Archetype: 3250330 Archetype Description: 1965-1975, semi / end terraced dwelling, timber frame walls, oil / gas / electric warm air heating, E This archetype represents 823 dwellings, which accounts for approximately 0.21% of the target dwelling stock
property type: semi detached bungalow
age: built c.1975
number of storeys: 1 number of habitable rooms: 4
extensions: none number of heated habitable rooms: 4
rooms in the roof: none
total floor area: 62m
2internal
heat loss floor area: 62m
2floor construction: suspended timber, as built U-value: 0.63
gross heat loss wall area: 52m
2wall construction: timber frame wall, as built U-value: 0.8
heat loss roof area: 62m
2roof construction: pitched, 100mm insulation U-value: 0.4
glazed area: 15.01m
2glazing type: 100% wood / upvc double glazing, pre2003 U-value: 2.8
main heating: pre1998 ducted warm air system main heating fuel: mains gas main heating SAP efficiency: 70.0%
main heating controls: programmer
secondary heating: none secondary heating fuel: n/a secondary heating efficiency: n/a
hot water provision: single immersion
hot water cylinder: yes cylinder size: 120 litres cylinder insulation: 25mm spray foam cylinder thermostat: yes
chimneys: 0 electricty meter: single
flues: 0 gas meter: yes
extract fans: 1
draught lobby: no percentage of low energy lighting: 90%
draughtproofing: 100% windows 0% doors
EPC Band E Environmental Impact Band: E
EPC Score 53 Environmental Impact Score: 52
These characteristics were modelled in SAP 2012 to create the base case dwelling for this archetype. A number of single improvements were modelled against
the base case dwelling to assess their impact on the EPC band, the SAP score, the Environmental Impact band, and the Environmental Impact score, as well as their
impact on the SAP-calculated fuel costs, CO2 emissions and delivered energy consumption. These results are set out in Table 1.
Table 1: Modelled Single Improvements: EPC Band, SAP Score, Environmental Impact Band, Environmental Impact Score, SAP Annual Fuel Costs, SAP CO2 emissions, and SAP Delivered Energy Consumption (ordered by impact on the SAP score (lowest to highest))
SAP Annual Fuel Costs: £ per year SAP CO2 Emissions: kg of CO2 per year SAP Delivered Energy Consumption: kWh per year
code Improvement Description EPC SAP EI EIs MH SecH HW L ren tot MH SecH HW L ren tot MH SecH HW L ren tot
Base as existing E 53 E 52 £429 £0 £264 £52 £0 £865 2665 0 1037 204 0 3906 12336 0 1998 394 0 14728
M33 low energy lighting 100% E 53 E 52 £430 £0 £264 £48 £0 £862 2668 0 1037 190 0 3895 12353 0 1998 366 0 14717
M12 draughtproof windows and doors E 53 E 52 £427 £0 £264 £52 £0 £862 2647 0 1037 204 0 3889 12257 0 1998 394 0 14648
M10 insulated external doors E 54 E 53 £409 £0 £264 £52 £0 £845 2541 0 1037 204 0 3782 11764 0 1998 394 0 14156
M11 hot water tank jacket 80mm E 54 E 53 £434 £0 £225 £52 £0 £832 2695 0 887 204 0 3786 12476 0 1709 394 0 14579
M9 triple glazing to 1.4 E 54 E 54 £400 £0 £264 £52 £0 £835 2482 0 1037 205 0 3723 11490 0 1998 394 0 13882
M24 room thermostat E 54 E 53 £413 £0 £264 £52 £0 £848 2561 0 1037 204 0 3802 11857 0 1998 394 0 14249
M31 2m diameter wind turbine on roof E 54 E 52 £430 £0 £264 £48 -£19 £843 2668 0 1037 190 -74 3821 12353 0 1998 366 -143 14574
M5 solid wall insulation D 55 E 54 £394 £0 £264 £52 £0 £830 2448 0 1037 204 0 3689 11334 0 1998 394 0 13726
M1 loft insulation, including top up D 55 E 54 £390 £0 £264 £52 £0 £826 2422 0 1037 204 0 3663 11214 0 1998 394 0 13606
M6 floor insulation D 56 D 56 £369 £0 £264 £52 £0 £805 2293 0 1037 204 0 3534 10615 0 1998 394 0 13007
M14 replace gas boiler with condensing boiler 88% D 56 D 55 £371 £0 £264 £58 £0 £812 2303 0 1037 228 0 3567 10661 0 1998 439 0 13097
M32 5m wind turbine on stand-alone mast D 64 D 61 £430 £0 £264 £48 -£208 £654 2668 0 1037 190 -818 3077 12353 0 1998 366 -1575 13142
EPC = EPC band / SAP = SAP 2012 score / EI = Environmental Impact band / EIs = Environmental Impact score
MH = main heating / SecH secondary heating / HW = hot water / L = lighting and other costs (e.g. fans and pumps) / ren = impact of renewable generation / tot = total of category
The starting point for this dwelling (i.e. as existing) is a Band E SAP score of 53, that is, 2 points below Band D.
