Future Homes Standard - Homes that Cannot Meet the 40% Solar Requirement

 

The Future Homes Standard (FHS) will make solar PV panels mandatory on all new homes from 2027, with the government announcing that panels will have an area of at least 40% of the ground floor area of the building.  

In this article I'll take a look at how the calculation works, what amount of solar it might result in and how exceptions are dealt with when roofs don't have enough room.  I'll also share an early estimate of how many houses might not be able to meet the requirement in full.

How Much Solar?

The actual requirement for the amount of solar is, quite rightly defined in terms of the total rated power, which means that if you use higher performance panels, you can reduce the area or conversely if the panels you use are of low power rating then a greater area must be installed.  

The actual target is to install solar PV that has the same annual output as a solar array with the following characteristics: an area of 40% of the ground floor area, a specific power of 0.22 kWp/m2, facing SE or SW at a pitch angle of 45 degrees and with little or no shading.

So for an 85 m2 semi detached home, arranged across two floors we might have 42.5m2 of ground floor area and a target solar installation of:

40% x 42.5 x 0.22 = 3.74kWp

This figure could be met for example with ten 405Wp solar panels, or nine 445Wp panels.  It's worth noting that the current average installation we see under Part L 2021 is between four and five panels per house, so the Future Homes Standard represents a rough doubling in the quantity required.

Any amount by which the solar provided exceeds the target counts towards achieving the overall energy targets for the building, so there are benefits to going higher if the roof can fit more.

What About Complex Roofs?

The regulations makes allowances for roofs that are an interesting shape or that have features that limit the amount of solar that is possible, and this is outlined in Appendix B9.  The developer must provide evidence to the building control body to show that it is not possible to install sufficient solar on the roof to meet the requirement.

Roof diagrams showing the roof with and without solar panels showing that the installation provides the maximum PV capacity and annual generation possible for the roof orientation and layout must be provided.

The diagram showing the maximum possible roof area for solar PV has to be made using specific guidance given on the minimum allowable offset distances from other roof features.

An example of a suitable diagram showing the maximum solar possible on a house is shown at the top of the page.

The target for solar PV then becomes a system that produces an amount of energy each year that matches that of a system with the area of solar in the drawing, a specific panel power of 0.22kWp/m2 and the orientation and angle of the actual roof pitches.  This figure is then also used in the Notional House specification so there is no penalty there for having to use a smaller solar system.

At present there are no restrictions on how close to roof edges a solar panel installation can be made (subject to having a sufficient wind resistance to install in an edge zone and a sufficient fire rating to install adjacent to a party wall).  Consequently it might be possible to provide a B9 drawing showing a maximum solar area, and install something different -  so long as it matches or exceeds the annual power generation 

For example this could be achieved by using higher efficiency panels than those in the standard, and covering more of the most advantageous roof pitch, while dropping solar off the less advantageous roof pitches, to meet or exceed the annual energy yield of the B9 drawing.

However, on the same day that the FHS was revealed, the Health and Safety Executive opened a consultation on Approved Document B - the building regulations for fire safety.  This includes what would become mandatory provisions for minimum offset distances for solar panels, so reducing the possibility to use tighter margins to outperform the regulated max-fit.

Something that has been missed in the guidance is to define what size of solar panel should be used in the assessment. This really needs to be clarified because otherwise people will get very different outcomes depending on what panel size is chosen. 

How different panel sizes give different maximum-fit outcomes

 I have discussed this point with colleagues at the Future Homes Hub and the plan is to develop an industry guide in conjunction with representatives from building control bodies to fill in some of the missing detail from Appendix B9.  This way we can hopefully have a consistent approach across industry.

What Proportion of Homes Will Fit 40%

As part of our work at Viridian Solar in support of our housebuilder partners, the design team has performed studies on sample developments to assess which house types can meet a 40% requirement and which cannot.

So far we have seen around 80% of houses on a typical site can fit the full requirement of solar panels on the best elevation.  Of the houses that could not fit the requirement, on average one half of the requirement could be fit on the best elevation, so around 20% of the ground floor area. 

Under the approach in Appendix B9, these homes would need to use all the possible other elevations as well as the best elevation to maximise the solar generation possible, including North facing elevations if necessary.  Depending on the size of the less advantageous roof pitches, this might result in a greater number of solar panels being used due to the penalty that comes as panel orientation moves further away from South facing.  

Of course, this analysis was done before the final regulations were published, and so was using our own manufacturers' guidelines on offset distances which are tighter than those in the FHS.  It is likely that a higher proportion of houses will struggle to meet the 40% target using the Appendix B9 guidance.  No doubt the design team will continue to be working with housebuilders re-evaluating their house types to the final version of the standard.  I will post an update when we have got more data from this work.

