CPD 04 2021: The future of heating – Part L 2022 options

This CPD sponsored by WMS explains the implementation of changes to Part L affecting energy usage, and the role underfloor heating can play in driving household efficiencies. DEADLINE TO COMPLETE: 9 August 2021

The future of new-build is changing


In seeking to tackle climate change and reduce carbon emissions the government is rolling out changes to Part L of the Building Regulations, covering the efficiency of energy and power. The UK’s housing stock is the fourth-largest emitter of emissions, a situation ministers seek to remedy by banning gas-powered new-build homes from 2025.

As part of the drive to improve energy efficiency, homeowners and developers should consider a range of heating options, not least underfloor heating systems.

The climate crisis and the UK housing sector

In its fight against the impact of climate change, the UK government has prioritised reducing carbon emissions across the country, setting a target of slashing emissions by 78% by 2035 compared with 1990 levels, and achieving net zero carbon by 2050.

These targets are ambitious, but necessary. The world cannot afford to see the predicted rise in global temperature of 2°C. In its efforts to tackle the problem, the government has sought to reduce carbon emissions in every area of life, and similarly increase energy efficiency. Inevitably its attention has turned to the country’s housing stock.

According to data published by the Office for National Statistics (ONS) earlier this year, UK residential properties ranked fourth among the biggest emissions contributors, accounting for around 15% – after transport (27%), energy supply (21%) and business (17%).

The ONS said the main source of emissions from the residential sector was the use of natural gas for heating and cooking, and the government has taken the bold step of addressing the former, legislating for a ban on gas boilers being installed in new-build homes from 2025.

With revised building regulations coming in next year as part of a phased strategy, and looming efforts to tackle the country’s existing housing stock via its “heat and build strategy”, the government has shown that it means business.

Part L – change is here

Changes to Part L of the Building Regulations to address the conservation of fuel and power are part of the phased approach to delivering zero carbon homes from 2025.

The changes build on the Future Homes Standard consultation by setting out energy and ventilation standards for non-domestic buildings and existing homes, and include proposals to mitigate against overheating in residential buildings.

Make no mistake, this is the biggest change the UK housing market has ever witnessed.

Among the revisions to Part L, coming into effect in June 2022, are that the average UK home will need to produce at least 75% lower carbon emissions than one built to current energy efficiency requirements. There will also be an enforced 31% reduction in carbon dioxide from new dwellings, compared with current standards.

There will be flexibility on how to meet the target, but the government expects heat pumps to be the primary heating technology for new homes. Direct electric technology has been taken out due to issues around occupier affordability.

New heating systems will need to be designed with a maximum flow temperature of 55°C or lower (which defines low temperature as 50°C or lower), and zones within a property will require self-regulating control devices for heating systems.

Meanwhile the government will establish a format for a home user guide in order to inform homeowners how to efficiently operate their dwelling.

It is worth noting that local authorities will retain the ability to set their own local (higher) energy efficiency standards if they so wish.

Measurement shift

One of the key elements of the changes to Part L 2021 is in how energy running costs will be measured. SAP (standard assessment procedure) calculations will be used to work out the energy need for the technology in the home and that will give an indication on occupier bills.

Part of this process will be achieved by the adoption of the latest version of SAP (10.3) – the calculation required to produce a predicted energy assessment and an on-construction energy performance certificate – at implementation of Part L 2021.

The principal performance metrics will be:

1) Primary energy target
2) Carbon emissions target
3) Fabric energy efficiency target
4) Minimum standards for fabric and fixed building services.

This will also mean a change in SAP and what it will calculate. A new version of SAP will be introduced at the same time.

With the need to make homes more energy efficient, technologies such as underfloor heating, which operate at low temperatures but can generate sufficient heat for occupier comfort, can be considered properly.

Benefits of radiant heating

Radiant temperature is recognised by a number of organisations, including the Wellbeing Institute, as the best way of heating for comfort. With underfloor heating, warm water is circulated through continuous loops to create a large radiant surface that heats a room from the floor upwards.

Radiators, on the other hand, are less efficient, drawing cold air across the floor before heating it and then convects the warm air upwards towards the ceiling.

There are many know benefits of underfloor heating, such as increased space for furniture design, but using underfloor heating helps to promote healthier living conditions.

In the UK an average of one in eight people receive daily treatment for a respiratory condition such as asthma. Heating systems based on convection exacerbate such conditions by encouraging the movement of dust and dust mites in the air. By using radiant heat underfloor heating is able to reduce such movement, providing a healthier environment.

Given that underfloor heating is concealed it affords architects considerable freedom when designing a home, not only in terms of configuring furniture within a room but also through being able to factor in full-height, floor-to-ceiling windows more easily, thus increasing the amount of natural light being let into the building. It is also safer for children and the vulnerable, with no hard or hot surfaces to touch or fall against.

Low temperature radiators are one of the ways of conforming with the coming changes to Part L and the new maximum flow temperature of 55°C; however, there are issues with low-temperature radiators. To achieve the required 55°C, radiators need to significantly increase in size, presenting location and aesthetic issues, even more so with the trend for new homes to be more open-plan.

The new low-temperature required for homes (55°C) will make radiators much cooler and occupiers may think their heating is not working properly. There will also be an increased cost due to the larger size and subsequently higher steel costs, which are already on the rise.

In terms of lifecycle, radiators will still need to be replaced after about 20 years, which creates a landfill waste issue (underfloor heating pipes, by contrast, generally have a 75-year warranty). There is also the risk of balancing problems and uneven heat distribution with low-temperature radiators.

Heat pump and underfloor heating working in partnership

Underfloor heating can cover a greater surface area and can therefore run at lower temperatures – for example, at 35°C rather than 80°C. Therefore the demand that underfloor heating places on energy sources is considerably less, making them ideal for use with heat pumps.

Combining both technologies – heat pumps and underfloor heating – makes the overall system between 15% and 40% cheaper to run compared with systems that lack both.

For heat pumps to work at their most efficient (best for homeowners’ bills) they need to run at 35°C – something only underfloor heating can do.

Design and installation, however, are critically important, not least because heat pumps have far smaller tolerances than boilers. If the system is not designed or installed properly, it will not reach its required efficiency and occupier bills will rocket.

Future policy and the move to 2025

This table is extracted from the government consultation response document. It shows the 2021 Part L standard move to low-temperature systems, and then moving further to 2025 and the green highlighted element that shows low carbon heating. Heat pumps combined with underfloor heating is the favoured option for compliance with the 2025 legislation.


With new UK housing stock required to be gas-free in less than five years’ time in response to the climate crisis, and with moves to reduce the energy use of existing residential properties under way, the industry is only heading in one direction.

Installing energy-efficient technology such as underfloor heating can play a part in reducing energy use, lowering carbon emissions and providing a safer, comfortable environment for occupiers.

Timeline for changes to Part L 2021

December 2021Interim Part L regulated
June 2022Interim Part L comes into effect
2025Ongoing work towards the fossil fuel ban

To take the module, click the link below…