part L that affects all installers is regulation 8.8, which determines that, before a new heating appliance is installed, all central heating and primary hot water circuits should be thoroughly cleaned and flushed out. This is to make domestic central heating systems comply with BS 7593. 

Therefore, all new boilers installed require a magnetic filter, the system water will need to be checked, cleaned if needed, and an inhibitor will need to be added to ensure that PH levels are kept correct, and the system does not cause corrosion.

Furthermore, not only do these systems need to be commissioned correctly, but there also needs to be evidence of this.

Part O

Finally, the new Part O document details many changes that will affect installers too. 

This document affects houses, flats and apartments, student accommodation, HMOs, and care homes, including shared communal areas, such as foyers with concierge desks, however it does not affect hotels. 

Similarly, the document does not apply to non-residential areas of mixed-use buildings, or residential areas formed by material change of use.

Firstly, if you begin work after June 2023 or the application was not received before June 2022, you must adhere to Part O. 

Secondly, there are two routes to compliance specified in Part O; the simplified method and the dynamic thermal modelling method (DTM). The simplified methods will be used more commonly in domestic properties, while the DTM method is applicable in commercial properties.

The simplified method details that the strategy for preventing overheating is based on the location of the building and whether it has cross ventilation or not; where cross ventilation is categorised as common spaces having openings on both facades. Therefore, single facades and corner flats do not have the capacity for cross ventilation.

Part O states that the simplified model is not suitable for multi-unit buildings with significant horizontal pipework in a communal heating or hot water system. 

Furthermore, the primary distribution of pipework should be through vertical risers to minimise heat gains to corridors, with vertical distribution the simplified method can be used.