Scottish House Condition Survey: 2022 Key Findings
Figures from the 2022 survey, including updated fuel poverty rates, energy efficiency ratings, the condition of housing and the Scottish Housing Quality Standard.
2 Energy Efficiency
The energy efficiency of a dwelling depends on its physical characteristics. Factors such as the age of construction, the dwelling type, the heating and hot water systems in use and the extent to which the building fabric is insulated, all affect energy efficiency.
Based on information about the characteristics of the dwelling collected in the SHCS physical survey and using standard assumptions about the make-up and the behaviour of the occupying household, the energy consumption associated with the dwelling is modelled. This allows us to make comparisons of energy use, emissions and energy efficiency ratings between dwellings that are independent of occupant behaviour. Further details on the methodology underpinning these measures of energy efficiency are provided in the Methodological and Technical notes.
In this chapter we report on:
- levels of insulation in Scottish dwellings (section 2.1);
- boiler efficiencies (section 2.2);
- Energy Efficiency Ratings (EER), also known as SAP ratings (section 2.3);
- modelled carbon dioxide (CO2) emissions from dwellings (section 2.4); and
- Environmental Impact Ratings (EIR) (section 2.5).
A breakdown of findings is also provided by tenure of the household and other relevant dwelling characteristics.
Scottish House Condition Survey results for 2022 have been assessed to be comparable in the most part to 2019 and earlier years. However, there is some evidence to suggest that social and private rented households, may be under-represented in the 2022 achieved sample and owner-occupied households, may be over-represented as laid out in section 1.1.5 of the Methodological and Technical notes. Due to this national level estimates of EPC ratings, loft, and solid wall insulation may be slightly under-estimated, as socially rented households tend to have higher rates of solid wall insulation and higher EPC ratings than owner-occupied households and private renters. However, we expect any effects to be minor as solid wall insulation makes up only around a quarter of all dwellings. Furthermore private rented dwellings (which are underestimated more significantly than socially rented properties) tend to have similar EPC scores to owner occupiers (50% C or above and 48% C or above respectively).
2.1 Insulation Measures
Installing or upgrading insulation is one of the most effective ways to improve the energy efficiency of a building. The Energy Saving Trust estimates that an un-insulated dwelling loses a third of all its heat through the walls and a further quarter through the roof. As a result, insulation can significantly reduce energy consumption and therefore lower heating bills, making it cheaper to enjoy satisfactory levels of thermal comfort. (See Chapter 3 on Fuel Poverty.)
Additional insulation is most commonly added to a property through the insulation of loft spaces and by adding insulating material to external walls.
Key Points
- The majority of loft spaces are insulated. In 2022, loft insulation with a thickness of 100 mm or more had been installed in 95% of dwellings. This has been broadly stable since 2017 but represents an increase of 23 percentage points on 2007 levels.
- In 2022, 32% of lofts were insulated to a high standard of insulation (300 mm or more). This proportion has remained about this level since 2015, following year on year increases from the 2010 figure of 5%.
- The proportion of insulated cavity walls recorded by the SHCS was 69% in 2022.
- The proportion of solid wall dwellings with insulation was 16% in 2022, an increase of 5 percentage points on the 2012 figure.
- Levels of insulation (both loft and wall) are higher in the social sector than in the private sector. 53% of homes in the private sector have wall insulation compared to 67% in the social sector. In the private sector, 63% of lofts are insulated to 200 mm or more compared to 76% in the social sector.
2.1.1 Loft Insulation
The majority of loft spaces in Scotland are insulated.
Figure 2.1: Loft insulation (where applicable), 2003/2004 to 2022
Figure 2.1 shows that since 2007, there has been an overall improvement in the uptake of loft insulation. The proportion of all housing with 100 mm or more of loft insulation has increased by 23 percentage points on 2007 levels with 95% of applicable dwellings insulated in 2022. Most of this improvement occurred before 2014. The share of dwellings with no loft insulation has fallen from 6% in 2003/4 to 1% in 2022. Most of this decline occurred before 2011. Since then, improvement has slowed down, suggesting that there may be barriers preventing the installation of insulation in the relatively few remaining uninsulated lofts.
Data Source: Table EE1 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 3]
In 2022, 32% of lofts were insulated to a high standard of insulation (300 mm or more).
