Sprouto/rdsap10 huggingface dataset:
BRE
RdSAP10
Specification
February 2024
Table of Contents
Reduced Data SAP specification v. 10 for existing dwellings (former appendix S) ..... 3
1 Introduction ..... 3
2 Definitions of the extent of the dwelling ..... 5
2.1 Dwelling types ..... 5
2.2 Extensions ..... 6
2.3 Building elements having different construction ..... 6
2.4 Walls (sheltered, alternative, party) ..... 6
2.5 Curtain wall (type of main wall) ..... 7
2.6 Basements ..... 7
2.7 Rooms within a Mansard roof ..... 7
2.8 Whole dwelling (or building part) within roof ..... 7
2.9 Porches ..... 8
2.10 Mezzanine floor ..... 8
2.11 Extensions ..... 8
2.12 Store room / utility room ..... 8
2.13 Garages ..... 8
2.14 Dwelling adjacent to commercial premises or other unheated space above ..... 9
2.15 Sloping sites ..... 9
2.16 Room in Roof (RR) ..... 9
2.17 Stairwells and Corridors ..... 10
2.18 Private access stairwell to a single dwelling ..... 10
2.19 Park homes ..... 10
3 Age bands ..... 12
4 Areas and dimensions ..... 13
4.1 Building elements ..... 13
Table of Contents
2.18 Private access stairwell to a single dwelling ..... 10
2.19 Park homes ..... 10
3 Age bands ..... 12
4 Areas and dimensions ..... 13
4.1 Building elements ..... 13
4.2 Extensions and Alternative walls ..... 14
4.3 Adjustment to levels of storeys for houses and bungalows ..... 14
4.4 Conversion to internal dimensions ..... 14
4.5 Wall thickness ..... 15
4.6 Heights and exposed wall areas ..... 16
4.7 Door and window areas ..... 16
4.8 Roof area ..... 17
4.9 Room in Roof ..... 17
4.10 Detailed measurements of roof room ..... 21
4.11 Heat loss area for houses and bungalows ..... 21
4.12 Heat loss floor area for flats and maisonettes ..... 22
4.13 Sheltered walls for flats and maisonettes ..... 22
5 Ventilation ..... 24
5.1 Infiltration (SAP algorithm) ..... 24
5.2 Provision of ventilation ..... 27
6 Construction types and insulation (U-values) ..... 28
6.1 Wall options ..... 28
6.2 Wall types ..... 28
6.3 U-value for walls, roofs, floors ..... 29
Table of Contents
5.2 Provision of ventilation ..... 27
6 Construction types and insulation (U-values) ..... 28
6.1 Wall options ..... 28
6.2 Wall types ..... 28
6.3 U-value for walls, roofs, floors ..... 29
6.4 Default U-values of external walls ..... 29
6.5 U-values for Park home walls ..... 35
6.6 U-values of uninsulated stone walls, age bands A to E ..... 35
6.7 U-values for uninsulated brick walls, age bands A to E ..... 35
6.8 U-value for insulated walls in age bands A to E ..... 35
6.9 U-values of sheltered walls (adjacent to unheated corridor or stairwell) ..... 36
6.10 U-values of party walls and walls adjacent to heated corridor and stairwell ..... 37
6.11 U-values of roofs ..... 37
6.12 U-values of floors next to the ground ..... 41
6.13 U-values of exposed and semi-exposed upper floors ..... 42
6.14 U-value of floor above a partially heated space ..... 42  
6.15 Allowance for thermal bridging ..... 42
6.16 Thermal Mass ..... 43
6.17 Basement U-values ..... 43
Table of Contents
6.14 U-value of floor above a partially heated space ..... 42  
6.15 Allowance for thermal bridging ..... 42
6.16 Thermal Mass ..... 43
6.17 Basement U-values ..... 43
6.18 Curtain wall - U-value and other parameters ..... 43
7 Conservatory ..... 44
7.1 Non-separated conservatory ..... 44
7.2 Separated conservatory. ..... 44
8 Solar gains ..... 44
9 Windows and doors ..... 44
9.1 Draught proofing ..... 44
9.2 Window U-values and g-values ..... 44
9.3 Door U-values ..... 46
10 Room count and living area ..... 47
10.1 Room count (habitable room count) ..... 47
10.2 Living area ..... 47
11 Space and water heating (refer to SAP10.2 Appendix A) ..... 48
11.1 Main space heating system(s) ..... 48
11.2 Two main heating systems ..... 48
11.3 Space heating controls ..... 48
11.4 Secondary heating ..... 48
11.5 Water heating ..... 49
11.6 Back boilers ..... 49
11.7 No water heating system ..... 50
11.8 Solar water heating ..... 50
11.9 Flue gas heat recovery ..... 50
Table of Contents
11.4 Secondary heating ..... 48
11.5 Water heating ..... 49
11.6 Back boilers ..... 49
11.7 No water heating system ..... 50
11.8 Solar water heating ..... 50
11.9 Flue gas heat recovery ..... 50
11.10 Waste water heat recovery ..... 50
11.11 Space and water heating assumptions ..... 50
12 Additional items ..... 53
12.1 Photovoltaics ..... 53
12.2 PV diverters and PV batteries ..... 53
12.3 Wind turbine ..... 53
12.4 Small scale hydro generators ..... 53
12.5 Shutters and blinds ..... 53
12.6 Special features (Appendix Q technologies) ..... 54
12.7 Technical Notes ..... 54
12.8 Terrain ..... 54
13 Electricity tariff ..... 55
14 Addendum to EPCs ..... 56
15 Climate data ..... 58
16 Rounding of data ..... 59
17 Improvement measures ..... 60
18 Data to be collected ..... 61
19 Additional climate Data for Isle of Man ..... 80
20 RdSAP10-specific Metrics ..... 85
20.1 RdSAP10-specific SAP rating equations (referred to as EER) ..... 85
Table of Contents
18 Data to be collected ..... 61
19 Additional climate Data for Isle of Man ..... 80
20 RdSAP10-specific Metrics ..... 85
20.1 RdSAP10-specific SAP rating equations (referred to as EER) ..... 85
20.2 Carbon Dioxide emissions and Primary Energy in RdSAP10 ..... 85
21 Improvement measures for Energy Performance Certificates (former Appendix T) ..... 89
Reduced Data SAP specification v. 10 for existing dwellings (former appendix S)
1 INTRODUCTION
Reduced data SAP (RdSAP) is the UK approved ${ }^{1}$ methodology for assessing energy performance and generating EPCs for the existing dwellings.  
