Developing an Energy Efficiency Standard for Social Housing: consultation

ANNEX A: CASE STUDY

Purpose

In order to assist landlords in their planning for the Energy Efficiency Standard for social housing we have developed a series of case studies showing how various measures can improve the energy efficiency of their dwellings and help them to meet the standard.

The types of upgrades which can be made depend on the exact location and nature of the property. These are case study examples. They are not meant as technical guidance. You should ensure that any improvements are assessed by a technically competent professional to take into account the unique construction and location of your dwellings. You should also consider the level of information and advice given to tenants to ensure that they can utilise the dwelling to reduce their energy bills and emissions.

Methodology

The case studies are based on RdSAP methodology. All landlords should be familiar with this because of their requirement to provide new tenants with Energy Performance Certificates. Dwellings are graded from A to G and given scores for energy efficiency and environmental impact between 0 and 100.

Each case study provides an example of the 1990 baseline data for the dwelling type and an example of the energy efficiency improvements likely to be implemented by a reasonably performing landlord to achieve the Scottish Housing Quality Standard. It then provides additional suggestions of the types of improvements that landlords could use to meet the new Energy Efficiency Standard and any further measures. The case studies cover examples of gas and electrically heated dwellings. For each fuel type an example of a ground, mid and top floor flat has been provided along with a semi-detached and a mid terraced house. The case studies have been modelled on an older version of RdSAP, although the final version will be based on RdSAP 2009 (v9.91) to ensure its compatibility with the new Green Deal software being utilised from October 2012.

Range of Energy efficiency measures

A full list of improvement measures is available in Appendix T of the SAP 2012 methodology: http://www.bre.co.uk/filelibrary/SAP/2009/SAP-2009_9-90.pdf

A summary is provided below:

Loft insulation
Cavity wall insulation
Floor insulation
Hot water cylinder insulation
Draught proofing
Cylinder thermostat
Heating controls - Programmer, room thermostat and TRVs
Heating controls - Time and temperature zone control
100% low energy lighting
Upgrade boiler - condensing (mains gas)
New or replacement storage heaters (electricity)
Air Source Heat Pumps
Solar water heating
Secondary glazing
Double or triple glazing
Solid wall insulation
Photovoltaics

Applying Energy Efficiency Improvements in the Model

Improvements have been applied on a cost basis, starting with lower cost measures.

Installation costs, fuel bill savings and cost effectiveness of different technologies will vary depending on the type, size and location of dwellings.

Considering Costs, Savings and Carbon

To calculate fuel bill savings you will need to multiply the change in energy use for the fuel (KWh per m2) by the current fuel price. Fuel prices can be found here: http://www.decc.gov.uk/en/content/cms/statistics/energy_stats/prices/prices.aspx

To calculate cost effectiveness you will need to divide the estimated cost of the measures installed by the amount of carbon saved.

The following table can be used as example installation costs for measures but if you procure measures in bulk you may expect to get a reduced cost. The source of this data is from DEMScot (the Scottish Government's carbon model where approximate costs were gathered in an industry survey in 2009) and the UK Government's call for market information from the industry in 2011 as part of the Green Deal consultation process. In some cases, e.g. remote locations, larger properties, difficult to access or expensive to treat properties, costs will be significantly higher. Many landlords will already have a good idea of the costs of installation of energy efficiency measures.

Measure	DEMScot Cost	Green Deal Market Information for Impact Assessment 44
Solid wall (external)	£5500	£4800 for LA semi or £3160 for a flat. Individual installations are costed at £7600 up to U=0.35
Solid wall (internal	Inc above	£5,000 including time and lost floor space factors
Cavity wall	£500	Range from hard at £1,620 to easy at £376
Loft insulation	£500	Loft top-ups £283
Floor insulation	£1200 per dwelling	n/a
Heating controls	£300	n/a
Condensing boiler	£2500	n/a
Double glazing (single to A or C to A)	£3700	£450 per window
Secondary glazing	Inc above	n/a
Under floor heating	n/a	n/a
Biomass boiler	£9,000	n/a
Solar water	£4,000	n/a
PhotoVoltaic Cells	£8,000	n/a
Ground Source Heat Pump	£10,000	n/a
Air Source Heat Pump	£8,400	n/a
Micro CHP	£4,500	n/a
Wind turbine	£8,000	n/a

Example 1 - A post-1982 gas heated flat

The dwelling used as the case study ⁴⁵ for an urban dwelling of this age and type has a SAP rating of 76, a NHER rating of 8.7 and passes the SHQS energy efficiency criterion. Its external walls are timber frame (rendered) and it is a tenement. For modelling purposes we have situated this dwelling in Edinburgh.