Figure 2.2: Depth of loft insulation (where applicable), 2003/2004 to 2022
Since 2010 the thickness of loft insulation has increased significantly. In 2022, 66% of dwellings with lofts had insulation with a depth of 200 mm or more. Much of this increase has occurred between 2009 and 2013, when the percentage increased from 27% to 62%. This can largely be attributed to the installation of top-up insulation. The increase in the estimated number of dwellings with loft insulation between 100-199 mm and with 200 mm or more between 2019 and 2022, are both within the margin of error of the survey.
Data Source: Table EE1 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Levels of loft insulation are higher in the social sector than in the private sector.
Figure 2.3: Depth of loft insulation (where applicable) by tenure, 2003/2004 to 2022
As shown in Figure 2.3 in 2022, 30% of private sector dwellings had a high standard (300 mm or more) of loft insulation, lower than 43% of dwellings in the social sector. 95% of private housing lofts were insulated to 100 mm or more and 63% to 200 mm or more. In the social sector, 98% of dwellings had lofts insulated to 100 mm or more, and 76% had 200 mm or more of loft insulation.
One of the reasons for the difference in uptake of loft insulation over time between the private and social sector is that the Scottish Housing Quality Standard (SHQS), which was introduced in 2004 and applies only to social sector housing, requires at least 100 mm of loft insulation (see section 5.2.3 for more information).
The difference in the proportion of lofts with 100 mm or more of insulation between the private and the social sector has been reducing gradually, from 17 percentage points in 2003/04 (81% in the social and 64% in the private sector) to 3 percentage points in 2022 (98% in the social sector and 95% in the private sector). This likely reflects the benefits of loft insulation also recognised by the private sector households.
Data Source: Table EE2a in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 3]
2.1.2 Wall Insulation
The presence of cavity wall insulation (CWI) added since built is becoming increasingly difficult for SHCS surveyors to identify as over time the injection holes age, fade or are covered up by later work. Contractors are also getting better at concealing their work. This may mean that the SHCS underestimates the number of homes which have had CWI installed (see also section 6.2.2.4 of the 2019 SHCS key findings report). Despite efforts to maintain the high quality of the SHCS physical survey fieldwork, some misclassifications may remain.
In Scotland around 76% of dwellings have external cavity walls and the remaining 24% have solid or other construction types of external wall. These “other” types include steel or timber-frame dwellings and dwellings made from prefabricated concrete. As the improvement of solid and other wall types generally requires more expensive interventions than CWI, this diverse group is addressed together in this chapter.
Higher insulation levels in new buildings have been required by building standards since 1983 when the Building Standards (Scotland) Amendment Regulations 1982 came into force. These dwellings are therefore treated as insulated when built.
In 2022, 69% of cavity wall dwellings in Scotland were insulated.
Figure 2.4: Cavity wall insulation, 2012 to 2022
In 2022, 69% of cavity wall dwellings in Scotland were insulated. The longer term trend, showing a decrease in the share of uninsulated cavity walls of 3 percentage points since 2012.
Data Source: Table EE3a in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 4]
In 2022, 16% of dwellings with solid and other wall types in Scotland were insulated.
Figure 2.5: Wall insulation of solid and other wall types, 2012 to 2022
Figure 2.5 shows the levels of insulation in dwellings with solid or other construction type walls recorded by the survey from 2012 to 2022. The results show that 16% of dwellings in this category had insulated walls in 2022; the difference with the level recorded in 2019 (18%) is not statistically significant but is an increase of 5 percentage points from 2012. Only 769 dwellings with solid walls were surveyed in 2022 as part of the SHCS.
Data Source: Table EE3a in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
The information in Table 2.1 is broken down by type of cavity wall into hard to treat cavities (HTTC) and standard cavity walls using the ECO definition as far as possible with the available data (further details are available in section 2.6 in the Methodological and technical notes).
HTTCs have certain attributes which make CWI more expensive, complex or inadvisable. Standard cavity walls have no such barriers.
Levels of wall insulation were higher in the social sector than in the private sector.
In the social sector, 70% of cavity wall dwellings and 40% of dwellings with solid and other wall types were found to be insulated in 2022. 67% of social housing overall had insulated walls.