According to The Energy Performance of Buildings (England and Wales) Regulations ${ }^{2}$ the energy performance is expressed as "asset rating" (which is a numerical indicator of the cost of energy derived from the energy needed to meet different needs associated with standardised use of building) calculated in a way approved by the Secretary of State under Regulation 24 of the Building Regulations $2010^{3}$.  
The methodology is compliant with the Energy Performance of Buildings Directive (2018/844/EU) ${ }^{4}$. following the national annexes of the overarching standards, namely ISO 52000-1, 52003-1, 52010-1, 52016-1, and 52018-1, developed under mandate M/480 given to the European Committee for Standardisation (CEN).
Reduced Data SAP specification v. 10 for existing dwellings (former appendix S)
1 INTRODUCTION
RdSAP specification has been developed by BRE on behalf of the government for use in existing dwellings based on a site assessment of the property, when the complete data set for SAP calculation is not available. It consists of a system of data collection (defined in Table 30 : Addendum) together with defaults and inference procedures, as defined by the rules given in this document, that generate a complete set of input data for the SAP calculation. For any item not mentioned in this document, the procedures and data given elsewhere in the SAP10.25 specification apply.  
The calculation should be conducted using a computer program that implements the RdSAP10 Specification (this document), the appropriate parts of SAP10.2 specification and the worksheet referred to in this document and is approved for RdSAP calculations.  
Reduced Data SAP is for existing dwellings only. Any new dwelling must be assessed using SAP specification and software.
Reduced Data SAP specification v. 10 for existing dwellings (former appendix S)
1 INTRODUCTION
Reduced Data SAP is for existing dwellings only. Any new dwelling must be assessed using SAP specification and software.  
The RdSAP calculation starting from reduced data is done in two stages. First the collected data (reduced data set) is expanded into a full data set, and then the SAP calculation is undertaken using the expanded data set. The SAP calculation is therefore identical, whether starting from a reduced data set or a full data set.  
This version of RdSAP forms part of SAP 10.2 specification and provides a data input set for use with version 10.2 of SAP. All references made to SAP in this document refer to SAP 10.2, unless otherwise stated. RdSAP Specification contains the data and rules for expanding the data collected in a Reduced Data assessment into the data required for the RdSAP calculation. Table 31 : Data to be collected lists the Reduced Data set.
Reduced Data SAP specification v. 10 for existing dwellings (former appendix S)
1 INTRODUCTION
Information in RdSAP Conventions ${ }^{6}$ is primarily concerned with the consistency of data collection and is addressed to energy assessors. RdSAP Assessors should read RdSAP specification in conjunction with the RdSAP Conventions applicable at the time of assessment.  
[^0]
[^0]:    ${ }^{1}$ Notice of approval of the methodologies for expressing the energy performance of buildings in England and Wales - GOV.UK (www.gov.uk)
${ }^{2}$ The Energy Performance of Buildings (England and Wales) Regulations 2012 (legislation.gov.uk)
${ }^{3}$ The Building Regulations 2010 (legislation.gov.uk)
${ }^{4}$ Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings (recast) (legislation.gov.uk)
${ }^{5}$ SAP 10.2 - 21-04-2022.pdf (bregroup.com)
${ }^{6}$ SAP10 - Standard Assessment Procedure - BRE Group
Reduced Data SAP specification v. 10 for existing dwellings (former appendix S)
1 INTRODUCTION
${ }^{5}$ SAP 10.2 - 21-04-2022.pdf (bregroup.com)
${ }^{6}$ SAP10 - Standard Assessment Procedure - BRE Group  
Any deviation from the RdSAP10 specification described in this document and RdSAP Conventions applicable at the time of assessment invalidates the calculation and therefore cannot be used for generating EPC.  
This edition is RdSAP10.
Significant changes compared to RdSAP2012 specification include:  
- Window measurements required for all windows
- Location of each window allocated to main walls or each extension, or alternative walls
- Thermal properties of insulation revised
- Roof insulation details have more options
- Floor insulation revised; heated basement details added
- Table of Window U-Values expanded
- U-values of brick wall revised to account wall thickness
- U-values of stone walls revised
- Curtain wall added as new wall type
- Window shutters added as a new feature
- Hot water tank size included
- Hot water tank insulation included
Reduced Data SAP specification v. 10 for existing dwellings (former appendix S)
1 INTRODUCTION
- U-values of stone walls revised
- Curtain wall added as new wall type
- Window shutters added as a new feature
- Hot water tank size included
- Hot water tank insulation included
- Room in roof (RR) revised to take into the account all elements inclu9ding continuous main wall
- Additional alternative/shelter wall added
- Mechanical ventilation is treated as in full SAP allowing PCDB entry, still allowing default values
- PV calculated as in SAP10.2
- PV Diverter for water heating added
- PV Batteries added
- Ventilation algorithm allows more options
- Air pressure test result can be used if available
- New age-band M added, and all tables of U-values updated
- Data for Isle of Man added for completeness of information
- Table 32 with the RdSAP10-specific fuel prices replaces fuel prices in Table 12 of SAP10.2
- RdSAP10-specific metrics added to replace SAP metrics in SAP10.2
- Small scale hydro added as in SAP10.2
- Flue gas heat recovery -calculation according to SAP 10.2.
