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Change to London Plan policy means a staggering shift away from CHP systems

For many years the largest new developments in London have favoured district heating networks with Combined Heat and Power. However, a recent revision to the London Plan now means policy is driving us towards electric fed systems instead. As a seemingly small tweak to the policy, how has this revision created such a change?

In 2018, the Greater London Authority (GLA) announced a few adjustments to the London Plan, to tide us over until the whole document is rewritten in the next year or so. One of the revisions affected how the SAP and SBEM models (which assess energy efficiency) are calculated, by requiring Energy Strategies to use the new SAP 10 emission factors. This revision went live on 1st of January and the implications of changing the emission factors means a staggering shift away from CHP systems.

What is an emission factor, and why is it having such an impact?

Towards the very back of the SAP methodology, you’ll find a list of fuel types showing how ‘green’ each one is. It’s often referred to as the ‘carbon emission factor’ but the maths behind it also considers methane and nitrous oxide.

In the last two updates to SAP (2012 and 2009), this data hasn’t changed much; Mains gas is treated as middling on the green spectrum and electricity is considered the worst fuel type environmentally, down to the UK’s reliance on coal power stations. By using the emission factor figures from SAP 2012 or 2009 in a SAP calculation, electric heating will perform badly compared to gas and any opportunity to generate onsite electricity is considered very favourable. These are both wins for the CHP option.

Although never adopted, SAP 2016 brought in a change and showed that electricity was becoming greener. The phasing out of coal power stations and their replacement with solar, wind and nuclear sites meant the total pollution from the National Grid was reducing. When the draft SAP 10 was released in 2018, this figure had dropped further and showed that emissions caused by electricity are only marginally higher than those produced by gas. This means electric fed heating systems are no longer a disadvantage but also that onsite generation (from CHP and PV) is not treated as kindly.

Despite this big adjustment in the figures, the Government has so far refused to write SAP 2016 or SAP 10 into Building Regulations. Part L will continue to use the 2012 data until the Approved Document is fully updated, which is expected in Spring 2020.

Noticing that SAP wasn’t up to date, the GLA made the decision to enforce the emission factors from the draft SAP 10 on new planning applications from January 1st. This has meant that designers have had to come to terms with this change overnight and re-write their rule books on the heating options that are the most viable.

It’s not as simple as getting rid of CHP completely, as the GLA still expect large developments to include district heating. The challenge for these new sites is to approach the proposed heating systems with an open mind, and not expect the ‘same as last time’ approach to work.

Another potential headache with electric heating options is that Building Control is not allowed to adopt SAP 10, so any specification that works for the new London Plan must also comply with the current Part L (using SAP 2012).

The Energist Planning Team is fully up to speed with how to implement SAP 10 emissions, ensuring compliance with these latest London Plan Policy changes. Contact us to find out how we can help with your next project in the capital.

The London Plan switches to SAP 10 – will this end CHP dominance in the capital?

The GLA’s changes – coming into force in January – are set to end CHP dominance in the capital. Jon Ponting from the Energist Technical Team explains why.

The Greater London Authority (GLA) has surprised many in the construction industry by announcing changes to the London Plan; starting this January.

The seemingly small adjustments will change how developers invest in heating systems on large projects, and without so much as a fanfare to announce these changes, many could be caught out by this policy change.

Meanwhile, the London Plan is currently going through a major rewrite, which isn’t due to go live until the end of 2019 or later.

These latest announcements apply to the current London Plan which means sites currently getting ready to go into planning will need to follow the new guidance. It’s primarily focused on ‘referable’ schemes (which is the bigger housing developments), however the changes are being encouraged on smaller sites also.

The big change is the adoption of SAP10 emission factors. This will significantly change the result of the SAP and SBEM models which are used in planning strategies.

To unpack what this means we need to rewind to 2012, and the launch of the current Approved Document Part L. This building regulation requires all new homes and businesses to meet a strict Target Emission Rate, based on how much energy is needed for heating, hot water, ventilation and lighting.

The energy use is multiplied by the emission factors of relevant fuel types used (gas, oil, electric, wood) to create the Building Emission Rate. The higher the emission factor of a fuel, the higher emission rate a dwelling will have.

In 2012, the emission factor of electricity was 2.5x higher than gas. This was because of the UK’s reliance on coal power stations.

Six years on and we still use the same set of Building Regulations, which means we still use these emission factors.

In reality, the CO2 associated with the National Grid has plummeted. Every year we are breaking records for energy produced by wind and solar technology, which means the emission factor of electricity is much lower than what Building Regulations suggests.

Earlier this year, the BRE released a draft revision of the SAP calculator. In it, the emission factors were updated, and electricity was shown to no longer be the fly in the ointment. However, with no confirmed date for Part L to change, these emission factors have been left to sit on the shelf.

The GLA has taken the unprecedented move of asking for all new planning submissions to use SAP10 emission factors for calculating energy use, while still using the rest of the current SAP2012 methodology.

Under this adjustment, the use of electricity on site will provide much lower CO2 readings, which means electric heating systems will be more viable than before.