In the private sector, 68% of cavity wall dwellings and 13% of solid and other wall dwellings, had insulation in 2022. Over half (53%) of all private sector dwellings had insulated walls.
Overall, 69% of cavity wall dwellings in Scotland have wall insulation. 30% have had retrofit cavity wall insulation, which is generally the lowest cost improvement available; the remainder of insulated cavity walls were insulated as built (33%) or insulated in another way such as with internal and external wall insulation (6%).
Levels of insulation are higher in the social sector at 67% (all wall types) compared with 53% in the private sector. This is being driven by higher levels of insulated solid walls in the social sector (40%) compared to the private sector (13%). Within wall type, this tenure divide is also apparent for the more expensive insulation measures: internal / external insulation of cavity walls (12% of cavity wall dwellings in the social sector; 4% of private dwellings) and retrofit solid wall insulation measures 36% of solid wall dwellings in the social sector; 10% in the private sector).
2.2 Boilers
The heating system is a key factor in the thermal efficiency of a dwelling. Around 86% of households use a gas or oil-fuelled boiler (see Figure 1.7). Trends in boiler efficiency are closely related to developments in energy efficiency and building standards regulations:
- From 1998, minimum boiler efficiency standards were set by European Council Directive 92/42/EEC
- In 2007, Scottish Building Standards increased the efficiency requirements for all new and replacement boilers, details are available in the Domestic Building Services Compliance Guide for Scotland.
Building regulations in Scotland effectively require the installation of a condensing boiler[1] for gas and oil-fuelled heating in new builds or when boilers are replaced in any dwelling.
The SHCS has recorded the age of the household's heating system since 2010 and contains sufficient data to derive the Seasonal Efficiency (SEDBUK) ratings of surveyed boilers in the 2012-2019 and 2022 data collections. For these years we can track the improved efficiency of gas and oil boilers associated with the rising standards of the regulatory framework.
The methodology by which boiler efficiency ratings are calculated changed in 2016 and the time series was updated at that point to reflect this and to account for the minimum efficiency required of new oil combination condensing boilers. All subsequent data is published on the basis of the new methodology and further details can be found in section 1.4 in the Methodological and Technical notes.
The minimum requirements applied in the assessment of whether a boiler is compliant with standards are: a minimum efficiency of 88% for condensing standard gas, oil and LPG boilers; for condensing combination boilers, 86% for oil, and 88% for gas and LPG; for ranges, back boiler and combined primary storage units (CPSUs), 75% when gas, and 80% when oil[2].
Three-quarters of gas and oil boilers met the minimum efficiencies specified by the current Building Standards, in 2022.
Figure 2.6: Gas and oil boiler types, 2012 to 2022
In 2022 the survey found that 96% of the domestic gas and oil boilers in Scotland have been installed since 1998, when the European Boiler Efficiency Directive minimum standards came into effect. The proportion of new boilers, those installed since 1998, has increased by 15 percentage points since 2012. In 2022, 84% of gas and oil boilers were condensing boilers. This represents an increase of 46 percentage points since 2012. Three-quarters (75%) of gas and oil boilers met the minimum efficiencies specified by the current Building Standards. This has increased substantially from 30% in 2012.
Data Source: Table EE5a in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
2.3 Energy Performance Certificates
Key Points
- In 2022, 52% of Scottish homes were rated as EPC band C or better under SAP 2012 (RdSAP v9.93), compared to 45% in 2019. The proportion of properties in the lowest EPC bands (E, F or G) under SAP 2012 (RdSAP v9.93), was 12% in 2022, down from 15% in 2019.
- Under SAP 2009, which allows comparisons over a longer period, over half of dwellings (56%) were rated C or better, up 32 percentage points since 2010. In the same period, the proportion of properties in the lowest EPC bands (E, F or G) has reduced from 27% in 2010 to 9% in 2022.
- Under SAP 2009, the median EE rating in 2022 was 70, which is equivalent to Band C. This is an increase from 62 in 2010 which is equivalent to band D.
Energy Performance Certificates (EPC) were introduced in January 2009 under the requirements of the EU Energy Performance Building Directive (EPBD). They provide energy efficiency and environmental impact ratings for buildings based on standardised usage. EPCs are required when a property is either sold or rented to a new tenant.
