Planning policy - section 3F: research

6. Proposal 2: A Whole Building Approach

6.1 Key Points

Policy Overview

• This proposal takes a whole building approach to CO₂ emission reduction and diverges significantly from current single issue Section 3F Policy.
• It reinvents this policy in a way that plays to the strengths and skillsets of Planning, whilst complementing and aligning constructively with the whole-building approach taken by Building Standards.
• It focuses on the domestic sector
• The overarching intention is to limit the annual energy demand (AED) in new buildings to an acceptable level:
  i. This acceptable annual energy demand (AAED) will be calculated on a per capita basis.
  ii. It will be based on the predicted AED of a modest-sized energy-efficient dwelling, to avoid adverse impact on the ability to deliver essential domestic infrastructure such as affordable housing.
  iii. A modest-sized dwelling will be defined as between 45m² and 100m² (Appendix E)
• The objective of this mechanism is to:
  i. Realise the recommended 3-step holistic approach to reducing CO₂ emission from buildings: reduce energy demand, increase efficiency of energy use, and increase the use of zero-carbon renewable energy.
  ii. Recognise that design plays a significant role in reducing energy demand, and incentivise good design, passive design responses and innovative approaches.
  iii. Prioritise fabric energy efficiency as a means of reducing energy demand.
  iv. Promote the use of zero-carbon renewable energy sources (LZCGT).
  v. Address the finite nature of resources, issues of personal responsibility and determine a more fair and equitable share of resources for everyone.
  vi. Directly address the energy consumption issues related to scale and excessive per capita heated living space in large domestic buildings.
• Compliance with the policy will be allowed through any combination of design, fabric energy efficiency, equipment efficiency or LZCGT: i. The use of LZCGT will not be mandatory but it is expected this will be needed to meet the target levels. As emissions reductions targets from buildings get closer to 100% net-zero emissions, then by default LZCGT would need to be employed to offset the remaining energy demand after other passive measures have been adopted.
  ii. Applicants will be encouraged to meet the acceptable annual energy demand (AAED) calculated for their proposed dwelling through good design and fabric energy efficiency measures alone if possible.
  iii. If a building does not initially meet the acceptable annual energy demand (AAED), then any remaining energy demand above the acceptable level must be met by zero-carbon renewable energy sources.
• It is recognised that this policy will impact far greater on large dwellings than more modest ones, due to the small average occupancy rates of large dwellings (BRE, 2008).
• The metric used will be kWh/annum rather than a carbon metric, because: i. Data extracted from SAP will be expressed thus.
  ii. It emphasises the need to first and foremost reduce energy demand.
  iii. It is a tangible and easy to understand metric with real world meaning for all stakeholders. As such it is easier to directly manipulate and comprehend the impact of specific changes during the design process.
  iv. It allows the contribution of LZCGT to the annual energy demand to be clearly and easily quantified.
  v. It is the obvious metric to link LZCGT contribution, annual energy demand, and other regional or national energy networks. It is therefore extremely useful for ongoing reporting and in the development of future regional or national energy policy.

Compliance Targets

• The acceptable annual energy demand per capita (AAED/Capita) was calculated by modelling the predicted annual energy demand for dwellings ranging in size from 25m² to 300m² using formula prescribed in SAP 2012 (BRE, 2014).
• Two different scenarios were developed to represent evolving fabric energy efficiency standards. These were based on space heat demands of 30kWh/m².annum (Present and Near Future 2020-2021) and 15kWh/m².annum (Future 2024 - 2050).
• The AAED/Capita level determined through this process is based on the predicted annual energy demand of a modest-sized energy-efficient dwelling between 45m² and 100m². It will be applied to all dwellings regardless of size.
• The recommended AAED/Capita targets levels are:

2021 AAED/Capita = 1910 kWh/annum
2024 AAED/Capita = 1500 kWh/annum

• As the country evolves towards 2045 and net-zero carbon buildings, if the annual energy demand/capita of the proposed dwelling exceeds this acceptable level, the surplus demand must be met through zero-carbon renewable energy sources.

Compliance Documentation

• Compliance is basically determined by comparing three values calculated for the proposed dwelling.

Acceptable Annual Energy Demand
AAED

Annual Energy Demand
AED

Zero-Carbon Adjusted Annual Energy Demand
ZCAED

• Compliance is achieved if either of the following hold true:

Compliance Method 1: (With / Without LZCGT)
AED ≤ AAED

Compliance Method 2: (With LZCGT)
ZCAED ≤ AAED

• The compliance documentation was designed with the objective of making the entire process as easy as possible for all stakeholders, whilst taking the opportunity to collect useful data for research and planning purposes.
• It comprises of a standardised Excel spreadsheet, which should take no more than 10 minutes to complete (Appendix C); data used is extracted from the DER worksheet of the SAP document submitted to Building Standards; there is no need to have knowledge of SAP calculations to complete the spreadsheet; Excel will perform all necessary calculations automatically.
• The calculation process is simplified as much as possible and remains focussed on the annual energy demand of the proposed dwelling and the contribution of the different systems, fuels and LZCGT.
  i. The metric used throughout is kWh/m².
  ii. The contributions of different systems, fuels and LZCGT are defined as zero-carbon, low-carbon, grid electricity, bio-carbon or fossil fuels.
  iii. These are colour coded to indicate preferable choices.
  iv. Only zero-carbon energy sources are used to calculate the zero-carbon adjusted energy demand (ZCAED)
• The compliance procedure is quite flexible and there are several ways that a designer can bring a non-compliant building into compliance, either by reducing the annual energy demand (i. – iv.) or employing additional zero-carbon renewable energy systems (iv. – vii.). The compliance spreadsheet used alongside SAP can be exploited as a design tool to explore these options:
  i. Revise the Building Design: consider scale, built form, solar orientation, and other passive design measures to reduce overall heat demand.
  ii. Increase fabric energy efficiency.
  iii. Increase air tightness and employ MVHR.
  iv. Consider Solar Thermal or Waste Water Heat Recovery (WWHR).
  v. Consider Zero Carbon Electricity Generation: PV, Wind, Water etc.
  vi. Consider Zero Carbon Heat Generation: All types of Heat Pumps: GSHP, GWSHP, SWSHP, ASHP, EASHP, and SASHP. Be aware that in calculating the zero-carbon contribution, the electrical input will be subtracted from the output.
  vii. Community Heating: Numerous different energy sources may be employed within district heating schemes; these will be considered on their individual merits. Scaled zero-carbon renewable energy systems might include PV, Wind, Water, Tidal or Geothermal Energy, Waste Heat Recovery from Power Stations, or Waste Heat Recovery from Industrial or Agricultural processes.
• Only zero-carbon energy sources are used to calculate the zero-carbon adjusted energy demand (ZCAED). These do not include:
  i. Combined Heat and Power (CHP) that are based on fossil fuels or biomass. These are designated either low-carbon or bio-carbon depending on their fuel source.
  ii. Biomass and Biogas. These are designated bio-carbon. Both emit substantial amounts of CO₂ when burnt.