At present the dwelling has:

• 200mm loft insulation
• Double glazing
• Mains gas
• Full central heating
• Combi boiler
• Programmer and TRV

Although this dwelling passes the current SHQS there are still some upgrades which would make it more energy efficient and decrease its carbon emissions. The below table shows the type of upgrades which could be made and the difference this would make to the SAP and NHER ratings as well as the CO ₂ emissions.

	Now	Roof	Heating System	Renewables		All three combined
		Upgrade loft insulation	Replace boiler (increasing efficiency to 91%)	Add photovoltaic panels to roof	100% LEL
NHER	8.7	8.8	9.5	9.9	9.1	11.5
SAP	76 (C)	76 (C)	80 (C)	84 (B)	78 (C)	91 (B)
Environmental impact rating	76 (C)	77 (C)	82 (B)	84 (B)	77 (C)	92 (B)
CO 2 emissions (kg/year)	2,705	2,645	2,292	2,131	2,636	1,591
CO 2 savings (kg/year)	-	60	413	574	69	1114
Fuel bill savings (£/year)	-	£10	£85	£106	£25	£213
Install cost	-	£500	£2,500	£8,000	£20	£11,120
Lifetime of install	-	30	30	30	5	30
Cost per tonne of CO 2	-	£111	£278	-£4	-£304	£142
Pay back period (years)	-	50	75	29	1	52

Although the dwelling already has 200mm of loft insulation this could be upgraded to 300mm, this would make little difference to the SAP or NHER scores but would decrease annual CO ₂ emissions by about 2%.

If the boiler was upgraded to a more efficient boiler (example uses a boiler of 90.8% efficiency) then the SAP would increase to 80 (band C), NHER to 9.5 and there would be a 15% reduction in CO ₂ emissions per year.

Note: If the boiler already in place is relatively new and efficient the full value of a change to a newer very energy efficient boiler may not be received by the tenant and landlord.

If photovoltaics were added to 20% of the roof area, then this would also increase the SAP and NHER to 84 and 9.9 respectively and CO ₂ emissions would decrease by just over 20% per year.

Installing 100% low energy lighting will increase both the SAP and NHER ratings, plus reduce carbon emissions by about 3%.

If all of these upgrades were made to the dwelling then there would be an overall increase of 15 SAP points from current stock, to 91 and an increase of 2.8 NHER points to 11.5. CO ₂ emissions would also reduce by about 40%.

Example 2 - Four in a block (lower) 1920-1950

The dwelling used as the case study for an urban dwelling of this age and type has a SAP rating of 63, an NHER rating of 6.6 and fails the SHQS energy efficiency criterion. It is a ground floor, 4-in-a-block style flat constructed from rendered brick. For modelling purposes we have situated this dwelling in Falkirk. At present the dwelling has:

• Uninsulated cavity walls;
• Double glazing;
• Full mains gas central heating from a condensing boiler, which also supplies hot water;
• Programmer and TRVs;
• Secondary heating - gas fire; and
• 50% low energy lighting.

The table below shows the type of upgrades which could be made and the difference this would make to the SAP and NHER ratings as well as the CO ₂ emissions.

	Now	cavity wall insulation	upgrade boiler to 90.8% efficiency	100% LEL	Solar water heating	All measures
NHER	6.6	7.9	7.7	6.7	6.8	9.1
SAP	63	70	71	64	64	79
SAP band	D	C	C	D	D	C
Environmental impact rating	D	D	D	D	D	C
CO 2 emissions (kg/year)	5,966	4,825	4,983	5,931	5,747	3,816
CO 2 savings (kg/year)		1141	983	35	219	2150
Fuel bill savings (£/year)		199	173	17	34	387
Install cost		500	2500	60	4000	7360
Lifetime of install		30	30	30	30	30
Cost per tonne of CO 2		-£159.80	-£91.22	-£428.57	£453.58	-£65.89
Pay back period (years)		3	14	4	118	19

Cavity wall insulation would add 7 SAP points - or 1.3 NHER points - to this home, reducing carbon emissions by a fifth and reducing annual heating costs by £200.

The addition of a more efficient boiler and removal of the secondary heating system would increase SAP to 71 and NHER to 7.7. This would translate to a 16% carbon reduction.

Note: If the boiler already in place is relatively new and efficient the full value of a change to a newer very energy efficient boiler may not be received by the tenant and landlord.

If solar water heating were added there would be marginal changes to NHER, SAP and fuel costs. The combined package would improve this house to NHER 9.1, over a third off carbon emissions and nearly £400 of savings on fuel per year.