BB20 Energy Performance of Scottish Housing Stock

Over half (55%) of Scotland’s total energy demand is for heating (Scottish Government, 2015).  Improving the energy efficiency of dwellings reduces the energy required for heating and such improvements will help Scotland to attain its target to reduce energy consumption by 12% by 2020 from the baseline of 2005 - 2007 (ibid).  It can also help to reduce Fuel Poverty (see Indicator CRS61).

The energy efficiency of a dwelling depends on its physical characteristics.  Factors such as the age and type of building, its heating and hot water systems and the extent of insulation all affect its energy efficiency (SHCS, 2014).  Improvements are gained by improving insulation levels (lofts spaces, walls and windows) and improving the efficiency of boilers and electrical appliances. 

While the overall energy use of a household depends on factors including the energy efficiency of the dwelling and the behaviour of the occupant, this indicator only tracks energy efficiency – i.e. it is independent of occupant behaviour and of other determinants. 

The energy efficiency of a dwelling is shown through an ‘Energy Efficiency Rating’ (EER), based on the cost of space and water heating, ventilation and lighting per square metre of floor area. EERs cover all aspects of domestic energy and thermal efficiency, including the energy demand for heating (taking into account likely heat loss rates), and the energy demand from (electric) heating and domestic appliances. The latter contribute about 9% of the total energy demand from domestic electricity use (BRE, 2013; SHCS, 2014 and Scottish Government, 2015). 

EERs are expressed on a scale of 1-100, where a dwelling with a rating of 1 have very poor insulation, energy efficiency and high fuel bills, while 100 represents very high insulation, energy efficiency and the use of lower-cost fuel for heating (eg mains gas rather than electricity or oil) . Ratings can exceed 100 where the dwelling generates more energy than it uses.

‘Energy Performance Certificates’ (EPCs) divide EER ratings into bands from A (most energy efficient) to G (least energy efficient).  EPCs were introduced in January 2009 and are intended to stimulate improvements to domestic energy efficiency (by influencing owners to take action to improve energy efficiency before putting their homes on the market (Scottish Government, 2013b).  Thus EPCs may be more familiar to the general public, as they are now required whenever a building is sold or rented to a new tenant. 

A related measure is the Energy Impact Rating (EIR) which measures the environmental impact of a dwelling in terms of carbon emissions associated with the fuels used for heating, hot water, lighting and ventilation. A rating of 1 indicates very high carbon emissions, and 100 indicates low emissions. This measure is not covered in this indicator, but is useful for those assessing building stock and carbon emissions.  More information is available in the SHCS (2014).

Scottish domestic gas consumption per consumer is currently the highest in the UK, due to the effect of weather differences on heating demand (Scottish Government, 2015).  The energy demand for heating in Scotland may reduce in future as average winter temperatures rise, but only if factors such as energy efficiency remain constant or improve. 

Related Indicators: 

BB26 Natural gas usage; domestic

CRS61 Number of households in fuel poverty

CRS64 Uptake of Domestic Energy Efficiency Measures

Table 1 shows there is a slight upward progression in mean EE Ratings (EERs), from below 60 in 2010 to above 63 in 2013. These EERs all fall into band D of the EPC scheme.

There has been around a one point increase in the average EERs each year since 2010. Overall the median EER for Scottish housing is 66, an increase of 4 points since 2010 (SHCS, 2014).  This rise in the median rating in relation to Energy Performance Certificate bands is depicted in Figure 1.

Table 1  Average EERs for 2010 - 2013

Source: Scottish House Condition Survey, 2014

Figure 1 Median EERs relative to EPC bands, 2010-2013

Source: Scottish House Condition Survey, 2014

Figure 2 shows distribution of housing stock across the bands for the four years 2010 – 2013.  This shows an increase in band C for each year and ongoing reductions across bands E and F (ibid). Over a third of all Scottish dwellings (36%) are now in EPC band C or better.  It is notable that only 1% are in band B, and no property has yet met the requirements to be placed in band A.  Nonetheless, Scottish housing is gradually moving up through the EPC bands. As previously indicated, these improvements arise through improvements such as loft and wall insulation, and the use of energy efficient boilers and appliances.  A summary of issues and their implications is given in Indicator CRS61.

Figure 2  EPC Ratings of the Scottish Housing Stock, 2010 – 2013

Source: Scottish House Condition Survey, 2014

The energy performance of the Scottish building stock has been improving since 2007.  However, direct comparison is not possible as the method for calculating Energy Efficiency Ratings changed in 2010 to use the SAP 2009 methodology (BRE, 2009). Previous ratings are based on SAP 2005 and SAP 2001 methods which are not directly comparable (SHCS, 2014). While no methodology will ever be perfect, the use of an agreed, standard methodology does allow the energy performance of housing stock as a whole to be tracked, as well as the assessment and comparison of the performance of different housing types.

The impact of the new methodology on the energy efficiency profile of the Scottish housing stock is shown in Figure 2 below, which also shows a steady improvement in performance.  This improvement has been driven by a range of energy efficiency legislation and incentive schemes. For example, the heating system is a key factor in the thermal efficiency of a dwelling.  Since 2007 around 83% of households have used a gas or oil boiler. Two significant legislated improvements in gas and oil-fuelled boiler were as follows:

• In 1998, boiler efficiency standards were set by European Council Directive 92/42/EEC21
• In 2010, Scottish Building Standards increased efficiency requirements for new and replacement boilers (Scottish Government, 2013a)

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 Scottish Government (ibid).

