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Part L consultation

What do housebuilders need to be aware of?

On 1st of October 2019, the Ministry of Housing, Communities and Local Government published a consultation on The Future Homes Standard: changes to Part L (conservation of fuel and power) and Part F (ventilation) of the Building Regulations for new dwellings. Mark Wilkins, head of training and external affairs for Vaillant Group UK, examines the likely outcomes and the implications for UK housebuilders.


Building practices

Transitional arrangements

Calculations and compliance


The Buildings Regulation Part L consultation document presents two possible routes to increase the energy efficiency requirements for new homes in 2020:

Option one: Future Homes Fabric - a 20% reduction in CO2 from new dwellings, compared to current standards.

This performance standard is based on the energy usage and carbon emissions of a home with:

a. Very high fabric standards to minimise heat loss from, walls, floors, roofs and windows (typically triple glazing)

b. A gas boiler

c. A wastewater heat recovery system


Option two: Fabric Plus Technology - a 31% reduction in CO2 from new dwellings, compared to the current standards.

This performance standard is based on energy usage and carbon emissions of a home with:

d. An increase in fabric standards (but not as high as option one – likely to be double glazing rather than triple glazing)

e. A gas boiler

f. A wastewater heat recovery system

g. Photovoltaic (PV) panels


This option is expected to encourage the use of low carbon technology, such as heat pumps, as it may present a more cost-effective method of achieving the requirements compared to fabric improvements and PV panels.

The good news for developers is that the consultation does not present a prescriptive way to comply. So, as long as carbon reductions are met, developers are free to use whichever combination of energy efficiency measures suits their needs. Vaillant welcomes this, as it offers the flexibility and scope for innovative new technologies. Many developers are already mixing different solutions to meet or even exceed the targets set by the regulations, creating variances not only by region but also by property type and developer.

Out of the two options, Fabric Plus Technology is the government’s preferred route as it offers higher potential carbon savings and lays a clearer path to the Future Homes Standard.

The Future Homes Standard, which will be implemented from 2025, will include the fabric standards of option one alongside a low carbon heating system, with heat pumps and heat networks named as the main technologies to deliver heat to new homes. It is anticipated that the Future Homes Standard – based around a heat pump, waste water heat recovery, triple glazing and minimum standards for walls, floors and roofs – will deliver a reduction in carbon emissions of 75 - 80%.

Building practices

No matter which route is taken, the inevitable outcome is increased build costs for new homes. Option one “Future Homes Fabric” is estimated to add £2557 to the build cost of a new home, whilst option 2 “Fabric Plus Technology” would increase build cost by approximately £4847. Opting for low carbon heating within the second option is expected to be a less costly approach, with roughly £3134 of additional cost for a semi-detached house .

Developers will not need to shoulder these costs as the likely outcome is that they will be passed on to homeowners in the purchase price of the property. Due to reduced energy bills, with routes one and two offering a £59 or £257 annual saving respectively, long-term homeowners will see a return on their investment.

The consultation also asks for future-proofing of developments in anticipation of the widespread use of heat pumps and low carbon technologies outlined in the Future Homes Standard for 2025 and beyond.

Since heat pumps operate most efficiently at low flow temperatures, the government’s preferred approach to future-proofing is for developers to install larger heat emitters designed to operate at lower flow temperatures of 55°C of less. This would also provide the immediate benefit of maximising the efficiency of condensing boilers, resulting in energy savings for the consumer. It would also mean lower cost and less disruption to householders when low-carbon heat is installed in the future because they will not need to have new radiators or pipework installed.

Transitional arrangements

The consultation also considers the tightening up of transitional arrangements. Transitional arrangements provide developers with assurance about the standards they have to work to and that no material changes are required when new regulations enter force.

Part of the Building Regulations overhaul will involve more stringent transitional arrangements to close the current ‘loophole’ that allows new developments to be built to much older standards.

Under the proposed changes, the government says: “where work has not commenced on a specific building covered by the building notice, initial notice, or full plans within a reasonable period, that building would not benefit from the transitional provisions and so it (and any other non-commenced buildings covered by the notice/plans) would need to comply with the latest set of energy efficiency standards. Those already benefiting from transitional provisions applied to earlier changes to Part L and the energy efficiency standards would not be affected” .

The government is proposing to withdraw the ability of local planning authorities to set their own energy efficiency standards, which will eliminate disparate targets – levelling the playing field in areas where homes are more expensive to build due to more rigorous requirements.

It is important for developers to be aware of these changes as they may have to revise project timescales and build homes quicker to remain compliant. This could result in different dwellings on the same site being built to different standards, but the government envisages that these changes will nevertheless “pave the way for Future Homes Standard”.

Calculations and compliance

Measures of calculating building performance and proving compliance will also change. Primary Energy Factor (PEF) will become the principal performance metric, replacing the fabric energy efficiency assessment, and carbon emissions will be kept as an additional target. There will also be a householder affordability rating and minimum standards for fabric and fixed building services.

The affordability rating is an interesting proposal as it aims to prevent the use of compliance methods that would result in excessively high energy bills for the end-user. This is because electricity will have a lower CO2 rating than natural gas and therefore technologies such as electric panel heaters could present a lower capital cost route to compliance, if affordability wasn’t also a consideration.

In basic terms, PEF looks at how much of each fuel, and therefore how much energy, is used in the production of another fuel.

PEF will be used in to calculate total primary energy demand of the dwelling. First, the SAP calculation is carried out to find the energy demand of the dwelling for each of the uses specified, for example space heating, water heating and lighting. Each energy demand is then multiplied by the primary energy factor for the fuel being used to meet it.

To coincide with the Future Homes Standard consultation, SAP 10.1 has been published and we anticipate there will be a further update to version 10.2 once the outcome of the consultation has been confirmed.

Under current proposals, developers will also need to familiarise themselves with a new compliance report. This would be the domestic version of the Building Regulations UK Part L

(BRUKL) report currently produced for non-domestic building, known as a Building Regulations England Part L report (BREL).

Using information from SAP, the BREL report would provide evidence that the completed work matches the as-built energy model and would have to be signed by the energy assessor to confirm that the calculations are accurate. It would also require a signature from a representative of the developer to confirm that the as-built specifications are correct. This would then be sent to Building Control and could be used as a checklist for site inspection of thermal elements.

Vaillant Group welcomes these proposals and, as a manufacturer of both gas boilers and heat pumps, is well placed to deliver both the 2020 route outlined in the consultation and the 2025 measures to meet the Future Homes Standard. The most effective way to increase energy efficiency and reduce CO2 is to enforce changes at point of construction; therefore, we envisage developers playing a pivotal role in the UK’s transition to zero carbon.