Scottish House Condition Survey: 2021 Key Findings

7 Technical Notes and Definitions

7.1 Survey Estimation

From 2012 the Scottish House Condition Survey (SHCS) has been a module of the Scottish Household Survey (SHS). In 2012, around a third (36%) of respondents to the SHS were invited to participate in a follow-up inspection by SHCS surveyors. This proportion has had to increase over time as the conversion rate from the social interview to the physical survey has decreased. Almost half of respondents (47%) to the 2019 SHS were invited to participate in the 2019 SHCS to ensure that the required number of physical surveys were achieved.

Due to the change in approach for 2021, respondents to the 2021 SHS were invited to participate in the 2021 external+ SHCS based on their response to the tenure question in the social interview, with renters having a higher probability of being invited to participate than owner occupiers. (For further details see the section of this report on external+ data quality.) A total of 3,980 households (40%) that responded to the 2021 SHS were invited to participate in the 2021 SHCS, with 3,174 going on to do so. The proportion of SHS respondents asked to participate in the 2021 external+ SHCS was lower than previous years as the conversion rate was higher.

7.1.1 Sample Sizes and Gross Dwelling Numbers

In Table 7.1 we provide the sample sizes in the social interview and physical dwelling inspection follow-up for all years of the annual SHCS to 2021.

Table 7.1: Achieved sample for the social interview and physical survey and the number of occupied dwellings by survey year, 2003/04 to 2021

Survey year	Social interview (achieved sample)	Physical survey (achieved sample)	Number of occupied dwellings (thousands)
2003/4	3,870	3,090	2,269
2004/5	3,783	3,093	2,301
2005/6	3,679	3,147	2,315
2007	3,867	3,033	2,314
2008	3,763	3,015	2,331
2009	4,153	3,346	2,344
2010	3,853	3,115	2,357
2011	3,949	3,219	2,368
2012	3,813	2,787	2,386
2013	3,780	2,725	2,402
2014	3,787	2,682	2,420
2015	4,083	2,754	2,434
2016	4,220	2,850	2,452
2017	5,049	3,002	2,464
2018	4,843	2,964	2,477
2019	4,843	2,997	2,496
2021	3,980	3,174	2,529

Table 7.1 also shows the total number of households (occupied dwellings) in Scotland for each survey year which provides the basis for grossing up the estimates of households and dwellings in this report. These figures are produced annually by the National Records of Scotland as part of their inter-censal household estimates publication.

The SHCS is a sample survey. All survey results are estimates of the true prevalence within the population and will contain some error associated with sampling variability. The likely size of such variability can be identified, by taking account of the size and design of the sample, as described in the subsections on confidence intervals, design effects and statistical significance.

In addition to sampling variability, there are other sources of uncertainty, such as those arising from incomplete responses or failure to secure participation in the survey from each sampled household. Where non-response is not random, i.e., some types of households are less likely to participate than others, bias is introduced into the survey data. Such errors have not been quantified in this report.

In general, the smaller the sample size, the greater the likelihood the estimate could be misleading, so more care must be taken when using smaller subsets of the survey sample for analysis. In this report estimates representing 2 or fewer cases, or where the base sample is below 30 have been suppressed.

Different types of estimates are subject to different levels of uncertainty associated with sampling and design. For example, estimates of change (i.e., figures relating to comparisons across survey years) are generally subject to greater sampling error than point-in-time estimates (i.e., figures relating to one survey year only) and such errors would be understated by the confidence intervals in Table 7.2. There is more uncertainty associated with complex measures, such as the fuel poverty rate and this is not quantified in this report or reflected by the confidence intervals in Table 7.2.

7.1.2 Confidence Intervals

By convention, a 95% confidence interval is used to quantify the variability of a sample estimate, under which there is a 1 in 20 chance that the true value will fall outside the given confidence interval.

Table 7.2 shows the 95% confidence limits for estimates of proportions based on sub-samples of various sizes before design effects are considered.

