The "Home Energy Model" - The Artist Formerly Known as SAP

 

Alongside its consultation on the Future Homes Standard building regulations, the government has revealed sweeping changes to the calculation underpinning Part L of the building regulations (Conservation of Fuel and Power), and launched a consultation on the new approach.

The StandardAssessment Procedure (SAP) has been the government approved methodology to estimate the energy performance of homes in the UK since 1993, a time when it was felt to be important that the method be simple enough to be completed with pen and paper and calculator. 

Inevitably, computer software emerged to make the job of energy assessors more convenient.  Provided by third party companies, these applications needed to be checked by the Building Research Establishment (BRE), the body responsible for the development of SAP, before they could be used to demonstrate compliance with building regulations.

Over subsequent versions of SAP issued in 1998, 2001, 2005, 2009, 2012 and 2022 the complexity of the model increased.  Building elements were dealt with in more sophisticated ways to improve the accuracy of the model (for example the treatment of junctions in thermal insulation or - a personal favourite – an improved treatment of the performance of solar thermal systems in 2005).  New technologies were more widely adopted in construction and needed to be added (for example battery storage in 2022).

SAP's Growing Pains

Shortcomings of this approach had begun to emerge over time but were brought into sharp focus by the 2022 implementation.  Developers found themselves struggling to work out how to build new homes that complied with the new building regulations already in force even as the third-party software was unavailable due to delays in the certification process.

Another reason for a wholesale review of the model, flagged by the Climate Change Committee, was the emergence of key technologies that couldn’t be easily or accurately added to the existing framework in a timely way:

• Solar PV and self-consumption of generated electricity
• Battery storage of electricity
• Solar PV diverters
• Time of use energy tariffs
• Smart energy controls – timing the use of energy to coincide with cheap tariffs and the availability of renewable energy.

The SAP model was based on a monthly time resolution.  This meant that the impact of new technologies had to be demonstrated in real life studies and an average performance across multiple households derived before a simplified month by month impact could be added to the model.

A case in point was the introduction of battery storage in the 2022 version.  Data was scarce because the technology was relatively new.  A simplified average performance that linked installed solar capacity, total energy use and battery storage capacity was derived by applying a line of best fit to the available data.  This formula was incorporated into the monthly SAP model.  No data was available on homes that combined battery storage with solar PV diverters, so SAP only allowed one of the technologies to be used at a time.

 

 A New Approach

The government is consulting on a fundamental re-working of the model.  It’s such a big change that SAP has been dropped in favour of a new name ‘The Home Energy Model’.  Changes include:

• The model will be available as a cloud-based software ‘core engine’, with the source code published on GitHub
• ‘Wrappers’ will be published for different applications – comprising different starting assumptions as inputs which will then feed into the same core engine.  The first wrapper to be published will be for the 2025 building regulations, followed by a wrapper for the generation of Energy Performance Certificates (EPCs) for existing homes.
• The software runs on a 30-minute time resolution, allowing better modelling of smart technologies such as solar, battery storage and time-of-use energy tariffs
• An updated solar PV generation calculation is based on the hourly methodology in BS EN 15316-4-3:2017, which includes the effect of ventilation on the rear of the panels.

Impact on Solar

 The solar industry should welcome the change from SAP to the new Home Energy Model.

The move to cloud-based software brings the approach up to date.  The separation of a core engine, based on best available building physics modelling, from the ‘wrappers’ which clearly surface the assumptions and inputs into the model for specific applications such as building regulations or EPCs makes it much easier to interrogate how the ‘black box’ is working.

The change to a half-hour resolution better supports enabling technologies that work with solar PV – battery storage, smart energy controls and hot water from PV fed immersion heaters.  This will further cement the position of solar PV as a normal part of any new home built in the UK.

The change to the hourly methodology for solar generation needs to be carefully assessed, I will be writing about this in my next blog. 

 

 

 

 

 

 

 

How Progressive Building Regulations Made Scotland a Solar Powerhouse

 

Statistics recently published by the Microgeneration Certification Scheme (MCS) show how much solar PV different regions in the UK installed in 2021.  Scotland really stood out from the pack, with more than 25% of all installations.  However, because the graphic only showed the number of installations, and didn't take into account the population of each region it doesn't really do justice to the wide differences between different parts of the UK.

The Solarblogger has restated the figures above as the number of installations in 2021 per 100,000 of population in the region (the blue boxes).  

On this measure you can see that Scotland is installing two times more solar per head of population than the next nearest UK region (the South West) and more than three times the national average.

Compared to laggards like Northern Ireland and London, Scotland is installing more than ten times more solar PV installations per capita.  What is behind this incredible performance?

In 2015, Scotland brought in new building regulations that required housebuilders to construct homes that were significantly more energy efficient than those being built in the rest of the UK.  A year later George Osborne killed off the Zero Carbon Homes policy and developers in England have been building to performance levels largely unchanged from 2010 ever since.

The preferred option of housebuilders in Scotland has been to meet the regulations with a combination of improved thermal insulation and airtightness, combined with a solar PV on the roof (or to be more accurate a solar PV installation in the roof).  As housing developments started under previous regulations came to an end and new projects started up that needed to meet the new regulations, the proportion of homes built with solar rose from around 10% before the regulations to nearly 70% in 2020.

According to an analysis of the EPC database in Scotland by Kevin McCann at Solar Energy UK, of the 15,447 EPCs registered for new homes in Scotland in 2020, 10,324 listed solar PV as an energy efficiency measure.

So of the 16,437 Scottish solar PV installations registered with MCS in 2021, it is likely that at least 10,324 were new homes, which would leave 6,113 that were retro-fitted to existing buildings. 

Taking this retrofit figure per head of population alone would give Scotland a score of 112 installations per 100,000 people - still impressive but it is clear that Scotland's stand out performance in solar PV installation has been driven by the building regulations for new homes.

In 2021 it is possible that there was an even higher figure for solar on new homes than that we have for 2020.   Lockdowns paralysed the construction industry for a good part of 2020, and 16,000 new homes is some way behind the long run average of around 20,000.  So the contribution to Scotland's performance from Building Regulations is likely to be higher still.

The good news is that regulations for England and Wales will soon exceed those in Scotland, with new regulations in England coming into force this June.  When that happens we should see solar PV installations per capita start to close the gap with those in Scotland.

 

Options, Options - The Building Regulations Review & the Notional House

I have read commentary in recent weeks on the 2020 Building Regulations Review that suggests an alarming level of ignorance about the way the building regulations work.  It would be a real shame if the organisations behind these comments were to base their response to the consultation on such a fundamental misunderstanding.