6.2 Approach Rationale

By embracing a more holistic approach to CO₂ emission reduction, this proposal re-envisions Section 3F policy as an ambitious standard that complements and aligns constructively with the whole building approach taken by Scottish Building Standards. Focussed on the domestic sector; the proposed policy centres on the idea of capping annual energy demand in new dwellings at an acceptable level per capita; and through this mechanism leverages better design solutions that address fundamental issues not tackled by the current system, prioritises fabric energy efficiency and simultaneously promotes the appropriate and responsible use of LZCGT.

6.2.1 A holistic Approach to CO₂ Emission Reduction.

Population growth, increased urbanisation and the pursuit of affluent modern lifestyles have relentlessly increased energy demand across the globe, despite attempts to reduce consumption and CO₂ emissions. In many developed countries, sociological shifts have led to the decrease in the size of households but a corresponding growth in their number, increases in per capita living space, higher expectations of thermal comfort, and ever expanding demands on electricity grids to satisfy highly technological lifestyles (Urge-Vorsatz et al., 2013; Beradi, 2016; Grove-Smith et al., 2018).

With respect to reducing CO₂ emissions in the built environment; the consensus among academics and industry professionals is that the most effective long-term strategy is to tackle the problem in a holistic manner (Urge-Vorsatz et al., 2013; Beradi, 2016; Grove-Smith et al., 2018). Typically by following three fundamental steps:

i. Reduce energy demand:

From a sociological viewpoint, this might involve questioning unsustainable expectations or taking measures to prompt lifestyle or behavioural change at either an individual or a societal level. From the perspective of building design it might involve greater reflection on the appropriateness, scale and sustainability of design proposals, consideration of passive design solutions, or increasing building fabric energy efficiency.

ii. Increase efficiency of energy use:

This should take into consideration all aspects of the design and construction process and might involve taking a systems approach to architectural design to optimize efficiency at a building level. Key areas for examination might include the embodied energy of building materials; judicious consideration of different materials, components and technologies; reducing energy losses and the reuse of energy through cascading energy systems or heat recovery; technological efficiencies of equipment and systems; and the optimization and maintenance of building systems.

iii. Increase the use of renewable energy:

The intention of the first two actions in this strategic approach is to reduce the energy requirements of the building by such an extent that the remaining energy demands can be practically and economically met by zero-carbon renewable energy sources. To maximise sustainability and reduce reliance and impact on centrally generated grid electricity these energy sources should preferably be generated locally.

In developed countries where demand for energy is very high and already far exceeds long-term sustainable levels, Urge-Vorsatz et al. (2013) suggest further measures might be necessary to change attitudes and behaviours at a societal level, including:

iv. Capping energy demand:

The concept of a '2000 Watt Society' developed in 1998 by the Swiss Federal Institute of Technology is an example of this type of tactic. It envisages an energy-sober society where total primary energy use per capita is limited to the global average of 17,520kWh/annum without any attendant loss in the quality of life (Morosini, 2010). This level of sustainability is achievable; however it requires commitment to a more frugal lifestyle that avoids excess particularly in relation to limiting heated living space and transport use, and avoiding excessive consumption of goods and services (Ettlin, 2013).

6.2.2 Prioritising Fabric Energy Efficiency.

Whilst supporting this holistic, integrated design approach which relies first and foremost on demand reduction through improvements in building design, fabric and services and also challenging individual behaviour and consumption of energy; most of the literature also advises prioritising fabric energy efficiency (Urge-Vorsatz et al., 2013). There are numerous reasons for this.

In our cold northern climate, the need for space heating tends to dominate energy demand. In 2018, it represented 64.8% of the total annual energy demand in the domestic sector in the UK (BEIS, 2019a). Improving fabric energy efficiency, by increasing insulation levels and airtightness, is therefore the most obvious and cost-effective way to cut energy demand and CO₂ emissions in new buildings (Beradi, 2016). At very high fabric energy efficiency levels there are balances to be made between embodied and operational energy, and initial investment and operational costs (Copiello, 2017; Grove-Smith et al., 2018). The optimum point for both appears to fall within the general region of the Passivhaus standard (Space Heat Demand ≤ 15kWh/m².annum). At this high level of fabric energy efficiency the size of heating system is reduced significantly and the associated cost savings tend to largely offset the cost of improving the fabric (Cotterell and Dadeby, 2013; Copiello, 2017; Currie and Brown, 2019).

On a macro scale, taking a fabric first approach reduces peak energy demand, and minimises the impact the building has on the national energy infrastructure and the ability to meet future energy demands (Currie and Brown, 2019). This is particularly important because the on-going decarbonisation of the national grid has already resulted in the need for increased capacity to cope with intermittent renewable energy sources, and electricity demands are only expected grow due to changing lifestyles, the switch to electrical vehicles and the increased use of heat pumps. Reducing energy demand where possible is vital for maintaining energy security in the long-term.

The timeframe over which CO₂ emission savings can be reasonably expected to be made also needs to be considered. Increasing fabric energy efficiency effectively reduces operational energy demand and CO₂ emission over the entire lifetime of the building (>100 years), whilst the effect of specifying LZCGT will be limited to the equipment's operational lifespan (15 - 20 years). Furthermore, because poor fabric energy efficiency is more difficult and costly to remedy at a later date than during initial construction; buildings that don't take a fabric first approach will tend to underperform over their entire lifespan. This leads to a certain level of CO₂ emissions being effectively locked-in to the built infrastructure (Urge-Vorsatz et al., 2013; Beradi, 2016).

Obviously for building occupants increased fabric energy efficiency also has many practical benefits including reduced energy bills, increased disposable income and a positive impact on their comfort, health and well-being (Payne et al., 2015; Copiello, 2017; IEA, 2019).