Figure 3 Grouped EPC Bands under New and Old Energy Models, 2007-2013

Source: Scottish House Condition Survey, 2014

In the social housing sector, efficiency across all measures (boilers and insulation) has been improved through the Scottish Housing Quality Standard (SHQS).  The SHQS was introduced in 2004, and all social rented dwellings must meet its criteria by 2015. For example, in relation to loft insulation, the SHQS requirement is for at least 100 mm. It appears that in the process of meeting these standards, many social landlords have now exceeded them (SHCS, 2014).

Improvement in insulation and energy efficiency has been driven by a range of legislation, incentives and programmes, including the Climate Change and Sustainable Energy Act 2006[1] , The Carbon Emissions Reduction Target (CERT) scheme and the Energy Company Obligation (ECO) scheme (see CRS64 for more detail). 

As of 2013, at least 100 mm of loft insulation had been installed in 92% of lofts and 69% of homes with cavity walls had cavity wall insulation in 2013 (SHCS, 2014).   Provisional analysis from NEED shows that installing cavity wall insulation in Scotland gives a typical saving of almost 10% on heating energy (or 1,800 kWh). Savings from loft insulation are smaller, at almost 3% (ibid).  However, uptake of solid wall insulation is slow and the majority (89%) of such dwellings are not insulated.    

As noted earlier, as older boilers are replaced, they will have to meet the new minimum 86% efficiency requirement of Scottish Building Standards (Scottish Government, 2013a).  Just 7% of boilers were condensing boilers in 2007, as compared with 43% in 2013 (Scottish Government, 2015).  A further revision of the current building regulations is expected in October 2015.

Other Factors - Dwelling and Heating Type

• EPC ratings vary by dwelling type. Older dwellings tend to have lower ratings; 11% of pre-1919 dwellings are rated F or G, compared with under 1% of post-1982 dwellings (SHCS, 2014)
• Dwellings with fewer external surfaces lose less heat to their surroundings. Detached houses with large surface areas are more likely to have lower energy efficiency ratings; 8% are rated F or G compared with just 2% of terraced houses (SHCS, 2014)
• Mains gas is currently the cheapest mainstream fuel. Only 2% of gas-heated dwellings have an F or G-rating compared with 11% of electrically heated dwellings (SHCS, 2014)

Trends in other domestic energy usage

DECC (2014) provides UK-wide figures for energy usage.  The energy usage for lighting and cold appliances has reduced due to efficiency improvements, but energy usage for consumer electronics and home computing is on the increase.

Building Research Establishment (BRE) (2009) The Government’s Standard Assessment Procedure for the Energy Rating of Dwellings (revised 2011), available at: www.bre.co.uk/filelibrary/SAP/2009/SAP-2009_9-90.pdf

Building Research Establishment [BRE] (2013) BREDEM 2012 A technical description of the BRE Domestic Energy Model http://www.bre.co.uk/filelibrary/bredem/BREDEM-2012-specification.pdf

DECC (2013) National Energy Efficiency Data Framework [NEED], available at www.gov.uk/government/collections/national-energy-efficiency-data-need-framework

DECC (2014) Energy Consumption in the UK [ECUK] (2014) Chapter 3: Domestic Energy Consumption in the UK between 1970 and 2013 and corresponding data sheets, available at: https://www.gov.uk/government/statistics/energy-consumption-in-the-uk

Scottish Government (2012)  Energy in Scotland: A Compendium of Scottish Energy Statistics and Information Available at:  http://www.gov.scot/Publications/2012/03/2818/5  (accessed 14/07/15)

Scottish Government (2013a) Building Standards Technical Handbook – Domestic – Energy Section 6.3.1  http://www.scotland.gov.uk/Resource/0045/00459729.pdf

Scottish Government (2013b) Electricity Generation Policy Statement, available at: www.gov.scot/Resource/0042/00427293.pdf (accessed 20 July 2015).

Scottish Government (2013c) Scotland’s Sustainable Housing Strategy, available at: www.gov.scot/Resource/0042/00425697.pdf  (accessed 20 July 2015).

Scottish Government (2014a) Ambition, Opportunity, Place:  Scotland’s Third National Planning Framework, available at: www.gov.scot/Resource/0045/00453683.pdf

Scottish Government (2014b) The Energy Efficiency Standard for Social Housing [EESSH]. Available at www.gov.scot/Resource/0044/00447123.pdf

Scottish Government (2014c) Towards Decarbonising Heat: Maximising the Opportunities for Scotland.  Draft Heat Generation Policy Statement (for Consultation), available at: www.gov.scot/Resource/0044/00445639.pdf

Scottish Government (2015) Energy in Scotland, available at: www.gov.scot/Resource/0046/00469235.pdf  (accessed 20 July 2015)

Scottish House Condition Survey (SHCS) (2014) Mueller, G., Robertson, J., Leadbetter, C., Laing, N., McMeneny, M and Kyriakou, A. (2014) Scottish House Conditions Survey 2013, Key Findings.  Directorate for Housing, Regeneration and Welfare, Scottish Government.  Available at: www.gov.scot/Resource/0046/00465627.pdf  (accessed 10 February 2015)

Lead author: Katherine Beckmann (Heriot-Watt University)

Scottish Government Staff responsible for the Scottish House Conditions Survey