Wednesday 28 November 2018

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.


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. 

Thursday 23 August 2018

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.


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.


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.


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.


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).


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.


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.

Wednesday 25 July 2018

Solar By Others

How to Get What you Want and not Get What You're Given

Architects, developers and planning officers often go to exacting lengths to make absolutely sure that they get the look that they're aiming for in a building. For houses that can mean specifying the type of brick, the tile on the roof, and specific styles of windows and doors. Even soffits and guttering do not escape careful scrutiny, selection and specification.

Damn right, too! These materials have a huge impact on the overall appearance of the house and should be defined carefully to preserve the integrity of the design, and the quality and sale-ability of the finished product.

Which makes it all the more surprising to find in developers' design packages a great big rectangle drawn on the roof labelled "solar by others" or "solar by specialist installer".

Surely you know that once you hand over your beautiful, carefully considered design to a Quantity Surveyor, if your specification does not nail down the materials you're looking for, then the words "solar by others" might as well say: "solar - the cheapest you can find, no I honestly don't care what it looks like - yes, I know I was really fussy about the exact make and model of cavity closer, but really, just get what you want for the solar - it's not like anyone will notice it's there."

It doesn't all look this good.  Image credit: ARPower

Solar PV is becoming more and more common on roofs. Incentivised by Feed in Tariffs, more than 800,000 households have now chosen to install solar as a retrofit. Building regulations in Scotland have made solar the norm on new homes and planning conditions in many local authorities (including zero carbon homes in London) also mean new homes are more likely than ever to need solar.

With the coming shift towards electric transport - (the speed of which I predict will take policy makers and energy companies completely by surprise), economies of scale for battery manufacture will drive the availability of cost effective electricity storage, and make solar an even more compelling feature of a mainstream home.

What you Need to Know

The cheapest panels have silver frames, a white backing sheet and polycrystalline cells. Sticking them on a framing system above the roof covering is still (only a little) cheaper than going inline with the roof. If you don't specify what solar you want, this is what you're likely to get.

Here are the choices you face, starting with those that have the greatest impact on 'kerb appeal'.

1. Panel Layout

The number one impact on the overall look of the building is the layout of panels on the roof.  Early design engagement with solar specialists means that cluttered designs fitted around other roofing features can be avoided.  Higher power panels can be selected to achieve energy goals in the most aesthetically balanced way.  See also this guidance on panel design by the  Campaign to Protect Rural England.

2. Frame colour. 

Solar panel frames are most commonly either silver or black. Both have a protective anodised surface finish, but a silver (natural) colour avoids the dyeing process needed to make a black frame so is slightly cheaper.  In most (but not all) situations black frames are considered the most discreet and harmonious choice.

3. Mounting System

Panels can be mounted on metal racking above the tiles or slates or conventional roof covering, or they can be sunk into the roof covering (roof integrated), replacing the conventional roof covering and looking more like an intended part of the building design and less like a 'bolt-on'. Many systems use a 'top clamp' arrangement to hold down the panels to the framing, but some systems have hidden fixings, resulting in a less cluttered finish above the plane of the panels.

Roof integrated systems with visible clamps (top) and invisible fixings (bottom) 

4. Backsheet.

A white backing sheet means you can use ever-so-slightly lower power cells in your panel for the same overall panel output (the white sheet reflects light and keeps temperatures a little lower so the same cells perform better). When combined with mono crystalline cells (which are not quite square and have missing corners), a white backing sheet will produce a characteristic pattern of diamonds running up the panel in columns.

Monocrystalline cells (left) and polycrystalline cells (right) in combination with a white backsheet showing the characteristic diamond pattern of a monocrystalline panel

5. Cell Type. 

Polycrystalline cells are sometimes a similar price to mono crystalline cells, but in times of over-supply often seem to fall further and faster. Right now modules based on polycrystalline cells are around 10% lower in cost than those based on mono crystalline cells. In general poly cells will look a bit bluer than mono, and may have little more colour variation across and between panels , but modern cell production technologies can mean that nowadays they rarely show the crystalline pattern that used to be so characteristic of this type of panel.

(More information on the differences between polycrystalline and monocrystalline cells can be found in this blog).