For this dwelling, 12 improvement measures were assessed. Those that were not assessed, and the reasons, are set out in Table 2.
Five measures on their own (highlighted in yellow in Table 1) would raise the SAP rating into the Band D category; none are mutually exclusive.
None of the measures assessed on their own raised the SAP rating here into Band C or higher.
Table 1 above is ordered in terms of the smallest impact on the increase in the SAP score to the highest. Two measures (i.e. M12 - draughtproof windows and doors; and M33 - low energy lighting) do not have an impact on the SAP score. While they do improve the dwelling's overall energy efficiency, the improvements are not sufficient in themselves to increase the SAP score by 1 full SAP point.
Table 2: Reasons for Measures Not Assessed in this Property
code Improvement Description Improvement Modelled?
M2 flat roof insulation not applicable
M3 room in the roof insulation not applicable
M4 cavity wall insulation not applicable
M7 double glazing to 1.8 already present
M8 secondary glazing to 2.4 not recommended
M13 baffle / damper to open fire not applicable
M15 replace oil boiler with condensing boiler 90% not applicable
M16 full gas central heating system inc controls not recommended
M17 full oil central heating system inc controls not recommended
M18 full biomass central heating system inc controls not recommended M19 fan electric storage heaters with auto charge control not recommended
M20 quantum storage heaters not recommended
M21 full electric radiator system inc controls - off peak tariff not recommended
M22 air source heat pump not recommended
M23 ground source heat pump not recommended
M25 programmer for heating system already present
M26 TRVs not applicable
M27 full controls package (r/stat, programmer and TRVs) not recommended
M28 Auto charge control not applicable
M29 Solar thermal 4m2 not recommended
M30 PV 2kWp not recommended
M34 Cylinder stat for hot water cylinder already present
M35 Air to Air heat pump not recommended
M36 replace secondary heating with one more efficient not recommended M37 electric CPSU with raidtors and controls on E18 tariff not recommended
M38 switch to E24 tariff not applicable
A number of the improvement measures were not assessed with regard to this dwelling. Appendix 2 of the Final Report sets out the methodology associated with modelling the 38
improvements, including why measures were not recommended, or not applicable.
Table 3: Impact of Single Improvements on Annual and LifetimeSAP Fuel Costs, CO2 emissions, Delivered Energy Consumption - ordered by Capital Costs (lowest to highest)
annual reductions lifetime reductions
code Improvement Description
EPC Band
Change in SAP score
EI Band
Change in EI score
SAP
£/year SAP kg CO2/year
SAP delivered kWh/year
lifetime (years)
SAP
£
SAP kg CO2
SAP delivered kWh
unit costs units
capital cost
net lifetime £ saving / capital
cost
payback (years)
M33 low energy lighting 100% E 0 E 0 3 11 11 5 16 54 54 £5 1 £5 £2.10 1.6
M11 hot water tank jacket 80mm E 1 E 1 33 120 149 10 332 1197 1489 £23 1 £23 £13.77 0.7
M12 draughtproof windows and doors E 0 E 0 3 17 80 10 28 172 796 £100 1 £100 -£0.72 36.0
M24 room thermostat E 1 E 1 17 103 479 12 200 1242 5748 £200 1 £200 £0.00 12.0
M1 loft insulation, including top up D 2 E 2 39 242 1122 42 1640 10180 47126 £350 1 £350 £3.69 9.0
M6 floor insulation D 3 D 4 60 372 1721 42 2515 15611 72271 £1,000 1 £1,000 £1.52 16.7
M10 insulated external doors E 1 E 1 20 124 572 30 597 3705 17154 £500 2 £1,000 -£0.40 50.3
M14 replace gas boiler with condensing boiler 88% D 3 D 3 52 339 1630 12 628 4062 19563 £2,600 1 £2,600 -£0.76 49.6
M31 2m diameter wind turbine on roof E 1 E 0 22 85 297 10 220 851 2970 £2,750 1 £2,750 -£0.92 125.1
M9 triple glazing to 1.4 E 1 E 2 29 182 845 20 587 3648 16905 £7,500 1 £7,500 -£0.92 255.4
M5 solid wall insulation D 2 E 2 35 216 1002 36 1256 7793 36076 £9,000 1 £9,000 -£0.86 258.0
M32 5m wind turbine on stand-alone mast D 11 D 9 211 828 3161 10 2109 8284 31612 £20,000 1 £20,000 -£0.89 94.8
nb. because of the rounding of the annual reductions to the nearest integer, some of the lifetime reductions may not equal a measure's annual reduction multiplied by its respective lifetime