Warm Homes Fund to Go All-in on Solar

 Announcement in January Expected to Include Grants for Solar PV

Zero Bills Homes by Keepmoat and Platform Housing Group (C) Viridian Solar

It is widely expected that a £13bn 'Warm Homes Fund' to be announced by Ed Miliband in January will include grants for the installation of solar PV and batteries.  If so, this will represent a big departure from previous policy in this area which have almost exclusively emphasised retrofit insulation measures.

Until recently the accepted wisdom has been coined 'fabric first’.  This catchy phrase summarised a prevailing energy-efficiency orthodoxy which held that until you fix the insulation and airtightness of a building (its fabric) there is no point using ‘expensive bolt-ons’ like solar.  

Fabric first became sacrosanct for some in the energy efficiency industry (and not only those who manufacture insulation), with every consultation on building regulations met with howls of criticism from some quarters for not going far enough on required insulation levels and any inclusion of solar or other technology criticised as 'green bling'.  

Numerous government policies have been influenced by fabric first thought – with ECO, Low Carbon Buildings Programme, and most recently the ‘Scottish Passivhaus’ rabbit hole that building regulations north of the border appear to be about to disappear down all prioritising insulation over renewable energy.

This dismissal of solar bling as unserious and insulation as the only ideologically pure approach to decarbonisation misses three important points: 

First, that thermal efficiency is a game of diminishing returns.  

Second, (and linked to the previous point), having run out of easy targets such as loft and cavity wall insulation, more ambitious retrofit approaches aiming for big improvements in thermal efficiency can be highly invasive, complex and risk unwanted side effects like damp and mould.

Third, that the orthodoxy arose at a time when our energy system was dominated by fossil fuel and renewable energy was expensive.  This is now out of date.  What matters more today and in future is when you use energy not how much you use.

Diminishing Returns

It's physics.  The more you insulate a building the more difficult becomes the next improvement in performance, until you are adding large amounts of insulation for only marginal gains.  Building regulations for new homes appear to have now reached this point since the Future Homes Standard consultation proposes no change to the fabric performance of new homes over those of current (2021) regulations.

In retrofit scenarios, the payback for simple low cost measures like loft insulation chimney balloons, lagging hot water tanks and pipes and draft excluders is measured in months while more expensive improvements like external wall insulation for solid walls can take many years to pay back their costs.

Unwanted Side Effects

Once you've lagged every hot water cylinder, topped up loft insulation where you can and blown insulation into walls with cavities, you're left with a large number of hard-to-treat properties with solid brick or block walls.  These require a layer of insulation to be fixed to the external walls either on the inside face which makes the rooms smaller or on the outside face which needs to be carefully protected against the weather. 

The challenges with solid wall insulation really became apparent once we moved from theory and pilot studies to pushing into volume in the real world.  The work is complex, expensive and intrusive and has sadly proven to be easy to get badly wrong at scale, with unwanted side effects such as damp and mould widely reported. 

A National Audit Office review of works done under the ECO4 and the Great British Insulation Scheme found that an amazing 98% of homes fitted with external wall insulation and 29% of those with internal wall insulation had major issues that need fixing.

The Economics Has Shifted

Fabric first approaches to energy conservation in buildings emerged at a time when renewable energy was ruinously expensive and the energy supply system was dominated by coal, oil and gas.  At this time, the careful conservation of energy was the only logical way to reduce emissions and lower energy bills.

Renewable energy is now the cheapest form of energy.  It getting more and more plentiful as investments in new solar and wind capacity expands.  The nature of renewables is that the timing of generation cannot be controlled in the same way as it can for fossil fuel based energy, but the falling cost of battery energy storage and advent of smart controls that react to time-of-use pricing signals are combining to overcome the weakness of intermittency in renewable generation.

Those who can adjust their energy demand to use power when energy is in over-supply can now take advantage of these tariffs to pay very low (sometimes zero, sometimes negative) prices for their power.  Space heating, domestic hot water and electric vehicle charging are all amenable to time-shifting or rate shifting.

New housing developments such as Hollymead Square in Essex and Beeston Canalside in Nottingham offer so-called Zero Bills Homes where the combination of solar PV, battery energy storage and electric heating with time of use tariffs and smart energy controls allow the energy supplier, Octopus Energy, to guarantee that the householders will pay nothing for energy for ten years after moving in. 

In this approach to low-carbon living it's not how much energy you use, its when you use it and how you combine that with maximising the use of low cost renewable energy you generate for yourself.

Learn to Love the Bling 

The case for using energy sparingly has not gone away, and simple, low-cost insulation improvements will always be high up the to-do list.  

However renewable energy is combining with smart energy management, electrification of transport and heating and battery energy storage to offer an alternative vision in which the when of your energy use is as important as the how much.  If the Warm Homes Fund recognises this fundamental shift, then that is to be welcomed.