Table 7.2: 95% confidence limits for estimates based on sub-samples of various sizes (excluding design effects)

Sub-sample size	Estimate of 10% or 90%	Estimate of 20% or 80%	Estimate of 30% or 70%	Estimate of 40% or 60%	Estimate of 50%
100	5.9%	7.8%	9.0%	9.6%	9.8%
250	3.7%	5.0%	5.7%	6.1%	6.2%
500	2.6%	3.5%	4.0%	4.3%	4.4%
1,000	1.9%	2.5%	2.8%	3.0%	3.1%
1,500	1.5%	2.0%	2.3%	2.5%	2.5%
2,000	1.3%	1.8%	2.0%	2.1%	2.2%
3,000	1.1%	1.4%	1.6%	1.8%	1.8%

7.1.3 Design Effects

The design effect is the ratio between the variance (average squared deviation of a set of data points from their mean value) of a variable under the actual sampling method used and the variance computed under the assumption of simple random sampling. In short, a design effect of 2 would mean doubling the size of the sample used to obtain the same level of precision as with a simple random sample; a design effect of 0.5 implies the reverse. Design effect adjustments are necessary where standard errors (and confidence intervals) are affected by the design and complexity of the survey.

Disproportionate stratification and sampling with non-equal probabilities tends to increase standard errors, giving a design effect greater than 1. However, this can be controlled by deliberately over-sampling in stratum where the item of interest is either very rare or variable. The impact of non-response weighting on standard errors tends to be, although with exceptions, comparatively limited. The sampling design of the SHCS meets the criteria above in that disproportionate stratification is applied across the 32 local authority areas with over-sampling of remote rural areas - for example in Orkney Islands and Shetland Islands. As a result, one would expect the design effect to be above 1 although only modestly so.

Table 7.3 shows the design factors (the design factor is the square root of the design effect) for all the SHCS waves since 2003/04. When using a mixture of the physical and social survey data, the physical survey design factor must be used. The physical survey design factor for the 2021 SHCS is 1.12. It was not possible to produce social weights for the 2021 SHCS as there were no dwelling descriptions or abbreviated dwelling descriptions. Therefore, it is not possible to produce a social survey design factor.

Table 7.3: Design factors for the SHCS by survey year, 2003/04 to 2021

Survey year	Physical survey design factor	Social survey design factor
2003/04	1.14	1.13
2004/05	1.18	1.17
2005/06	1.14	1.14
2007	1.13	1.11
2008	1.11	1.11
2009	1.09	1.08
2010	1.11	1.10
2011	1.12	1.11
2012	1.09	1.08
2013	1.09	1.08
2014	1.09	1.08
2015	1.10	1.08
2016	1.10	1.08
2017	1.10	1.08
2018	1.11	1.08
2019	1.12	1.08
2021	1.12	[z]

In general, when producing estimates at a local authority level from the SHCS, no design effect adjustment of standard errors is necessary because simple (equal interval) random sampling is carried out within each local authority. However, if producing estimates at a local authority level using the 2021 SHCS, which is not recommended, the unequal selection probabilities for owner occupiers and renters would have to be accounted for.

7.1.4 Statistical Significance

Because the survey’s estimates may be affected by sampling errors, apparent differences may not reflect real differences in the population. A difference is significant if it is so large that a difference of that size is unlikely to have occurred purely by chance.

Comparisons in this publication are tested at the 5 per cent level as described in the subsection on confidence intervals. Testing significance involves comparing the difference between two statistics (for example, the percentage of households rated as EPC band C or better for the social sector compared to the private sector) with the 95 per cent confidence limits for each of the two estimates considered.

Our approach to testing statistical significance follows that described in the Scottish Household Survey 2019 supporting document.

In the example above (see Table EE10 the supporting energy efficiency tables), the percentage of social sector households rated as EPC band C or better is 65% with a 95 per cent confidence interval of 4 percentage points, having accounted for the design factor of 1.12 in Table 7.3. The percentage of private sector households rated as EPC band C or better is 48% with a 95 per cent confidence interval of 2 percentage points. As the absolute difference between the estimates (17 percentage points) is greater than the square root of the sum of the squared confidence intervals (5 percentage points), we conclude that the difference between the estimates is statistically significant at the 5 per cent level.

7.1.5 Table Conventions

The following conventions are used in tables:

• [low] indicates a value is less than 0.5% or 500 households
• [w] indicates there are no sample cases
• [c] indicates that the base sample is too small to report (below 30 cases) or the estimate represents 2 or fewer sampled households
• [z] indicates that a value is unavailable as it is not applicable

These conventions are consistent with the guidance on using symbols and shorthand when publishing data tables on public sector websites.