EPCs are generated through the use of a standard calculation methodology, known as Standard Assessment Procedure (SAP). SAP is the UK Government approved way of assessing the energy performance of a dwelling, taking into account the energy needed for space and water heating, ventilation and lighting and, where relevant, energy generated by renewables.
The Energy Efficiency Rating (EER) is expressed on a scale of 1-100 where a dwelling with a rating of 1 will have very poor energy efficiency and higher fuel bills, while 100 represents very high energy efficiency and lower fuel bills. Ratings can exceed 100 where the dwelling generates more energy than it uses.
Ratings are adjusted for floor area so that they are essentially independent of dwelling size for a given built form.
For Energy Performance Certificates EERs are presented over 7 bands, labelled A to G. Band A represents low energy cost and high energy efficiency, while band G denotes high energy cost (and low energy efficiency).
Energy Efficiency Ratings reported in this publication are calculated under two versions of SAP, the SAP 2009 methodology and the SAP 2012 methodology. Using SAP 2009 enables us to examine the trend in the energy efficiency of the housing stock since 2010.
SAP is periodically reviewed by the UK government to ensure it remains fit for purpose and to address its continued application across an increasing range of carbon and energy reduction policy areas. SAP is used for assessment of new buildings whilst a ‘reduced data’ version of the methodology, RdSAP, is applied to the assessment of existing buildings.
SHCS energy modelling for SAP 2012 in this report is based on RdSAP (v9.93). The RdSAP (v9.93) was released on 19 November 2017 and contains revisions to the underlying assumptions used within the SAP calculations. The most notable update to the methodology in v9.93 was a change to the default U-values of cavity, solid and stone walls, built prior to 1976. Compared to v9.92, U-values for solid, insulated stone and uninsulated cavity walls have improved, whereas they have declined for insulated cavity walls.These U-values are used to calculate the rate of heat loss through the walls, which contributes to the overall thermal performance of the building fabric of the dwelling. Data on the basis of RdSAP v9.93 is presented for 2018, 2019 and 2022 only.
2.3.1 Energy Efficiency Rating, SAP 2009
This section examines the energy efficiency profile of the Scottish housing stock in 2022 under the SAP 2009 methodology.
Dwellings with main heating fuels other than mains gas (for example oil or coal) have systematically lower SAP ratings in SAP 2012 than in SAP 2009 and this is particularly true at the lower end of the SAP range. The main reason for this is that between SAP versions 2009 and 2012, fuel prices for these fuels increased more than for mains gas. As a result, average EERs tend to be slightly lower under SAP 2012 compared to SAP 2009.
The Scottish housing stock is gradually becoming more energy efficient.
Infographic 2.1: Mean and median EER relative to EPC bands, SAP 2009, 2010-2022
Infographic 2.1 shows the trend in mean EERs based on SAP 2009, which rose from 59.9 in 2010 to 67.7 in 2022. These ratings fall into band D. There was around a 1-point increase in the mean EER each year between 2010 and 2014. Improvement since then has been slower, and the increase between 2019 and 2022 was 1.3 points.
The median EE Rating has also improved since 2010. In 2022, half of all Scottish dwellings were rated 70 or better, fall into EPC band C or above, an increase of 8 SAP points from 62 in 2010.
Data Source: Table EE6 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 19]
A strong trend of improvement has been observed in the energy efficiency profile of the housing stock since 2010.
Figure 2.7: Distribution of the Scottish Housing Stock by EPC Band, SAP 2009, 2010-2022
As shown in Figure 2.7, 56% of the housing stock in 2022 had an EPC rating of C or better, up 32 percentage points since 2010. Over the same period, the proportion of properties in the lowest EPC bands, E, F and G, has dropped 18 percentage points: 27% of properties were rated E, F or G in 2010 compared with 9% in 2022.
Data Source: Table EE7a in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
2.3.2 Energy Efficiency Rating, SAP 2012
This section examines the energy efficiency profile of the Scottish housing stock under the SAP 2012 methodology (RdSAP v9.93). Time series analysis is presented for 2018, 2019 and 2022. Further breakdowns by household and dwelling characteristics for 2022 are also presented.
The Scottish housing stock is gradually becoming more energy efficient.
