Data and variables

The stock model used to examine the implementation of the energy certif- icate consists of seven age classes of residential stock covering the entire UK dwelling stock. It used data from the English Housing Condition Survey

(EHCS) in line with the UKDC model in the 40% House research project. On the basis of the qualitative analysis and the discussion in the research team, suit- able variables were selected to examine the potential contribution that energy certificates could make to reducing carbon emissions from the existing hous- ing stock. Four core elements were identified, which are assumed to differ de- pending on the type of tenure. The principle can be described as follows: Carbon reduction =

Transactions (t) x Compliance (c) x Adoption of measures (a) x Measures (m)

where: Transactions (t) is the number of property transactions in the UK per year (t₁ = owner-occupied sector, t₂ = social rented sector, t₃ = private rented sector).

Compliance (c) is the estimated number of transactions actually labelled in the UK per year (c₁ = owner-occupied sector, c₂ = social rented sec- tor, c₃ = private rented sector).

Adoption of measures (a) is the estimated number of labelled house- holds acting on the recommendations of the energy certificate (a₁ = owner-occupied sector, a₂ = social rented sector, a₃ = private rented sector).

Measures (m) is the average saving in space heating demand (in kWh) resulting from the energy efficiency measures adopted.

This gives us the following equation:

Carbon reduction = [(t₁ x c₁ x a₁) + (t₂ x c₂ x a₂) + (t₃ x c₃ x a₃)] x m Transactions (t)

Since an energy certificate has to be issued when a dwelling is built, sold or

Source: National Centre for Social Research, 2003; Petersdorff et al., 2002; Sak and Raponi, 2002 2,500,000 2,000,000 1,500,000 1,000,000 500,000 0 180,400 437,800 87,600 175,100 2,569,100

new all refurbishment refurbishment property

construction refurbishments >1,000 m2 >200 m2 transactions

let, the annual number of energy certificates depends on annual property transactions (t). Fig. 6.2 shows the annual rates of new construction, refurbish- ment and property transactions in the UK in 2001/2. In view of Article 6 of the Directive the renovation rates for thresholds of 200 m2 _{and 1,000 m}2 _{were also}

examined. Table 6.1 gives an estimate of annual property transactions in the UK in relation to type of tenure and total housing stock.

The figures show that transactions in the UK can cover about 14% of the housing stock per year, although this proportion is not directly representative of annually labelled dwellings, as an energy certificate is valid for 10 years and the average renovation interval for a building is at least 25-30 years, so a household is not going to act each time an energy certificate is obtained. Some properties may also not change hands for a long time.

Compliance (c) and adoption of measures (a)

There is no consensus on what number is appropriate for compliance (c) and adoption (a) in the analysis of the UK situation, but Table 6.2 gives an esti-

Table 6.1 Annual property transactions in the UK by type of tenure in 2001/2002

Tenure Annual transactions % of all % of

(UK) transactions housing stock

Owner-occupied 1,215,550 47.3 6.75

Social rented 447,350 17.4 2.49

Private rented 906,200 35.3 5.03

Total 2,569,100 100 14.27

Source: National Centre for Social Research, 2003

Table 6.2 Estimate of labelled buildings and households taking action in the UK

Scenario Tenure Compliance Adoption of recommendations

(% of annual transactions made in the certificate

in the UK) (% of compliance)

Scenario 1 Owner-occupied 50.0 5.0 Social rented 60.0 5.0 Private rented 30.0 2.0 Scenario 2 Owner-occupied 50.0 30.0 Social rented 60.0 30.0 Private rented 30.0 5.0 Scenario 3 Owner-occupied 80.0 60.0 Social rented 90.0 70.0 Private rented 70.0 20.0 Source: author

mate of the compliance and adoption rates as percentages of annual property transactions. For the purpose of the sensitivity analysis two parameter chang- es in compliance and three parameter changes in adoption, by type of ten- ure, were selected. The data was derived from the qualitative analysis (section 3), interviews with officials of the ministries and discussions in the research team of the 40% House project (discussed in section 5). It should be noted that these rates apply to the UK and reflect occupants and owners who are motivated to take action in response to an energy certificate that they would have not taken otherwise. Compliance is likely to be better in countries such as Germany or Finland, where public awareness of energy efficiency is high- er than in the UK and there are fewer problems with compliance with build- ing regulations.