The government consultation is proposing two options for new 2020 building regulations - one that it estimates would deliver a 20% reduction in carbon emissions compared to current regulations and another expected to deliver a 30% reduction.

So you would expect that groups interested in energy efficiency would support the second option - producing a 30% reduction.  But no, some seem to prefer Option 1, because they wrongly think it will result in homes with higher levels of thermal insulation.

It won't.

Let me explain.

The Building Regulations for Energy - How it Works

To comply with the Building Regulations for energy efficiency, housebuilders must use a calculation called the Standard Assessment Procedure (SAP) to demonstrate that the house they plan to build will meet requirements to limit carbon emissions and (new in the upcoming version of building regulations) primary energy consumption and affordable energy bills.

Related article: What is Primary Energy?

Focusing on carbon emissions and primary energy, the way the calculation works is as follows.  (See also the figure above).

1. You decide the geometry of the house you want to build (it's dimensions, shape and openings - number and size of windows and doors)

2. You calculate a Target Emissions Rate (TER) and Target Primary Energy (TPE) for a "Notional House".  The Notional House is the same shape as the actual house you want to build but has a technical specification based on Reference Values defined in Appendix R of SAP.  The Reference Values include insulation performance (U-values) for all the building elements (walls, windows, roof, floor), a maximum allowable amount of openings, as well as air change rates, a heating system and renewable technologies.

3. You then choose the technical specification you actually want to build the house to.  These can differ from the Reference Values - you are free to choose a different heating system, to build to higher or lower insulation levels, to aim for higher or lower air-tightness and whether to include more or less renewable or energy saving measures.  The only constraint is that insulation levels must be higher than so-called backstop values, which are also defined in the regulations.  You calculate the Dwelling Emission Rate (DER) and Dwelling Primary Energy (DPE) based on this house design.

4. So long as the carbon emissions and primary energy for the actual house are lower than the target figures generated by the Notional House, you're good to go, the design is compliant.

This elegant system defines a level of performance for the energy efficiency of new homes while giving developers a free hand in how they want to build.

Option 1 in the consultation sets the Reference Values for the notional house to have highly insulated walls, floor roof  and openings.  The Reference Values given for Option 2 come with slightly lower insulation levels, but add in solar PV and waste water heat recovery to the specification, resulting in lower overall energy use and carbon emissions than Option 1.

Just because Option 1 has higher insulation in the reference values it does not mean that houses will be built with this level of insulation.  As mentioned earlier, developers have complete freedom to choose a specification so long as it meets the target emissions and primary energy levels.  If it is a lower cost option, they are just as likely to reduce the insulation levels and add solar PV to meet Option 1.

If you are interested in lobbying for a 'Fabric First' approach, then you should focus on arguing for more ambitious backstop values for insulation and airtightness, but please don't argue for Option 1 Reference Values.  Option 2 will deliver higher-performing homes and will force housebuilders to push energy efficiency further and faster.  It will also likely result in higher levels of insulation in as-built homes.



 

The Future Homes Standard Consultation

Where next for Building Regulations?

In the week where Extinction Rebellion activists were arrested for hosing the Treasury in 'blood' in protest at the lack of progress on tackling a climate emergency, the consultation on the Future Homes Standard came out.  There's talk of solar panels for all new homes - so let's take a look under the hood of the consultation.

The consultation itself consists of two main parts - consideration of the Future Homes Standard due to come into force in 2025 which is intended to deliver "world-leading levels of energy efficiency" for new homes and  an update to the Building Regulations Part L (energy efficiency) and Part F (ventilation) in 2020 to provide a "meaningful but achievable" uplift in energy efficiency as a first step towards the 2025 vision.

There's also a raft of supporting documentation

The Standard Assessment Procedure (SAP) calculation version 10.1
An Impact Assessment, which includes details of cost assumptions
Approved Documents L and F 

2020 Part L - a Stepping Stone to Future Homes 2025

There's a lot to talk about here.  This is no 'tweak' but a significant revision, at least in part forced by the significant changes to the carbon intensity of grid electricity, but also by the Grand Challenge Mission for Buildings, announced by Theresa May about a year ago.

1. Primary Energy Use is the new Gold Standard

Until today, Part L has always used carbon dioxide emissions as its measure of compliance with regulations.  Buildings had to achieve a certain Dwelling Emissions Rate (DER) in kgCO2/m2.

DCLG has rightly concluded that as the electricity provided by the grid comes with a lower and lower carbon intensity, developers could switch to electric heating and hit a carbon target without improving the energy efficiency of buildings.  If energy efficiency of buildings is not improved, then decarbonising the grid becomes more challenging and costly.  So a new measure is required and primary energy, which has the benefit of aligning UK regulations with the measures chosen in the EU Energy Performance of Buildings Directive, is added as a new metric.

(See this article on the rapid progress made in decarbonising the grid.)

The latest revision to the government's Standard Assessment Procedure (SAP) version 10.1 has been published alongside the consultation.  This is the calculation used to demonstrate a house complies with the building regulations.  In this version of SAP the carbon intensity of electricity is set to 136gCO2/kWh, a projection of the average from 2020-2025, and a massive reduction from the value of 519gCO2/kWh in the current version of SAP 2012.  Electricity now produces less than 65% of the carbon emissions of mains gas (which is at 210gCO2/kWh).

By contrast, the primary energy content of a unit of electricity is 1.501 compared to gas at 1.130.

This document explains primary energy and how the values were arrived at

Fitting solar PV to a property reduces the grid electricity that is needed by the house, solar PV generation used in the building (self-consumption) reduces both the carbon emissions and primary energy by the same factor as grid electricity.

Electricity sold to grid also reduces both the carbon and primary energy use of the dwelling but it's primary energy factor is only 0.501.

The impact of this is that a unit of electricity generated by PV and used in the building would save 1.501 kWh of primary energy use, but a unit of PV generated electricity exported to the grid would only save 0.501 kWh of primary energy use in the calculation.

Since the benefits of battery storage (SAP Appendix M) and PV diverters (SAP Appendix G4)  have also been added to this update to SAP, the combination of using primary energy as the main regulatory target and the low primary energy factor for PV export has the effect of incentivising measures such as these to use as much PV-generated electricity within the building.

The trouble with this is that

(a) developers prefer combi boilers so there's no hot water cylinder in most new homes for a PV diverter to divert excess electricity into.
(b) batteries are approaching cost effectiveness but are likely to be seen by developers as an additional cost and not a sellable benefit.