6. Cell Interconnections. 

Some manufacturers hide the bus-bars (silver strips at the top and bottom edges of the panel that electrically connect the cells together, but obviously this also adds cost. Some panels have cells with rear face connections so there's no silver lines visible on the top face of the panel.

How About Just Asking For Roof Integrated Solar?

For sure there are some great looking roof integrated solar systems available. But specifying roof integrated can still result in a wide range of outcomes when you hand it over to the commercial team. This is particularly the case for roof integration systems that give freedom to use any old panel. 

I took the pictures below at the same site and they show two phases of the same development.  The specification called only for "in-roof solar", opening the door to the silver-framed installations in the lower image which meet the letter, if perhaps not the spirit, of the specification. 

Both are roof integrated solar

For something that has such a big impact on the way a building looks, surely it's time for designers to take control of the solar they get, rather than giving the commercial team carte-blanche to go with the cheapest option offered.  

Unfortunately there’s no substitute for carefully choosing and specifying the product you want, just like you do for other building materials.

Tuesday 8 May 2018


What is BIPV and what are the advantages of this approach to using solar on our buildings?

Building Integrated Photovoltaics (BIPV) are photovoltaic materials that are used to replace conventional materials to form part of a building envelope.  Buildings come in all sorts of shapes and sizes from the smallest homes to huge tower blocks, but photovoltaics is such a versatile technology that as we'll see the potential applications for BIPV are very wide.


The most obvious location to put BIPV is the places that get the most sunshine.  This is normally high up the building (to avoid shade) and (in the northern hemisphere) tilted towards the south.  Roofing, roof windows and sloping patent glazing are ideal parts of building envelopes where photovoltaic materials can be used.

As part of a refurbishment of Kings Cross railway station, London, the historic barrel-vaulted roofing was renewed in 2014.  The patent glazing at the top of each arch was fitted with 1,400 glass-glass BIPV laminates by Sundog Energy (now part of Photon Energy).  In glass-glass laminates the silicon solar cells are encapsulated in clear plastic and sandwiched between two clear sheets of glass.  The gaps between cells allow light transmission into the building through the BIPV laminates.  Both sides of the apex were treated in this way, facing east and west.

Kings Cross Station 
240kWp BIPV patent glazing, generating 175,000kWh/year ( 730kWh/kWp)

At the Ziekenhuis (hospital) in Aalst, Belgium, an eye-shaped atrium is formed from sloping curtain walling system with glass-glass BIPV laminates supplied by SAPA building systems forming the entire cladding.  Cells are spaced further apart than in a standard PV panel to create the desired light transmission into the atrium behind, resulting in a beautiful dappled light in the enclosed space.

Ziekenhuis, Aalst, Belgium 
46kWp sloping curtain walling, generating 31,000kWh/year (675 kWh/kWp)

It's not only new build projects that can benefit from BIPV.  The renovation of the Appleton Tower at Edinburgh University included 80 solar PV modules attached to the building with the Schletter Efa facade mounting system by installers Absolute Solar and Wind.

Appleton Tower, Edinburgh University
26kWp facade cladding, generating 19,000kWh/year (703 kWh/kWp)

At a more modest scale, buildings such as homes and offices often have a sloping roof covered with tiles or slate.  Here, more standardised BIPV products are available that replace the tiles and slates.

This house in Cambridgeshire has a patch of BIPV solar interlocking tiles, each tile replacing a row of standard concrete tiles.

Tile format BIPV integrated in concrete interlocking tiles

This roof is on the set of "Desperate Housewives" where Elon Musk launched his BIPV glass slates and tiles.  Details of these products are still emerging as (aside from those of Tesla executives), only one or two homes have been completed with this product.  Early indications are that this is a premium product with a very high price - one of the first customers said the product was "not for financially sensitive people", describing an installation process that took 10-15 people 2 weeks and cost him $100,000.

Tesla glass slates for launch event, Desperate Housewives set, California

A more cost effective approach is to take advantage of the huge economies of scale in solar PV panels that are mass produced in standard formats and figure out a clever way to make them part of the roof covering.  This house near York has Clearline fusion roof integrated solar panels covering the whole roof.  The installer, The Phoenix Works were involved in the design of the new build eco home from an early stage so could work closely with the architect, with stunning results.

