New Scottish Building Regulations Torpedo a Solar Success Story

On December 22nd 2023 Scottish Government published an update to the Building Standards Technical Handbook which will apply to new building sites where a building warrant is applied for after April 1st 2024.

The update to the handbook was made to implement the New Build Heat Standard which bans the use of ‘Direct Emission Heating Systems’ - gas or oil boilers in plain English - from newly built homes and some conversions of existing properties.  Instead, developers must now choose from a heat pump, direct electric heating (storage heaters or infrared panels) and connecting to a heat network (if available).

In 2015 Scottish Government introduced solar PV into its building regulations - well ahead of England which was to take until 2021 to catch up.  This has resulted in a thriving solar industry in Scotland, installing far more solar to domestic properties per head of population than the rest of the UK (see my earlier blog: How Progressive Building Regulations Made Scotland a Solar Powerhouse).  

Unfortunately, Scottish Government has ignored repeated warnings from Solar Energy Scotland that the introduction of the New Build Heat Standard without an accompanying adjustment to the Building Standards could threaten the success story of Scottish solar.

Working in Silos

To understand how the new regulations could harm the solar industry in Scotland we need a little background on how the building regulations work.  The regulations are not prescriptive, they aim to give the designer freedom to choose how to build the house - instead of defining each and every building element, the set a level of  energy performance that the house must achieve.

A developer must show that the house they are planning to build uses no more energy than a home of the same size and shape built according to a defined specification called the Notional House Specification.  (For more details on how this works see my earlier post on Energy in Building Regulations).  Over time the regulations have made new homes more and more energy efficient by changing the Notional House Specification to have a better and better energy performance.

The last major review of Building Regulations in Scotland (in 2021) introduced two specifications for the notional house - one for homes with heating by a gas boiler, the second for a house with a heat pump.

In order to 'nudge' developers towards using more heat pumps and away from polluting gas boilers the specification with the heat pump included a number of cost-saving relaxations in other areas - notably the omission of solar PV panels which were included in the gas heating specification. 

Although it might have been an admirable intention to nudge developers towards heat pumps (it didn't work by the way - gas boiler and solar remained the preferred design choice), it was clear that if the New Build Heat Standard was to come in without changing the notional house specification at the same time, then the only legal specification becomes the one with the heat pump, and solar would be dropped from the notional house in Scotland for the first time since 2015.

Unfortunately we were talking to two different sets of officials from Scottish Government - one working on the building regulations and the other working on the New Build Heat Standard.  Our concerns were ignored.  The latest regulations have enacted the boiler ban and left the Notional House Specification unchanged.

The Impact on Solar  for New Homes in Scotland

This unwelcome development is not necessarily all bad news for solar.  

First of all, housebuilders may choose to combine solar PV with a heat pump in their designs, not least as a way of keeping a lid on energy bills for their customers.  This change to the building regulations is probably the first ever update to result in higher bills for consumers.  Electricity costs far more than gas does - and the enhanced efficiency of heat pumps does not make up for the difference.  Developers can offset this rise in bills by keeping solar in their design.

Secondly, solar has become a common sight in new developments across Scotland and customers have come to expect it on new homes and increasingly see energy efficiency as a reason to buy new rather than in the general housing market.

Third the gas boiler plus PV specification still applies to homes with direct electric heating.  Developers may explore this option, adding better insulation to the point where space heating demand is reduced to an absolute minimum - especially for smaller properties.

Finally, since new regulations only come into force from the point of applying for a building warrant it is likely to take a year or so before sites begin construction under the new regulations, and 2-3 years before the majority new homes being built are to the new standard.  What could change in this time?  Here are some thoughts:

• Alex Rowley MSP proposed that Scotland move to a Passivhaus basis for building regulations, and in December 2022 Scottish Government announced that it would legislate for this by December 2024.  We may have a new version of the regulations in less than 12 months time.
• The European Commission announced a strengthened Energy Performance of Buildings Directive in December 2023 in which "Installing solar energy installations will become the norm for new buildings".  The current Scottish Government is very keen on aligning its regulations with the EU with its goal of quitting one union and re-joining another.
• A new Future Homes Standard for England is embracing smart energy, time of use electricity tariffs, energy storage and solar generation with a new half-hourly calculation method, and is beginning to make the Scottish approach look rather passé.  A strong Future Homes standard specification with heat pump and solar will encourage the Scottish Government to surpass it.
• Who knows how far battery storage, solar and smart energy technology will developed by this time?  If we were to go back four years, battery storage was only for dedicated enthusiasts and off-grid applications - now it's included with around half of all retrofit solar installations.  The performance and cost of solar and energy storage continues to make the technology more widely applicable and attractive.  More recent innovations such as time of use tariffs and electric vehicle to grid charging will only add to the advantages of having solar on your home.

Whether the omission of solar PV from the notional house specification in Scottish building regulations slows the adoption of solar PV in Scotland remains to be seen.  What is clear is that, at worst, it will only temporarily slow its rise.

