Developing regulation of energy efficiency of private sector housing (REEPS): modelling improvements to the target stock - Main Research Report

This report describes how the least energy efficient dwellings in the private sector were identified and how their ratings could be improved by a range of improvement measures. Modelling was used to ascertain the least cost way of reaching different standards, with findings presented on capital costs, fuel cost savings, carbon and energy reductions.

17 Appendix 11: Example Archetype

17.1 The base data for creating all of the individual archetypes was drawn directly from the SHCS data set, which was made available to the contractors for this research project.

17.2 The representative sample dwellings for each archetype were identified through the establishment of the typology and further segmentation as already set out in the main report.

17.3 Once the representative sample dwellings were identified, the base data for each archetype was extracted from the full SHCS data set and organised into a survey template that was created for this purpose. Effectively, a mail merge was performed to populate the template survey form with the necessary data for each archetype.

17.4 The survey data template for AT 1320130 is set out over the page in Figure A11.1. This archetype dwelling was a bungalow with an extension and a room in the roof.

17.5 To convert the SHCS data into a data set for the purposes of a full SAP assessment needed additional calculations.

17.6 The total floor area of the dwelling is the aggregation of the floor area of all levels of the dwelling:

  • the ground level: 44m2 (main dwelling) + 18m2 (extension) [from SHCS data]:
  • plus the upper level (which in this dwelling was the room in the roof area): 35m2 [from SHCS data]
  • = total floor area: 97m2

17.7 As these were all internal measurements on this occasion, they did not need to be converted to internal dimensions - so 44m2, 18m2, and 35m2 for the main dwelling, extension and room in the roof area floor area respectively were used.

17.8 The house volume was calculated by program from:

  • ground level: ground level floor area: 62m2 x storey height: 2.5m [from SHCS data]
  • upper level: upper level floor area 35m2 x 2.3m (2.05m [from SHCS data] + 0.25 [RdSAP convention])

17.9 Gross wall areas were calculated by multiplying the exposed perimeter for each part of the dwelling (main house and extension in this archetype) by the respective storey heights (both of which are collected by the SHCS)

  • main house gross wall area: 21m [exposed perimeter] x 2.5m [storey height] = 52.5m2
  • extension gross wall area: 12m [exposed perimeter] x 2.5m [storey height] = 30.0m2
  • party wall area estimated: 3.26m [perimeter] x 2.5m [storey height] x 2 party walls = 16.3m2

Figure A11.1: Base data extracted from SHCS

figure A11.1: Base data extracted from SHCS

17.10 The areas of the room in the roof components were obtained by entering the room in the roof area of 35m2 [from SHCS data] into an RdSAP program and then turning on the extended data entry option:

  • flat ceiling area 35m2
  • stud walls 18.6m2
  • sloping ceiling 18.6m2
  • gables 15.9m2

17.11 The main house heat loss roof area (i.e. the area at the eaves) was calculated by subtracting the room in the roof area from the main house floor area:

  • 44m2 [from SHCS data] - 35m2 [from SHCS data] = 9m2

17.12 The extension heat loss roof area was taken as the extension floor area, so 18m2

17.13 The heat loss ground floor areas of the main dwelling and extension were taken as the respective floor areas of these parts of the dwelling, as measured by the SHCS, so 44m2 and 18m2 respectively.

17.14 Window areas (which are not measured during SHCS, and are usually not measured during RdSAP surveys) were derived by entering the dwelling's dimensions, and its constructions and age details into a RdSAP program, and noting the calculated areas.

17.15 For this archetype, the calculated window areas were 10.25m2 for main dwelling and 4.19m2 for extension.

17.16 The SHCS for this archetype identified that between 75% and 85% of glazed area was double glazed with pre-2003 windows, so the midpoint of 80% was used to pro rata the window areas between the areas double glazed and areas single glazed in both parts of the dwelling, which produced:

  • main dwelling: 8.2m2 double glazed and 2.05m2 single glazed
  • extension: 3.35m2 double glazed and 0.84m2 single glazed

17.17 The area of doors was calculated from RdSAP defaults: 2 doors @ 1.85m2 per door, so = 3.7m2. One was assumed to be in the main dwelling; the other, in the extension.