Infographic 2.2: Mean and median EER relative to EPC bands, SAP 2012, 2010-2022
In 2022, the mean energy efficiency rating of the Scottish housing stock under SAP 2012 (RdSAP v9.93) was 66.6 and the median was 69 points, indicating that half of the housing stock has an energy efficiency rating of 69 or better. The mean rating increased between 2019 and 2022, from 64.7 to 66.6.
Data Source: Table EE6 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 19]
Scottish housing is gradually moving up through the EPC bands.
Figure 2.8: Distribution of the Scottish Housing Stock by EPC Band, SAP 2012, 2018-2022
Figure 2.8 shows that 52% of all properties in 2022 were rated C or better under SAP 2012 (RdSAP v9.93), compared to 45% in 2019. 12% of properties in 2022 were in bands E, F or G, down from 15% in 2019.
Data Source: Table EE7a in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Housing in the social sector tends to be more energy efficient than the owner occupied or private rented sector.
Figure 2.9: Percentage of dwellings by EPC band and tenure in 2022
As shown in Figure 2.9, 65% of social housing is in band C or better under SAP 2012 (RdSAP v9.93), compared to 50% in the private rented sector and to 48% in the owner-occupied sector. Around 4% of dwellings in the social sector are within EPC bands E, F or G, while 14% of owner occupied dwellings and 19% of the private rented sector are within these EPC bands. Housing in the social sector tends to be more energy efficient than the owner occupied or private rented sector. This could be driven by the Scottish Housing Quality Standard and the Energy Efficiency Standard for Social Housing which introduced minimum energy efficiency levels for that sector.
Data Source: Table EE8a in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Across Scotland, 4% of properties were in bands F or G in 2022.
Figure 2.10: Proportion of homes in EPC Band F or G by dwelling and household characteristics in 2022, SAP 2012
Figure 2.10 shows that dwellings in the lowest energy efficiency bands (F and G) are more likely to be pre-1919 dwellings (11%), non-gas heated properties (16% for electric, 17% for oil and 19% for other fuels), detached properties (8%), off gas grid properties (20%), and in rural areas (14%). Across Scotland as a whole, 4% of properties were in bands F or G in 2022.
Data Source: Table EE9 and EE10 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 1] [note 2] [note 4]
There is a strong association between household characteristics and energy efficiency rating.
Mean SAP 2012 (RdSAP v9.93) ratings ranged from 64.3 in dwellings owned outright to 73.2 in housing association dwellings, a statistically significant difference. Social housing as a whole is more energy efficient than the private sector, with a mean EER of 70.5 compared to 65.3 for private dwellings.
Older households (64.6) have lower average EER ratings than families (68.4) and other (adults without children) households (67.5).
Mean EER ratings ranged from 66.1 to 67.1 across income bands. Average EER ratings ranged from 65.1 to 67.6 across council tax bands with dwellings in higher council tax bands being less energy efficient.
For more information and sample sizes, please see Table EE9 and EE10 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 19]
There is a strong association between dwelling characteristics and energy efficiency rating.
Table 2.3 shows that across dwelling types, detached properties have the lowest energy efficiency ratings on average (mean EER 63.2) while flats have the highest ratings (70.3 for tenements and 69.5 for other flats).
The oldest, pre-1919, properties are the least energy efficient (mean EER of 58.8 and 29% rated C or better) while those built after 1982 have the highest energy efficiency ratings (mean EER of 74.2, with 83% in band C or better).
Primary heating fuel is a key determinant of the energy efficiency of the dwelling. Properties heated by mains gas have an average rating of 69.1 and 58% are in band C or better. Dwellings heated by other fuels (including electric and oil) have considerably lower ratings. The average energy efficiency rating for oil heated properties is 51.7 (corresponding to EPC band E) and only 9% are in band C or better. For electric heated dwellings the average energy efficiency rating was 56.1 and 29% are in band C or better.
Proximity to the gas grid has a similar effect on the energy efficiency rating (average SAP rating 68.5 for dwellings near the gas grid, higher than the 52.1 for off grid dwellings).
As dwelling characteristics associated with lower energy efficiency are disproportionately represented in rural areas, the average energy efficiency profile of rural properties is lower than that for urban areas. Table 2.3 shows that the mean SAP 2012 (RdSAP v9.93) rating is 68.2 for dwellings in urban areas with 56% in band C or above, higher than the 58.6 for dwellings in rural areas, where 33% of dwellings are in band C or better.