We understand that the logic for choosing this value for exported energy is that the exported energy has a primary energy factor of 1.0 (renewable energy), and displaces a unit of energy from being fed into the grid at the grid average of 1.501, so the net benefit to primary energy added to the grid is 0.501.

The solar industry might argue that considering things from the point of view of the building produces a different logic (and after all what we're supposed to be modelling is the energy performance of the building).  The net primary energy consumption of the building is the electricity imported at a primary energy factor of 1.501 less the PV generated electricity exported which should have a primary energy factor of 1.0. 

A minimum carbon emissions requirement is retained in addition to the primary energy requirement as this remains an important consideration for government and there is concern that certain solutions could produce low primary energy figures with high carbon emissions - for example heating oil and coal both have low primary energy but  high associated carbon emissions.

Finally, the current fabric efficiency requirement is dropped to make way for a new householder affordability target, with fabric efficiency now considered adequately protected by tougher minimum heat loss standards for building elements.  As discussed, electricity has low and falling primary energy and carbon emissions factors, and government is concerned that direct electric heating would be a viable option for meeting both the carbon and primary energy targets, but with the side-effect of saddling occupants with too-high energy bills.  To guard against this the new affordability rating is likely to be set at a level that means direct electric heating would only be an option when combined to other measures to reduce electricity bills such as increased thermal insulation, PV panels or battery storage.

2. Uplift of the Minimum Standard

The minimum performance standard is defined by publishing a build specification (insulation levels, heating system, light fittings, microgeneration technologies) to be used by the developer to model a 'notional house'.  The developer then has to design the house they plan to build to produce modelled carbon emissions and primary energy lower than that of the notional house.  It's an elegant way to allow the developer complete freedom in design but control the outcome.

 The consultation proposes two options for the minimum performance standard:

Option 1 - "Future Homes Fabric"

This specification would produce a 20% reduction in CO2 emissions when compared against the specification in current building regulations .  The standard is based on a notional home with improved insulation measures (including triple glazing) plus a gas boiler and waste water heat recovery.

The estimate given in the consultation is that this option adds £2557 to the build cost of a semi-detached house and saves households £59 a year in energy bills.  (Payback 43 years)

Given that by 2025 the Future Homes Standard needs to be at a 75% of the carbon emissions of 2013 regulations, 20% does not seem like a big enough step - it only brings England roughly to the level that  Scotland's developers have been achieving since 2015.  DCLG appears to agree, stating that it's preferred option is Option 2.

Option 2 - "Fabric plus Technology"

In this option, the specification of the notional house is set at a level to produce a 30% reduction in carbon dioxide emissions across the build-mix.  The specification has slightly lower insulation than Option 1 plus waste water heat recovery and a solar PV system.

SAP 10.1 Appendix R outlines the specification for the notional house.  The size of the PV system in kWp for the notional house is 40% of the building foundation area divided by 6.5.  So for example for a typical two-storey semi-detached house of total floor area 85m2, this would be

[40% x (85/2) ] / 6.5 = 2.6kWp (around 9 or 10 panels)

DCLG's modelling estimates that building to this new notional home adds £4847 to the building costs and saves £257 a year in energy bills.  (Payback 19 years).

The costs used in the accompanying impact assessment for solar PV are £1,100 fixed costs plus £800 variable per kWp installed.  This implies the following installed costs:

1kWp  £1,900  £1.90/kWp
2kWp  £2,700  £1.35/kWp
3kWp  £3,500  £1.17/kWp

Solar is a fast-paced technology and it would be unusual if a government consultation were to use up-to-date cost information.  My understanding is that solar installers operating in the new-build sector are typically charging an installed price the range of £1.10-£1.20/kWp for four or five panel systems (1 -1.25 kWp).  So it is likely that the costs of Option 2 are over-stated relative to Option 1.

If the solar industry can provide evidence that costs in Option 2 are over-stated, it will make it easier for government to hold the line on its preferred option.

DCLG reckons that Option 2 might result in developers moving away from gas boilers to air-sourced heat pumps.  A specification based on ASHP alone over-shoots the Option 2 target at a lower cost than the notional house (£3,134), which would allow some relaxation of the fabric for further cost savings.  The experience in Scotland suggests that housebuilders will avoid ASHP for as long as possible because customers neither like nor understand them.

3. Heat Pumps - "Lord Make Me Chaste - but not yet!"

The consultation steps away from banning gas heating in 2020, this change is timetabled for 2025.  However it does impose extra conditions on wet space heating systems to ensure that they are 'future proof'.  In practice this will mean that 'emitters' (normal people call them radiators) will be increased to a size that would work at lower temperature, and so the house would be suitable for later conversion to a heat pump heating system without the cost of replacing all the radiators.

A side effect of this requirement is that increasing the cost and space requirements for wet systems could push developers towards direct electric heating with panel heaters, simple underfloor electric or radiant heat panels.  The removal of the entire cost of the wet heating system would offset a considerable chunk of the costs for the additional measures (PV solar, more insulation) needed to stay within the householder affordability target.  A house without a wet heating system would be low on maintenance and low cost to build, coupled with better insulation plus lower cost PV and battery storage to keep bills down this could become a favoured option for new homes.

4. Transitional Arrangements

This proposed change is likely to cause significant concerns at housebuilding companies.

The current situation is that as new Building Regulations come into force, they apply only to whole developments as new planning applications are lodged with local authority planning offices and work has started on site.

The practical outcome of this rule is that new homes are still being built to versions of building regulations in force many years ago, because:

(a) Developers rush to submit planning applications in the run up to new regulations coming into force, banking large numbers of homes to be built under the old regulations
(b) Large sites of many hundreds of homes are built out over many years, but there is a site-wide application of the regulations.

This was clearly demonstrated by the 2015 Scottish building regulations change, where it is only now (nearly 4 years later) that pretty much all new sites coming forward for tender require solar.

The consultation proposes moving from a site-based application of building regulations to one based on specific buildings.  Large developments spanning many years would have to redesign to meet new building regulations that apply as the building is being built.

Housebuilders will be alarmed by this proposal because all developments still under construction under 2013 regulations will be caught in this net.  The land for these sites would have been bought at a price based on the construction costs expected under those 2013 regulations and the housebuilders will argue that this measure is a retrospective action that will harm their profitability.  How much sympathy there is for the housebuilders having to shoulder the extra costs remains to be seen, when government has been subsidising the housing market through the Help to Buy scheme and the chief executives of some companies have been given bonuses amounting to £10,000 per house built .