Reduced Data SAP specification v. 10 for existing dwellings (former appendix S)
1 INTRODUCTION
- RdSAP10-specific metrics added to replace SAP metrics in SAP10.2
- Small scale hydro added as in SAP10.2
- Flue gas heat recovery -calculation according to SAP 10.2.
- Waste water heat recovery - calculation according to SAP 10.2.
- Heat pumps - Calculation according to SAP 10.2.  
Changes to Table 21 of improvement measures (former RdSAP Appendix T) include:  
- Improved U-values revised for all building elements
- Measure to insulate party wall removed
- Order of measures for Northern Ireland removed
- Air and ground source heat pumps not alternative measures anymore
- PV battery and PV diverters added
2 DEFINITIONS OF THE EXTENT OF THE DWELLING
2.1 Dwelling types
Dwellings are classified as one of  
- house
- bungalow
- flat
- maisonette
- park home  
For houses and bungalows one of  
- detached
- semi-detached
- mid-terrace
- end-terrace
- enclosed mid-terrace
- enclosed end-terrace  
For flats and maisonettes one of  
- ground floor
- mid floor
- top floor  
A house or bungalow has a complete heat loss ground floor and a completely exposed roof (it includes houses and bungalows with room in roof and with basements).  
The approach to Rooms in Roof is given in section 4.9.
The rules for including Rooms in Roof and Basements are included in the RdSAP Conventions applicable at the time of assessment.  
A dwelling without a heat loss ground floor cannot be a house and must be treated as a flat or maisonette.
RdSAP makes no distinction between a flat and a maisonette as regards calculations; it is acceptable to select either type as definitions vary across the UK.
2 DEFINITIONS OF THE EXTENT OF THE DWELLING
2.1 Dwelling types
RdSAP makes no distinction between a flat and a maisonette as regards calculations; it is acceptable to select either type as definitions vary across the UK.
'Enclosed' is typically applicable for 'back-to-back' type of terraces and has the following meaning:  
- a mid-terrace dwelling has external walls on two opposite sides; while
- an enclosed mid terrace dwelling has an external wall on one side only;
- an end-terrace dwelling has three external walls;
- an enclosed end-terrace dwellings has two adjacent external walls (effectively forming a corner) on two facades and two adjacent party walls on the other two facades.
2 DEFINITIONS OF THE EXTENT OF THE DWELLING
2.1.1 Building part and Building element
Building parts are:  
- main dwelling
- extension 1
- extension 2
- extension 3
- extension 4  
Building elements of each building part are:  
- wall
- roof
- floor
- window/door
- room in roof
2.2 Extensions
An extension is when another room/s added to the building to make an existing one/s larger.
The term 'extension' is used in RdSAP to identify areas of the dwelling that are thermally different to the main dwelling.  
Provision is made for the main dwelling and up to four extensions, each with their own age band, dimensions and other characteristics.
2.2 Extensions
2.3 Building elements having different construction
In addition, dwellings can have a different construction for some parts of the building elements (for example, a timber framed bay window in otherwise masonry construction).
If the area of a building element with a different construction is less than $10 \%$ of the total area of the building element, it can be assumed to be the same as prevailing building element of that building part. However, if thermal properties of insulation are specified in form of U-values (rather than thickness of insulation) then the area of an alternative element which is less than $10 \%$ of the total area of the whole element can be accounted as area-weighted average U-value of the building element.  
Generally, rooms and other spaces, such as built-in cupboards, are included as part of the dwelling where these are directly accessible from the occupied area of the dwelling, whereas unheated spaces clearly divided from the dwelling are not.
2.2 Extensions
2.4 Walls (sheltered, alternative, party)
RdSAP allows the following types of walls: main walls, sheltered walls, alternative walls and party walls.
2.2 Extensions
2.4.1 Sheltered walls
A sheltered wall is a wall adjacent to an unheated corridor or stairwell, typically found in blocks of flats, but can be found in houses and bungalows. Sheltered walls are always included in the heat loss perimeter. The sheltered wall can be in any building part but must be recorded as an alternative wall.
See also sections 4.2.2, 4.7 and 4.13 .
See RdSAP Conventions for the details of specifying shelter wall.
2.2 Extensions
2.4.2 Alternative walls
If there are two areas of external wall of different construction types within a building part that should be regarded as alternative wall. Each building part can have two alternative walls.  
An alternative wall can be:
(i) A sheltered wall (to unheated corridor or stairwell), or
(ii) A wall that has a construction type or heat-loss characteristics (U-value) different from the main external wall.  
Alternative walls are always included in the assessment in case (i):
and in case (ii) treated according to section 2.3 if less than $10 \%$ of total exposed wall area of the building part (including windows and doors).  
See also section 4.2.2 for areas and dimensions of alternative walls.
Refer for RdSAP conventions for further details.