# - because this measure has no impact on the SAP-calculated fuel bill no payback period can be calculated.
Table 3 sets out the resultant EPC and Environmental Impact (EI) banding for each of the individual improvement measures assessed for this dwelling, along with the changes in the respective SAP and EI scores. It then displays the impact on the respective SAP-calculated annual fuel bill, CO2 emissions and delivered energy consumption for the dwelling (the pink columns in Table 3 above). Multipling the annual change in the calculated SAP fuel costs, CO2 emissions, and delivered energy consumption for this property, by the respective lifetime of each of the measures assessed, produces the lifetime change for each measure (see the blue columns in Table 3 above). This allows us to compare the capital costs against both the cost of the saving on the fuel bill on an annual basis (i.e. the payback), and over the lifetime of the measure (i.e. the net lifetime £ saving / capital cost). The net lifetime £ saving / capital cost subtracts the capital cost of the measure from the calculated lifetime SAP £ reduction. In this column, a value greater than 0 here means the calculated lifetime fuel bill savings are greater than the capital cost of installing the measure. Where the net lifetime saving is a negative number, that is, it has a cost effectiveness of less than 0 (and highlighted in orange in Table 3), the measure will not return the cost of the original investment through savings in the fuel bills alone.
Table 3 is ordered from the lowest capital cost for the improvement measure assessed to the highest. The capital costs of the individual measures ranged from £5 for one low energy light bulb, up to £20,000 for the stand-alone wind turbine. A low capital cost does not necessarily equate to a good return on an investment or short payback period; similarly, a high capital cost does not necessarily mean a poor return on the cost of the investment or a long payback. In terms of cost effectiveness, the measure with the shortest payback for this archetype is adding an insulating jacket to the hot water cylinder, with a payback of 0.7 years. Fitting the hot water tank jacket also provides the largest lifetime return on the cost of the improvement, with a return of £13.77 for every pound invested over the lifetime of the measure.
Seven of the measures have a cost effectiveness of less than 0 (highlighted in orange in Table 3) and will not return the cost of the original investment through savings in the fuel bills alone. However, the eligibility for other incentive schemes (e.g. Feed in Tariffs for installing wind turbines) are likely to have a significant impact on the financial return associated with these measures. The financial benefits associated with these
Table 4a: Cheapest Package of improvement Measures to Increase the SAP EPC Band to SAP Band D
code Improvement Description EPC Band SAP EI Band EI score SAP £/year
SAP kg CO2/year
SAP delivered kWh/year
lifetime
(years) SAP £ SAP kg CO2 SAP delivered
kWh unit costs units
cummulative capital cost
cummulative net lifetime £ saving / capital cost
cummulative payback
(years)
Base as existing E 53 E 52
M24 room thermostat E 54 E 53 17 103 479 12 200 1242 5748 £200 1 £200 0.00 12.0
M24+M11 + hot water tank jacket 80mm D 55 E 54 50 224 630 10 533 2443 7258 £23 1 £223 1.40 4.5
From the characteristics of this archetype, the starting point for this dwelling was assessed to be a RdSAP 2012 Band E SAP score of 53. Only one package was assessed for this archetype: the cheapest package of measures to raise the SAP score so that it achieved a SAP Band D score of at least 55.
cummulative annual reductions cummulative lifetime reductions
While single measures were assessed that would achieve a Band D rating for this dwelling, there are cheaper alternatives. Adding a room thermostat to the heating controls and fitting an insulating jacket on the hot water cylinder was assessed as the cheapest package to move the SAP rating for this property into Band D (see Table 4a). The total indicative cost of this package is estimated at approximately £223.