6.2.3 Promoting Design Solutions.

Tackling climate change is the fundamental issue of our time. Planning, with its wide sphere of influence, has the opportunity to mitigate the effects of climate change and reduce greenhouse gas emissions in many contexts and at a variety of scales (Appendix A). These include taking strategic macro-scale decisions related to Landscape Scale Planning, Sustainable Place-making and Large Scale LZCGT as well as offering individual micro-scale guidance in relation to Architectural Design, Architectural Design Details, and Building Scale LZCGT.

Focussing on the issue of reducing CO₂ emissions from buildings; Planning and Building Standards could be considered complementary to each other in terms of outlook. Planning approaches the issue from the perspective of exploring the appropriateness and sustainability of design proposals, and the interaction of the building as a whole with its environment. Whereas, Building Standards is focussed on technical regulations that ensure buildings meet minimum acceptable standards including those for fabric energy efficiency, equipment efficiency and CO₂ emissions reduction. Collaboration between Planning and Building Standards is essential if we are to develop effective joined-up policies to address climate change.

In Scotland, limiting energy consumption and CO₂ emissions from new buildings is primarily legislated for through Section 6 of the Scottish Building Standards. Building Standards take a whole building approach based on reducing energy demand, increasing energy efficiency and the judicious use of LZCGT. They sanction meeting the mandatory CO₂ emission reduction target by whatever means Architects and Developers deem suitable, subject to the design meeting robust fabric energy efficiency and equipment efficiency backstops. The use of LZCGT is not mandatory (Scottish Government, 2019a). This holistic approach allows architectural designers the valuable freedom to innovate and find new and cost effective solutions.

However, the UK government's SAP used by Section 6 to determine CO₂ emissions from buildings is not without a few fundamental flaws (BRE, 2014). It is not clear which of the national policy aims: reducing fuel poverty, increasing energy efficiency decreasing overall energy use, or reducing carbon emissions is being captured by the various performance measures contained in SAP. It has been shown that this can lead to confusion and disconnect between performance measures, policy instruments and policy objectives and which of the policy aims is being improved by a particular strategy which can result in perverse incentives (Kelly et al., 2012). Prime among these flaws is that the calculation methodology is based on comparing the proposed building to a notionally similar building to adjudicate the level of CO₂ emission reduction. This removes any semblance of an absolute CO₂ emissions target, effectively ignores much of the impact architectural design can have on overall CO₂ emissions, and fails to incentivise sensible design solutions.

In contrast, most planning authorities rightly recognise the potential of sustainable design approaches and actively promote simple passive design responses in their planning guidance. These design measures might include consideration of site microclimate, topography and natural environment on the general positioning of development as well as the impact of landscape design, shelter, shade, solar orientation, scale, built form, fenestration, solar gain, natural daylight, sunspaces, protected entrances, material choices etc. These types of design choices can contribute significantly to reducing energy demand and CO₂ emissions from buildings and sit well with other sustainability measures addressed through planning policy, but they need to be incorporated and incentivised early in the design process. Planning is ideally-placed to undertake this task.

Early engagement with applicants, either through pre-application discussions or during the process of determining planning applications can be used to advise applicants about their responsibilities at a stage when it could positively influence design responses. During this engagement process planners can address the long-term need to reduce energy demand; facilitate discussions about the pros and cons of specific design and technological solutions; and influence choices made with respect to design, energy efficiency and the use of LZCGT.

6.2.4 Determining a Fair and Equitable Share of Resources for Everyone.

In advancing the concept of a 2000 Watt Society, the Swiss recognised that the current level of consumption in developed countries is unsustainable and that we each need to take responsibility for our choices, and use only what is a fair and equitable share of the world's resources (Morosini, 2008; Stulz et al., 2011).

An example of this type of unsustainable level of energy consumption was evident in the SAP data collected for an earlier study into LZCGT use in new domestic buildings in Scotland (Onyango et al., 2016; Burford et al., 2019). This study clearly recorded excessively large annual energy demands relating directly to the size of the per capita heated living space observed in large dwellings because of their low average occupancy rates (BRE, 2008; Ettlin, 2013). The data captured during this study in relation to size, occupancy and space heat demand suggests that the 50% of occupants who live in dwellings less than 100m² were responsible for only 36% of annual energy demand (Appendix E: Table E.1). These figures suggest that bringing the per capita annual energy demand in buildings greater than 100m² in line with more modest dwellings could have a significant impact on overall energy consumption and CO₂ emissions.

This inequitable division of resources is currently obscured by the convention of defining metrics in terms of per m², because this effectively disguises the real magnitude of annual energy demand and CO₂ emissions in large dwellings. In a domestic setting an absolute target defined in terms of per capita is potentially more useful, because it could be used to leverage either higher fabric efficiency standards or increased LZCGT provision in large dwellings to bring excess consumption down to acceptable levels. It should be noted that the sole Passivhaus example recorded in the above study; whilst representing a vast improvement over many other houses of a similar scale, still only equalled the energy consumption per capita readily achieved by more modest dwellings because of their compact design and built form (Appendix C: Worked Example 1).

6.2.5 A Whole Building Standard.

This proposal is substantially different to the current 3F Policy. Although it takes a holistic approach, its underlying aim of reducing CO₂ emissions and ultimately promoting the use of LZCGT, remains unchanged.

By adhering to the recommended 3-step strategy for reducing CO₂ emissions; the proposal aims to avoid conflict with the approach taken by Scottish Building Standards which allows architect and developers the freedom to innovate and choose the most appropriate and cost effective approach to CO₂ emission reduction for any given site. It achieves this primarily by allowing compliance through any combination of design, fabric efficiency and LZCGT. If a dwelling can meet the acceptable annual energy demand (AAED) calculated for it through good design and fabric energy efficiency measures alone, this should be encouraged. However, if it does not, then any remaining energy demand above the acceptable level must be met through zero-carbon renewable energy sources.

The use of LZCGT is not compulsory under this proposal; but by setting the acceptable annual energy demand per capita (AAED/Capita) at a level that is ambitious but achievable by most modest sized dwellings, it should force larger dwellings to either substantially cut energy demand through good design and fabric energy efficiency and/or markedly increase their use of LZCGT. It is expected that overall the use of LZCGT will be higher than with the minimum standard approach previously discussed. Furthermore, by making LZCGT non-compulsory the proposal should not interfere with the cost effective delivery of essential domestic infrastructure such as social or affordable housing. With increased CO₂ emissions reduction requirements anticipated in future Section 6 standards it is inevitable that the proportion of LZCGT needed to satisfy remaining energy demand will automatically increase.

