New Part L & F Consultation

Following months of speculation after the release of SAP 10.0 the Government has published the first of two Approved Document L (conservation of fuel and power) consultations and the BRE has published SAP 10.1. The release of these consultations has been anticipated for some time, introducing plans for a significant improvement in carbon dioxide emissions over current standards as well as including changes to Part F (Ventilation), air tightness and improving the ‘as built’ performance of the constructed home.

Energy efficiency requirements

In response to the new UK law which targets to bring all greenhouse gas emissions to net zero by 2050, the proposed draft Approved Document aims to provide the roadmap to future energy standards. Two options are being discussed on how to meet this target. The preferred approach is a 31% reduction in carbon emissions when compared to current standards (option 2), with the second approach suggesting a less demanding 20% reduction (option 1). These are considered to be stepping stones to the 75-80% reduction targets in the Future of Housing Consultation. Each option is provided with a potential specification in order to meet these requirements but is clear that a wide variety of approaches to meet these performance targets are expected.

Transitional phase

In the past new Building Regulation changes have taken time to be adopted, typically with a year grace period, and in some instances with phased developments able to use old Regulations for future phases.  To mitigate this, the consultation is proposing to encourage a quicker implementation of the new energy requirements, where any specific building yet to have any work commenced is to be built to the latest standards. The introduction of this stricter implementation may result in sites with the same planning consent being constructed to different Building Regulations.

Performance metrics

The new Part L is proposing four performance metrics for buildings to be measured against, which are as follows:

  • Primary energy target
  • Carbon dioxide emission target
  • Householder affordability rating
  • Minimum standards for fabric and fixed building services

It is proposed that primary energy will be the principal performance metric and carbon dioxide emissions will be used as a secondary metric. This would measure the total energy demand of the building, accounting for the whole heating fuel Lifecyle rather than just the heat demand of the dwelling.

The currently used fabric energy efficiency metric has been removed, with the proposal to encourage good fabric by retaining and improving the minimum standards for the individual fabric elements (walls, roofs, floors, windows etc).

Electric heating

The latest CO2 emission factors released by the BRE in SAP10.1 considers electricity to be less carbon intensive than gas. In combination with the proposed removal of fuel factors this allows electric heating to become more appealing. However, the new Approved Document is careful to note electric heaters are very expensive to run, and if introduced on a large scale it may have a significant impact on the National Grid.

To address the above issue, there is the proposal for the introduction of the householder affordability rating to reduce the risk of high energy bills for consumers, which will be based on the theoretical energy cost of the dwelling. As a result of the lower fuel factors for electricity, heat pump technologies are looking more promising as they have the same low-carbon benefits as direct electric heating, but can deliver heat much more efficiently overcoming affordability issues and grid-resource constraints.

Phasing out high-carbon fossil fuels

It is the Government’s intention to phase out high-carbon fossil fuels in new build housing developments by 2025 with the new Part L supporting this intention. The removal of fuel factors will no longer provide any relief to the high-carbon heating systems like LPG and oil, which was previously introduced to help developments that did not have access to mains gas. The new Part L does not look to ban these heating systems but it will make it considerably more difficult to comply with substantial mitigating measures being required.

Energy planning requirements

The draft Approved Document proposes to streamline the planning process to potentially prevent Local planning authorities from having the power to set their own energy efficiency standards in an effort to avoid confusion and inconsistencies across the country. The move to the higher energy standards required by the new Part L may lead to the Planning and Energy Act 2008 becoming amended or even made redundant.


Following the 2018 Environmental Audit Committee it was recommended that the Government should create a new regulation to stop buildings being built which are prone to overheating. In response the Government is committed to consult around introducing a new overheating standard in an effort to manage internal temperatures but the details are yet to be released.  If you want to find out more about the risk of overheating we recently published an article about this on our website

Air testing

Consideration is being given as to whether developers should test all individual homes on a development instead of having the option to sample test, to avoid the potential of untested dwellings not meeting the required standard. Developers will also need to include all failed air tests within the pack of documents submitted to Building Control to indicate remedial works have been completed.

The air tightness testing scheme methodology is under review and consideration is being given to alternative testing methods such as a pulse test. The proposed new minimum standards for fabric performance for air permeability is being lowered from 10 to 8m3/m2.K at 50Pa.