17.18 By assigning windows and doors to specific parts of the dwelling, the SAP program subtracted these components automatically from the respective gross wall areas to produce net wall areas for each part of the dwelling

17.19 The U-values for the various fabric components of the dwelling were entered into a RdSAP program, noted, and then entered into the SAP program. The various Uvalues used for this sample archetype are set out on the Archetype Summary page below.

17.20 The main living area of the dwelling (that is, the area of the dwelling that SAP and RdSAP assume to be heated to the higher temperature standard of 21oC, compared to 18oC in the rest of the dwelling) was derived from the habitable room count in the SHCS data and the RdSAP defaults.

  • number of habitable rooms inc kitchen: 5 [from SHCS data]
  • SHCS room record kitchen description: kitchen only
  • RdSAP habitable room count: 4 (as RdSAP explicitly does not include kitchens in the habitable room count)
  • Table S11 of SAP (2012) default: 4 habitable rooms = 25% main living area
  • main living area: 25% of total floor area of 97m2 = 24.25m2

17.21 The various ventilation factors were

  • draught lobby: no porch in this dwelling [from SHCS data], so no
  • number of chimneys / open fireplaces / large vents: 3 [from SHCS data]
  • number of flues / small vents / air bricks: 0 [from SHCS data]
  • number of extract fans: 0 [from SHCS data]
  • number of flueless gas fires 0 [from SHCS data]
  • presence of a mechanical ventilation system no [from SHCS data]

17.22 Draught proofing:

  • 80% windows assumed to be draught proofed (all of the double glazed ones).
  • 20% assumed to be not draught proofed (all of the single glazed ones).
  • doors assumed to be not draught proofed.

17.23 The boiler in this dwelling was identified by the SHCS as a post-1998 standard, fan assisted Ideal Mexico mains gas boiler. As there are a large number of Ideal Mexico models of varying efficiencies in the PCDF, the boiler identification information on this occasion not sufficient to identify the specific boiler and its respective efficiency within the PCDF so SAP Table 4b default was used, which is 74%.

17.24 The SHCS found all habitable rooms were heated.

  • Heating controls: programmer and TRVs [from SHCS data]
  • Secondary heating: electric room heater [from SHCS data]
  • Water heating: from primary heating [from SHCS data]
  • Hot water cylinder details: normal 90-130 litres / 30mm spray foam [from SHCS data] (120 litres assumed)
  • Cylinder thermostat: yes [from SHCS data]
  • Conservatory: no conservatory [from SHCS data]
  • Low energy lighting: up to 30% [from SHCS data]

17.25 The dwelling was identified as suitable for solar thermal panels and PVs, but none were installed already [from SHCS data]

17.26 Private generation on site: No [from SHCS data] (so, no wind turbine or other form of independent electricity generation

17.27 This data was entered into NES's Plan Assessor v6.1program, which produced the base case SAP worksheet for the respective archetype. The base case SAP worksheet for archetype 1320130 is shown over the next pages.

17.28 The delivered energy consumption figures, broken down by fuel use in the home, are set out in Table 9a of the worksheet between lines [219] and [238]; the calculated fuel costs, in Table 10a of the SAP worksheet; the CO2e emission figures in Table 12a of the SAP worksheet; and the primary energy figures in Table 13a of the SAP worksheet

17.29 The SAP score and banding are set out in Table 11a of the SAP worksheet.

17.30 The Environmental Index score and banding are set out in Table 12a of the SAP worksheet

17.31 Each of the improvement measures were then modelled individually, and then combined into packages as necessary to achieve the respective SAP target scores.

17.32 This information was extracted for the base case, each of the individual measures, and the necessary packages, entered into a spreadsheet to calculate the various impacts of the measures and performance indicators.

17.33 The spreadsheet for each archetype is the source of the data published in the summary description of the archetype. The Summary description for archetype 1320130 is shown at the end of Chapter 4. All of the Summary descriptions are available on line at a Scottish Government-hosted web site.

Figure A11.2: Data for archetype 1320130 before measures in the SAP worksheet

Figure A11.2: Data for archetype 1320130 before measures in the SAP worksheet


Email: Silvia Palombi

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