The Future Homes Standard Consultation

 

The Future Homes Standard (FHS) consultation is here and while the consultation itself seems at first glance to be relatively straightforward, the whole thing is, in fact, an absolute beast.  Why?  Because at the same time as issuing the FHS consultation, the Department for Levelling up, Housing and Communities (DLUHC) also dropped consultations on its plans for a wholesale redesign of the underpinning calculation methodology that the building regulations require to demonstrate compliance with the energy performance of new buildings.

I decided to tackle the meal in bite-size portions, starting with the underpinning calculations and working my way up to this, my final blog on the consultation.  You can find my earlier blogs looking at the changes to the calculation on the links below:

The Home Energy Model

The Solar Calculation in the Home Energy Model

The FHS 'Wrapper' to the Home Energy Model

In summary the solar industry should welcome the change to the Home Energy Model which moves from a monthly calculation of energy to a half-hourly one, better positioning the building regulations to properly account for the benefits of technological advances such as solar PV, battery storage, solar diverters, and time of use electricity tariffs. 

At the same time, I found a concerning calculation error in the HEM that under-represents the energy generation of solar PV as its orientation shifts away from south-facing.  This needs to be corrected before the HEM can be used, and should also be taken into account when the government is assessing the responses from housebuilders, who will have been taking the results from the HEM at face value.

What's in the FHS consultation Itself?

The FHS consultation itself is on the face of it a pretty simple choice between two options for each of domestic and non-domestic buildings.  

Domestic Buildings

It will not be possible to meet the standard with gas heating, so all new homes built after the regulations come into force will be electrically heated or use a heat network.  For clarification this exclusion also applies to so-called 'hydrogen-ready' boilers that have been proposed by those advocating for the interests of the gas and gas boiler industry.  

In this way, as the electricity grid is decarbonised over time, homes built under the FHS will naturally become zero carbon.  (Note the circularity of this argument if the FHS itself only increases electricity demand without renewable generation then the job of decarbonising the grid becomes harder and takes longer, a point we return to later).

Government does not propose to change the minimum building fabric (insulation) standards for homes compared to the 2021 standards.  It believes that the 2021 standards provide a good basis for the Future Homes Standard.

The Option 1 specification is based on an air-sourced heat pump for domestic heating, solar PV covering an area of the roof equal to 40% of ground floor area, an enhanced air-tightness compared to current regulations, decentralised mechanical extract ventilation (dMEV) and a waste-water heat recovery (WWHR) system on any showers not on ground floor.

Option 2 removes the solar PV, heat recovery and ventilation and relaxes the air-tightness requirement.

The table below summarises the two options and compares the key specifications to the current building regulations.  At this point it is worth mentioning that housebuilders do not need to slavishly follow the specification in the building regulations.  They simply need to meet or exceed the performance given by a house of that specification.  For a fuller explanation of how the 'notional house specification' in the building regulations works please see my earlier blog on the topic.

Selected Elements in Notional House Specification by Building Regulations Update

Non-Domestic Buildings

Similar to housing, the new requirements for non-domestic buildings will be for electric heating and will have the same fabric as in current regulations.  There is an increase to airtightness for top-lit buildings to better support new requirement for heat pump plus more efficient lighting and heat recovery.

The two options

Option 1 (recommended) solar PV to 40% of foundation area for side lit spaces and 75% of foundation area for top-lit spaces

Option 2 (not recommended) solar PV to 20% of foundation area for side lit spaces and 40% of foundation area for top-lit spaces

Analysis and Comment

Domestic Buildings

If you assume grid electricity will soon be zero carbon, you could heat an open cave electrically and it would be a zero carbon home.  Once you've mandated electric heating you've met your goal and all other energy efficiency choices simply come down to the trade off between construction costs and running costs for the occupants.  

The consultation lists the government's desired policy outcomes from FHS in order of priority as follows:

1. Protect occupants against high energy bills

2. Reduce energy demand of homes

3. Reduce operational carbon emissions

4. Simple to understand and use

5. Consider peak electricity demand

The consultation also presents an analysis of the estimated extra building costs and the energy bills associated with the regulated energy - that is the energy demand in the building for heating, hot water, lighting and pumps and fans, not counting energy used for electrical appliances such as TVs, dishwasher, fridges and freezers.

It concludes that Option 1 (with solar) imposes additional build costs of £6,100 compared to current building regulations but reduces regulated energy bills by between £910 and £2,120 compared to a typical existing home.

By contrast Option 2 (without solar) imposes additional build costs of £1000 while resulting in a saving of between £210 and £1,420 on regulated energy bills compared to a typical existing home.

The consultation fails to compare the regulated energy bills from Option 1 and Option 2 to those from a house built to current building regulations (I suspect deliberately, and to flatter Option 2).  I have added a column on the right side of the table below showing this figure.

If the government chooses Option 2 then this will be the first time ever that a change to the building regulations on the conservation of fuel and energy results in an increase to householder's bills compared to the previous regulations, and at £580 per year, the increase is not small, in fact it nearly doubles the regulated energy bill compared to new homes being built today.