6.2.6 An Acceptable Annual Energy Demand Per Capita: (AAED/Capita)

Framing the standard in terms of an acceptable annual energy demand per capita (AAED/Capita), and basing that level on the annual energy demand of a modestly-sized energy-efficient dwelling, has several positive inferences:

i. It emphasises the fact that resources are finite and individuals need to take responsibility for their lifestyle choices and the impact these will have on CO₂ emissions and ultimately climate change. This focus on individual energy consumption echoes the Swiss concept of a 2000-Watt Society.

ii. It acknowledges that the surest way to reduce CO₂ emissions from buildings is to simply reduce energy demand, and that this is the vital first step in achieving net zero-carbon buildings. Reducing energy demand is also vital for maintaining energy security in the long-term.

iii. By setting an absolute target, it recognises that the design of a building has a significant impact on energy demand and CO₂ emissions, and incentivises innovative approaches and passive design solutions.

iv. For modest dwellings it allows architects and developers to take a purely fabric first approach if they wish to do so, without incurring additional costs providing LZCGT. This reduces the risk of higher levels of CO₂ emissions being effectively locked-in to the built infrastructure over the long-term because a certain amount of LZCGT is mandatory.

v. It clearly recognises that dwelling scale has a huge impact on per capita operational and embodied energy demand, consumption levels and CO₂ emissions (Appendix E; Burford et al., 2019). This is because the average occupancy rate in large dwellings in the UK is small relative to more modest dwellings and saturates at around 3 in buildings over 90m² (BRE, 2008). This can result in very large per capita heated living spaces.

vi. It countenances a more equitable and fair division of resources in the future and incentivises more sensible levels of consumption. While the policy will be effective universally, its impact will be much greater on larger dwellings. The design proposals for very large dwellings may need to be re-evaluated, the performance of the building fabric improved dramatically and zero-carbon renewable energy invested in heavily to bring the per capita annual energy demand down to acceptable levels. Conversely, as most modest dwellings are inherently energy efficient because of their scale and built form, the policy will have a lot less impact.

6.2.7 Target Level

We consider that the acceptable annual energy demand per capita (AAED/Capita) should be set at an ambitious but readily achievable level based on the predicted annual energy demand (AED) of a modestly sized energy-efficient dwelling built to Scottish Building Standards. It is extremely important that the level should not interfere with the ability to deliver essential domestic infrastructure such as affordable housing in a cost effective way. To determine the appropriate target level, the predicted annual energy demand of dwellings ranging in size from 25m² to 300m² will be modelled using the same methodology adopted in Proposal 1.

We propose that initially the target level, AAED/Capita 2020-2021, should be achievable without the use of LZCGT for modest dwellings. This will offer architects and developers a wide range of options as to how to achieve compliance and should allow familiarity with the policy and compliance procedures to develop without any major discontent settling in before the target is tightened. We therefore suggest that the AAED/Capita 2020-2021 be calculated relative to the predicted annual energy demand of a modestly-sized energy-efficient dwelling with a space heat demand of 30kWh/m².annum (Proposal 1: Scenario 2). A modestly-sized dwelling will be defined as between 45m² and 100m² (Appendix E).

The subsequent target level, AAED/Capita 2024-2050 should likewise reflect expected advances in Scottish Building Standards. A recent cost-analysis suggests that it will be more cost effective to aim for very high fabric efficiency comparable to Passivhaus by the mid-2020s, than take a slower step by step approach which would result in further infrastructural carbon lock-in (Currie and Brown, 2019). We therefore suggest that the AAED/Capita 2024-2050 be calculated relative to the predicted annual energy demand of a modestly-sized energy-efficient dwelling with a space heat demand of 15kWh/m².annum (Proposal 1: Scenario 3). This will be significantly more challenging for large buildings to achieve through fabric energy efficiency alone (Appendix C: Worked Examples 1 & 3).

As the country evolves towards 2050 and net-zero carbon buildings, the AAED/capita could be progressively reduced until it reaches zero. At this point all remaining energy demands will have to be met by zero-carbon renewable energy sources.

6.2.8 Compliance

The policy design takes in consideration the need for a standard compliance procedure that presents information to planning authorities in a clear, comprehensible and useful format, but does not place overly onerous demands on architects and developers. For this reason we suggest that the data used as evidence be extracted from the building's SAP document and a standardised excel spreadsheet developed for the compliance calculation (Appendix C).

This spreadsheet is seen as more than a simple means of showing policy compliance; it is envisaged as a potential tool through which planners, architects and developers can explore and discuss the impact of different options. It is also seen as a potential means of accurately recording information in a simple format that could be fed forward for reporting and future regional or national energy planning purposes.

Unlike the comparative procedure used to determine compliance with Building Standard 6.1; this policy will use the absolute values calculated by SAP for the building as designed. There is no need to refer to values calculated for the notionally similar building and there is no need for a second SAP calculation as required by Proposal 1. This simplifies the compliance procedure. With its emphasis on the overall annual energy demand of a building and factors that can be best addressed through the design process at the planning stage, this policy is seen as complementary to the existing more technical focussed building standards. The metric used throughout will be kWh/annum for several reasons:

i. It is a tangible and easy to understand metric with real world meaning for all stakeholders. As such it is easy to directly manipulate in the design process.

ii. It emphasises the need to first and foremost reduce energy demand.

iii. It is the principal metric used in SAP calculations.

iv. It allows the contribution of LZCGT to the annual energy demand to be clearly and easily quantified.

v. It is the obvious metric to link the building's annual energy demand, LZCGT contribution and other regional or national energy networks. It is therefore extremely useful for ongoing reporting and in the development of future regional or national energy policy.

vi. It avoids conflict with Building Standards as they do not seek to quantify or limit the annual energy demand of a building.

vii. It promotes transparency, by making clear and apparent the true extent of annual energy consumption in individual buildings.