 5. Other Stuff

Solar PV on Apartment Blocks

 In the original SAP10, PV on apartment blocks connected to the landlords' supply did not improve the DER of the individual apartment, whereas in SAP 2012 the carbon savings were apportioned across apartments by floor area.  The Solar Trade Association argued that connection to Landlord's supply was often by far the most cost-effective and practical way to install solar on apartment blocks, that the changes would force systems to be split into mini-systems serving each apartment at great cost, and that the carbon savings were real.  It seems that this argument has prevailed as SAP 10.1 has changed the treatment of solar PV in apartment blocks back to as it was in SAP 2012. 

Heat Networks Get a Free Pass

SAP 10 introduced punitive heat losses on district heating networks, based on evidence that large amounts of heat are lost in the underground pipework of these systems (40-50% even for best practice new ones).  It seems that government thinks that heat networks will be an important part of the energy future, and that their drawbacks should be ignored.  So a fudge-factor (they call it a 'technology factor') is applied to buildings that use a heat network.  These are allowed to emit 45% more carbon for heating and 5% more primary energy.

The Government's enthusiasm for heat networks is baffling considering that there is a perfectly good electricity network that loses far lower energy in transmission and is already connected to every single property.  A heat network is not of itself low carbon - it depends what you're doing to make the heat.

The Future Homes Standard - for 2025

The second part of the consultation is some early range-finding questions for the Future Homes Standard due to come into force in 2025.

The government reckons a 70-80% reduction in carbon emissions compared to current housing is possible.  This will be achieved by adding low carbon heating (heat pump or district heating) to the Option 1 fabric proposed in the 2020 regulations, and relying on further decarbonisation of grid electricity to do the rest.  Government is seeking views on whether this is achievable.

Local authorities which have been using planning powers under the Planning and Energy Act 2008 to require developers in their region to build to standards above those of the current building regulations.  This role for local authorities has been crucial for pushing forward on energy efficiency during a period of inaction from Westminster.  The consultation considers whether these powers should be removed alongside the 2020 regulations, the 2025 Future Homes Standard or not at all.

Summary

This change is significant and there's still some modelling to be done to figure out which packages of technology developers are likely to favour, but given the simplicity and popularity of solar it seems unlikely that the technology will not be a big winner from these changes to building regulations.

The Grand Challenge Mission for Buildings

It Can be Done - but not Without Solar

In a speech at Jodrell Bank, Prime Minister Theresa May outlined her government's  Industrial Strategy and set out a range of so-called Grand Challenge Missions .

These missions include:

• Using Artificial Intelligence in the Diagnosis and Treatment of Chronic Diseases
• Meeting the needs of an ageing society
• Reducing Energy Use in Buildings, and
• Zero Emissions Vehicles

The missions aim to bring together government, businesses and organisations across the to develop 'industries of the future'.

According to the government website, for buildings the mission is to :

At least halve the energy use of new buildings by 2030

Heating and powering buildings accounts for 40% of our total energy usage in the UK. By making our buildings more energy efficient and embracing smart technologies, we can cut household energy bills, reduce demand for energy, and boost economic growth while meeting our targets for carbon reduction.

For homes this will mean halving the total use of energy compared to today’s standards for new build. This will include a building’s use of energy for heating and cooling and appliances, but not transport.

The mission also includes a target to reduce the cost of low energy retrofits of existing stock (for example Energiesprong approaches I've already written about), but in this article I'll be taking a look at what it means for new buildings.

Unpacking What The Buildings Mission Means

There's some key phrases in the above announcement, with far-reaching implications.

1. 'use of energy'

Up until now, the energy performance of new homes for Building Regulations has been assessed in terms of carbon dioxide emissions rather than energy. The argument for this has been persuasive - that there are UK carbon budgets to aim for and policies should be directly targeted towards achieving this.

However, as grid electricity has decarbonised rapidly, it has created a significant challenge for this approach. With very low carbon electricity, it would be possible to meet regulations for low carbon emissions in buildings simply by heating electrically and doing the bare minimum on energy efficiency. Clearly, adding many new buildings of low energy efficiency this would make the task of maintaining a low carbon grid that much more difficult.

Secondly, and increasingly, the time of day that you take off electricity from the grid affects the carbon intensity (and price) of your energy. Smart technologies are available that control energy use that has flexibility in its timing (technologies such as heating, running a washing machine, cycling a fridge freezer, charging an electric vehicle or discharging a domestic battery). Though consumers are likely to favour technologies that lower their energy costs, periods of low wholesale energy prices tend to coincide with periods of low demand and therefore a high proportion of renewable energy input.  So these technologies will reduce carbon emissions and bills. 

Regulations will struggle to keep up with the complexity and innovation as this sector develops. Using an average grid carbon intensity will fail to incentivise or account for these valuable approaches.

As an 'energy consuming product' it makes far more sense for regulations for buildings to move to energy consumption rather than carbon emissions . Of course, the lower the energy consumption, the less energy is needed and the easier it will be to lower carbon emissions in the electricity supply.

Yet to be determined is what measure of energy we're talking about. If it is straightforward energy use, then one kilowatt hour (kWh) of gas burned to heat the house will count the same as a kWh of electricity taken from the grid. If, instead, it is Primary Energy (which takes into account conversion efficiencies from the original fuel), then electricity use will count more highly than gas.


2.'compared to today's standards'

Progress on carbon emissions is often measured against 1990 levels - the base year for Annex I parties to the Kyoto Protocol, the countries that signed up in 1997. The UK Zero Carbon Homes policy was enacted in 2007, and progress on energy efficiency standards for buildings has been measured relative to a building constructed to 2006 building regulations.

Improvements in energy efficiency of new build homes has been less than impressive. In the 12 years since 2006, the regulated carbon emissions from a new home built in England is only 29% lower than a house built in 2006. Scotland has pushed further forward, homes built here achieve carbon emissions levels 45% better than 2006.

Significantly, the comparison will be relative to today's performance levels. Progress to date will not count towards the mission.


3. 'include a building's use of energy for heating and cooling and appliances'

Until now, Building Regulations have only including 'regulated' energy - that used for heating, hot water, pumps fans and fixed lighting. In homes the regulations ignore energy used for cooking, fridges, freezers, washing machines, dishwashers, clothes dryers, audio visual equipment, IT equipment, plug in lighting and charging battery powered devices.

Housebuilders argue that they shouldn’t be held responsible for the electrical equipment that people use in the homes they build, and the government has up until now accepted that argument.