Stating that Option 2 is better than a 'typical house' is like saying that a new regulation that allows water companies to discharge 50% of sewage into rivers untreated is just fine because back in the 1920's we used to allow them to dump all of it.

Why the increase?  Well simply put although heat pumps generate heat at a far higher efficiency than a gas boiler, the energy supply (electricity) is more expensive than gas, which offsets the benefit completely.  Keeping solar PV in the specification generates energy that offsets the increase in bills.

Measured against the stated highest priority desired outcome from the regulations, Option 2 simply fails to deliver.

It should be remembered that tens of thousands of new social housing properties each year are also built to the building regulations.  Option 2 increases energy bills for these homes too, putting some of society's most vulnerable people at increasing risk of energy poverty.

Furthermore, the entire premise that these FHS homes will be zero carbon ready is based on an assumption that grid electricity becomes zero carbon pretty quickly.  Adding hundreds of thousands of electrically heated homes to the grid without at the same time taking an opportunity to add millions solar PV panels to the grid each year on the roofs of those homes will delay and make more difficult the job of decarbonising the grid, so Option 2 fails on the measure of reducing operational carbon emissions as well.

How Much Solar?

The consultation document says the amount of solar is 40% of ground floor area, but tucked away in an uncharted corner of the associated documents (the full notional house specification) is the calculation that turns the area into something more meaningful - the total panel power in kilowatt-peak (kWp), and there has been a significant change here too.

While 40% of ground floor area is unchanged from the current building regulations, the conversion factor from area to power has changed, see the illustration below. 

Solar PV provision in the Notional House of Selected Building Regulations

The previous conversion factor (1/6.5) assumed solar PV panels have a power density of 153Wp/m2.  The new factor (1/4.5) is a figure of 222Wp/m2.  So while at first glance the solar PV provision in the specification has not changed, it has in fact increased by 45%.

Is this justified?  Well the simple answer is yes.  Solar panel power density has increased over time from around 150Wp/m2 in 2015 to 207Wp/m2 today, with 220Wp/m2 looking probable by the time the regulations are in force.  (The table below shows the increase in specific power for Clearline fusion solar PV panels since 2015).

Specific Power Density of Clearline fusion solar PV panels since 2015

The challenge that is being voiced by colleagues in the housebuilding industry is that some of their house designs do not have sufficient roof space to accommodate the amount of solar called for in the notional house specification in Option 1.  These houses will have hipped roofs, dormer windows or other roof designs that limit the roof area available for solar. 

Under current regulations these house types can be compliant because the amount of solar in the 2021 regulations is lower than the FHS and also because other improvements can be made to the specification in excess of the notional house.  With the addition of higher air tightness, ventilation and heat recovery in Option 1 as standard, the opportunities to make up for less solar with improvements elsewhere are reduced.

The fact that the orientation of the solar in the notional house is assumed to be South, rather than following the orientation of the actual house makes it even harder to comply with the specification, the whole further exacerbated by the error in the Home Energy Model mentioned earlier, that grows as orientation deviates from South.

For this reason, housebuilders are saying that they cannot get behind Option 1 and will (regretfully and with heavy heart) be shouting loudly for the cheaper Option 2.

If government is minded to agree with housebuilder's arguments that they should not be required to ever change the design of houses they offer, then there are a number of potential adjustments that would make Option 1 more feasible for housebuilders:

• Fix the HEM so that it correctly accounts for solar orientations away from South
• Change the notional house specification so that the solar orientation is as per the actual house, or the best elevation of the actual house rather than assuming always south
• Change the notional house specification so that the actual roof design is taken into account when setting the % of floor area to solar.  It is far more expensive to build a complex roof than to put solar on a simple roof so the risk that this could become a loophole is slim.  This approach would better follow the logic of the notional house - the actual shape of the building below the roof is taken to be the same as the actual house, why not the roof?  A suitable formulation would be to ask for 40% of floor area or a max-fit power based on the available roof, agreed by the energy assessor, whichever is lower.
• Finally, regulators could go for Option 1.5, half way between Option 1 and 2 - retain solar, which is the measure with the highest impact on primary energy and protects residents from increased and volatile energy bills, but to leave out the other additional measures in Option 1.  This would give housebuilders design choices to allow them to 'flex' their specification for homes that struggle to accommodate the solar to match the notional house by increasing specification elsewhere.

I believe that many people that work for housebuilders genuinely want to be part of the solution to the climate crisis, and that with a few simple changes, Option 1 can and should be made to work for both the housing industry and the solar industry.

Scotland to Adopt Passivhaus Standard for new Houses

 

Linn Way, Garelochhead - a Passivhaus Development of 10 homes by Argyll Community Housing Association (ACHA) 

On 15th December 2022, Patrick Harvie, Minister for Zero Carbon Buildings, Active Travel and Tenant's Rights (there's a job title for you), wrote to Alex Rowley, a member of the Scottish Parliament to inform him that his campaign for new homes in Scotland to be built to Passivhaus standard would become law.