Whole roof BIPV roof on a new eco home
6kWp Clearline Fusion roof integrated solar from Viridian Solar

Walls and Facades

Of course as building become taller, the available roof area becomes ever smaller in proportion to the building size.  However, an unshaded south facing vertical wall will still get 70% as much incident light each year as an unshaded south facing pitched roof at optimum angle, and a much larger available surface area on the walls can easily makes up for any shortfall

The very first large scale BIPV project in the UK was a facade system on the Northumberland Building at the University of Northumbria in Newcastle upon Tyne.  BIPV solar was installed to a south facing wall as part of a building renovation in 1994.   The 85Wp BP Solar modules were mounted on frames on a south facing facade, tilted to catch more light and to partially shade the windows below from the high summer sun, so helping the building avoid over-heating in summer.

Northumberland Building, University of Northumbria, Newcastle upon Tyne
40kWp facade and solar shade, generating 25,000kWh/year (625 kWp/kWh)

Fast forward to the present day and the 230m high Heron Tower in London, completed in 2011 has 153kWp of glass-glass laminates built into the south elevation of curtain walling in two great stripes running from street level to the top of the tower in front of the two lift shafts.

Heron Tower, London
153kWp BIPV curtain walling  generating 92,000kWh/year (620kWh/kWp)

As well as being a stunning example of what is possible with BIPV, Heron Tower is, unfortunately something of a cautionary tale too.  For across the road  from the south facing elevation at [[110]]] Broadgate, another tower that will top out at 181m is rising from the ground.  When complete this tower will obscure the entire south elevation from direct sunlight for large parts of the day (see image).


We've already seen how BIPV curtain walling and patent glazing can be configured to allow light through, but from time to time reports come out of new materials that will enable the creation of BIPV windows that you can see through but which generate electricity too.  It's normally accompanied by a picture of a hand holding a clear piece of glass.  Sometimes the hand has a latex glove on it.  Most of these remain lab curiosities for the present, however thin film solar panels are already available that are partially transparent.  They tend to finish up with a finish that is either orange in colour or smoked.

Bus station at Bournemouth University has two power generating BIPV canopies
20% transparent CdTe thin film modules from Polysolar

Advantages of BIPV

The principal advantage of BIPV is an aesthetic one.  At its best, BIPV alooks like a considered part of the building, rather than a bolt-on.

New home in Sussex with Clearline fusion roof integrated solar replacing slates

BIPV also produces offset costs - the cost of the materials that you would have used if the BIPV was not there plus the cost of fitting it. Sometimes these costs can be substantial, for example in this project where Welsh slate was substituted for integrated solar PV and the saved costs for slate were equivalent to the cost of the PV roofing.

There are also advantages in the ease of ongoing maintenance compared to bolt-on PV. For example access to tiles on roofs. If a tile fails and needs replacement, the task of doing so is made very much more complex and costly if it is behind an above-roof solar PV system. The system must be decommissioned, removed and the tile replaced before the system is reassembled and recommissioned. A job that could have been completed from a ladder now involves scaffolding and electrical works.

It is becoming evident that birds nesting behind bolt-on solar is an issue, especially for domestic installations where the noise nuisance is disturbing. A mini-industry has sprung up to bird proof above-roof solar by fitting wire mesh around the system.


When you take the time to include solar as part of your design for a new building or refurbishment, BIPV means that your solar can be beautiful as well as functional.

Wednesday 18 April 2018

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.

Thursday 22 February 2018

Stop Worrying About Lithium, Start Worrying about Cobalt

How the Energy Transition is Critically Dependent on a Failing State in Africa

I recently wrote a blog about how much Lithium we might need to make all the batteries to electrify transport, and whether we might run out of the stuff.  It's natural that people focus on Lithium - after all, the favoured battery technology is called "Lithium-ion", but  it turns out that Cobalt is a much greater concern.

Cobalt is a crucial element of many types of Lithium-ion battery cathodes.  The first Lithium-ion battery was commercialised by Sony and the cathode was based on Lithium Cobalt Oxide (LCO).  This type of battery is still widely used in electronic devices.

One of the most common types of Lithium ion battery for electric powertrain applications and power storage is the NCA lithium ion battery which contains lithium oxide in combination with nickel, cobalt and aluminium in the cathode together with a graphite anode.  This type of battery has higher specific energy.  Different manufacturers have their own 'recipes' but typical proportions for the cathode are:

Li(Ni 0.85, Co 0.1, Al 0.05)O2

Cobalt has atomic weight of 59 (compared to Lithium at 7), so although cobalt is present in the ratio of 1/10 the number of atoms in the battery, you need a similar mass of Cobalt as Lithium in the battery - around 600g of Cobalt for every kg of Lithium.