6.3 Proposed Methodology: Identifying an Acceptable Annual Energy Demand per Capita in new buildings

6.3.1 Methodological Steps

1 Calculate and graph the predicted annual energy demand (AED) of dwellings sized 25m² to 300m², under two different fabric energy efficiency scenarios: (These scenarios have already been used for Proposal 1, so for clarity and consistency we will apply the same nomenclature)

i. Space heat demand

Scenario 2: 30kWh/m².annum (Present/Near Future 2020 to 2021)

Scenario 3: 15kWh/m².annum (Future 2024 to 2050)

ii. The hot water demand calculation method outlined in SAP 2012 (BRE, 2014).

iii. The electricity for lighting demand calculation method outlined in SAP 2012 (BRE, 2014). Assuming 75% fixed low energy lighting outlets (Scottish Government, 2015).

iv. Electricity consumed by pumps and fans associated with building services.

Scenario 2: 75kWh/annum for general building services.

Scenario 3: 75kWh/annum plus electricity to operate an MVHR unit. This was calculated using the method outlined in SAP 2012 (BRE, 2014).

2 With respect to each scenario; calculate and graph the annual energy demand per capita (AED/Capita) relative to dwelling size.

3 Utilizing the information modelled for each scenario; determine what would represent an acceptable annual energy demand per capita. This judgement was based on the predicted annual energy demand of a modestly-sized energy-efficient dwelling. This was defined as a dwelling between 45m² and 100m² because:

i. The average size of a new dwelling in the UK is just 76m² (Joyce, 2011).

ii. In Scotland the average size of a dwelling built post 1982 is 101m² (Scottish Government, 2017b)

iii. Average occupancy patterns begin to change at around 90m² and thereafter soon saturate at close to 3 occupants in larger homes (BRE, 2008).

iv. In Scotland, approximately half of all new dwellings fall in the 45m² to 100m² size category (Appendix E; Onyango et al., 2016).

v. It is considered vital that the level set should not interfere with the ability to deliver essential housing needs in a cost-effective way, and this definition will include most social and affordable housing.

6.3.2 STEP 1: Calculate the Annual Energy Demand (AED) of Dwellings.

To represent the change expected as CO₂ emission reduction standards tighten over time; the AEDs were modelled with respect to two different fabric energy efficiency scenarios. The first scenario, with a space heating & space cooling demand of 30kWh/m².annum, represents the level of fabric energy efficiency that could be reasonably expected of an energy efficient dwelling in the present or near future. The second scenario, with a space heating & space cooling demand of 15kWh/m².annum, represents the future normalisation of very highly energy efficient dwellings, possibly as early as the mid-2020s (Currie and Brown, 2019). As these scenarios have previously been defined for Proposal 1, we will for clarity and consistency retain that nomenclature and colour coding.

Scenario 2:
30kWh/m².annum
Present/Near Future
2020 - 2021

Scenario 3:
15kWh/m².annum
Future
2024 - 2050

The annual energy demands (AED) for dwellings sized 25m² to 300m² were calculated as set out in detail in Proposal 1. The results are graphically represented in Figure 11. This graph clearly illustrates the impact tackling fabric energy efficiency has on reducing the annual energy demand and by extension CO₂ emissions from a building. This in turn reduces the scale and cost of the heating plant or LZCGT required to satisfy this demand.

6.3.3 STEP 2: Calculate the Annual Energy Demand Per Capita of Dwelling

With respect to each scenario, the predicted annual energy demand per capita (AED/Capita) was calculated for dwellings sized 25m² to 300m² using Formula 23. Occupancy (N) is defined by Formula 1 (BRE, 2014). The results are represented graphically in Figure 12.

Formula 23

6.3.4 STEP 3: Determine an Acceptable Annual Energy Demand Per Capita.

It was determined that the acceptable annual energy demand per capita (AAED/Capita) in all new dwellings would be calculated in kWh/annum and be based on the annual energy demand (AED) of a modestly-sized energy-efficient dwelling because it was considered vital that the level deemed acceptable should not interfere with the ability to deliver essential infrastructure such as social and affordable housing in a cost-effective way.

For the purposes of this study a modestly-sized dwelling was defined as falling in the 45m² to 100m² size range. In making this judgement we considered:

i. The average size of a new dwelling in the UK is just 76m² (Joyce, 2011).

ii. In Scotland the average size of a dwelling built post 1982 is 101m²; the average urban dwelling being 93m² and the average rural dwelling was 47% larger at 137m² (Scottish Government, 2017b, pp. 18-19).

iii. Average occupancy patterns begin to change at around 90m² and thereafter soon saturate at close to 3 occupants in larger homes (BRE, 2008).

iv. SAP data was collected from an earlier study containing 402 randomly selected dwellings built in Scotland between 2012 and 2014. These dwellings ranged in size from 49m² to 481m² (Onyango et al., 2016). When analysed with respect to average expected occupancy and dwelling size, it became clear that 50% of all occupants lived in dwellings with a total floor area of between 45m² and 100m², and this size range represented 56% of the total sample (Appendix E: Table E.1).

v. It was considered highly likely that the vast majority of social and affordable housing would fall within this range.

The AAED/Capita for each scenario was determined with reference to Figure 12; by reading the peak value for each curve respectively for dwellings within the 45m² to 100m² size range. With slight rounding up this gives the following values for acceptable annual energy demands:

22021 AAED/Capita = 1910
kWh/annum
(Scenario 2)

2024 AAED/Capita = 1500
kWh/annum
(Scenario 3)

This AAED/Capita is applied to all dwellings regardless of size. If the annual energy demand of the proposed dwelling exceeds this acceptable level, the surplus demand must be met through zero-carbon renewable energy sources.

6.4 Compliance Targets

Essentially, compliance with this policy will be determined by comparing three values calculated for the proposed dwelling:

Acceptable Annual Energy Demand
AAED

Annual Energy Demand
AED

Zero-Carbon Adjusted Annual Energy Demand
ZCAED

Each will be calculated automatically in the proposed compliance spreadsheet from data extracted from the building's SAP document. The formula used to do this are set out below:

6.4.1 The Acceptable Annual Energy Demand of the Proposed Dwelling: AAED

Calculating the acceptable annual energy demand (AAED) for a proposed dwelling is simply a matter of multiplying the relevant acceptable annual energy demand per capita (AAED/Capita), by the occupancy (N) of the proposed dwelling (Formula 24). Occupancy (N) is calculated by Formula 1 and is contained within the SAP document as [SAP box No. 42].