7.2 Missing Tenure Information

Because of a routing error tenure information is not available for a small number of cases in the 2012 and 2013 surveys (46 in 2012, 42 in 2013). This was rectified for the 2014 fieldwork and the full sample has been used when reporting on tenure for subsequent years. This introduces some discontinuities in comparing statistics for the social (or the private) sector for 2014 onwards, on the one hand, and previous years, on the other. For further details please refer to the respective earlier key findings reports. Tables in key findings reports from the SHCS are clear whether data for 2011 and earlier are presented including or excluding rent free cases.

7.3 Energy Models

Two domestic energy models, summarised in Table 7.4, are used to produce the energy outputs in this report. They are based on the same core methodology but have some different assumptions and calculations affecting the output values.

Table 7.4: Summary of domestic energy models used on SHCS data

Model	SAP	BREDEM 2012
Version	SAP 2009 SAP 2012 (RdSAP 9.92) for 2014 to 2019 SAP 2012 (RdSAP 9.93) from 2018 onwards	Version 1.0 for data up to 2013 Version 1.1 for data from 2014 onwards
Outputs	Energy efficiency ratings Environmental impact ratings	Fuel poverty energy use and running costs Carbon emissions
Fuel prices	SAP standard	Based on a range of sources. For more details see Table 1 in the section on Measuring Fuel Poverty in SHCS methodology notes 2019
Occupancy	Number of occupants derived based on total floor area of the dwelling	Actual number of occupants in the dwelling
Heating regime	21°C in the main living area and 18°C elsewhere; 9 hours per weekday and 16 hours at the weekend	For carbon emissions, as SAP For fuel poverty energy use/running costs for 2021 onwards, as described in paragraph 50 of the SHCS methodology notes 2019 For fuel poverty energy use/running costs for 2012 to 2019, as described in paragraph 48 of the SHCS methodology notes 2019
Climate	East Pennines	Based on geographical location. For fuel poverty energy use/running costs postcode district-level weather data is being used for 2021 onwards
Energy end-use included	• space heating • water heating • fixed lighting • gains from renewable energy technologies	As SAP but also energy used for: • cooking • running appliances

All energy efficiency and environmental impact rating related statistics for 2021 presented in this report are based on SAP 2012 (RdSAP 9.93).

Carbon emissions are calculated based on the standard heating regime, applying carbon intensity values to each fuel type used. Emissions factors for the BREDEM 2012 model come from SAP 2012 and are provided in Table 7.5.

Table 7.5: Carbon intensity of common heating fuels, SAP 2012

Fuel	Kilograms (kg) of carbon dioxide (CO2) per kilowatt hour (kWh)
Mains gas	0.216
LPG	0.241
Oil	0.298
Coal	0.394
Anthracite	0.394
Smokeless fuel	0.433
Wood - logs	0.019
Wood - pellets	0.039
Wood - chips	0.016
Electricity	0.519

From 2018 to 2019 SAP based energy variables under SAP 2012 RdSAP v9.92 and v9.93 were reported. For 2021 onwards energy variables under SAP 2012 RdSAP v9.92 are not available. Compared to v9.92, U-values for solid, insulated stone and uninsulated cavity walls improved, whereas they declined for insulated cavity walls. As a result, the mean SAP rating under v9.93 was 0.16 SAP points less than under v9.92 in 2019 and 0.17 points less in 2018.

Over the years improvements have been made to how the BREDEM 2012 model is used to produce energy outputs from the SHCS.

From 2016 the SHCS has collected information about the presence of pre-payment meters in dwellings which allows more accurate fuel prices to be assigned to these dwellings.

From 2019 more detailed information on combi boilers has been included to improve the accuracy of calculations surrounding hot water losses. As a result, the mean BREDEM 2012 modelled energy consumption is expected to increase by around 33 kWh per year.

Furthermore, from 2019 a household’s lights and appliances are assigned as using an off-peak tariff if an off-peak electricity meter is present, even if there is no form of electric heating in the dwelling. Previously, where a household did not have a form of electric heating, the lights and appliances were assumed to use standard electricity. This change does not affect the energy consumption of a dwelling, only the fuel prices applied to the energy associated with lighting and appliance use.

Climate factors such as external temperature, wind speed, latitude, mean global solar irradiance and height above sea level are determined by the area in which the dwelling is located. Prior to 2021, weather data for the nine Scottish regions in Table U6 in SAP 2012 was used. From 2021 more detailed postcode district weather data is being used from Table 172 of the Product Characteristic Database (PCDB).