2.2 Extensions
2.4.3 Party walls
Party walls are walls between the dwelling being assessed and another heated space which can be: - another dwelling  
- commercial premises
- a heated corridor or stairwell in a block of flats
- a heated common area
2.5 Curtain wall (type of main wall)
Unlike other walls, a curtain wall system is thin and lightweight, usually consists of assemblies consisting of aluminium or steel frames and glass. These walls are not usually structural, and by design, they are only able to carry their own weight, while transferring the load of wind and gravity to the structure of the building. The assemblies are attached to the building structure by mullions and transoms. The design makes it air and water resistant, to ensure that the interior of the building remains airtight.  
Regardless of which material used, curtain walls are usually non-structural, which differs from many forms of traditional construction where all external walls are an integral aspect of a building's primary structure.
2.5 Curtain wall (type of main wall)
Curtain wall system can be installed in small or large buildings, depending on the needs. The curtain walls may span the distance of the floor to ceiling or be installed across multiple floors. Some curtain wall systems also make use of other in-fills from materials such as stone, veneer or metal panels.  
Curtain wall can be:  
- main wall (in this case the available U-value is for the whole wall including translucent and nontranslucent parts)
- an alternative wall
- treated according to section 2.3 if its area is less than $10 \%$ or total wall area (i.e. its area included into the area of prevailing wall)
2.5 Curtain wall (type of main wall)
2.6 Basements
Basement is the floor of the building which is partly (at least 50\%) or entirely below ground level.
Included when accessed via a permanent fixed staircase such that one is able to walk downwards facing forwards and either:-  
- basement is heated via fixed heat emitters, or
- basement is open to the rest of the dwelling, - (no door or internal door)  
Does not necessarily contain habitable rooms.
See also section 4 for areas and dimensions and Table 23 : Basement U-values.
2.5 Curtain wall (type of main wall)
2.7 Rooms within a Mansard roof
A storey having non-vertical walls of at least $70^{\circ}$ pitch constitutes a separate
storey; it is not treated as roof rooms and 1.8 m rule described in sections 2.16 .2 and 4.9 .2 is not applicable.  
Use alternative wall if appropriate.
2.5 Curtain wall (type of main wall)
2.8 Whole dwelling (or building part) within roof
When property is a single storey entirely located within a roof, enter it as:  
- Built form - flat
- Lowest occupied level
- Below this building part - another dwelling below
- timber frame construction of appropriate age band
- room height 2.2 m
- include area and perimeter measurements as a normal storey
- enter roof as pitched roof.  
For such dwellings with non-timber gables treat gable walls as "alternative wall".
If there are two storeys within roof, enter the lower storey as above and the upper storey as rooms-in-roof.
2.9 Porches
Porch is a shelter projecting of the heated envelope of the dwelling.
It could be an external porch (outside the door) usually with a separate roof or internal porch (behind the door).
A floor above internal porch is a semi-exposed floor.
See sections 2.3 Building elements having different construction and 4.11 Heat loss area for houses and bungalows.
![img-0.jpeg](img_ref_1)  
If heated by fixed emitters always include (separated or not).
If external, thermally separated and not heated, disregard.
If internal, not heated and thermally separated, disregard.
('external' means an addition protruding from the line of the external wall of the dwelling).
2.9 Porches
2.10 Mezzanine floor
A mezzanine is an intermediate floor in a building which is partly open to the floor below, or which does not extend over the whole floorspace of the floor, e.g. where the original floor has been split horizontally into two floors.
Refer to RdSAP Conventions.
2.9 Porches
2.11 Extensions
An extension is when another room/s added to the building to make an existing one/s larger. See relevant RdSAP conventions.
2.9 Porches
2.12 Store room / utility room
Rooms used as storage / rooms equipped with appliances for washing or other domestic work.
If heated by fixed emitters always include.
If accessible only via a separate external door and not heated, disregard.
If directly accessible, not heated and thermally separated, disregard.
2.9 Porches
2.13 Garages
Unheated garages are excluded from the assessment.
If heated from main heating system or fixed emitters, always include.
The presence of a boiler within the garage does not make it heated.
A door from inside the dwelling into the garage is included in the 'external' door count.
2.14 Dwelling adjacent to commercial premises or other unheated space above
If a dwelling has commercial premises or other unheated space above refer to Table 18 : Assumed roof Uvalues when Table 16 or Table 17 do not apply.  
In the case of unheated space above a building part, use U-values for the "Flat roof" in Table 18 column (3) and apply resistance $\mathrm{Ru}=0.5 \mathrm{~m}^{2} \mathrm{~K} / \mathrm{W}$ in the equation:
$U=\frac{1}{\frac{1}{U_{\text {flat roof }}}+R_{\text {unheated space }}}$ where $R_{\text {unheated space }}$ is $0.5 \mathrm{~m}^{2} \mathrm{~K} / \mathrm{W}$
Where: $U_{\text {flat roof }}$ is value from column (3) in Table 18.
2.14 Dwelling adjacent to commercial premises or other unheated space above
2.15 Sloping sites
Sites where an individual wall (elevation) is not a heat loss wall for its full height because of stepped arrangements either within the dwelling or between the dwelling and an adjacent one.  
Refer to RdSAP Conventions.
2.14 Dwelling adjacent to commercial premises or other unheated space above
2.16 Room in Roof (RR)
RdSAP10 distinguishes between RR fully within roof and RR where accessible part of common wall is part of RR.
2.14 Dwelling adjacent to commercial premises or other unheated space above
2.16.1 Room in Roof fully within roof (true Room in Roof):
![img-1.jpeg](img_ref_2)  
Figure 1: RR fully within the roof (RR type 1)  
This RR type includes:  
- Room in Roof fully within roof;
- Room in Roof built into a roof space where RR stud walls are bult inside the common walls, leaving the common walls outside the boundary of heated space).  