AAED = AAED/Capita x N

Formula 24

Using the values determined previously from Figure 12,

2021 AAED = 1910 N kWh/annum
(Scenario 2)

2024 AAED = 1500 N kWh/annum
(Scenario 3)

Using Formula 24, the acceptable annual energy demand (AAED) was calculated for dwellings ranging in size from 25m² to 300m² for both scenarios. These values are graphically represented in Figure 13. This curve clearly mirrors Figure 5.

To illustrate the extent of potential energy savings that capping annual energy demand relative to occupancy might achieve, Figure 13 also includes, for reference as dotted lines, the uncapped predicted annual energy demand for dwellings sized between 25m² and 300m² calculated under the same fabric energy efficiency scenario. It is apparent that the potential savings in respect to large dwellings are substantial.

With reference to Figure 13; for both scenarios the two lines representing predicted and acceptable annual energy demand intersect at around 100m². This means that dwellings between 45m² and 100m² and built to achieve a space heating and space cooling demand of less than or equal to 30 or 15 kWh/m².annum respectively, should not have to use LZCGT under this policy, unless they elect to do so to achieve the CO₂ emissions reductions target set by Scottish Building Standard 6.1. This ensures that the cost of social and affordable housing is not adversely affected by the insistence on the use of LZCGT. Expanding this simple analysis for Scenario 2 to include the predicted annual energy demand of dwellings built to achieve a space heating and space cooling demand of less than or equal to 15 kWh/m².annum (Scenario 3); it is clear that dwellings of up to approximately 175m² could also comply with this policy without recourse to LZCGT if they chose to build to this higher fabric energy efficiency standard.

Figure 14 depicts the level of fabric energy efficiency dwellings ranging in size from 25m² to 400m² would need to achieve if they wished to comply with this policy without recourse to LZCGT. This becomes progressively more onerous for large dwelling as the per capita heated living space increases, and it is expected that most of these dwellings will find use of LZCGT essential even with increased fabric energy efficiency levels.

Note: Different assumptions were made relative to Pumps and Fans for Scenario 2 and 3 because it was considered at very high fabric energy efficiency (space heating demand ≤15kWh/m².annum) a MVHR unit would likely be required for ventilation purposes. The values depicted in Figure14 for Scenario 2 may therefore need to be reduced by a few Kwh/m².annum at fabric energy efficiencies approaching and below 15kWh/m².annum.

6.4.2 The Annual Energy Demand of the Proposed Dwelling: AED

The actual annual energy demand for the proposed dwelling will be calculated automatically by the compliance spreadsheet from the input SAP data. It will comprise of the sum of the annual energy demands per annum calculated for space heating [SAP box No. 98], space cooling [SAP box No. 107], water heating [SAP box No. 64], lighting [SAP Box 232], and pumps and fans [SAP Box 231]. This was previously defined in Proposal 1, by Formula 8.

AED = [SAP Box 98] + [SAP Box 107] + [SAP Box 64] + [SAP Box 232] + [SAP Box 231]

Formula 8

6.4.3 The Zero-Carbon Adjusted Annual Energy Demand for the Proposed Dwelling: ZCAED

This is the actual annual energy demand for the proposed dwelling adjusted to take into account the contribution of zero-carbon renewable energy sources that are used to meet this demand. The compliance spreadsheet will automatically calculate the contribution of each energy source used; classifying them as zero-carbon, low-carbon, grid electricity, bio-carbon or fossil fuel. It will then automatically calculate the zero-carbon adjusted annual energy demand (ZCAED).

ZCAED = AED - ∑ zero-carbon renewable energy sources

Formula 25

6.4.4 Determining Compliance:

There are two possible ways that a dwelling can achieve compliance with this policy. Both calculations will be automatically performed by the proposed compliance spreadsheet.

Compliance Method 1

The annual energy demand (AED) of the dwelling is less than or equal to the acceptable annual energy demand (AAED) calculated for it on the basis of the predicted occupancy.

AED ≤ AAED

Formula 26

It is possible to achieve compliance through sensible energy-efficient design and fabric energy efficiency measures alone, and although this method does not depend on the use of LZCGT to achieve compliance, neither does it preclude its use. This method of compliance will become progressively more difficult as dwelling size increases and the AAED target tightens.

Compliance Method 2

The annual energy demand of the dwelling adjusted to take into account the contribution of zero-carbon renewable energy sources (ZCAED) is less than or equal to the acceptable annual energy demand (AAED) calculated for it on the basis of the predicted occupancy.

ZCAED ≤ AAED

Formula 27

This method depends on the use of LZCGT to achieve compliance, and will probably be necessary for large dwellings.

6.5 Compliance Procedures

6.5.1 Compliance Workflow

Having reflected on the opinions expressed by survey respondents; we suggest that Planning should focus its efforts on getting architects and developers to prioritise making better decisions with respect to climate change, energy consumption and CO₂ emissions at an early stage in the design process (Appendix A). The recent revisions to the RIBA Plan of Work reinforce this viewpoint (RIBA, 2020). At this early stage the design is more mutable, with opportunities to incorporate passive design principles, reconsider scale and built form, explore potential LZCGT, and set ambitions relating to fabric energy efficiency.

This approach will require that architects, developers and planners move beyond relying on simplistic approaches to CO₂ emission reduction, and see the building as a holistic system and devise solutions accordingly. It also presupposes that planners have sufficient knowledge and depth of understanding of the issues to offer guidance; alongside signposting throughout the planning process that these are serious issues that need to be addressed in submitted planning applications.

The following is a suggestion of how this policy could be administered and incorporated into the existing workflow of planning officers. It is informed by insights gained by planning officers in administrating current Section 3F policy (Appendix A).

Pre-application Stage

The strategy at this stage should be to forewarn and forearm applicants. Where planners have pre-application discussions with applicants, the need to develop sustainable and energy efficient buildings and communities should be emphasised. The policy aim of reducing CO₂ emissions through reducing energy demand, increasing energy efficiency and using zero-carbon renewable energy sources should be explained and promoted, and initial advice given on the means applicants can potentially employ to meet this objective. Architects and Developers should be encouraged to use the compliance spreadsheet as a design tool to explore the impact and implications of taking different design approaches or employing specific LZCGT. They should also be advised that larger dwellings will in all probability have to perform to substantially higher standards than currently expected to achieve compliance with this policy, to compensate for their tendency to have very high per capita energy use (Figures 12, 13 and 14).