But why stop there?  Surely housebuilders cannot be held responsible for how often people choose to take a shower, or the fact that they don't want to wear thermals and down jackets while they're watching TV. The precedent of taking an average for domestic hot water use and internal temperature is well accepted, so there's no reason why we shouldn’t regulate based on an average electricity use for appliances and gadgets too.

Still to be clarified is how appliances will be defined – what will be included in electricity use. SAP includes Appendix L with a methodology to calculate the energy use for lighting and electrical appliances and cooking, but it is not clear what range of electrical equipment is included in this estimate and what is not, or indeed whether this estimate of energy for appliances will be used for the Mission

Achieving the Mission

The Solar Trade Association has commissioned analysis by Think Three Consultancy on the future direction for building regulations in a world of low-carbon electricity. The report used SAP 9.92 with new SAP 10 carbon emissions factors to model the energy use a number of house types with a variety of combinations of heating technologies and fabric performance. The 3-bedroom, 94m2 end terrace house modelled in the report, has been used to assess potential approaches towards reducing energy by 50% from today’s performance.

For a home like this built to current regulations in England, space heating and hot water are the dominant energy uses. However, the total of regulated and unregulated electricity use for appliances, lighting, pumps and fans represents 41% of energy use.

Increasing the fabric specification of the building significantly (to Passivhaus levels) greatly reduces the demand for space heating, but leaves all the other energy demands unaffected. A solar PV system of 3.9kWp (12 panels based on high performance panels available today) would be easily accommodated on a house of this size and would bridge the gap from this specification to the mission target.

Improved fabric in combination with a heat pump reduces the space heating and hot water energy by the coefficient of performance of the heat pump (assumed to be 2.5 for heating and 2.0 for hot water). A solar PV system of only 1.2kWp (around 4 panels) would enable this design to meet the Mission target.  

Clearly designers will look for the most cost effective combinations, which as the cost of solar energy declines could involve more solar than this analysis suggests, but given the inclusion of appliance energy use, there seems to be no way to get to 50% reduction that doesn't need solar electricity generation on the building.

Conclusions

1. The Mission can be achieved without the development of fundamental new technological approaches.  Single self-build homes and small developments of social housing are routinely being built to Passivhaus levels of fabric efficiency today. Heat pumps and solar PV are available today. The challenge is more around helping the construction industry deliver high specification fabric efficiencies at volume.

2. The inclusion of energy use by appliances means that the target simply cannot be achieved without some element of renewable electricity generation on the building.

3. The requirement for on-site renewable generation will be even more the case for buildings with form factors that give lower heat losses such as terrace homes and apartments – here there are less gains to be made by improved building fabric and more efficient heating systems.

4. Gas heating currently has Primary Energy Factor (PEF) of 1.222 whereas electricity has PEF 1.738 (SAP10 figures). Unless the PEF for grid electricity falls over the period, a move to electric heating technologies from gas heating will have smaller benefits if the metric is Primary Energy. The more renewable generation on buildings, the more contributions these can make to reducing the PEF of grid electricity.

5. In recognition of the above, forthcoming updates to building regulations should be framed in a way that encourages the use of solar PV on new buildings. 

SAP 10 - Big Changes Afoot for Solar

Image: Viridian Solar

A new version of the Government's Standard Assessment Procedure (SAP) for the calculation of energy use in dwellings has been published and it contains a number of changes to the way the impact of solar technologies is assessed. 

The key outputs of the calculation described in SAP are:

Dwelling Emission Rate (DER) - the carbon emissions from energy use to heat the house, provide hot water and power lighting, pumps and ventilation. It is expressed in kgCO2 per square metre of floor area per year.

SAP Score - a figure rating the energy costs normalised by floor area to heat the house , provide hot water and power lighting, pumps and ventilation. A house with a score of 100 has energy cost of zero each year, a house with a score of 0 has huge energy costs. The scores from 0-100 are divided into bands corresponding to EPC ratings from 'A' to 'G'

Fabric Energy Efficiency (FEE) - the space heating requirements for the dwelling in kWh/m2

Energy Consumption per Unit Floor Area - which can exclude plug-in appliances (as the above measures do), or include an allowance for appliances and electrical equipment.

Not Just for New Build

SAP is used to calculate the energy efficiency of newly built homes to meet Building Regulations. New homes must currently have a Fabric Energy Efficiency and Dwelling Emission Rate below a mandatory maximum.

Through Reduced Dataset SAP (or RdSAP), the calculation is also used to generate Energy Performance Certificates for existing properties. Over time the SAP rating of homes has become embedded in a range of government initiatives and incentives, for example EESSH in Scotland requires that all social rented homes in Scotland achieve a minimum SAP score by a certain date, and access to preferential Feed in Tariffs are linked to the house having an EPC rating higher than D.

What's Changed?

Carbon Intensity of Grid Electricity

The electricity grid has decarbonised with the move away from coal burning power stations and greater input from gas fired generation and from renewables (see my blog on this subject here). The proposal is to reduce the carbon intensity of electricity from 0.519kgCO2/kWh in SAP 2012 to 0.233 kgCO2/kWh in SAP10.

Discussion

This is a huge (55%) reduction compared to the current version of SAP, and lower than the figure consulted upon (0.398 gCO2/kWh). However, it is only a reflection of the huge progress that has been made in decarbonising the grid.

The impact for solar photovoltaics is that solar systems will need to be more than double the size of current systems to produce the same carbon benefit in the calculation, which could reduce the competitiveness of solar PV as a means of meeting building regulations. SAP10 will only be brought into use for the next update to the Building Regulations, and government will need to carefully consider whether it is now time to change the primary focus of the regulations away from emissions and towards energy consumption (like for appliances).

For example, emissions from mains gas will be 0.210kgCO2/kWh in SAP10. When you take into account efficiency losses from burning gas in a boiler to heat a house, developers will be able to achieve the same dwelling emissions rate using simple electric heating instead of gas - for example panel heaters and a hot water tank with immersion heater. It may be possible to remove the whole wet heating system and gas supply from new homes, yielding considerable construction and maintenance savings, but possibly saddling house buyers with unaffordable energy bills (unless, perhaps, solar is also fitted).

Export of Solar Generated Electricity

The value of exported electricity in SAP10 is 3.8p/kWh, whereas the cost of grid electricity is 16.6p/kWh on standard tariff. In SAP2012, exported solar electricity is assumed to be of the same value as electricity bought by the householder (which was dubiously justified by the existence of Feed in Tariffs - despite that in solar schemes for social tenants the tariffs went to financiers).