The impact of using postcode district weather data has been measured using data from the 2015, 2016, 2017 and 2021 Scottish House Condition Surveys. It was found that many dwellings in the achieved sample were clustered in postcode districts where the average external temperature was higher and wind speed was lower than the regional averages previously used. As expected, a decrease in wind speed (which is most likely to be affected by local geography) combined with an increase in external temperature resulted in a decrease in mean energy consumption and mean annual running costs.

7.4 Fuel Poverty: income after housing costs

For the 2017 Scottish Household Survey (SHS), an updated set of questions collecting council tax information were incorporated and accounted for in fuel poverty analysis. Previously respondents were only asked to provide what they paid in council tax whether or not they received any deductions or reductions. The survey now distinguishes between reported council tax after any deductions or reductions, and full council tax. This reduces the risk of double counting Council Tax Reduction in household income in the former case.

For the 2018 SHS onwards, income data for up to three other adults in addition to the highest income householder and/or their spouse is collected. Prior to 2021, fuel poverty calculations have included only the income of the highest income householder and/or their spouse. For 2021 onwards the income of up to three other adults is included.

For the 2019 SHS onwards, housing costs are imputed when they are not provided. For 2021 onwards, imputed housing costs are used in fuel poverty calculations. Prior to 2019, when housing costs were not provided, they were assumed to be nil.

7.5 Boilers

Testing compliance of boilers with current Scottish Building Standards for domestic properties is carried out by comparing the boiler efficiency to minimum requirements. Data on the efficiency of household heating systems was first produced for the 2012 SHCS. However, there was a change to the methodology for the 2014 and 2015 SHCS which made an adjustment to the modelling to allow for the assumption that a poorly controlled system is, in effect, less efficient.

In the 2016 SHCS report, the full boiler efficiency dataset was revised to ensure it was on a consistent basis across years and represented the efficiency of the heating system before any adjustments for lack of controls. Efficiencies are taken directly from the Product Characteristics Database whenever possible and from the SAP default efficiencies for that system otherwise. This is therefore more representative of the actual boiler efficiency.

Furthermore, the thresholds used to test compliance for oil condensing boilers were also updated in 2016 to reflect current minimum standards. The full time series presented from 2017 onwards continues to reflect these changes.

7.6 Definitions of Categories in the Key Findings Report

7.6.1 Dwelling Types

The SHCS uses the following definitions of dwelling types:

• Detached house: a house that is free standing with no party walls
• Semi-detached house: a house that is only attached to one other dwelling, commercial premise etc. The two properties taken together should be detached from any other properties
• Terraced house: a house forming part of a row of three or more dwellings, commercial premises etc.
• Tenement flat: a dwelling within a common block of two or more floors (commonly up to five storeys but may be higher in certain circumstances) where some or all the flats have a shared or common vertical access. The selected dwelling need not share the access, but may be situated within the block with shared/common access (own door flat)
• 4-in-a-block: each flat in a block has its own independent access. Flats on the upper level have an internal or external stair
• Tower/slab: flats in a high rise (ten or more storeys) or flats where the common circulation is predominantly horizontal (maisonette, balcony, or gallery access)
• Flat from a conversion: flats resulting from the conversion of a house only. A flat converted from a non-residential building (e.g., a warehouse) is classified according to the above flat types

7.6.2 Household Types

The SHCS uses the following classification of household types:

• Families: households which contain at least one child aged under 16. Resident adults may be of any age
• Older households: small households made up of one or two residents, at least one of which is aged 65 or older
• Other households: these are all other households with adult residents (of any age) and no children

The pensionable age threshold used for SHCS key findings reports from 2015 onwards is 65 years for both men and women. Previous publications used 65 for men and 60 for women. Therefore, the categories ‘Older households’ and ‘Other households’ used from 2015 are not fully comparable with previous years.

7.6.3 Urban Rural Classifications

The urban/rural classification in SHCS key findings reports is the Scottish Government’s 2-fold and 6-fold urban rural classification. Dwellings in settlements with over 3,000 people are considered urban by this definition. For 2021 onwards, the 2020 urban rural classification is used for reporting, calibration weighting and in fuel poverty calculations to identify households in remote rural, remote small town and island (RRRSTI) areas for which uplifts to the UK Minimum Income Standard are applicable.