Planning Application Stage

Ideally, compliance documentation will be submitted at this stage, and if so, could form the basis of discussions between planners and applicants. If the compliance spreadsheet cannot be completed at this stage for lack of finalised SAP data, the drawings and design statements submitted should clearly indicate how the applicant intends to comply with the proposed policy. They should allow the planning officer to assess the extent to which passive design principles have been incorporated into the design, the intentions with regard to fabric energy efficiency and building energy services, and the level of LZCGT provision. Whether the design makes it easy and cost-effective to incorporate improvements such as adding a PV array or switching the heating system from a gas boiler to a heat pump at a future date should also be reflected on. Moreover, in the absence of the compliance spreadsheet, the planning officer will need to judge whether these measures seem sufficient to meet policy requirements. Depending on the level of information provided different responses may be appropriate.

i. An informal chat: If the drawings fail to meet the expected standards by a large margin and/or there are other issues with the application that arise during the public consultation, then the first response should be an informal chat with the applicant. This should draw attention to climate change issues and offer advice on the specific expectations of the policy. Where appropriate, planners could make recommendations as to potential improvements to the application. The applicant then has the choice to submit revised drawings and statements, or withdraw the application and resubmit at a later date.

ii. A formal letter or email: If the information submitted is incomplete or there are discrepancies between drawings and statements, a formal letter or email asking for clarification and drawing attention to the policy and its expectations would be in order. An invite to discuss the issues further could also be issued.

iii. Planning approval subject to a suspensive condition: If it is clear from the drawings and design statements that the application has considered policy requirements and there are no other major issues; planning permission should be granted subject to a suspensive condition. If the compliance spreadsheet has not yet been submitted, this should instruct the applicant that 'as designed' compliance documentation should be submitted once SAP has been finalised and prior to any works starting on site. Applicants should also be advised that they will be required to submit 'as built' compliance documentation once the building is complete.

Building Warrant Stage

As soon as the design has been finalised and the SAP calculation performed, the applicant should complete and submit the policy compliance spreadsheet to show that the building will meet its acceptable annual energy demand target by either of the permitted compliance methods. Works should not start on site before this document has been received. If an applicant is struggling with compliance, planning officers should be available to offer free guidance on how this might be practically achieved. The compliance methodology is flexible in this regard.

Construction Phase

At the end of the construction phase, applicants should submit 'as built' compliance documents to both planning and building standards to ensure that any changes during the construction phase have not been to the detriment of the policy. If building standards does not receive this document they should advise the applicant that it is required prior to them issuing the completion certificate.

Reporting and Future Planning

Ideally for ongoing reporting, research and planning of future energy infrastructures, the key information contained within the compliance documents should be recorded in a national database.

Key statistical data should include:

i. Size of dwelling (m²)

ii. Annual Energy demand (kWh/annum)

iii. Specified systems, fuels and LZCGT

iv. The contribution of individual LZCGT to the energy mix (kWh/annum)

v. The means of compliance

6.5.2 Design of Compliance Documentation

The proposed compliance documentation will consist of a standardised Excel spreadsheet submitted to planning either during the planning application process or prior to the commencement of building works (Appendix C). This spreadsheet will record details about the proposed building's annual energy demand and the type of systems, fuels and LZCGT employed. The data used to complete the spreadsheet will be extracted from the finalised SAP calculation submitted to Building Standards. The Excel spreadsheet will automatically calculate whether the dwelling is in compliance, and clearly tabulate the contribution of individual energy sources with particular emphasis on capturing the zero-carbon contribution of LZCGT. The metric used will be kWh/annum.

The compliance documentation was designed with the objective of making the entire process as easy as possible for all stakeholders whilst providing the opportunity to collect energy data for forward planning of local and national energy networks. The design parameters included:

1. A clear and concise standardised compliance document in Microsoft Excel to allow for familiarity, ease of completion and comprehension by all stakeholders.

2. Input data to be the minimum necessary to accurately describe the building's energy systems and should be solely sourced from the SAP 2012 document submitted to Building Standards.

3. The spreadsheet should document and/or calculate:

i. The size of the dwelling (m²).

ii. The occupancy of the dwelling.

iii. The annual energy demands for space heating, space cooling, hot water, lighting and pumps & fans (kWh/annum).

iv. The contribution of each specified system, fuel and LZCGT (kWh/annum)

v. The total contribution of zero-carbon renewable energy sources (kWh/annum)

4. It should provide a clear statement of how compliance is achieved.

i. Compliance Method 1: AED ≤ AAED

ii. Compliance Method 1: ZCAED ≤ AAED

5. The calculation methodology should be transparent, and information should be presented in an easy to understand tabulated format so that designers and planners can quickly comprehend the impact and implications of specific design choices and use the spreadsheet as a conceptual design tool.

6. The use of certain technologies and systems should be encouraged or discouraged through simple colour-coding.

7. The data collected should be capable of being compiled into a database and used for research and reporting purposes to aid in the development of appropriate government energy policies and regional or national energy networks.

6.5.3 The Calculation Methodology

To avoid undue complexity and reduce the amount of information that is needed to be input into the compliance spreadsheet, the calculation methodology has been simplified as far as possible. It should be noted that this methodology remains firmly focussed on energy demand, energy consumption and the contribution made by zero-carbon renewable energy sources. The metrics used throughout are kWh/annum.

Unlike SAP it does not apply carbon factors or attempt to quantify CO₂ emission reduction in any way. This is after all adequately legislated for through Building Standards. Instead it takes a much more broad brush approach; in the certain knowledge that reducing annual energy demand and/or replacing a proportion of that demand with zero-carbon renewable energy sources will inevitably reduce CO₂ emissions. It therefore simply defines the energy sources used as zero-carbon, low-carbon, grid electricity, bio-carbon or fossil fuels, and uses a simple colour coding system to indicate preferable choices. Only zero-carbon designated energy sources are used to mitigate the annual energy demand.

It should be noted that different LZCGT are accounted for in different ways within the calculation process. Most zero-carbon renewable energy sources and heat recovery processes require at most only a minor energy input for their effective operation. If this is clearly recorded and attributed to a certain LZCGT in the SAP calculation [SAP box Nos. 230 a-h] this is simply subtracted from their calculated contribution. Heat pumps however require a substantial amount of electricity to operate. To account for this, the electricity consumed is simply subtracted from the heat demand delivered effectively reducing the heat pump's zero-carbon contribution in line with their efficiency. It should be noted that grid electricity has specifically been separated into its own category, as the proportion generated nationally from zero-carbon or renewable energy sources might be captured and reflected within the zero-carbon total in future refinements of the calculation process.