SAP2012 also assumed that 50% of generated electricity was used in the house (called the beta-factor) and 50% exported.  While this generally accepted assumption has started to look rather shaky as installed solar systems got larger, it didn't really matter because the value of exported electricity was the same as the saving made for energy not bought from the grid.

For SAP10, a more sophisticated treatment of the beta factor is used. The proportion of energy used in the house is now a function of the size of the solar system's energy output as a proportion of the energy demand. Larger solar systems attached to small energy demands will have a smaller beta factor and smaller solar systems attched to a large energy demand will have a higher beta factor. Adding a battery into the property will increase the beta factor.

PV diverters can also contribute towards energy for hot water in SAP10, so long as a battery is not present and the hot water cylinder has a sufficient volume (more than daily demand). 80% of generation, less the beta factor is available for input to the hot water cylinder, and the benefit is further diminished by a factor of 0.9 to take into account increased cylinder losses due to higher average storage temperatures.

Discussion

None of these changes affect the Dwelling Emissions Rate used for current building regulations. Solar PV saves carbon whether the electricity is used in the house or not.

These changes do, however, impact the SAP score and EPC band, as they impact on the calculation of the energy bills associated with the house.

The calculation of the beta factor was derived from a relatively small data-set, some of which was provided to BRE by the Solar Trade Association. An industry group is working to develop a much more comprehensive set of data to improve confidence in the value that SAP produces and to feed into the Microgeneration Certification Scheme guidance to solar / battery installers.

Shading

The PV shading penalty has been increased, that for solar thermal remains unchanged.

SAP2012 applies the following penalties to energy production - Modest shade 0.8, Significant shade 0.65, Heavy shade 0.5

SAP10 modifies as follows - Modest shade 0.5, Significant shade 0.35, Heavy shade 0.2
As an alternative the MCS overshading figure can be used.

Discussion

Industry were concerned about a complex two-step shading calculation process that was proposed in the consultation, and it seems that these concerns were noted, albeit with what look like penalty default values for systems with shading.

Hot Water Demand

A new, more complex calculation for domestic hot water demand reflects the growing importance of this area of energy consumption as increased insulation levels drive down space heating requirements. This is an area that the solar industry has been lobbying for change.

The new calculation takes into account the higher flow rates and lower inlet temperatures associated with the now more common mains hot water showers (either from pressurised hot water cylinders or combi boilers), when compared with header-tank fed systems.

Inlet temperatures have also been reduced for both header tank and mains fed systems as a result of input from the solar industry (by 2-3 degrees).

Discussion

I calculated a 10% increase in hot water demand for mains pressure fed systems compared to SAP2012. The decrease in inlet temperature will add a further 5% or so to the energy required to heat the water.

An increase in the assumed hot water energy will be welcomed by the solar thermal industry in particular, but higher general energy consumption will aid all energy producing technologies.

Solar Thermal Space Heating

In previous versions of SAP, solar thermal could only be applied to meeting hot water demand, which created an restriction on its potential contribution to household energy demands.

The Solar Trade Association proposed EN 15316-4-3 as a potential route to the inclusion of solar space heating in addition to solar water heating, and provided BRE with guidance and assistance in assessing the new method.

The published version of SAP 10 did not include details of the new method as testing was not complete at the time of publication, so the solar thermal appendix currently has holding text. I will be able to discuss more about how the new calculation works and the results it gives once the final version is revealed.

Discussion

The solar industry will welcome that SAP includes solar space heating. Less for the opportunities it brings in new build (where space heating demands are limited due to high levels of insulation), rather for the possibilities it opens up to improve the EPC ratings of existing properties with high space heating demand. The domestic Renewable Heat Incentive only supports solar water heating at present due to there being no approved method of 'deeming' (calculating) the expectd savings. The new SAP methodology will open up the enticing prospect of solar themal payments under dRHI linked to heat generated for both water and space heating.

Housebuilding Rates Unaffected by Higher Energy Efficiency

So Where's the Cliff Edge?

When faced with  potential legislation that would require them to build homes that use less energy, emit less carbon dioxide and reduce energy bills for their customers, housing developers have often expressed concerns that this would increase their costs and reduce the number of homes that get built.  Westminster politicians, concerned themselves about the 'housing crisis', seem to have bought into this argument and there has been no meaningful tightening of the building regulations for energy efficiency in England and Wales since 2010.  In 2015, plans to have regulated that all new homes would be net zero carbon emissions were dropped and as yet there is no sign of any interest from government in making new homes more energy efficient.  Instead of being zero carbon, a new home in England built today still emits 71% of the carbon of a new home built in 2005.

By contrast in Scotland, ministers pushed on with improvements to energy efficiency in new homes and new regulations introduced in 2015 mean that carbon emissions from newly built homes in Scotland emit significantly less CO2 than similar homes in the rest of the UK (around three quarters).

So now it is possible to test this assertion that building more efficient homes would reduce the numbers by comparing what happened in Scotland after the rules changed to what happened in England.

The graph shows the number of homes built by private developers in Scotland as a percentage of the number of homes built in England by private developers for each quarter between 2010 and Q3 2017 (the latest quarter for which data for both regions is available).

The rate of housebuilding in Scotland remains within historical norms despite significantly tougher energy regulations

With a population of 5.4m compared to England's 55.2m, the ratio might be expected to have a long term average around 10%, and indeed this is the case.

What is also clear is that since Q3 2015 when the new regulations came into force, the rate of housebuilding in Scotland has remained within its long-term range.  Where is the cliff edge of which we were warned?  Why don't the higher costs in Scotland put off house builders from building?  The answer is called the residual valuation model for land pricing.  Given clear guidance on direction of travel of policy, builders will adjust the amount that they are willing to pay for land.  The houses still get built, the builders still make money.  All that happens is that the windfall to the landowner when land achieves planning permission gets a tiny bit smaller.

So those local authorities that are lining up to fill the gap left by Westminster inaction by using their local plans to require higher that building regulations performance should take heart from the evidence and press on with their plans.

This article is an update of an earlier blog.

What is Energiesprong?

Deeply revealing - the depth of the window reveals indicate the thickness of insulation in warm, comfortable Energiesprong homes.  Image: Energiesprong International

 

Could this Idea from the Netherlands Crack the Toughest Challenge in Energy Efficiency?

Into the gaping hole in UK energy efficiency policy (see previous blog) left by the UK government inaction and disinterest springs Energiesprong, a concept that originates in the Netherlands and could totally revolutionise the way we approach domestic energy efficiency.