Back in November, Rowley had  introduced a Member's bill to the Scottish Parliament, the "Proposed Domestic Building Environmental Standards (Scotland) Bill" – which would introduce new minimum environmental design standards for all new-build housing to meet a Scottish equivalent to the Passivhaus standard.

The bill followed on from a public consultation which Rowley had organised earlier in the year.  

The consultation received 629 responses which included submissions from  Cala Group Ltd,  Barratt Developments PLC, the Scottish Federation of Housing Associations and The Royal Incorporation of Architects in Scotland - people were taking this seriously!

Having garnered the support of more than 18 MSPs from at least two political parties, the Bill was due to be debated in the Scottish Parliament.  Instead the Scottish Government choose to avoid the debate by announcing that it intended to give the Bill effect through subordinate legislation within two years.

"I hereby state that the Scottish Government will make subordinate legislation within two years, to introduce new minimum environmental design standards for all new-build housing to meet a Scottish equivalent to the Passivhaus standard"  Patrick Harvie MSP, 15 December 2022

So where does this leave the future direction of Scottish Building Regulations?

The Passivhaus standard is remarkably simple to summarise

1. Maximum space heating demand cannot exceed 15kWh per square metre of net living space per year, or 10W/m2 of peak demand

2. The Primary Energy Demand (total energy used for all domestic applications (heating, hot water and domestic electricity) must be less than 60kWh/m2 per year.

3. Airtightness cannot exceed 0.6 air changes per hour at 50 Pascals pressure.

A key difference between the Passivhaus standard and the Scottish (and rest of UK) building regulations is that Passivhaus is absolute while Building Regulations are relative.  

UK building regulations work by taking a house shape you want to build, calculating the annual energy use if that house was built following an approved specification (the notional house).  The specification for the house you build cannot be worse than the notional house.  

You can read more about how UK building regulations for energy work in this earlier post.

Buildings that minimise the ratio of their surface area to their inside volume are intrinsically more energy efficient than buildings with a high surface area to volume ratio.  Simple rectangles outperform complicated (but architecturally appealing) building forms with cross wings, porches, bay windows, dormer windows and the like.  Large buildings out perform smaller buildings on this measure too.  Linked buildings (terraced, semi-detached) outperform individual buildings.

Credit: BRE Passivhaus Designers Guide

Passivhaus rewards efficient building form because it is concerned with the absolute energy use, UK building regulations ignores building form because it compares the performance of that house design with a notional house of the same shape.

In terms of the resulting specification that might achieve the standard, the Passivhaus Institute estimates that for most cool-temperate climates : 

Walls, floors, roofs: A heat transfer coefficient (U-value) of 0.15 W/(m²K)

Windows:  U-value of 0.80 W/(m²K) 

The notional house specification for Scottish Building Regulations 2022 uses a U value of 0.15 for walls, 0.12 for floor, 0.09 for roofs and 1.2 for windows.   So with the exception of windows, Scotland will be building homes that already largely meet or exceed the specification, so long as building shape and orientation does not require higher levels.

Air permeability is 5m3/h.m2 in Scottish Building regulations notional house.  Taking a storey height of 3m, this translates into 1.67 air changes/hour.  To get to 0.6 air changes/hour will require a big improvement to an area that has proven to be challenging in the past, especially when building in volume with traditional methods rather than off-site manufacture.

The final big change is  that Scottish (and UK) Building Regulations only consider energy used for space heating, domestic hot water, and electricity for lights and services (pumps and controls).  It ignores the main part of electricity used in the house to run appliances and plug-in devices - a weakness that becomes increasingly noticeable as homes become better insulated.

By contrast the Primary Energy Demand requirement in the Passivhaus standard considers all the energy use in the property with allowances for electricity consumption by residents using appliances and electronic devices.

It is worth noting that energy generated by Photovoltaic (PV) systems may not be counted against the Primary Energy target in the Passivhaus calculator (called PHPP). This is a deliberate implemented to prevent poor standards of energy efficiency being offset by the use of renewable energy.  As emerging technology maximises the use of solar generated electricity (for example solar diverters and battery storage), this is looking increasingly anachronistic.

The Passivhaus Institut is moving towards including PV  generation in Passivhaus certification. This will be in the form of new classes "Passivhaus Plus" and "Passivhaus Premium". These standards require the same fabric standard as any other Passivhaus but higher reductions in the primary energy demand compared with the existing Passivhaus standard, normally achieved using on-site generation.

This decision by the Scottish Government has really has the potential to overturn an orthodoxy that for years has based energy efficiency standards for homes on the government's own calculation - the Standard Assessment Protocol (SAP), which has been the overarching mechanism to demonstrate compliance with building regulations on energy for decades.  