 

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.

Do We Need to Talk About Fugitive Emissions from Heat Pumps?

 Could the Benefits of Future Building Standards be Affected?

It’s not a recent study, but its contents may have become newly relevant.  In March 2014, the then Department for Energy and Climate Change (DECC) published the results of a study commissioned from Eunomia Research and London Southbank University - “Impacts of Leakage from Refrigerants in Heat Pumps”.  

Governments are looking for a huge increase in the number of heat pump installations in an attempt to decarbonize the heating of buildings.  Leading the charge will be developers of new homes, since these are the easiest to legislate for.  The UK government has unveiled its Future Homes Standard and Scottish Government is consulting on a New Build Heat Standard.  Neither of these regulations would force developers to install heat pumps in the homes they build, but the standards will be set in such a way that fossil-fuel powered boilers will not comply - the clear intention is to use regulation of the new-build sector to scale-up the heat pump industry.

The approach being considered by Scottish Government is to require heating systems to emit no carbon dioxide at the point of use.  Technologies considered to meet this requirement are direct electric heating (panel heaters, underfloor electric, electric boilers), heat pumps and also heat networks (where you could be burning coal at the far end of the pipe but this doesn't count as point of use).

But since the goal of all of this is to reduce global warming, then surely the emissions of other gases that cause global warming should also be considered.  It turns out that the refrigerant gases used inside some heat pumps are greenhouse gases that are thousands of times more powerful than carbon dioxide.  So long as they stay safely inside the heat pump during its life and are collected up at end of life, there is no problem, but the question the report set out to answer was how much of this refrigerant gas is lost to leaks, and how big an issue could that be?

The researchers examined the logbooks of heat pumps to see how often they had to be re-charged with refrigerant, and also conducted experiments where heat pumps were emptied and then recharged with refrigerant gases and the amount lost in the process was measured.

How Much Refrigerant is Lost?

The report found that:

• 10% of domestic heat pumps experience a leak of refrigerant in any given year
• The median amount lost was 35% of  charge (the total refrigerant gas in the system)
• So the equivalent annual leakage rate was 3.48% of the charge
• The mean refrigerant charge for a domestic heat pump was 3.3kg
• So the mean annual leakage for a domestic heat pump is 0.114kg of refrigerant
• Decommissioning losses at end of life were 15% of charge 
• Commissioning and recharging losses were around 0.06kg

So if we assume a 20 year life for the heat pump, a charge at commissioning, one recharge and decommissioning at the end of life then the total losses are:

Filling: 0.06kg 

Recharge: 0.06kg

Leakage: 10% x 35% x 3.3kg x 20 years = 2.31kg

Decommissioning: 15% x 3.3kg = 0.495kg

Total Refrigerant Losses over 20 year life: 2.925kg

Refrigerant loss per year: 0.146kg

Does it Matter?

At the time of the report, R410A was the most used refrigerant.   It has a Global Warming Potential (or GWP) of 2,088, which means that 1kg of R410A released into the atmosphere has the same effect on global warming as if 2.088 tonnes of carbon dioxide were emitted.

So, a refrigerant leakage of 0.146kg per year from a heat pump is like it emitted 305kg of CO2 per year.  This is expressed as 305kgCO2e (CO2 equivalent)

The authors of the report compared the impact of refrigerant leakage to the benefits of the low-carbon energy delivered by the heat pump.  The annual heating load for a domestic property was assumed to be between 10 and 25 thousand kWh and it was concluded that the impact of leakages was small. 

 

However, the leakage losses from the heat pump does not vary with the amount of heat it supplies.  The more heat the heat pump delivers, the less of a penalty the refrigerant leakage is per unit of heat delivered.  Conversely the more energy efficient is the building and the lower its heat demand, the more of a penalty the leakage becomes per unit of heat.

Since the regulations are aimed at new homes, perhaps we should instead consider refrigerant emissions in relation to the heat demand of these.

Homes that are built today have very much higher levels of airtightness and insulation than the average building stock.  Based on energy calculations we see in our design team, an average sized new build house (say 85m2 total floor area) will have space heating demand around 3,300kWh per year to which you can add 1,600kWh per year for domestic hot water.  The proposed standards envisage tightening rules on insulation too, so by then buildings will have an even higher level of thermal efficiency than this.

Many houses are now being built to ‘passivhaus’ standards which remain at a comfortable temperature most of the year without heating, so the annual heating demand approaches a minimum which is that needed for hot water for showers and baths.

If we divide our 305kgCO2e figure by these lower figures for annual energy demand, the contribution to global warming per unit of heat delivered looks very different.

Table 1: Release of refrigerant gases per  kWh heat delivered (CO2e)

Annual Heating Budget (kWh)	2,000	3,000	5,000	10,000	25,000	Gas Heating CO2 emissions for comparison
Annual Emissions from Refrigerant Leakage per kWh of heat delivered (kgCO2e)	0.152	0.102	0.061	0.031	0.012	0.208

 

The table shows the global warming impact of refrigerant leakage for each unit of heat provided by a heat pump running R410A for different levels of annual heat demand.