Energiesprong translates as 'Energy Leap', and in contrast to the piecemeal, step by step approach that UK government has been trying to prod us down, Energiesprong aims to do it all in one go.  An Energiesprong refurbishment must meet five simple requirements:

1. The finished house should be zero energy - over the course of each year it generates sufficient energy to heat the house, provide hot water and power household appliances.
2. The renovation work is done in only one week
3. The residents do not have to leave their property while the work is going on
4. The work is covered by a 30-year warranty covering the indoor climate and the energy performance of the house
5. The combined savings from energy bills and maintenance as a result of the renovation should finance the cost of the work

The requirements may be easy to set out, but the technical challenges they present to the construction sector are far from simple.  How to cost effectively making millions of individual and unique homes cosy, comfortable and cheap to run.  Nothing less than a new era of mass-customised construction  is required.

Insulated wall panel being craned into place at the first Energiesprong in the UK
Image: Energiesprong International

The prevailing technical approach to an Energiesprong renovation is for the house to be surveyed externally to millimetre accuracy with laser scanners.  A highly-insulated timber frame cladding system is made in a factory off-site before arriving on a lorry and being lifted into place by a crane and attached to the existing walls.  A new roof, almost always covered with solar panels is lifted on top of the existing roof (sometimes even leaving the old tiles in place).  In effect you build a whole new house around the existing one.

Windows and doors are removed and replaced, and heating systems go electric - typically either heat pump or electric panel heaters, depending on how far the insulation has driven down the space heating demand.  Solar thermal, battery energy storage and ventilation may also figure in designs.

The fourth and fifth requirements are utterly crucial to the whole thing working, as they make it 'investable' .  Residents pay an 'energy services fee' which is the same as their current energy bill, but get a better looking, warmer and more comfortable house.  The goal is for the cost savings on future planned maintenance (e.g. window replacements, roofing renewal, heating system replacement) plus the energy services charge to total up to a figure high enough to be able to give financial markets a sufficient return for financing the upfront costs.  If this can be achieved, then the scope for expansion of the scheme is effectively unlimited.  It works without government support.  It is completely scalable and social landlords can raise private sector finance to refurbish their entire stocks of housing.





Row of Energiesprong homes, Melick, Netherlands. 
Image: Energiesprong International

It is this possibility, of funded deployment at scale that has got the construction industry, social landlords and local authorities so excited about Energiesprong.

Consider the challenges, though.  At the current cost of energy, Energiesprong UK estimates that the whole refurbishment must be done for around £40,000 per house to be properly self-financing.

For this cost point to be reached, serious economies of scale need to be unlocked.

Energiesprong UK, and sister organisations in France, Netherlands and other countries aim to create these economies of scale by encouraging social landlords with large portfolios of property to bring forward volume refurbishment programmes and at the same time encourage the construction sector to develop the innovative products and techniques that will be needed to deliver these projects at low cost.  This stage could then be followed by a roll-out to owner-occupied homes and even new build properties, where the model might finance the difference between building regulations energy efficiency levels and building to zero net energy.

So far, around 2,000 Energiesprong homes have been completed in the Netherlands, of which around 60% were renovations of existing properties and 40% new builds.  The first Energiesprong homes outside of the Netherlands have recently been completed in a pilot of 10 homes in Sneinton, Nottingham by Melius Homes for Nottingham City Homes.

The pilot programmes so far undertaken have cost more than the £40k target, and so have required top-up funding, but the volumes have been relatively small, predominantly pilot programmes.

Implications for Policy and Energy Efficiency

A couple of observations on current approaches to energy efficiency and government policy arise when considering the great potential from Energiesprong.

1. Many government policies are based on the prevailing concept of a long journey of many small steps.  For example the Energy Efficiency Standard for Social Housing (EESSH) in Scotland requires social landlords to lift the energy efficiency of all homes, and it is envisaged that the minimum performance will ratchet up in small steps over time. This approach is not compatible with Energiesprong, for which it would make more sense to set targets for the average efficiency of stock.  This would give social landlords the flexibility to refurbish homes to a very high level and work their way through the whole stock year by year.  To allay fuel poverty concerns for people living in the homes that get dealt with later on, perhaps all stock should reach a minimum before an average score could be used.
2. Funded schemes, such as 'rent-a-roof' solar could be a complete dead end and indeed prove an impediment to the whole-house approach.  If you want to stick a new, cosy roof over an existing one as part of an Energiesprong refurb, but someone has already signed up to a 'free solar' plan which hands over the roof for 25 years to a financier, then you may find that you cannot remove the panels without paying to get out of that contract.  Similar, funded schemes, based on the Renewable Heat Incentive (RHI), for example for biomass boilers, could also prevent progress, as the RHI payment is based on the heat provided, which would be curtailed in a more energy efficient building.



Before and After.  Energiesprong refurbishment for Lefier Housing Association in the Netherlands. 
Image: Energiesprong International

It's About the Regeneration not the Generation

The main difference between Energiesprong and previous attempts at improving energy efficiency is the potential it provides for the redevelopment of entire streets and localities.

The whole outside of the house is renewed, and as the images show, the improvement can be extraordinary.  The scope for regeneration of tired old housing estates has got social housing providers and local authorities really interested.  Suddenly we're not only talking about energy saving, we're talking about regeneration and investment in the value of housing assets, funded by energy savings.

Consequently, it is possible that even before the £40k/house cost target is reached, significant projects can go ahead by combining with funds earmarked for the redevelopment of deprived areas.

Either way, the possibility of regenerating whole areas, with funding either partially or wholly paid for from future savings on energy bills is revolutionary and well worth reaching for!

Useful Resources

Energiesprong Foundation
Gallery of International Energiesprong Projects
Energiesprong UK
Energiesprong France

The Carbon Intensity of UK Grid Electricity

What it Means for Low Carbon Buildings

Take a look at this chart. It's nothing short of astonishing. Up to 2012 the amount of carbon dioxide emissions associated with the delivery of one unit (kilowatt hour, or kWh) of electricity in the UK was hovering around 500gCO2/kWh. Since then, the amount of carbon dioxide that is emitted for each unit of electricity has plummeted. In 2016 the average was 269gCO2/kWh, a fall of nearly half in only four years. This change has far-reaching implications for regulators, not least those involved in ensuring the low carbon transition of the UK building stock, both newly constructed buildings and the improvement of the existing stock.

So what's behind the fall?