Air quality

The proposed Part F changes will look to include mandatory opening restrictions on buildings in low air quality areas in an effort to promote healthy indoor air quality in new homes. Consideration is also being given to the noise output of ventilation installations as research has shown this to be one of the factors contributing to home owners turning off fans, resulting in poor air quality. The draft Approved Document is clear that systems should not be unduly noisy but further consideration may be given in a future Part E consultation.


Currently this consultation relates only to the Building Regulations for England, which will remain open for comment until the 10th January 2020. If you wish to respond, please see the online survey at The Government has released a preferred option in relation to timings with the proposal of mid/late 2020 for the new regulations to come into force. It is expected in the near future for Welsh Building Regulations to also go out for consultation.

We are still reviewing all the proposed changes and further articles will be released over the coming months to keep you up to date and assist you in preparing for the new Regulations.  Feel free to get in touch with us if you want any further information on this in the meantime at

Proposed Timetable

Late 2019 / early 2020

Subsequent consultation on:

  • Overheating in new dwellings
  • Energy efficiency standards for work carried out in existing dwellings
  • Energy efficiency standards for new buildings other than dwellings
  • Energy efficiency standards for work to existing buildings other than dwellings

Early / mid 2020

Publication of new Part L, Part F and overheating regulations, associated guidance and supporting analysed consultation response documents.

Mid / late 2020

Part L, Part F and overheating regulations come into force.

Further Links

Future homes standard:

Draft Part L and F:

SAP 10.1:

The future of solar storage innovation and the influence of legislation

Can the ‘Smart Export Guarantee’ and complementary technologies continue the solar trend despite an axe to the feed-in tariff?


There’s no doubt that solar photovoltaic (PV) panels represent a huge chunk of renewable energy generation in the UK. In 2018, 3.9% of total energy consumption was generated by PV panels. The UK is the 3rd highest generator of solar energy in the EU, behind Italy and Germany, and the 6th worldwide (behind Japan, USA and China). Primarily, this is a result of falling costs as the technology becomes more established.

In 2010, the average cost for a 4-kilowatt (KW) PV array was between £12,000 and £14,000, whereas today it’s £6,000. However, despite this, recent decisions taken by the current government have thrown the industry into jeopardy.

House with PV
A 4 KW PV system has reduced in price by approximately 54% in 9 years

Feed-in Tariff

The Feed-In Tariff (FIT) was a government scheme that ensured consumers with renewable technologies received a fixed payment for both energy generated, and energy they exported back to the grid. The generation tariff was based on the assessed annual system output, and export tariff of 5.38p/kWh paid based on the assumed export of 50% of electricity generated back to the grid, regardless of actual export levels.

As of April 2019, the scheme was discontinued by the current government as it “did not align with the governments industrial strategy”, leaving prospective solar panel owners in turmoil. While it did not affect the ~800,000 homes who had installed PV since the scheme was introduced in 2010, with no replacement scheme in place new solar panel owners were facing the prospect of giving away excess solar energy for free.

However, upon consultation with the industry, the department for business, energy and industrial strategy have decided to introduce a new scheme.

Smart Export Guarantee

The Smart Export Guarantee (SEG) is a new scheme that is being introduced by the government from January 2020. It affects owners of renewable technologies with a capacity of up to 5 megawatts (MW) and is dependent on whether their main energy provider has over 150,000 customers. Technically, there is no right to receiving the payment if you were to use a very small utility company, however smaller utility companies might offer competitive tariffs in a bid to attract customers.

It is similar to the FIT in the fact that it will pay consumers for the energy they export back to the grid; however, it differs by paying a minimum rate per unit of energy rather than a fixed tariff dependent on the number of panels. In theory, this is meant to benefit small-scale renewable energy exporters as it will naturally allow the industry to become more market-oriented rather than subsidised.

Anyone installing solar panels between the end of the FIT (1st April 2019) and the start of the SEG in 2020 is eligible for the scheme, providing the installation is Microgeneration Certification Scheme (MCS) certified. Although at the early stages, the hope is that once the scheme is fully up and running it will be more generous than the FIT.

The first export tariff was launched in the UK on May 1st 2019 by Octopus Energy under the name “Outgoing Octopus” and offers a fixed rate of 5.5p per kWh (0.26p higher than the FIT) or a dynamic rate which changes every half hour and varies based on current demand. This, coupled with the continuing decrease in the cost of solar panels and an uptake in complementary technologies may represent a very appealing prospect for future clean energy exporters.