Measures (m)

Table 6.3 shows what energy efficiency measures are assumed to be adopted as a result of recommendations in energy certificates. The energy savings re- sulting from each measure have been calculated per average dwelling, based on the UK stock model (in kWh/year) (Anderson et al., 2002). The saving per measure is a weighted average, taking account of the number of different dwelling types in the stock, using the data from the English Housing Condi- tion Survey. It is assumed that half of the owners or occupants who take ac- tion in response to energy certificates will adopt one energy efficiency meas- ure (left column) and half of them will adopt two measures (right column).

In this study the measures focused on building physics, as improving the thermal envelope of the building can increase comfort and it is the necessary first step towards using more sustainable energy sources such as heat pumps. It does not assume building services that complement insulation measures, as, for example, energy-efficient boilers do not pay back in a reasonable time with the resulting reduction in energy costs; their life cycles differ from those of building physics measures; estimates of energy savings from replacing old boilers vary greatly in existing housing, being smaller in a better insulated home than a poorly insulated one; and boilers and air-conditioning systems are dealt with in Articles 8 and 9 of the EPBD. Domestic hot water, electrici-

Double glazing 2,049 Double glazing + cavity wall insulation 7,705

Loft insulation 7,853 Double glazing + loft insulation 9,902

Cavity wall insulation 5,655 Cavity wall insulation + loft insulation 13,508

Non-cavity wall insulation 9,693 Non-cavity wall insulation + loft insulation 17,546 High performance windows + cavity wall insulation 6,033 Source: Anderson et al., 2002 (weighted averages calculated by author)

ty demand for household appliances and lighting and the use of low and zero carbon technologies for energy supply are beyond the scope of this analysis. Draught proofing was not taken into consideration, as the take-up of double glazing should ensure partial draught proofing and sealing the envelope in other ways is technically complicated and unaffordable. The number of floor insulation measures was assumed to be very small, owing to the complexi- ty and cost of the work. New innovations will probably come onto the market, but owing to their high cost they are not expected to be adopted on a large scale in existing housing in the UK, at least for the time being. If energy prices and willingness-to-pay increase faster than expected, a more optimistic sce- nario would be valid.

In addition to the renovation work resulting from the recommendations in energy certificates, installation of insulation and double glazing is assumed to continue at the current rate. In 2001 93% of houses in the UK (excluding Northern Ireland) had some kind of loft insulation (but only 56% of them had more than 100 cm of insulation), 32% had cavity wall insulation and 75% had double glazing (52.1% of these dwellings had at least 60% of rooms double- glazed) (Shorrock and Utley, 2003). Business-as-usual installing cavity wall insulation (280,000 installations per year), full double glazing (1,200,000 instal- lations per year) and loft insulation (110,000 installations per year) is esti- mated to result in a 3.3 Mt annual reduction in carbon emissions from the total housing stock in the UK (DEFRA, 2004). As annual property transactions account for around 10% of the total housing stock in the UK, it is assumed that in the business-as-usual scenario these homes should contribute a 0.33 Mt annual reduction in carbon emissions; this needs to be distinguished from the carbon saving resulting from energy certificates in each scenario.

It is assumed that by 2016 most houses will have full double glazing and some level of loft insulation (after which the focus will be on improvements to existing loft insulation), and the amount of solid wall insulation is expected to increase slowly. Most UK dwellings are expected to have cavity wall insula- tion around 2050 – even sooner if annual take-up increases. Based on these uptakes, Table 6.4 gives an estimate of what insulation measures most house- holds or owners are likely to choose when renovating in response to energy

Table 6.4 Estimate of energy efficiency measures that owners and households are assumed to adopt when

renovating in response to energy certificates in the UK in 2006-16 and 2017-50 (%)

Measure adopted from recommend- In % of renovations Measures adopted from the energy In % of renovations

ations in energy certificate 2006-16 2017-50 certificate 2006-16 2017-50

Double glazing 40.0 – Double glazing + cavity wall insulation 30.0 –

Loft insulation 40.0 40.0 Double glazing + loft insulation 40.0 –

Cavity wall insulation 20.0 20.0 Cavity wall insulation + loft insulation 30.0 40.0 Non-cavity wall insulation – 40.0 Non-cavity wall insulation + loft insulation – 20.0 High performance windows + cavity wall – 40.0

insulation

certificates in 2006-16 and 2017-50.

Table 6.5 shows the transition from energy savings (in kWh) to carbon diox- ide emissions (in kg) and carbon emissions (in kg) given the current mix of fuels delivered to housing stock in the UK.