For more information and sample sizes, please see Table EE9 and EE10 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 1] [note 2] [note 4] [note 19]
The National Home Energy Ratings (NHER) system was the main methodology used in the SHCS to report on the energy efficiency of the housing stock prior to 2013. With the publication of the 2013 SHCS Key Findings Report the energy modelling methodology was updated and it is no longer possible to reproduce exactly the original NHER method, as the full documentation of this method is not publicly available. Further details can be found in the Methodology Notes to the 2013 SHCS report. However because of user interest (and because NHER scores were taken into account under the energy efficiency criterion of the SHQS) we provide an approximate NHER score by household and dwelling characteristics in Table EE11 and EE12 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’.
2.4 Carbon Emissions
Key Points
- Based on modelled energy use required to meet the SAP standard heating regime[3], the average Scottish home was estimated to produce 6.5 tonnes of carbon dioxide (CO2) per year in 2022, which is approximately double the average carbon emissions per household as reported by Department for Energy Security and Net Zero (3.3 tonnes per year) in 2020, based on actual energy use. This suggests that households are not heating their homes to the SAP standard heating regime.
- Average modelled carbon emissions for all properties was 69 kg per square meter of floor area in 2022.
Carbon Emissions are the amount of greenhouse gas emissions, expressed as their carbon dioxide gas equivalent, vented to the atmosphere. Estimates of emissions from the residential sector which take into account actual energy consumption by households are reported annually by Department for Energy Security and Net Zero in the Local and Regional Carbon Dioxide (CO2) Emissions Estimates. This methodology is consistent with the Greenhouse Gas Inventory (GHGI) which is the source for monitoring progress against the Scottish Government’s climate change commitments.
In contrast, emissions reported from the SHCS are modelled on the assumption of a standard pattern of domestic energy consumption and do not reflect differences in consumption behaviour due to cost, preferences or changes in weather conditions. As such, they are distinct from the carbon emissions figures published by Department for Energy Security and Net Zero and compiled in GHG inventories.
Estimates in the Climate Change Plan: Third Report on Proposals and Policies (RPP3) are also not comparable to SHCS estimates. RPP3 figures for the residential sector relate to non-traded emissions only (i.e. exclude electricity which is covered by the EU Emissions Trading System) while SHCS estimates cover all fuel types.
This report is only concerned with the level and variations in modelled emissions from the Scottish housing stock. These estimates are produced through the use of BREDEM 2012-based models, in line with other statistics on energy efficiency and fuel poverty reported here. Information on the energy modelling is available in section 1.3 of the Methodological and Technical notes.
To derive emissions estimates, modelled energy demand is combined with carbon intensity factors as adopted for the 2012 edition of the SAP (see section 1.3 of the Methodological and Technical note). These are carbon dioxide (CO2) equivalent figures which include the global warming impact of methane (CH4) and nitrous oxide (N2O) as well as carbon dioxide (CO2).
2.4.1 Modelled Emissions by Dwelling Type and Age of Construction
The annual modelled emissions from a property reflect the energy use for the whole dwelling heated according to the SAP standard heating regime[3].
Newer dwellings have lower modelled emissions than older ones.
Table 2.4 shows that newer dwellings have lower modelled emissions than older ones on average as a result of their better thermal performance and higher energy efficiency (as shown in section 2.3). Post-1982 tenement and other flats have the lowest modelled emissions on average (3.1 and 3.2 tonnes per year, respectively).
Across all age bands, detached houses have the highest modelled emissions due to a larger share of exposed surfaces (between 15.6 tonnes per year for pre-1919 dwellings to 7.4 tonnes per year for post-1982 dwellings). As shown in section 1.3 of this report, they are also the most likely to use high carbon-intensity fuels such as oil and coal in place of mains gas.
For more information, please see Table EE14 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Dwellings with larger floor areas have higher modelled carbon emissions.
By dividing modelled emissions by total internal floor area, we derive carbon dioxide (CO2) emissions per square meter (kg/m2). Controlling for floor area in this way (see Table 2.5) shows that pre-1919 detached (109 kg/m²) houses have the highest modelled emissions per square meter. Post-1982 dwellings have the lowest emissions, particularly tenements dwellings (50 kg/m2), terraced (52 kg/m2) and other flats (54 kg/m2).