In general, the convention in SAP is to consider the heat output of CHP plants as the intentional product of the process to which CO₂ emissions are attributed, and the electrical output is treated as a zero-carbon energy resource. However, depending on the fuel source, CHP plants can emit substantial amounts of CO₂, so within this calculation methodology they are recorded as low-carbon or bio-carbon. As they are not considered zero-carbon, their contribution is not used to mitigate annual energy demand. An exception would be geothermal and hydrogen fuel cell CHP which are zero carbon. In some circumstances local authorities might elect to relax this definition and allow a proportion of the energy produced to be used to mitigate annual energy demand in order to promote local community heat or electricity networks, but we do not recommend this. For similar reasons biomass and biogas are recorded as bio-carbon energy sources and similarly not used to mitigate annual energy demand (CCC, 2018, 2019b). Waste heat recovered from power stations, or industrial and agricultural processes will however be designated as zero-carbon.

6.5.4 The Compliance Spreadsheet

Evidencing compliance is simply a matter of completing the relevant data input section of the compliance spreadsheet, with information extracted from the DER worksheet of the SAP document submitted to Building Standards (Appendix C). Excel will perform all necessary calculations automatically. The process is as follows:

STEP 1: Data Input

Applicants complete the data input worksheet relevant to their proposed building: Section 1 is for dwellings with individual heating systems and micro-cogeneration; Section 2 is for dwellings with community heating systems (Appendix C: Figures C.3, C.5). Applicants need only fill in those shaded boxes that are relevant. Some boxes are pre-populated to reduce input further.

There is no need to understand SAP calculation to complete the spreadsheet, because the required SAP box numbers are clearly indicated on both documents. Particular care should be taken to ensure the SAP convention of entering generated or recovered energy as a negative value is followed. The only other information needed is knowledge of the type of heating system, fuel or LZCGT employed. This is usually contained within the summary of input data at the beginning of the SAP document. This type of data is entered into the worksheet using one of the system codes listed at right-hand edge of the spreadsheet. For clarity, when entering data related to pumps and fans the system code associated with their end use should be used, not electricity.

Unless the building is very complex, many of the boxes will equal zero, and can be left blank. The data input worksheet should therefore take less than 10 minutes to complete. Excel utilizes this information to automatically complete the relevant Compliance Calculation worksheets (Appendix C: Figures C.4, C.6).

STEP 2: Compliance Method 1

This method of compliance relies on an inherently low annual energy demand (AED) rather than the use of LZCGT; although it should be noted that the contribution of some LZCGT (Solar Thermal, MVHR, WWHR and FGHR) will already be embedded within the calculated AED if they are used.

i. Excel calculates the acceptable annual energy demand (AAED) measured in kWh/annum for the proposed dwelling, using Formula 24. (Note: both the 2021 AAED and the 2024 AAED are shown on the example worksheets in Appendix C. In reality only the level currently sought would be included).

ii. Excel calculates the annual energy demand (AED) measured in kWh/annum for the proposed dwelling, using Formula 8.

iii. Excel compares the AAED and the AED. If AED ≤ AAED (Formula 26) then the dwelling is considered to be in compliance without the need to employ LZCGT, unless these are required to meet CO₂ emissions reduction target set by Section 6 of the Scottish Building Standards. A compliance/non-compliance statement is automatically generated.

STEP 3: Compliance Method 2

If the AED of the proposed dwelling is greater than its calculated AAED, the dwelling can still achieve compliance, if the energy demand in excess of the acceptable level is met by zero-carbon renewable energy sources. This method of compliance relies on the use of LZCGT. However large buildings may have to employ design and fabric energy efficiency measures as well to lower energy demand sufficiently to make the use of LZCGT feasible and cost effective.

i. Excel uses the input SAP data to calculate and tabulate the contribution of each energy source used in the proposed dwelling in kWh/annum. The results are then clearly defined as zero-carbon, low-carbon, grid electricity, bio-carbon or fossil fuels; and colour-coded green, amber or red to help visually identify which technologies are considered most favourable. Zero-carbon energy contributions are colour-coded green.

ii. Excel calculates a zero-carbon adjusted annual energy demand (ZCAED) using Formula 25, by taking into consideration all the zero-carbon renewable energy sources used in the proposed dwelling.

iii. Excel compares the AAED and the ZCAED. If ZCAED ≤ AAED (Formula 27) then the dwelling is considered to be in compliance. A compliance/non-compliance statement is automatically generated.

STEP 4: Resolving Non-Compliance

If the AED and ZCAED for the proposed dwelling are both greater than its calculated AAED, then the dwelling is NOT in compliance and the designer must make alterations to the design, fabric energy efficiency and/or the LZCGT employed to bring it into compliance. The compliance procedure is quite flexible and there are several ways that a designer can bring a non-compliant building into compliance, either by reducing the annual energy demand (i. – iv.) or employing additional zero-carbon renewable energy systems (iv. – vii.). The compliance spreadsheet used alongside SAP can be exploited as a design tool to explore these options. The options are:

i. Revise the Building Design: consider scale, built form, solar orientation, and other passive measures to reduce overall heat demand.

ii. Increase fabric energy efficiency.

iii. Increase air tightness and employ Mechanical Ventilation Heat Recovery (MVHR). Consider a near Passivhaus approach.

iv. Consider Thermal Solar or Waste Water Heat Recovery (WWHR).

v. Consider Zero Carbon Electricity Generation: PV, Wind, Water etc.

vi. Consider Zero Carbon Heat Generation: All types of Heat Pumps: GSHP, GWSHP, SWSHP, ASHP, EASHP, and SASHP. Be aware that in calculating the zero-carbon contribution, the electrical input will be subtracted from the output.

vii. Community Heating: Numerous different energy sources may be employed within district heating schemes; these will be considered on their individual merits. Scaled zero-carbon renewable energy systems might include PV, Wind, Water, Tidal or Geothermal Energy, Waste Heat Recovery from Power Stations, or Waste Heat Recovery from Industrial or Agricultural processes.

For more details about the compliance spreadsheet and worked examples, see Appendix C.