Room in Roof fully within roof (true Room in Roof) is always treated as "room in roof " regardless of the height of the stud walls.
2.16.2 RR where accessible common wall is part of RR
Figure 2: RR not fully within the roof ("RR Type 2"), where accessible common wall is part of RR
![img-2.jpeg](img_ref_3)  
The common wall is a vertical continuation of the external wall of the storey below.
For the type of RR (where the accessible common wall is part of RR) to be classed as such and not a separate storey, the height of the common wall (measured from the floor to the point where the roof plane intersects with the wall head) must be less than 1.8 m for at least $50 \%$ of the common wall (excluding gable ends or party walls), see Figure 3.  
There is no explicit allowance for dormer windows except to include in the floor area of the roof rooms.
![img-3.jpeg](img_ref_4)  
Figure 3: Upper storey with common wall  
Note: 1.8 m rule applies only to Room in Roof where accessible common wall is part of Room in Roof. This rule does not apply to true Room in Roof.
2.16.2 RR where accessible common wall is part of RR
2.17 Stairwells and Corridors
Stairwells and access corridors are not regarded as parts of the dwelling and not included in the assessment. Heated stairwell/corridor is one with one or more controlled fixed heaters.
Refer to RdSAP Conventions.
2.16.2 RR where accessible common wall is part of RR
2.18 Private access stairwell to a single dwelling
Refer to RdSAP Conventions.
2.16.2 RR where accessible common wall is part of RR
2.19 Park homes
Park homes are detached bungalow-style homes. They are typically manufactured offsite and then placed on land that is owned privately or by a local authority.
The following data items apply to a park home.  
| Data items for park homes |  |
| :-- | :-- |
| Data item | Options |
| Built form | Detached only |
| Measurements | Internal or external |
| Number of storeys | One only |
| Number extension | Up to 4. Extensions must have park home attributes (wall, floor and roof types) |
| Habitable rooms | Up to 99 |  
| Data items for park homes |  |
| :--: | :--: |
| Data item | Options |
2.16.2 RR where accessible common wall is part of RR
2.19 Park homes
| Habitable rooms | Up to 99 |  
| Data items for park homes |  |
| :--: | :--: |
| Data item | Options |
| Roof type and insulation | Pitched access <br> Pitched no access <br> - Insulation at joists - use Table 16 : when measured or documentary evidence of insulation thickness is available; otherwise use Table 18 : Assumed roof U-values when Table 16 or Table 17 do not apply. <br> - Insulation at rafters - use Table 18 : Assumed roof U-values when Table 16 or Table 17 do not apply (park home column) <br> - Unknown - use Table 18 park home column <br> - As built - use Table 18 park home column <br> - None <br> Pitched sloping ceiling <br> Flat <br> As built - use park home column <br> - Unknown - use Table 18 park home column |
| Roof rooms | Disallowed |
| Walls | Park home wall only |
| Party walls | None - no party wall |
| Wall thickness | Measured or default from Table 3 |
| Dry lining | Disallowed |
2.16.2 RR where accessible common wall is part of RR
2.19 Park homes
| Roof rooms | Disallowed |
| Walls | Park home wall only |
| Party walls | None - no party wall |
| Wall thickness | Measured or default from Table 3 |
| Dry lining | Disallowed |
| Wall insulation | As built <br> Unknown <br> Internal (U-value entry only) <br> External (U-value entry only) |
| Alternative walls | No alternative wall |
| Floor | Ground <br> Suspended timber only <br> U-value entry possible. |
| Floor insulation | As built <br> Unknown <br> Retro- fitted (U-value entry only) |
| Glazing | Measured |
| Heating and hot water | All options as normal |
| Conservatory | Possible (one storey) |
| Open fireplaces | Always none |
| Ventilation | Always natural |
2.19.1 Insulation improvements for park homes
For the assessment of improvement measures for park homes the improved U-value of its wall, floor or roof is calculated using:  
$$
U_{\text {insulated }}=\frac{1}{\frac{1}{U_{\text {existing }}}+R_{\text {insulation }}}
$$  
where $U_{\text {insulated }}$ is the improved $U$-value, $U_{\text {existing }}$ is the $U$-value of the existing element and $R_{\text {insulation }}$ is the thermal resistance added. Resistance $R_{\text {insulation }}$ can be taken from Table 14 : Insulation thickness and corresponding resistance.
3 AGE BANDS
A set of age bands is defined according to Table 1 : Age bands for the purposes of assigning U-values and other data.  
Table 1 : Age bands  
|  | Years of construction |  |  |  |  |
| :-- | :-- | :-- | :-- | :-- | :-- |
| Age band | England | Wales | Scotland | Northern <br> Ireland | Park home <br> (UK) |
| A | before 1900 | before 1900 | before 1919 | before 1919 | - |
| B | $1900-1929$ | $1900-1929$ | $1919-1929$ | $1919-1929$ | - |
| C | $1930-1949$ | $1930-1949$ | $1930-1949$ | $1930-1949$ | - |
| D | $1950-1966$ | $1950-1966$ | $1950-1964$ | $1950-1973$ | - |
| E | $1967-1975$ | $1967-1975$ | $1965-1975$ | $1974-1977$ | - |
| F | $1976-1982$ | $1976-1982$ | $1976-1983$ | $1978-1985$ | before 1983 |
| G | $1983-1990$ | $1983-1990$ | $1984-1991$ | $1986-1991$ | $1983-1995$ |
| H | $1991-1995$ | $1991-1995$ | $1992-1998$ | $1992-1999$ | (not applicable) |
| I | $1996-2002$ | $1996-2002$ | $1999-2002$ | $2000-2006$ | $1996-2005$ |
3 AGE BANDS
| H | $1991-1995$ | $1991-1995$ | $1992-1998$ | $1992-1999$ | (not applicable) |
| I | $1996-2002$ | $1996-2002$ | $1999-2002$ | $2000-2006$ | $1996-2005$ |
| J | $2003-2006$ | $2003-2006$ | $2003-2007$ | (not applicable) | (not applicable) |
| K | $2007-2011$ | $2007-2011$ | $2008-2011$ | $2007-2013$ | 2006 onwards |
| L | $2012-2022$ | $2012-2022$ | $2012-2023$ | $2014-2022$ | (not applicable) |
| M | 2023 onwards | 2023 onwards | 2024 onwards | 2023 onwards | (not applicable) |  
Age bands in Table 1 relate to the age of each building part.
