All you need to know about the future of heating homes.

Why have these new building regulations been introduced?

The main aim of Part L is to reduce carbon emissions in preparation for the Future Homes Standard, which will come into effect in 2025. The Future Homes Standard will ensure that all new homes will produce at least 75% less CO2 emissions than a home that has been built to previous (2013) energy efficiency requirements. This will mean that from 2025 onward, all newly built homes will be net-zero ready and will not need retrofitting in the future.

As we all know, the way we heat our homes is one of the biggest contributors to carbon emissions in the UK, so reaching a reduction of 75% less emissions is certainly ambitious. This is where the changes to Part L come into play. To ease the transition between the old and new energy efficiency regulations, the government have enforced the new building regulations, in a bid to achieve a 31% reduction of carbon emissions in new and existing homes prior to the Future Homes Standard coming into force.

What is the new maximum flow temperature for heating systems?

One of the biggest changes to the regulations is that the maximum flow temperature for newly installed heating systems is now 55°C, which is much lower than the previous standard of 80°C.

To achieve this much lower temperature, the heat emitters in a home will need careful consideration and radiators may possibly need to significantly increase in size, presenting space and aesthetic issues. For example, to provide 900 watts of heat output with a flow and return of 45°C/35°C, a double panel radiator would need to be 1800mm L x 600mm H compared to 1000mm L x 600mm H when using 75°C/65°C – which is almost double the size. In cases like these, installers will need to explore alternative emitters that have been designed to run at 55°C, as laid out in the new regulations.

Heat emitters with a larger surface area, such as underfloor heating, are an ideal alternative as they can run at lower temperatures – between 33-55°C rather than 75°C. This also makes underfloor heating (UFH) ideal for use with low temperature boilers and renewables, such as heat pumps, as the demand it places on energy sources is significantly less.

In fact, due to its ability to run at lower temperatures, UFH can perfectly accommodate the optimal coefficient of performance (COP) for heat pumps, which is attained when they run at 35°C.

However, there may be certain cases where it’s not possible to achieve a flow temperature of 55°C, either in properties where there is insufficient space for larger radiators, or where the existing distribution system is provided with higher temperature heat from a low carbon district heat network. Where this occurs, the new system will need to be designed to achieve the lowest flow temperature possible, whilst still meeting the heating needs of the property.

When will the new regulations be enforced?

To ensure that as little energy as possible is wasted, new systems in homes with a floor area of 150m2 or greater will now need a minimum of two independently controlled zones with each room, or zone, requiring its own smart or thermostatic controls. By splitting the system into zones, residents can control the levels of heat being emitted in certain areas and choose to heat only the parts of the property that are in use. By turning the heating off in any room where heat is not required, less energy will be wasted.

For traditional convectional heating, this can be satisfied through a thermostat or thermostatic radiator valves on all heat emitters in the rooms that do not have a thermostat. For all hot water stores, a timer for heating and timer for hot water is required so that they can be controlled independently of the space heating circuit.

Another benefit of using underfloor heating is that it can be installed in the same way it always has been, as it is naturally designed and installed into zones. Therefore, underfloor heating manifolds can control multiple zones at once, allowing each area – or room – to be warmed to a different temperature depending on the user’s requirements.

It is also worth noting that the pump now needs to automatically turn off when heat is not required. So, the system controls need to be wired to ensure that the heating appliance and pump can be switched off when there is no demand for hot water.

Does all pipework need insulating under the new regulations?

Yes, any new pipework will now also have to be insulated to adhere to the new regulations. This includes primary circulating pipes for heating circuits, including those that pass into voids or ducts, pipework for domestic hot water, all cylinder pipework and all secondary circulation pipework. All pipes connecting to a hot water storage unit will also need to be insulated for at least 1m from where they connect to the unit.

As well as newly installed systems, any new exposed pipework in existing systems where the boiler or cylinder is replaced must also be insulated. New pipes also need to be heat pump ready and have at least a diameter of 15mm. Installers will need to comply with this when working on new builds in particular as photographic proof will be required.

Does Part L only apply to work on new builds?

Although Part L contains major changes to the way heating systems are installed in new builds to gear up for the Future Home Standard, many aspects of the new regulations will also have a large impact on how engineers design and install systems in refurbishment and retrofit projects.

This means that the regulations will have a direct impact on domestic installers across all projects – both new builds and existing homes – which is why it’s important for installers to familiarise themselves with the updates before they come into effect on 15th June 2023.

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