How revolutionary this change turns out to be, well, time will tell - after all the Scottish government only committed to a 'Scottish version of Passivhaus' which could be as limited as a new version of SAP with exceptionally high U values and airtightness in the notional house.  Alternatively if the founding principles of Passivhaus are followed, it could turn out to be a radical shift in the way the building regulations are delivered in the UK.

New Building Regulations for Scotland

In June 2022 the Scottish Government published its consultation response on changes to further tighten the Building Regulations for energy efficiency.  New developments in Scotland seeking a Building Warrant after 1 December 2022, will need to meet the new regulations.

Although most respondents to the consultation were in support of a higher performance target (delivering a 57% reduction in CO2 emissions), the government instead opted for the lower performance target which is expected to reduce the CO2 emissions of new homes in Scotland by 32%.

The central element of the building regulations for energy is the so-called 'Notional House Specification' which defines the target that a developer must meet. (For a full explanation of how the Notional House Specification works see this earlier blog).

The 2022 Building Regulations in Scotland gives three Notional House Specifications - one for homes heated with a heat pump, another for homes heated by a heat network and a third based on mains gas  for homes using any other heating systems.

The table below contrasts key elements of the new Notional House Specification with those in the previous version of Scottish Building Regulations and also with the new regulations that came into force in England this year.

As can be seen, the new Scottish Building regulations require a significant improvement in U-values (insulation) and airtightness compared to the current (2015) regulations.  They also come in slightly better than the latest regulations for England (it would have been a major surprise if they didn't!)

Of interest to solar industry participants will be the increase of PV provision in the gas heated notional house compared to the 2015 regulations.  

In 2015 Scotland became the first of the nations to add solar PV to the notional house - the amount asked for was the dwelling total floor area in m2 x 0.01kWp, which corresponds to 20Wp of solar per 1m2 of ground floor area (for a two storey building of equal ground and first floor areas).  The new requirement is for 0.4 x ground floor area in m2 / 6.5 -  which works out to be 62Wp of solar per 1m2 of ground floor area - around 3 times more solar per house.

Other Changes

Scottish Goverment also changed the way the benefits from solar are taken into account in the calculation.  The energy and carbon benefit of on-site generation is capped at the level assessed as being used on site (excluding the energy exported the grid).  This change is likely to incentivise the use of technologies to store excess solar energy for later use - for example battery storage or energy diverters that heat hot water with excess solar energy.

Good News for Solar?

The new regulations look like great news for solar in Scotland.  The Building Regulations are 'solution neutral' allowing developers to choose a combination of heating system, insulation and on-site generation that equals or exceeds the performance of the Notional House Specification.  Since both developers and house buyers prefer gas boilers to heat pumps, this regulation change is likely to increase the amount of solar installed on new homes in Scotland because of the three-fold increase in panel power in the specification.

However, the cloud on the horizon for the solar industry is another piece of legislation - the New Build Heating Standard, which will remove the gas boiler option for housebuilders by banning their use in new homes.  

Under these Building Regulations, once a housebuilder is forced to use heat pumps, the requirement for solar drops away because the Notional House Specification for heat pump heated homes does not include it.

Solar PV and heat pumps are a great match, with solar offsetting higher running costs of heat pumps - why would Scottish Government have no solar on the heat pump specification?  It all boils down to the cost for the developer - the regulations have been set up to encourage housebuilders to consider heat pumps before the 2024 regulations, and the notional house has been set up to try to level the playing field for build costs - leaving waste water heat recovery and solar off the heat pump specification.

No heed has been paid to the increased running costs the home owner will suffer in a heat pump heated home compared to a home with a gas boiler and solar PV.

Once there is a regulatory requirement in place to use a heat pump, then then the incentive to try to lower the cost of a heat pump installation versus gas plus solar falls away.  Scottish Government should commit to review the building regulations at the same time as bringing in its New Build Heat Standard to require solar PV on heat pump heated homes too.  This way it will ensure a just energy transition and reduce the risk of a consumer rejection of heat pumps.

Owner Occupiers - Government's Final Frontier for Energy Efficient Buildings

Dutch Householders Must Now Include Renewables When Making Major Home Improvements
Image (C) Viridian Solar

UK energy efficiency laws have been made for new homes and new commercial buildings, for houses owned by private landlords (in England) and those managed by Social Housing  Providers (in Scotland), but the biggest part of the building stock has so far sailed on without interference from lawmakers in the UK - those owned by private individuals.

Unlike owner-occupiers; house-building companies, local authorities and social landlords don't get to cast a vote in a general election, making them easier targets for potentially costly or unpopular new laws.  When David Cameron's celebrated coalition government put forward an idea to require improvements to energy efficiency alongside home renovations called 'Consequential Improvements' in 2012 it survived only a few days after being  dubbed the 'Conservatory Tax' by the Daily Mail.  

See also this post from 2013 on the death of the Consequential Improvements idea.