The Scottish Government published the 2016 urban rural classification in 2017. However, to remain consistent with the classification underpinning survey weight derivations, the 2013/14 urban rural classification (2011 data zone edition) is used for reporting 2016 to 2019 data. Prior to 2016, 2001 data zones are used.

7.6.4 Gas Grid Coverage Derivation

Determining whether a dwelling is within the coverage of the gas grid is primarily based on its proximity to gas distribution pipes. A dwelling is “on the gas grid” if it is within 63 meters of a low, medium, or intermediate pressure pipe, the usual maximum distance for a standard domestic connection. This methodology was used for deriving gas grid coverage for the 2013 to 2019 SHCS key findings reports.

Figure 7.1: Gas grid derivation using GIS mapping

Figure 7.1 shows how this is derived using GIS mapping. From the dwelling location information of surveyed properties, a 63-meter buffer is drawn. Where this buffer intersects a gas distribution pipe, the dwelling is said to be on the gas grid. In the example in Figure 7.1, dwelling A is on the gas grid, while dwelling B is not.

The gas grid information used for this mapping is provided by SGN.  It includes both the national gas network and the Scottish Independent Undertakings (SIUs), where gas is provided in areas remote from the national gas grid. It does not however include information on pipes owned and operated by Independent Gas Transporters (IGTs). Therefore, dwellings classified as off the gas grid by this method may be within 63 meters of an IGT operated gas distribution pipe and potentially have a connection to the gas grid. This methodology may therefore slightly undercount dwellings within the range of the gas grid.

The SHCS collects information on whether a dwelling has a mains gas connection. So, to account for the potential undercount of dwellings on the gas grid, from 2021 we have introduced an improvement to the gas grid coverage derivation whereby a dwelling categorised as being off the gas grid by the method described above but recorded as having a mains gas connection in the SHCS is re-categorised as being on the gas grid.

7.6.5 Reasons Why Home Heating is Difficult

Question HT14 in the Scottish Household Survey asks: “Which of these things, if any, make it difficult to heat your home”. There are 19 response categories and respondents can choose any combination of reasons why heating their home is difficult. Response categories are grouped for reporting in the energy perceptions section of the key findings reports from the SHCS.

“Poor or inadequate heating” corresponds to the response categories:

• No central heating
• Not enough heaters/radiators
• Position of heaters/radiators
• Poor system/need new system
• Radiators not big enough
• Heating not working
• Dislike storage heaters
• Inadequate heating
• Heating in part of house
• Can’t afford to replace system

“Hard to control heating” corresponds to the response categories:

• Difficult to control/regulate
• Hard to control heat

7.6.6 Hard to Treat Cavity Walls

Key findings reports from the SHCS use the Energy Company Obligation (ECO) definition of hard-to-treat cavity walls (HTTCs) to provide a breakdown of the remaining insulation potential of cavity wall dwellings in the Scottish housing stock.

Under this definition a cavity wall is considered hard-to-treat if:

• The building has three or more storeys. Dwelling spaces in lofts are not counted as storeys
• The building is severely exposed to wind-driven rain. The SHCS is not able to collect this information, which will lead to an underestimation of HTTCs
• Walls at risk of water penetration, i.e., walls requiring urgent repair to the wall finish and walls with penetrating damp[19]
• Non-traditional building types, e.g., timber frame, metal-frame, and prefabricated concrete
• Partially filled, narrow or uneven cavities as well as cavities with failed cavity wall insulation. The SHCS is not able to capture this information. As a result, HTTCs may be underestimated

Note that the presence of a conservatory alone does not cause a dwelling to be considered hard-to-treat under the ECO definition of HTTCs.

7.6.7 Disrepair

Key findings reports from the SHCS use different categories of disrepair to describe the state of disrepair of a dwelling.

A range of elements - both internal and external - are assessed for the extent of disrepair, the urgency of disrepair (relating to external and common elements only), and in some cases the residual life of the element.

In a small number of instances, surveyors may not be able to assess the state of repair of certain elements of a property. This results in a disrepair status of ‘unobtainable’ for the full property since we are unable to say for certain whether disrepair exists. This usually affects a small number of the properties surveyed. Tables and figures relating to disrepair describe where these properties have been counted for clarity in reporting.