The GLA is still keen to promote District Heating Networks (DHN), but this change means gas is no longer the only contender.

Greener electricity won’t just change the way we assess heating options in our buildings – it also means generating your own energy on site won’t result in as big a carbon offset as we see currently. That could discourage developers from systems such as PV and CHP.

With such a significant change coming into force so quickly, it makes sense to work with a team who are on top of the changes, who commit to your deadlines, and who are ready with the answers.

The Energist Planning Team is on hand to do just that, with a new-look Energy Strategy which fully complies with these London Plan changes.

What will SAP 10 changes mean for you?

After years of anticipation, we are now one step closer to knowing where the construction industry will need to push to meet the next wave of energy efficiency targets.

The Building Research Establishment (BRE) has, without fanfare, published a new SAP methodology – SAP 10.

SAP is the calculation used to work out a dwelling’s emission rate, compliance with Building Regulations, EPC scores and predicted fuel costs. It is a vital assessment for compliance with Part L and Section 6, and is also used as part of planning submissions (for energy and sustainability statements).

First and most importantly, this new SAP methodology is not yet in use, although it will eventually replace the current SAP, which has been in place since 2013. Our Building Regulations are still using SAP 2012, and there’s no news on when this will change. When Part L / Section 6 are updated, we’d expect the SAP 10 method to be adopted.

Highlighting some of the key points and changes in SAP 10, we’ve compiled a short list of all you need to know about how we’ll be building in the coming years:


1. Electric heating will be more favourable

Since the last SAP update (2012), there’s been a renaissance in the installation of wind and solar farms, giving us greener energy. So much so that the average CO2 factor from the UK’s electricity grid has halved in just six years. This means the carbon footprint of electric based heating is going to be far more favourable and could mean we start to see panel heaters becoming a favoured option for some developments.

2. On-site electricity generation will have less impact

The reduction in the CO2 factor of the electricity grid sounds like good news all round, but there is a flipside… having greener electricity means generating electricity on site isn’t going to have as big an impact as it does today. So PV systems and CHP units aren’t going to be as much help when trying to improve SAP scores.

3. Heat loss assumption for DHN will increase to 50%

Developments with district heating networks (DHN) could notice a big drop in SAP performance. Currently, default heat losses from the pipework of DHNs are assumed to be 5-20% in SAP. Going forward, a new development with no evidence of heat losses will have to assume 50%! When you consider many large inner-city schemes use DHN, CHP and PV panels, this is all going to add up to make compliance for this type of development much trickier.

4. Lower overall heat demand

To give consistent results, SAP has always worked with lots of assumptions in the background. One of these is to do with the number of hours in a day where our heating is switched on. Latest research has shown we’re in our homes less, and using our heating systems less. This will lead to lower heating demands overall. Plus, manufacturers of Wi-Fi based heating controls may be able to help improve things further if they can prove their devices mean we use our heating even less.

5. Bespoke thermal bridging encouraged

As expected, thermal bridging and fabric heat losses are being given more focus. The default thermal bridging figures are increasing by a third, which means if there are any developers still using default thermal bridging data, this is likely to push them into adopting recognised calculations. The Accredited Construction Details have been removed from SAP 10 as the ‘better case’ defaults. This is to encourage developers to research and adopt better and more specific junction details, although you’ll still be allowed to adopt ACDs if you want to.

6. Bath and shower flow rates will be considered

For the first time, SAP is going to count how many baths and showers a dwelling has, with the proposed flow rates, and whether showers are fed by electric or mains. This information will be used to more accurately work out hot water demand and could increase emissions for dwellings that are expected to use lots of water.

7. Overheating risk more likely to show on dwellings

Our lovely summer has raised the concern of overheating in our homes. SAP runs a basic check for summer overheating risks, which usually only flags up issues on heavily glazed penthouse apartments. SAP 10 is being tightened up which is likely to mean more dwellings recording an overheating risk. We’d recommend a thermal modelling assessment for a more in-depth analysis where overheating risks are anticipated.

8. Excess electricity from PV panels can be stored

A welcome addition to SAP 10 is PV storage, where excess electricity can either be sent to a battery or to heat an immersion cylinder. Currently, SAP assumes that half of the electricity generated by PVs is exported straight back to the grid.

9. Updates to reflect changes in lighting technology

Lighting technology and the efficiency of lamps has moved so fast in the last decade, that SAP hasn’t kept up. SAP 10 will record the amount and type of lamps in a dwelling. The more LED and compact fluorescent bulbs, the better result you’ll get.


The question on everyone’s lips is probably: ‘How difficult will it be to show compliance with SAP 10?’, and that’s a question we can’t answer yet. The Target Emission Rate is defined in Building Regulations, so until we get a sniff of a new Part L or Section 6, we can’t answer this question.

An initial thought is that Dwelling Emission Rates (DER) will be lower on most houses due to the new emission factors, lower heating demand and more specific lighting calculations. However, dwellings with district heating, CHP systems and those that intend to use default thermal bridging details could well see their expected emission rates increase.

We’ll issue more detailed advice when we know the timeframes for SAP 10’s official launch into the industry.