If you are doing building works on your home, the current building regulations apply to the new bits you build, so any new walls and roofs would be insulated to modern levels.  The idea of the Consequential Improvements proposals was that (subject to the work exceeding a threshold of size) you should also have an obligation to make energy efficiency improvements to other parts of the building (for example topping up loft insulation or installing an efficient boiler or solar panels).

Looked at from the perspective of today, with occupants of inefficient housing most exposed to rampant energy cost inflation it certainly looks like a missed opportunity.  Hooray for the Daily Mail - a genuine force for good and yet again, as so often, on the right side of history!  Householders were freed from having to pay "hundreds of pounds extra on energy efficiency when they build an extension or fit a new boiler" in return for the privilege of paying thousands of pounds extra every year for soaring energy bills.

10 Years Later, in The Netherlands

Across the North Sea, the Netherlands government has brought in something that looks uncannily like the UK proposals of 10 years ago.

From February 1, 2022 an update to the "Bouwbesluit 2012" (Building Decree) regulations  place a requirement on renovation projects in Netherlands to include renewable energy.

Only renovation projects that meet both of the following requirements fall under the new rules:

 (a) more than 25% of the external envelope (ground floor, walls and roof) of the building is changed, and

(b) a heating or cooling system is part of the renovation - for example changing a central heating boiler, or replacing a third or more of the radiators.

The law applies to both housing and non-domestic properties. 

If a renovation falls under the new rules then renewable energy must be installed.  The amount you should install is derived from a formula which specifies the amount of renewable energy per year the system should yield:

30 x Aroof / Ag  kWh/m2.yr  (subject to a maximum of 30kWh/m2.yr)

Aroof is the roof area and Ag the "Gebruiksoppervlak" (usable floor area) as defined in NTA 8800:2020+A1:2020

So taking the example of a house with 100m2 of total usable floor area split in the typical Dutch style over ground floor and first floor in the roof , say 60 m2 to ground and 40 m2 to first floors together with a roof pitch of 45 degrees.  By trigonometry, the roof area is 1.41 x the ground floor area - 84.6 m2.  The calculated annual renewable energy is 30 x 84.6/100 = 25.4 kWh/m2.yr, or 2,540kWh/year in total when multiplied by the 100m2 total floor area.

This quantity of renewable energy production is very easily met with solar - around 3kWp would do it.

Certain exemptions are possible.  If you can show that the measures to meet the requirement would have a payback longer than 10 years, then you can install a smaller amount that does pay back in under this time.  Buildings with an occupancy type with very low energy use are exempt.  Finally buildings with special circumstances such as monumental buildings can be exempt from the requirement altogether if their protected status prevents the installation of measures.

The building owner has a choice of options to meet the requirement - for example joining a heat network, solar PV or installing a heat pump.  For solar PV, the Dutch government has helpfully provided a solar calculator to determine how much Solar PV is needed, based on NTA 8800:2020+A1:2020, a standard providing a method for the determination of energy use in buildings.   The solar calculation is from Chapter 16 of NTA 8800 and takes the installation details into account (orientation, shading, etc…).

In most cases the requirement for solar PV works out at between 15 and 20% of the roof surface area.  For example: Using  Clearline fusion PV16-335-G1 roof integrated solar panels (which are classed as ‘moderately ventilated’ because the air gap behind the panels exceeds 100mm); on a South facing orientation; on a 35⁰ pitched non-shaded roof; on a building of 100m2, you would need 8 panels to meet the requirement.

From the point of view of the solar industry, which offers a simple, proven and low-cost way to comply with the renewable requirement, this is a welcome change that ought to result in a good deal more solar PV on homes in the Netherlands.  

Looking at the requirements more critically through the lens of energy efficiency it does strike me a somewhat one-dimensional.  Why not require changes that improve fabric efficiency - thermal insulation and draft-proofing as well?  Perhaps the Netherlands building stock is more air tight and better insulated than that in the UK, but I'd be very surprised if there isn't lots of stock that could also benefit from improvements in this area.  The 'fabric first' brigade in NL must be looking for their pitchforks and burning torches.

The new renewables obligation in the Dutch Bouwbesluit 2012 does have the advantage of being very simple to calculate, implement and install.  Perhaps it's an example of pragmatic legislation that doesn't letting the perfect become the enemy of the good?  Just getting on and doing something to make a difference!  Is there a Dutch equivalent of the Daily Mail?  Where was it when it was needed to stamp all over a progressive and practical idea for improving the world?

 

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.

 

The Social Housing Decarbonisation Fund – A Role for Solar PV

Padiham Near Burnley where 108 electrically heated homes were improved with external wall insulation, new windows and hot water systems, and Clearline fusion roof integrated solar PV by social landlord Places for People

On 19th October, the UK government revealed its much anticipated Heat in Buildings Strategy.  Headline writers entirely focused on only one element of the announcement -  the Boiler Upgrade Scheme, a plan to give grants of £5,000 to people replacing fossil fuel heating by installing a heat pump in their own home.  (See for example coverage from Sky News, Daily Telegraph, The Guardian, The Sun, BBC News).