The first factor is the retreat of coal-fired power stations. In 2012, the government's Digest of UK Energy Statistics (DUKES) has coal fired power stations producing 44% of our electricity nuclear plants were suffering from outages and gas prices had risen, so coal use was at a high. By 2016 the corresponding figure for coal was only 9%. In the same period, gas fired power stations rose from 24% to 42% of UK power generation. This matters for two reasons. First of all, because coal is made up of long-chain hydrocarbons, with a higher ratio of carbon atoms to hydrogen atoms it produces about 60% more carbon dioxide than natural gas for each unit of heat energy produced in burning. Second, gas is more often burnt in a Combined Cycle Gas Turbine (CCGT) power plants with conversion efficiencies of up to 60%, compared to 40% for conventional steam turbines.

The second factor is the increasing contribution from renewables in the electricity supply. Enormous amounts of wind energy, biofuel fired generation and solar energy have come online. In 2012 renewables and 'other' represented 11% of UK electricity supply. In 2016, this had risen to 27.8%.

As a result the average carbon intensity of electricity in 2016 at 269 gCO2/kWh was only just higher than that for gas (216 gCO2/kWh). When you add in an efficiency for a gas boiler at (say) 80%, the gap disappears.

This is huge.

For years electricity has been the bad boy in low carbon building design. People fretted as a series of reports from the Energy Savings Trust showed that heat pump installations in the UK were operating nowhere near their advertised efficiencies and were consequently underperforming gas boilers for carbon emissions. Simple resistive electrical heating by panel heaters or immersion heaters for hot water were to be avoided at all costs.

Four short years later and all this is is turned on its head.

And we're only just getting started with renewables. In September, Dong Energy announced that it would move forward with the world's largest offshore wind farm, Hornsea 2 off the Yorkshire coast, with development costs that had fallen by half compared to previous offshore farms. A couple of week later, and not to be outdone, the UK's first subsidy-free solar farm was announced. It's still a bit of an outlier combining solar with battery energy storage and using pre-existing grid connections from with an earlier development, but it's a clear sign of the direction of travel. The carbon intensity of grid electricity is heading only in one direction.

But there's another wrinkle to consider. The carbon intensity of the grid is not a static value. It varies constantly as the mix of generators fluctuate to meet different levels of electricity demand and in response to changes in wind and sunlight. On 11th June this year, it was windy and sunny at the same time. Records tumbled. The carbon intensity of grid electricity in the middle of the day on was below 80gCO2/kWh.

So now the moment when you choose to take power from the grid is a strong determinant of the actual instantaneous carbon emissions your electricity use is creating.

Some uses of electricity - for example for preparing domestic hot water, or to some extent space heating buildings could be relatively time independent.  If I'd known ahead of time that carbon emissions would be so low on 11th July, I'd have been able to set a timer for my immersion heater to heat water for me at midday and got my tank of hot water at fully one third of the carbon emissions of using gas heating.

And the technology to do this is just around the corner.  This awesome new grid carbon intensity forcasting service has been recently launched by the National Grid the Met Office and WWF, with an API that software developers could use to do just this kind of thing.

 

So where does this leave low carbon building?

The current building regulations in England and Wales were last reviewed in 2012 and set minimum carbon emissions rates that developers must design to. The carbon intensity of electricity in the approved calculation (the Standard Assessment Procedure or SAP) is currently 519gCO2/kWh, which was accurate at the time. Now it is woefully behind the curve.

Buildings are normally intended to be long-lasting. If we allow ourselves to imagine a future where digital technologies, the smart distribution of electricity, demand response, energy storage and renewables combine in a so-called 'Smart Grid' then a number of significant observations about low carbon building emerge:

• Even based on the current carbon intensity, never mind the future direction of travel over the life of a building, it is utterly beyond me that any new build or significant refurbishment should include gas heating.

• The current enthusiasm among UK policy makers and local authorities for district heating (for example this recent consultation by Scottish government) could also be a troubling dead end. District heating itself is neither intrinsically clean nor green - it all depends what heat source you put at the other end of the pipes you're going to dig up all the streets to install. Gas fired combined heat and power may be seen as low carbon at the moment, but how long will it look so appealing if electricity continues on its current path?

• Building codes are currently focused on regulating carbon emissions. In a world of low carbon electricity you can meet a carbon target with a draughty garden shed full of electric fan heaters. It's time to move to energy targets (kWh/m2) to create buildings that sip energy and liberate power for the demands created by the electrification of transportation.

If I was building my own Grand Design right now, my future-proof forever home based on these observations here's what I'd go for:

• High levels of insulation and air tightness to drive down space heating demand to a practical minimum

• Eliminate the wet heating system - I'd go underfloor electric coupled to a high thermal mass floor to allow price and carbon responsive electricity purchase to heat the slab at times of excess renewable generation

• Direct electric hot water cylinder - again allowing price-responsive purchase of electricity as well as diversion of excess generation from...

• the inevitable....beautiful solar panels on the roof - as many as possible!

Could this be the future direction energy efficient buildings? What do you think?

Higher Standards for Housebuilders Do Not Slow Development

The Truth has Been Revealed by Scottish Developers

NOTE - a new blog with updated data is available here

Housing developers say that if you make them build more energy efficient homes, they'll cost more and less houses will be built.

Our politicians have swallowed this argument hook line and sinker time and again.

I've written about this before - the flaw in the argument is the assumption that the developers costs have to rise. They don't. This is because one of the main costs of building the house is what you pay for the land, and if everyone is faced with the same regulations, then the value of the land is driven down and the landowner makes a slightly smaller profit from the deal.

Developers have successfully held up tighter building regulations on numerous occasions.

• The update to building regulations in England in 2012 ended up as only a 7% reduction in carbon emissions (compared to the significant cut required in the original zero carbon homes policy)
• In Scotland in 2012 there was no energy efficiency improvement at all.
• The Housing Standards Review resulted in legislation in 2015 with the intent of limiting local authorities powers to require higher energy efficiency homes through planning (legislation that is still not in force).
• Finally, after 10 years of clear policy direction, one of George Osborne's last acts before disappearing off to take lucrative directorships, was to tear up the Zero Carbon Homes plan (the existence of which had been mendaciously used to justify the changes in the Housing Standards Review).

So it's very interesting to see what's been happening in Scotland. After many years of shadowing Westminster on building regulations (apart from the obvious requirement to go just a percentage point or two lower on carbon emissions to make a point), Scotland really pulled ahead with its changes to regulations in 2015.  The graph at the top of this piece shows the gap opening up.

If developers' claims that higher levels of regulation would stop housebuilding in its tracks were true, you'd expect housebuilding in Scotland to have gone off a cliff.  Has it?

Has it hell.