7.6.7.1 Critical Elements

The critical elements are those whose condition is central to a dwelling being wind and weatherproof, structurally stable and safeguarded against further rapid deterioration. They are as follows:

• Roof covering
• Roof structure
• Chimney stacks
• Flashings
• Roof gutters and downpipes
• External walls - finish
• External walls - structure
• Access decks and balustrades (common areas - flats only)
• Foundations
• Damp-proof course
• External doors and windows (dwelling only)
• Doors, screens, windows, and roof lights (common areas - flats only)
• Internal walls/partitions [20]
• Floor structure
• Floor finish
• Dry/wet rot

Disrepair to critical elements is recorded where there is any disrepair, no matter how small, to the critical elements of the dwelling.

7.6.7.2 Urgent Disrepair

Urgent disrepair is recorded where the SHCS surveyor deems that a dwelling has any disrepair which, if not rectified, would cause the fabric of the building to deteriorate further and/or place the health and safety of the occupier at risk.

Urgency of disrepair is only assessed for external and common elements. Internal room floor structures and finishes as well as internal walls/partitions and the presence of dry/wet rot are the only critical elements for which urgency is not applicable.

The presence of urgent disrepair to critical elements was first reported in the 2019 SHCS key findings report, for 2018 onwards.

7.6.7.3 Extensive Disrepair

Extent of disrepair is usually measured on a 5 or 10-point scale.

The 5-point scale is as follows: 0 (no disrepair); 1 (small repairs up to 5%); 2 (minor repairs 5% to less than 25%); 3 (medium repairs 25% to less than 60%); and 4 (renew 60% to 100%).

The 10-point scale is as follows: 0 (no disrepair); 55 (less than 5%); 1 (5 to 15%); 2 (15 to 25%); 3 (25 to 35%); 4 (35 to 45%); 5 (45% to 55%); 6 (55 to 65%); 7 (65 to 75%); 8 (75 to 85%); 9 (85 to 95%); and 10 (95% or more).

Extensive disrepair is calculated to identify those dwellings where any disrepair present is of a relatively greater severity. It is recorded where:

• any building element has an overall disrepair score exceeding 20% by area; or
• any building element assessed has a score of 'medium' or 'renew' on the 5-point repair scale (equivalent to an area of around 25% or more of the element); or
• dry/wet rot is recorded in two or more rooms.

The average extent of disrepair is calculated from the 5 and 10-point scales by taking the mid-point of the relevant band for the element. So, for example, a chimney stack assessed as band 4 on the 10-point scale would contribute 40% toward the average value. Similarly, a bathroom wash hand basin assessed as medium on the 5-point scale would contribute 42.5% to the average value. The presence of dry/wet rot contributes 50% to the average value. Thus, measures of average extent should be considered approximate.

7.6.8 Damp and Condensation

Penetrating damp is usually the result of a defect in the building fabric, such as damage to the walls or roof, water ingress due to damaged seals on doors or windows or damp because of leaking plumbing.

Rising damp is the result of defective or missing damp proof coursing, leading to water leaching into the building fabric.

Condensation is the build-up of moisture inside a dwelling, which may be the result of insufficient or ineffective ventilation.

7.6.9 Bedroom Standard

The bedroom standard is defined in the Housing (Overcrowding) Bill 2003 based on the number of bedrooms in a dwelling and the people in a household who can share a bedroom.

Each of the following groups or individuals requires a separate bedroom:

• any couple
• a person aged 21 years or more
• two people of the same sex [21] aged between 10 and 20
• two children (whether of the same sex or not) under 10 years
• two people of the same sex where one person is aged between 10 years and 20 years and the other is aged less than 10 years and
• any further person who cannot be paired appropriately.

This definition is distinct from the rules introduced by the UK Government in April 2013 for the size of accommodation that Housing Benefit will cover for working age tenants renting in the social sector, known as the ‘spare room subsidy’ [22]. Applying the rules of the spare room subsidy requires information not collected in the SHCS. Statistics in this report relate to the bedroom standard only.

7.6.10 Tolerable Standard

The Tolerable Standard is a minimum standard for habitability introduced in the 1969 Housing (Scotland) Act, and updated by the 1987, 2001 and 2006 Acts and 2019 Order.