However the Strategy contained other initiatives which, while less-publicised, better address the barriers to the transition to electric heating - by helping mitigate both their high running costs and expensive installation. These funds aimed at social landlords and Local Authorities takes a more holistic approach since they can also be used for measures that tackle running costs by reducing heating demand and generating power on-site.

The Social Housing Decarbonisation Fund

Less reported, but with a budget many times higher than the headline-grabbing Boiler Upgrade Scheme is the funding announced for the next three years for delivery through Local Authorities and Social Landlords.  The Social Housing Decarbonisation Fund (£800m over three years) is for energy improvements to social housing and the Home Upgrade Grant (£950m) will be administered by Local Authorities and support energy efficiency improvements for low income households.

For the Social Housing Decarbonisation Fund, the approach is summarised as follows:

• Fabric first – heat loss prevention is prioritised before other energy efficiency measures
• Worst first – homes with lower starting energy performance attract more funding
• Upon completion homes must achieve a minimum Energy Performance Certificate (EPC) rating of C and maximum space heating demand of 90kWh/m2.year

It is set up as a competition, with applicants scored on how well they meet the goals above, as well as for deliverability and cost-effectiveness.  The landlord contributes at least 1/3 of the cost of the upgrade with 2/3 coming from the fund.  If a landlord takes the full grant and adds the minimum contribution only, then the amount that can be spent on each type of property is given below.  Landlords can elect to spend more on the property, but the extra is then provided by the landlord.

Starting EPC	Maximum Budget Supported (with maximum grant and minimum landlord contribution)
D	£15,000
E	£18,000
F	£24,000
G	£24,000

These are pretty chunky amounts.

Eligible measures are anything that improves the EPC, with the exception of new fossil fuel heating systems.  Low carbon heating is encouraged, but only after fabric measures have been implemented.  The tenant must be left better off - with lower energy bills.

This is where solar PV comes in -  due to the high cost of electricity compared to gas, replacing gas heating with electric heating will increase energy bills, unless the starting levels of thermal insulation are exceptionally low and can be improved by a very large amount.  (See my earlier blog – Real-World Heat Pump Running Costs)

The complementarity of solar PV and heat pumps is well-understood by social landlords, as can be seen by reviewing the successful bids in the Social Housing Decarbonisation Fund Demonstrator, which were announced March 2021 and I have put into summary form in the table below.

Bid	Award	Number  of homes	Measures
Aberdeen City Council	£2.2m	100	EWI, ASHP, PV
Argyll & Bute Council	£1.2m	130	EWI, ASHP, PV
Clackmannanshire Council	£0.3m	15	EWI, glazing, PV
Cornwall Council	£1m	75	EWI, ASHP, PV
Fenland District Council	£4.5m	160	EWI, glazing, PV
Leeds City Council	£4.2m	190	EWI, ASHP, PV
Barking and Dagenham	£9.6m	230	EWI, ASHP, PV
Manchester City Council	£3.1m	164	EWI, ASHP, glazing
Northampton Borough Council	£3m	150	EWI, ASHP, PV
Nottingham City Council	£2.3m	104	EWI, ASHP, PV
Nottinghamshire County Council	£0.8m	25	EWI, glazing, floor insulation
Kensington and Chelsea	£19.4m	535	EWI, ASHP, PV
Stratford-on-Avon DC	£1.4m	69	EWI, ASHP, PV
Stroud District Council	£1m	50	EWI, ASHP, PV
Sunderland City Council	£0.9m	59	EWI, glazing, PV
Warwick District Council	£1.4m	50	EWI, glazing, floor insulation
Wychavon District Council	£5.8m	236	EWI, ASHP, PV

Key: EWI – External Wall Insulation, ASHP – Air Source Heat Pump, PV – Solar photovoltaic panels

Fourteen out of seventeen successful bids, covering 2,103 out of 2,342 (90%) of the properties to be improved have solar PV among the measures to be installed.  In fact only one project (Manchester) is installing ASHP without PV.

With a total cost of £62.1m, the demonstrator projects grant component is an average of £26,000 per property – higher than the current ceiling, but due to solar PV being such a cost effective way to improve EPCs, it is likely to remain a feature of projects in the future waves.

This system approach to improving properties comprising significant improvements to insulation to lower heat demand, and combining low carbon heating with solar PV to keep a lid on the energy bills for residents seems far more sensible than a crude upfront grant to help cover some of the extra costs of the heat pump installation alone.

That winning combination of heat pumps and solar PV is well-understood by experienced practitioners of energy retrofit working in the social housing sector.  By contrast, owner-occupiers encouraged by generous grants to install heat pumps may find themselves on the phone to their local solar PV installer soon after their first electricity bills land on the doormat.