Complementary technologies – Solar batteries

One solution to the challenges faced by the industry could be solar batteries. These boiler-sized boxes can be installed in houses with a solar array, and can typically hold between 2 and 13 kWh at any one time. They offer great utility to PV owners in the UK, as unpredictable weather conditions often cause uncertainty about consistent power generation.

“The UK will need as many as 20 million ‘mini power stations’ to meet its target of net zero energy by 2050” Dr Andrew Crossland, an engineer with MCS’ Batter Installation Standard division has claimed. However, despite this, the UK government are set to increase the VAT for home solar-battery systems from 5% to 20%. All the while home coal supplies will continue to receive the 5% VAT rate. This is in direct contradiction to the governments ambition, and could push the take up of solar-battery systems back by years.

In spite of reduced government incentives for renewable technologies, the industry looks set to continue its growth as the technology develops in three areas:

1. Safety – It’s estimated that around one in 10 million lithium-ion batteries will fail in their lifetime at the cell level. However, poor installation and inadequate battery management systems (BMS) can magnify the risks.

Reputation is a huge driver of the development of the industry, and as the world becomes ever more connected through the internet, the quality of a company’s product and installation standards could be the difference between success and failure. This importance placed on safety standards will incentivise the whole industry to continue driving up standards.

2. Software – New energy management systems are using complex algorithms and artificial intelligence (AI) techniques to assess and manage individual home solar and storage. Through the use of data generated from smart meters, energy providers are able to monitor energy use in real-time, and can optimise delivery to provide consumers with the cheapest energy possible at any given time.

For example, Social Energy have created a system that dynamically manages energy supply every 5 minutes, enabling users to charge their solar battery using grid power when the price is low, and sell their self-generated power back to the grid when demand is high.

In short, this could produce the tantalising effect of making solar and storage systems so economical, they’d pay for themselves.This type of technology has the potential to radically enhance the effectiveness of the systems it manages, and could cause a shift in market share towards independent suppliers and away from the “big six”. However, for this type of technology is to become the mainstream a radical sea change in consumer behaviour is required.

Tesla Powerwall
The Tesla Powerwall has a capacity of 13.5 KWh, enough to last for over 24 hours in the event of an outage based on average energy consumption figures for a standard home

3. Cost – In 2010 when the FIT was introduced, the cost of 4 kW PV panels was roughly £13,000. Today however, a homeowner can buy a 4-kW PV array and 4 kWh solar battery for around £8500. This showcases a dramatic reduction in the cost of renewable energy system. Furthermore, the efficiency of PV panels has markedly improved as well, from around 4.11% on average in 2010, to 4.90%. In essence, this gives the consumer more energy for less money. If renewable technologies continue the trend of decreasing cost as the technology becomes more advanced, they will present a more viable option for energy delivery to consumers, and as such the uptake will be greater.


If the UK is to meet it’s target of being of being net-zero carbon by 2050, renewable energy systems for private homes must be embraced by the mainstream. It is uncertain how much damage has been caused by the scrapping of the Feed-in Tariff, however new legislation such as the Smart Export Guarantee give hope that it will be kept to a minimum.

Despite changes to UK legislation and the tax rate for renewables, the industry as a whole shows no sign of slowing down. Indeed, the charge of innovation is picking up pace, with solar systems providing safer, more efficient power at an increasingly lower price. Coupled with an uptake in complementary technologies such as solar batteries and electric cars, solar technology could become the primary method of energy generation in the future.

In summary, widescale uptake of renewable technology seems inevitable; it’s only a matter of time. Currently due to high start-up costs a simple payback for a PV and battery system is unlikely. However, with continuing reductions in panel and battery costs, anything is possible in the future. Once consumers can be convinced of a system’s safety and efficiency, solar systems will likely become the norm and assist with meeting the UK’s net zero ambitions to address the fight against climate change. However, the biggest obstacle remains the payback time for renewable systems.

Time will tell whether the trend in falling costs for panels and potentially increasing revenue for energy exports will account for the high start-up costs, however the necessity for this hurdle to be overcome has never been greater. With ambition and innovation, it is possible to achieve this goal.

Written by Ben Westall, Graduate Sustainability Consultant