For more information, please see Table EE14 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
2.4.2 Modelled Emissions by Tenure
Although data for 2014-2022 is not directly comparable to prior years due to changes in the carbon emissions methodology, the data suggests that there is a longer term trend of declining emissions. Average modelled carbon emissions reduced from 92 kg/m2 in 2010 to 80 kg/m2 in 2013. Based on the updated carbon emissions methodology, there was then a further decrease from 80 kg/m2 in 2014 to 74 kg/m2 in 2017 and then remaining stable at 73 kg/m2 in 2018 and 2019 and reducing to 69 kg/m2 in 2022.
Private sector have higher modelled carbon emissions than social sector.
Figure 2.11: Average modelled emissions by tenure, 2010 to 2022
Figure 2.11 shows how emissions differ across tenure for the period 2010 to 2022. In 2022, the highest emissions were observed for private rented dwellings (78 kg/m2) and lowest for housing association dwellings (59 kg/m2). The values were similar to the previous year across all tenures; however, the longer time series shows a decreasing trend over the 2010-2022 period for all tenures.
Changes to the tenure definitions and the revised carbon emissions methodology mean that figures for 2014 to 2022 by tenure are not fully comparable to earlier years. Differences that were statistically significant were seen in the mortgaged sector (reducing from 78 kg/m2 in 2014 to 66 kg/m2 in 2022) and households that are owned outright (reducing from 81 kg/m2 to 70 kg/m2 between 2014 and 2022).
Data Source: Table EE15 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 6]
2.5 Environmental Impact Rating
The Environmental Impact Rating (EIR) represents the environmental impact of a dwelling in terms of carbon emissions associated with fuels used for heating, hot water, lighting and ventilation. Ratings are adjusted for floor area, so they are independent of dwelling size for a given built form. Emissions for this measure are calculated using the SAP methodology.
EIRs for 2022 have been described in this report based on SAP 2012 under RdSAP v9.93.
The Environmental Impact Rating (EIR) of Scottish dwellings has gradually increased over time.
Infographic 2.3: Median EIR relative to Band, 2018 to 2022.
In 2022, the mean EIR rating was 63 and the median was 66, both of which fall in band D. Infographic 2.3 illustrates the increasing trend in the mean and median EIR between 2018 and 2022. This indicates that the environmental impact of Scottish housing is gradually falling over time but has remained within band D.
Data Source: Table EE16 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 19]
In 2022, 39% of dwellings had an EIR of band C or above
Figure 2.12: EIR Bands in the Scottish Housing Stock, 2018 - 2022 SAP 2012
As shown in Figure 2.12, 39% of dwellings had EI ratings in band C or better under SAP 2012 (RdSAP v9.93) in 2022, an improvement on the 2019 figure of 34%. 23% of dwellings were rated E, F or G in terms of their environmental impact in 2022, lower than 2019 rate.
Data Source: Table EE16 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 19]
Environmental Impact Ratings (EIRs) vary across different type of dwellings.
Dwellings built post-1982 have (higher) better EIRs than other dwellings, with 71% rated band C or better. Flats have a lower environmental impact (higher EIR) than houses, as do gas heated properties compared to those heating using oil or electricity.
Oil heating systems and houses are more common in rural areas, leading to higher environmental impacts (lower EIRs) for rural dwellings. Dwellings near the gas grid have better EIRs than dwellings off the gas grid, with 43% rated band C or better.
For more information and sample sizes, please see Table EE17 in ‘SHCS 2022- Chapter 02 Energy Efficiency- tables and figures’
Notes: [note 1] [note 2] [note 19]
[1] This design has higher running efficiencies; a portion of the heat that would be lost through vented water vapour is recovered through condensation in a heat exchanger.
[2] For existing dwellings, there are occasions where it may not be practical to install a condensing boiler. The Condensing Boiler Installation Assessment Procedure Guide offers further guidance in this area. Where a non-condensing boiler is installed this may result in a boiler with poorer efficiency than that of a newly installed condensing boiler of the same fuel type.
[3] The standard heating regime is: 21°C in the living room and 18°C in other rooms for 9 hours a day during the week and 16 hours a day during the weekend. See section 3.1 for a breakdown of the 4 heating regimes used in the SHCS.
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