A dwelling meets the tolerable standard if it:

• is structurally stable
• is substantially free from rising or penetrating damp
• has satisfactory provision for lighting, ventilation and heating
• has an adequate piped supply of wholesome water available within the house
• has a sink provided with a satisfactory supply of both hot and cold water within the house
• has a water closet or waterless closet available for the exclusive use of the occupants of the house and suitably located within the house
• has a fixed bath or shower and a wash-hand basin, each provided with a satisfactory supply of both hot and cold water and suitably located within the house
• has an effective system for the drainage and disposal of foul and surface water
• has satisfactory facilities for the cooking of food within the house
• has satisfactory access to all external doors and outbuildings
• has electrical installations[23] that are adequate and safe to use
• has satisfactory thermal insulation
• has satisfactory equipment for detecting fire and giving warning in the event of fire or suspected fire and
• has satisfactory equipment for giving warning if carbon monoxide is present in a concentration that is hazardous to health.

The criteria on electrical installations and thermal insulation were added by the Housing (Scotland) Act 2006. These requirements came into force in April 2009 and were first reported in the 2010 SHCS key findings report. The change in definition caused the fail rate for the tolerable standard to increase from 0.7% in 2009 to 3.9% in 2010.

The criteria on fire and carbon monoxide alarms were added by the Housing (Scotland) Act 1987 (Tolerable Standard) (Extension of Criterion) Order 2019. The Scottish Government has published guidance on these changes. These new standards came into to come into force on 1 February 2022 and are therefore not considered in this current report but will be included in the 2022 SHCS key findings reports onwards. For the first time in the 2022 SHCS, surveyors must consider the presence, type and condition of smoke, heat and carbon monoxide alarms in a house when deciding if the house meets the tolerable standard.

In general, fewer dwellings fail the tolerable standard based on the presence of rising or penetrating damp than experience this issue overall. This reflects the fact that low levels of penetrating damp would not give grounds for action under the tolerable standard. A dwelling will normally be below tolerable standard if a surveyor finds persistent visible penetrating damp that covers an area greater than approximately:

• 10% of the overall wall space in one habitable room; or
• 10% of the ceiling in one habitable room; or
• 20% of the overall wall space or ceiling in one or more other spaces in the dwelling.

7.6.11 Scottish Housing Quality Standard (SHQS)

The SHQS was announced by the Minister for Communities in February 2004. A target was agreed that all social landlords must ensure that all their dwellings pass the SHQS by 2015. Private owners and private landlords are currently under no obligation to bring their properties up to a standard which meets the SHQS. However, the SHCS collects the same data for all dwellings to allow comparison across the housing stock.

The SHQS is an aggregation of the results from 55 different elements grouped into 5 higher-level criteria, which in turn provide a single pass/fail classification for all dwellings. The 5 higher-level criteria specify that the dwelling must be:

• above the statutory tolerable standard;
• free from serious disrepair;
• energy efficient;
• with modern facilities and services; and
• healthy, safe, and secure.

A full list of assessed elements is available on the Scottish Government website. Only one element of the SHQS is not assessed using SHCS data: no information is collected on external noise insulation (element 43).

The data is assessed against the SHQS as it stood in the year the data relates to. So, for example, in 2019 dwellings were assessed against elements 31 to 35 (covering cavity wall insulation, loft insulation, water tank and pipe insulation, central heating and energy efficiency ratings based on NHER or SAP) in the energy efficiency criterion. However, from 1 January 2021 these were superseded by the Energy Efficiency Standard for Social Housing (EESSH). Similarly, from 1 February 2022, elements 11 and 44 were replaced by elements 11A and 11B to cover changes to the tolerable standard relating to smoke, heat and carbon monoxide alarms.

Figures on SHQS failure rates for 2014 onwards are not entirely comparable to previous years published in key findings reports from the SHCS. Because of missing tenure information, a small number of dwellings (see the subsection on missing tenure information for more detail) are excluded from tenure breakdowns in figures relating to years prior to 2014. In addition, small changes to data processing relating to failure thresholds for the energy efficiency criterion[24], as well as other minor data processing corrections were introduced in 2014. Although the effect of these corrections on the overall failure rates in the social sector was neutral, some discontinuities with previous years cannot be ruled out, especially when considering more detailed breakdowns.

[19] It should be noted that no information on the presence of rising or penetrating damp was collected in the 2021 SHCS due to the enforced methodological changes. Therefore, HTTCs may be underestimated in outputs from 2021 SHCS.