For Isle of Man use the same age bands as for England and Wales.
3 AGE BANDS
Age bands in Table 1 relate to the age of each building part.
For Isle of Man use the same age bands as for England and Wales.  
The basis of age bands: From the 1960s, constructional changes have been caused primarily by amendments to building regulations for the conservation of fuel and power, which have called for increasing levels of thermal insulation. The dates in Table 1 : Age bands are generally one year after a change in regulations, to allow for completion of dwellings approved under the previous regulations.  
For age band of converted buildings refer to RdSAP Conventions applicable at the time of assessment.  
Age band M can apply to extensions added to an older property.
4 AREAS AND DIMENSIONS
4.1 Building elements
The boundary of the assessment consists of all the building elements separating heated space from external environment, from adjacent dwellings or unheated spaces. Any internal elements (internal partition walls or intermediate floors within the dwelling) are disregarded.  
Areas of building elements (walls, floors, roofs) are determined and specified separately for the main part of the dwelling and any extension.  
Horizontal dimensions can be measured either internally or externally.
The measurements required are the floor area, exposed perimeter, party wall length and room height on each storey. For Room in Roof additional measurements required, see 4.9.  
Exposed floor perimeter is the perimeter between the dwelling and external environment, it includes the wall between the dwelling and an unheated garage or a separated conservatory and, in the case of a flat or maisonette, the wall between the dwelling and an unheated corridor/stairwell.
4 AREAS AND DIMENSIONS
4.1 Building elements
Internal dimensions are permissible in all cases. In the case of a house or bungalow external dimensions for area and perimeter are usually more convenient, except where access to all sides of the building is not possible or where there are differing wall thicknesses or other aspects that would make the dimensional conversion unreliable.
When using external measurements for a dwelling joined onto another dwelling (semi-detached and terraced houses) the measurement is to the mid-point of the party wall.  
The internal and external measurements should not be mixed. If a heated basement is included in the assessment, it is likely that internal dimensions will be used throughout the basement.  
Flats and maisonettes are measured internally.
Storey heights are always measured internally within the room.
It is recommended to state on site plans or floor plan sketches whether the dimensions recorded are external or internal.
4 AREAS AND DIMENSIONS
4.1 Building elements
Storey heights are always measured internally within the room.
It is recommended to state on site plans or floor plan sketches whether the dimensions recorded are external or internal.  
When measuring internally, measure between the finished internal surfaces of the walls bounding the dwelling. Where that cannot be done directly (i.e. when measuring room by room) include an allowance for the thickness of internal partitions.  
Measure all perturbations (e.g. bay windows) but disregard chimney breasts unless assessor considers significant e.g. large inglenook.  
False ceilings should be disregarded (i.e. where a room has a lower ceiling than the adjacent rooms.)
Refer to RdSAP Conventions.
Vertical dimensions (room heights) are always measured internally within the room. Also, the floor area of room(s)-in-roof are always measured internally (irrespective of the dimensions basis for other storeys).  
Length of party walls (see 2.4.3) is included in the assessment.
4 AREAS AND DIMENSIONS
4.1 Building elements
Length of party walls (see 2.4.3) is included in the assessment.
Length and height of building elements (including dimensions of windows) are measured in meters to two decimal places $(0.01 \mathrm{~m})$; for example 2 m 35 cm entered into RdSAP software as 2.35 m .  
Thickness of insulation is measured in mm (for example 50mm floor insulation). Note that all tables in this give thickness of insulation in mm .
4.2 Extensions and Alternative walls
4.2.1 Extensions
An extension can be alongside another part of the dwelling, or above another part of the dwelling or other premises. If alongside apply ground floor heat loss; if above another part of the same dwelling there is no floor heat loss for the extension and no roof loss for the part below it.  
Dwellings may have one or more extensions either added to the main part of the dwelling, or built at the same time but of different construction or insulation compared to the main dwelling. In these cases, the dimensions and constructional details of the main part of the dwelling and each extension are recorded separately, to allow the assignment of different $U$-values to the original and to the extension.  
Refer to RdSAP conventions for the details of specifying extensions.
4.2 Extensions and Alternative walls
4.2.2 Alternative wall(s)
Each building part (i.e. main dwelling or each of the extensions) can have one external wall and two additional wall types, -'alternative walls'.  
The RdSAP software calculates the area of external wall from the exposed perimeter multiplied by the storey height for each level of the dwelling. The assessor calculates the area(s) of the alternative wall(s), which are then deducted by software from the external wall area of the building part calculated as described in section 4.6.  
The U-value of an alternative wall is established on the same basis as other walls, as described in section 6.