It can be seen that for buildings with high heating demand (such as the levels assumed by the report authors), the CO2e figure is very low compared to delivering the same heat with gas heating.  However for very highly energy efficient properties the penalty from the refrigerant leakage rates is very significant – approaching that of gas heating.

Current Refrigerants in Use

Of course, we would expect heat pump technology to have moved on in the last six years and with regulations aiming to phase out the use of the refrigerants with the highest GWP, maybe R410A is no longer in use?

I did a quick straw-poll of the products available today from a range of heat pump manufacturers.  As you can see from the table below, there are clearly now models available that work with refrigerant with much lower GWP than the R410A used in the calculation above.  Notable leaders are products from Vaillant using R290 (which is propane gas and has a GWP of 3) and from Mitsubishi using R744 (which is carbon dioxide and so has GWP 1) - although both these manufacturers still offer models with the much higher GWP refrigerant for some reason, perhaps cost or efficiency?

It is also clear that there are also many, many models still being sold today that are using refrigerants with GWP above 1,000 and that R410A is still very popular.

 

Company	Model	Refrigerant	GWP	Source
Daikin	Altherma 3 H HT - EPRA014-018DW	R32	675	https://www.daikin.co.uk/en_gb/products/epra014-018dw.html
Daikin	Altherma 3 R - ERGA04-08EVA	R32	675	https://www.daikin.co.uk/en_gb/products/erga04-08eva.html
Daikin	Daikin Altherma - EDLQ-CV3	R410A	2,088	https://www.daikin.eu/en_us/products/edlq-cv3.html
Daikin	Altherma R - ERLQ-CV3	R410A	2,088	https://www.daikin.eu/en_us/products/erlq-cv3.html
Kensa	Shoebox	R134A	1,430	https://uh8ex3jph2xqg0pb4bs7if12-wpengine.netdna-ssl.com/wp-content/uploads/2014/03/TI-Shoebox-heat-pump-v6.3.pdf
Kensa	Evo	R407C	1,774	https://uh8ex3jph2xqg0pb4bs7if12-wpengine.netdna-ssl.com/wp-content/uploads/2017/02/TI-EVO-v6.0.pdf
Mitsubishi	Ecodan R744	R744	1	https://les.mitsubishielectric.co.uk/products/heating/domestic/outdoor/ecodan-quhz-monobloc-air-source-heat-pump
Mitsubishi	Ecodan R32	R32	675	https://les.mitsubishielectric.co.uk/products/heating/domestic/outdoor/ecodan-r32-ultra-quiet-puz-monobloc-air-source-heat-pump
Mitsubishi	Ecodan R410A	R410A	2,088	https://les.mitsubishielectric.co.uk/products/heating/domestic/outdoor/ecodan-puhz-ultra-quiet-monobloc-air-source-heat-pump
Panasonic	Aquarea HT Bi-bloc F Generation	R407C	1,774	https://www.aircon.panasonic.eu/GB_en/product/aquarea-f-generation-ht-bi-bloc-single-phase-three-phase-heating-only-shf/
Panasonic	Aquarea T-CAP Bi-bloc H Generation	R410A	2,088	https://www.aircon.panasonic.eu/GB_en/ranges/aquarea/t-cap/
Panasonic	Aquarea High Performance All in One Compact J Generation	R32	675	https://www.aircon.panasonic.eu/GB_en/product/aquarea-high-performance-all-in-one-compact-j-generation-1-phase-r32/
Vaillant	Arotherm plus	R290	3	https://www.vaillant.co.uk/downloads/aproducts/renewables-1/arotherm-plus/arotherm-plus-spec-sheet-1892564.pdf
Valillant	Arotherm Split	R410A	2,088	https://www.vaillant.co.uk/for-installers/products/arotherm-split-heat-pump-58752.html
Valillant	Arotherm	R410A	2,088	https://www.vaillant.co.uk/for-installers/products/arotherm-air-source-heat-pump-2944.html

 

Conclusions

Based on the report, it appears to me that the level of “Fugitive emissions” from heat pumps is significant enough that heat pumps with refrigerant of high GWP  should not be considered as zero carbon (equivalent) at the point of use.  

This is especially the case when the heat pump is providing heat to a highly energy efficient new building and the emissions ‘cost’ is spread over a much smaller heat ‘benefit’.

Perhaps legislators should consider the global warming potential of refrigerant in heating systems when they create new building standards?  Since heat pump models are available with improved refrigerants, perhaps they should consider applying a ceiling GWP value to the refrigerant in use?

I would be interested to hear from colleagues in the heat pump industry about whether this issue has been much discussed, and what the future direction of travel in heat pump technology is to address the likelihood or impact of leakage of refrigerant - please comment below!