In my previous blog, we estimated the quantity of Lithium to electrify the world's fleet of passenger cars as 13.2 million tonnes, which would imply that there's a requirement of 7.8 million tonnes of Cobalt to achieve the same goal.

How Much Cobalt?

The United States Geographical Survey (USGS) estimates the world reserves of Cobalt at 7.1 million tonnes.  The situation is similar to that of Lithium in that identified reserves of Cobalt are about the same size as the amount needed to electrify the whole world fleet of cars.  Just like for Lithium, it is likely that once there's a strong demand for the material, exploration will result in the identification of other locations and technological development will convert known resources into exploitable reserves.

Unlike Lithium though, take a look at where in the world Cobalt is found.

Lithium is spread around politically stable countries such as Chile and Australia.  By contrast, half of the world's identified Cobalt reserves and more than half of global production comes from The Democratic Republic of the Congo (DRC).

This mineral-rich central african country has suffered almost continuous conflicts since 1996, including civil war, invasion and spillover from conflicts in adjacent countries such as Rwanda.  Largely unreported in the West, the situation is desperate with estimates ranging from 1m to 5.5m dying as a result of the wars and associated famine and disease in the last twenty years.  Foreign businesses have curtailed operations due to uncertainty, lack of infrastructure, corruption, inflation and the uncertain legal framework.

The latest news is not good.  Joseph Kaliba, the country's President since his father was assassinated in 2001 finished his last term in 2016, but still clings to power.  Currently 10 of the 26 provinces in the country are suffering from civil war.

Add a proposed new law that could increase government royalties on 'strategic' minerals such as Cobalt to levels as high as 10% and concerns about child labour and human rights abuses in Cobalt mines in DRC, and the outlook is extremely troubling.

Assault and Battery

So what does this mean for battery storage and electric vehicles?  Well, war, bloodshed and chaos doesn't always mean that the product doesn't get out of the ground, after all, bullets, guns and general carnage has to be financed somehow.  Whichever warlord is currently in charge of the area where the mines are will likely as not keep the Cobalt coming for a world hungry for battery storage.  Whether the world can turn a blind eye to batteries financing war is another matter.

However, emerging battery chemistries may reduce the need for Cobalt, and new sources may come on line as demand and prices rise, but these are not quick fixes.  In the short term we must hope that DRC avoids the worst.

So, if you are ever asked "is there enough Lithium in the world for all these electric cars and batteries?" the correct answer is "Sure thing,  but don't ask about Cobalt."

Wednesday 17 January 2018

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

Tuesday 16 January 2018

A Brief History of UK Energy Efficiency Policy

The track record of UK initiatives to encourage us to make our homes more energy efficient has been patchy to say the least.

The schemes come and go, but the results are depressingly consistent.


A range of government schemes have required the larger energy providers to invest in energy efficiency measures such as loft and cavity wall insulation for homes. The current version is the Energy Company Obligation (ECO), but before that we had CESP and CERT and others. This bizarre concept - making a business responsible for implementing measures that reduce demand for its own products - seems like putting a fox in charge of security improvements to the chicken coop. It is perhaps unsurprising then that foot-dragging, missed targets and ineffective measures have been the result.

In 2014, many of the energy suppliers were fined for failing to meet their targets to install insulation. British Gas was fined £11million, a development which their PR department brazenly promoted as a charitable donation.  One is left wondering if the energy companies considered these fines a small price to pay rather than helping people spend less on energy.

Measures installed under this scheme crashed by more than 80% after 2012 when a panicking George Osborne announced huge cuts following a Labour proposal to cap the prices people pay for energy.

Green Deal

Greg Barker's Green Deal scheme to 'transform the energy efficiency market' was in trouble almost from the start. Having told us that he'd struggle to sleep if the number of home improvements it financed was less than 10,000 in the first year, the actual number came in at 626.