In determining whether an alternative wall is applicable, RdSAP Assessor should assess the significant features are construction type, dry lining, age band, insulation and whether sheltered by an unheated corridor or stairwell.  
A sheltered wall between the dwelling and an unheated corridor or stairwell is always counted as an alternative wall.
4.2 Extensions and Alternative walls
4.2.2 Alternative wall(s)
A sheltered wall between the dwelling and an unheated corridor or stairwell is always counted as an alternative wall.  
Walls of the same construction but different thickness within a building part are not considered alternative walls unless they are stone or solid brick walls.  
For stone or solid brick walls in the dwellings of age bands A to E, assess thickness at each external elevation and at each storey and use alternative wall if the thickness varies by more than 100 mm .  
When specifying windows and doors, for each building part assessor allocates windows and doors to the corresponding wall (the appropriate main wall or each alternative wall).  
For each building part, software will deduct window/door areas contained in the relevant wall areas. This assumes that software has a provision for allocating each window/door to the corresponding external wall or one of alternative walls.
4.2 Extensions and Alternative walls
4.2.2 Alternative wall(s)
If there are two areas of external wall of different construction types (i.e. two alternative walls) and also there is a wall separating the dwelling from an unheated corridor or stairwell (sheltered wall), consider the sheltered wall and one of the other alternative walls with the larger area.  
Note that the wall separating the dwelling from a heated corridor or stairwell is a party wall.
4.2 Extensions and Alternative walls
4.3 Adjustment to levels of storeys for houses and bungalows
In the RdSAP data set, the dimensions of each building part start at "lowest occupied" and these may not align if a building part has a heated or unheated space below the building part.
4.2 Extensions and Alternative walls
4.4 Conversion to internal dimensions
If horizontal dimensions are measured externally, they are converted to overall internal dimensions for use  
in SAP calculations by application of the appropriate equations in Table 2 : Conversion of dimensions, using wall thickness of the main dwelling (or the appropriate wall thickness from Table 3 : Wall thickness (mm) if thickness is unknown).  
The equations are applied on a storey-by-storey basis, for the whole dwelling (i.e. inclusive of any extension). This is done after any floor level adjustments (see 4.3). Storey heights are always measured internally within each room and handled by software according to 4.6.  
Table 2 : Conversion of dimensions  
| Dwelling type | Equations |
| :--: | :--: |
| Detached | $\begin{aligned} & \mathrm{P}_{\text {int }}=\mathrm{P}_{\text {ext }}-8 \mathrm{w} \\ & \mathrm{~A}_{\text {int }}=\mathrm{A}_{\text {ext }}-\mathrm{w} \mathrm{P}_{\text {int }}-4 \mathrm{w}^{2} \end{aligned}$ |
4.2 Extensions and Alternative walls
4.4 Conversion to internal dimensions
| Semi-detached or End-terrace | If $\mathrm{P}_{\text {ext }}^{2}>8 \mathrm{~A}_{\text {ext }}:$ <br> $$
\begin{aligned} & \mathrm{P}_{\text {int }}=\mathrm{P}_{\text {ext }}-5 \mathrm{w} \\ & \mathrm{a}=0.5\left(\mathrm{P}_{\text {ext }}-\sqrt{\mathrm{P}_{\text {ext }}^{2}-8 \mathrm{~A}_{\text {ext }}}\right) \\ & \mathrm{A}_{\text {int }}=\mathrm{A}_{\text {ext }}-\mathrm{w}\left(\mathrm{P}_{\text {ext }}+0.5 \mathrm{a}\right)+3 \mathrm{w}^{2} \end{aligned}$ <br> otherwise $\mathrm{P}_{\text {int }}=\mathrm{P}_{\text {ext }}-3 \mathrm{w}$ <br> $$
4.2 Extensions and Alternative walls
4.4 Conversion to internal dimensions
\mathrm{A}_{\text {int }}=\mathrm{A}_{\text {ext }}-\mathrm{w} \mathrm{P}_{\text {ext }}+3 \mathrm{w}^{2} \quad \mathrm{~W}^{2} \quad \mathrm{~W}^{2} \quad \mathrm{~W}^{2} \quad \mathrm{~W}^{2} \quad \mathrm{~W}^{2} \quad \mathrm{~W}^{2} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad
4.2 Extensions and Alternative walls
4.4 Conversion to internal dimensions
\mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad
4.2 Extensions and Alternative walls
4.4 Conversion to internal dimensions
\mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \mathrm{~W} \quad \
4.2 Extensions and Alternative walls
4.4 Conversion to internal dimensions
Use the values in Table 3 only when the wall thickness could not be measured.
Table 3 : Wall thickness (mm)  
| Age band | A | B | C | D | E | F | G | H | I, | J, K, L,M |
| :-- | :--: | :--: | :--: | :--: | :--: | :--: | :--: | :--: | :--: | :--: |
| Wall type |  |  |  |  |  |  |  |  |  |  |
| Stone* | 500 | 500 | 500 | 500 | 450 | 420 | 420 | 420 | 450 | 450 |
| Solid brick | 220 | 220 | 220 | 220 | 240 | 250 | 270 | 270 | 300 | 300 |
| Cavity** | 250 | 250 | 250 | 250 | 250 | 260 | 270 | 270 | 300 | 300 |
| Timber <br> frame | 150 | 150 | 150 | 250 | 270 | 270 | 270 | 270 | 300 | 300 |
| Cob | 540 | 540 | 540 | 540 | 540 | 540 | 560 | 560 | 590 | 590 |
| System <br> build | 250 | 250 | 250 | 250 | 250 | 300 | 300 | 300 | 300 | 300 |
| Park home |  |  |  |  |  | 50 | 50 |  | 75 | 100 |  
* If in Scotland add 200 mm for bands A and B, and 100 mm for other bands
** If in Scotland add 50 mm
4.6 Heights and exposed wall areas
Heights are measured internally within each room, and $\mathbf{0 . 2 5} \mathbf{m}$ is added by software to each room height except for the lowest storey, to obtain the storey height. For this purpose, the lowest storey is considered separately for each building part (main dwelling and any extension). The lowest storey of a building part is the lowest for the dwelling unless it has been indicated as having the same dwelling below.  