In what now looks like a rather desperate effort, Greg managed to convince the Treasury to throw in a few hundred millions to the Green Deal Home Improvement Fund (GDHIF), to give a further cash-back grant to householders who installed energy efficiency measures. Most of this stop-start funding was spent on boiler replacements (and how many of these would have happened anyway as they reached end of life is open to debate). The scheme was ignominiously withdrawn after writing only a few thousand energy efficiency loans.

The offer to consumers was complicated and unappealing. The interest rate was a hefty 7%, which compares unfavourably with mortgage finance. Only measures that met the so-called 'Golden Rule' could be fully financed - where the estimated savings on energy bills were greater or the same as the repayments collected through your energy bills. What this all added up to was - go through all the hassle of having all this work done in your house and your energy bills will be about the same as they were before.

The Green Deal Finance Company is now in private hands, but it is still unclear how the new owners will address the fundamental shortcomings of the scheme.

Feed in Tariff and Renewable Heat Incentive

These schemes pay for renewable energy - power and heat where homes and businesses install technologies such as solar PV panels, solar thermal panels, heat pumps and wood chip burning stoves in their homes or businesses. The intention was that these would provide long-lasting and stable support for renewables after a series of start-stop grant schemes that had preceded them.

The Feed in Tariff (FIT) is due to close in 2019 after a tumultuous few years in which government struggled to keep up with rapid reductions in the cost of solar PV panels. As a result of the payments being fixed while the costs fell sharply, the financial returns from the scheme rose rapidly. Returns of 15-20% were not uncommon, payback periods as short as four or five years reported. As more and more people joined the party the budget ballooned. Cue panic in Whitehall, an over-correction on the tariff rates and a return to the boom-bust market from which the scheme was supposed to mark a departure.

The Renewable Heat Incentive (RHI) for heat generating renewables came in after the first FIT crisis, and as a result was designed with many more controls to stop a runaway deployment if the tariffs were set too high (with the notable exception of Northern Ireland where the executive for some reason removed the controls and blew the budget - the whole Northern Ireland budget!). In consequence, the RHI suffers from a paucity of ambition and has only resulted in a few tens of thousands of households replacing their heating systems with a low carbon technology (33,500 new domestic installations of solar thermal, heat pump and biomass boiler from April 2014 to November 2017)


The Minimum Energy Efficiency Standard (MEES) applies in England and Wales and requires private landlords of both domestic and non-domestic properties to ensure that their properties meet a minimum level of energy efficiency.  Buildings that do not cannot be re-let after April 2018 and cannot be let at all after April 2020.

Unfortunately, as I revealed in an earlier blog, a landlord can apply for an exemption if they cannot do the required improvements without upfront costs, which relied on the Green Deal being available.  But this has now gone, leaving a loop-hole in the legislation so large you could drive an un-insulated house with broken windows through it.  Similar legislation being consulted upon in Scotland only deals with domestic properties, but sensibly places a limit on the maximum cost for a landlord.  So far, there's no apparent interest in fixing this mess at Westminster.


The Energy Efficiency Standard for Social Housing (EESSH) is legislation in Scotland that requires social housing providers to ensure that their housing stock is all above a minimum energy efficiency level by the end of December 2020, with an intention to gradually ramp up the required levels over time.

EESSH looks like its already producing some significant investments in Scottish social housing.  It really does look like the one to watch, at least of all the schemes listed.

Is There Another Way?

What all these schemes have in common is that they deal piecemeal with the challenge of making our buildings more energy efficient. They imagine that the 'journey' to having an energy efficient home fit for the future is taken one small step after another. First insulate your cavity walls and loft. Then change your boiler to an efficient new one. Have some solar panels on that roof. Now replace your whole radiator system take out your efficient new boiler and fit a heat pump.

Many also rely on government spending, a fickle foundation upon which to base investments in housing stocks or to build long-term business plans (as those of us in the solar industry will attest).

With the demise of the Green Deal, and no sign of anything to replace it, there's a huge hole in the government's policy to meet forthcoming carbon budgets. This is not something that has gone unnoticed by the government's own Committee on Climate Change (CCC), which in its 2017 report gave government policy for residential energy efficiency a red light for able to pay households and an amber light for low income households.

It is into this gaping hole left by the UK government inaction and disinterest springs Energiesprong.  This is a concept that originates in the Netherlands that could totally revolutionise the way we approach domestic energy efficiency and it is the subject of my next blog.