Gross areas (inclusive of openings) are obtained from the product of heat loss perimeter (after conversion to internal dimensions if relevant) and storey height, summed over all storeys. Party wall area is party wall length multiplied by storey height, summed over all storeys.
4.6 Heights and exposed wall areas
For the main dwelling and any extension(s), window and door areas are deducted from the gross areas to obtain the net wall areas for the heat loss calculations, except for the door of a flat/maisonette to an unheated stairwell or corridor which is deducted from the sheltered wall area.  
If an alternative wall is present, the area of the alternative wall is subtracted from the net wall area of the building part prior to the calculation of wall heat losses.
4.6 Heights and exposed wall areas
4.7 Door and window areas
The area of an external door can be taken as $\mathbf{1 . 8 5} \mathbf{m}^{2}$ (no need to measure doors because their dimensions are not as variable as dimensions of windows).  
A door to a heated access corridor is not included in the door count.
External doors except doors to an unheated corridor or stairwell are taken as being in the:  
- external wall of main part of the main dwelling or extension;
- alternative wall 1
- alternative wall 2  
In RdSAP the definition of what is a window and what is a door is defined by the area of glazing in relation to the area of the whole opening, i.e. door and frame. To be classed as a window a glazed door and frame must contain glazing amounting to $60 \%$ or more or its surface area.  
Generally, $60 \%$ or more glazing is likely to occur only in a patio door with a thin frame, e.g. metal frame as opposed to a uPVC frame.
4.6 Heights and exposed wall areas
4.7 Door and window areas
Generally, $60 \%$ or more glazing is likely to occur only in a patio door with a thin frame, e.g. metal frame as opposed to a uPVC frame.  
However, a window with less than $60 \%$ glazing is not a door; a door always provides a means of entry to the property.  
An external door is a door that forms part of the heat loss perimeter of the dwelling. A door to a heated access corridor/stairwell is not included in the door count. It is possible for a property to have no external  
door in the RdSAP data set (when any entrance to the property is via patio doors with more than $60 \%$ glazing which are counted as windows in SAP, or via a heated corridor).  
For more details see RdSAP Conventions.
4.7.1 Window data
Window area is assessed by measuring all windows and roof windows throughout the dwelling. This does not include conservatories, which are treated separately; see Section 7.  
The area of each window is calculated by assessor during the survey by measuring its height and width. Additional information to be noted are the type of glazing, the glazing age, the frame type, the thickness of the glazing gap (if one or more present), the location within the dwelling construction, and its orientation.  
Multiple glazing can be installed before $2002^{7}$, during/after 2002 (these windows are assumed to have lowemissivity coating), installed after $2022^{8}$, double glazing unknown date, secondary glazing or triple glazing. For multiple glazing the U-value can be known.  
The total window area is obtained by the assessor measuring each individual window, and the software aggregating the total. That also applies to park homes.
4.7.1 Window data
The total window area is obtained by the assessor measuring each individual window, and the software aggregating the total. That also applies to park homes.  
The location area of each window in the main part of the dwelling and in any alternative wall of each extension are recorded separately, along with:  
- single glazed, double glazed before or during/after 2002, secondary glazing or triple glazed;
- U-value if known;
- source of data (for U-value);
- window or roof window;
- orientation  
Multiple types of windows are allowed.
If external dimensions were used, all windows were measured and there is a roof window with area greater than the roof area of the building part concerned, change the roof window area to be equal to the roof area. This can occur with a fully glazed roof because the roof window area entered by the assessor does not take account of the reduction in areas that occurs when the dimensions are converted from external to internal.
4.7.1 Window data
4.7.2 Sun rooms
For a highly glazed part of the dwelling, such as a sun room, which does not meet the criteria for a conservatory ( $50 \%$ of walls and $75 \%$ of roof glazed), glazed parts are treated as windows and the dimensions are measured.
4.7.1 Window data
4.8 Roof area
Roof area is the greatest of the floor areas on each level, calculated separately for main dwelling and any extension. In the case of a pitched roof with a sloping ceiling, divide the area so obtained by $\cos \left(30^{\circ}\right)$.
4.7.1 Window data
4.9 Room in Roof
The following procedure is applied to main dwelling and separately to any extension with roof rooms as applicable.  
Note. A roof room cannot be an extension in its own right, roof rooms are defined only when a building part consisting of normal storey(s) has been defined.  
Where a roof room is built over a garage attached to the dwelling, treat the roof room as an extension (see section 4.2 for how to deal with this situation).  
[^0]
[^0]:    ${ }^{7} 2002$ in England \& Wales, 2003 in Scotland, 2006 in Northern Ireland
${ }^{8} 2022$ in England/Wales/Northern Ireland, 2023 in Scotland.  
If there are roof rooms, with a total floor area of $A_{R R \_f l o o r}$ (measured internally), then area $A_{R R \_f l o o r}$ is deducted from the roof area of a building part below determined in section 4.8.  
Two assessment options can be used for RR in RdSAP-10: