RdSAP age bands and default U-values

RdSAP 10 Tables 1, 3, 4, 6–26, reproduced in full from the BRE specification — the defaults an assessment falls back on for any element it cannot see. Give it a year and a country and it gives you the band, then the U-value.

Find the age band

Enter a year of construction.

The band applies to each building part, not the whole dwelling — an extension can sit several bands later than the original house. For converted buildings, use the RdSAP Conventions current at the date of assessment.

Table 1 — age bands

Years of construction by country. Isle of Man uses the England and Wales bands. A dash means the band does not exist for park homes; “(not applicable)” is the specification’s own wording for a band that country skips — Northern Ireland has no band J, so that whole column is blank in Table 8 below.

RdSAP 10 Table 1, age bands by country
Band England Wales Scotland Northern Ireland Park home (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
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)

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 1 (page 13).

Tables 6–10 — wall U-values

The default U-value in W/m²K for a wall whose construction cannot be evidenced. Pick the country; the table switches. Values marked see 6.6, 6.7 or 6.8 are not defaults at all — for those, RdSAP calculates from the measured wall thickness using the equations in that section of the specification.

RdSAP 10 Table 6, wall U-values for England, W/m²K
Wall type ABCDEFGHIJKLM
Years of construction <19001900-19291930-19491950-19661967-19751976-19821983-19901991-19951996-20022003-20062007-20112012-20222023+
Stone: granite or whinstone see 6.6 see 6.6 see 6.6 see 6.6 1.7 a 1.0 0.60 0.60 0.45 0.35 0.30 0.28 0.26
Stone: sandstone or limestone see 6.6 see 6.6 see 6.6 see 6.6 1.7 a 1.0 0.60 0.60 0.45 0.35 0.30 0.28 0.26
Solid brick as built see 6.7 see 6.7 see 6.7 see 6.7 1.7 b 1.0 0.60 0.60 0.45 0.35 0.30 0.28 0.26
Stone/solid brick with 50 mm external or internal insulation see 6.8 see 6.8 see 6.8 see 6.8 0.55 c 0.45 * 0.35 * 0.35 * 0.30 * 0.25 * 0.21 * 0.21 * 0.20 *
Stone/solid brick with 100 mm external or internal insulation see 6.8 see 6.8 see 6.8 see 6.8 0.32 c 0.28 * 0.24 * 0.24 * 0.21 * 0.19 * 0.17 * 0.16 * 0.15 *
Stone/solid brick with 150 mm external or internal insulation see 6.8 see 6.8 see 6.8 see 6.8 0.23 c 0.21 * 0.18 * 0.18 * 0.17 * 0.15 * 0.14 * 0.14 * 0.13 *
Stone/solid brick with 200 mm external or internal insulation see 6.8 see 6.8 see 6.8 see 6.8 0.18 c 0.17 * 0.15 * 0.15 * 0.14 * 0.13 * 0.12 * 0.12 * 0.11 *
Cob (as built) 0.80 0.80 0.80 0.80 0.80 0.80 0.60 0.60 0.45 0.35 0.30 0.28 0.26
Cob with 50 mm external or internal insulation 0.40 0.40 0.40 0.40 0.40 0.40 0.35 * 0.35 * 0.30 * 0.25 * 0.21 * 0.21 * 0.20 *
Cob with 100 mm external or internal insulation 0.26 0.26 0.26 0.26 0.26 0.26 0.24 * 0.24 * 0.21 * 0.19 * 0.17 * 0.16 * 0.15 *
Cob with 150 mm external or internal insulation 0.20 0.20 0.20 0.20 0.20 0.20 0.18 * 0.18 * 0.17 * 0.15 * 0.14 * 0.14 * 0.13 *
Cob with 200 mm external or internal insulation 0.16 0.16 0.16 0.16 0.16 0.16 0.15 * 0.15 * 0.14 * 0.13 * 0.12 * 0.12 * 0.11 *
Cavity as built 1.5 1.5 1.5 1.5 1.5 1.0 0.60 0.60 0.45 0.35 0.30 0.28 0.26
Unfilled cavity with 50 mm external or internal insulation 0.53 0.53 0.53 0.53 0.53 0.45 0.35 * 0.35 * 0.30 * 0.25 * 0.21 * 0.21 * 0.20 *
Unfilled cavity with 100 mm external or internal insulation 0.32 0.32 0.32 0.32 0.32 0.30 0.24 * 0.24 * 0.21 * 0.19 * 0.17 * 0.16 * 0.15 *
Unfilled cavity with 150 mm external or internal insulation 0.23 0.23 0.23 0.23 0.23 0.21 0.18 * 0.18 * 0.17 * 0.15 * 0.14 * 0.14 * 0.13 *
Unfilled cavity with 200 mm external or internal insulation 0.18 0.18 0.18 0.18 0.18 0.17 * 0.15 * 0.15 * 0.14 * 0.13 * 0.12 * 0.12 * 0.11 *
Filled cavity 0.70 0.70 0.70 0.70 0.70 0.40 0.35 0.35 0.45 † 0.35 † 0.30 † 0.28 † 0.26 †
Filled cavity with 50 mm external or internal insulation 0.37 0.37 0.37 0.37 0.37 0.27 0.25 * 0.25 * 0.25 * 0.25 * 0.21 * 0.21 * 0.20 *
Filled cavity with 100 mm external or internal insulation 0.25 0.25 0.25 0.25 0.25 0.20 0.19 * 0.19 * 0.19 * 0.19 * 0.17 * 0.16 * 0.15 *
Filled cavity with 150 mm external or internal insulation 0.19 0.19 0.19 0.19 0.19 0.16 0.15 * 0.15 * 0.15 * 0.15 * 0.14 * 0.14 * 0.13 *
Filled cavity with 200 mm external or internal insulation 0.16 0.16 0.16 0.16 0.16 0.13 0.13 * 0.13 * 0.13 * 0.13 * 0.12 * 0.12 * 0.11 *
Timber frame as built 2.5 1.9 1.9 1.0 0.80 0.45 0.40 0.40 0.40 0.35 0.30 0.28 0.26
Timber frame with internal insulation 0.60 0.55 0.55 0.40 0.40 0.40 0.40 † 0.40 † 0.40 † 0.35 † 0.30 † 0.28 † 0.26 †
System build as built 2.0 2.0 2.0 2.0 1.7 1.0 0.60 0.60 0.45 0.35 0.30 0.28 0.26
System build with 50 mm external or internal insulation 0.60 0.60 0.60 0.60 0.55 0.45 0.35 * 0.35 * 0.30 * 0.25 * 0.21 * 0.21 * 0.20 *
System build with 100 mm external or internal insulation 0.35 0.35 0.35 0.35 0.35 0.32 * 0.24 * 0.24 * 0.21 * 0.19 * 0.17 * 0.16 * 0.15 *
System build with 150 mm external or internal insulation 0.25 0.25 0.25 0.25 0.25 0.21 * 0.18 * 0.18 * 0.17 * 0.15 * 0.14 * 0.14 * 0.13 *
System build with 200 mm external or internal insulation 0.18 0.18 0.18 0.18 0.18 0.17 * 0.15 * 0.15 * 0.14 * 0.13 * 0.12 * 0.12 * 0.11 *
a
Or from equations in 6.6 if the calculated U-value is less than 1.7.
b
Or from 6.7 if wall thickness is other than 200mm to 280mm
c
According to 6.8
*
wall may have had internal or external insulation when originally built; this applies only if insulation is known to have been increased subsequently (otherwise ‘as built’ applies)
†
assumed as built

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 6 (page 31). If a wall is known to have additional insulation but the insulation thickness is unknown, use the row in the table for 50 mm insulation.

Table 18 — assumed roof U-values

Used when Tables 16 and 17 do not apply — that is, when the loft insulation thickness is neither measured nor evidenced. When you do have a measured thickness, Tables 16 and 17 are the ones to use, and they are further down this page.

RdSAP 10 Table 18, assumed roof U-values by age band, W/m²K
Age band Pitched, slates or tiles, insulation between joists or unknownPitched, slates or tiles, insulation at raftersFlat roof (b)Room-in-roof, all elementsThatched roof (c)Thatched roof, room-in-roofPark home
A, B, C, D 0.40 (100 mm) (1) (4) 2.3 (1) 2.3 (1) 2.3 (1) 0.35 0.25 -
E 0.40 (100 mm) (1) (4) 1.5 (1) 1.5 (1) 1.5 (1) 0.35 0.25 -
F 0.40 (100 mm) (1) (4) 0.68 (1) 0.68 (1) 0.80 (1) 0.35 0.25 1.7
G 0.40 (100 mm) (1) 0.40 (1) 0.40 (1) 0.50 (1) 0.35 0.25 0.6
H 0.30 (150 mm) (1) 0.35 (1) 0.35 (1) 0.35 (1) 0.35 0.25 -
I 0.26 (170 mm) (1) 0.35 (1) 0.35 (1) 0.35 (1) 0.35 0.25 0.35
J 0.16 (270 mm) (1) 0.20 (1) 0.25 (1) 0.30 (1) 0.30 0.25 -
K 0.16 (270 mm) (1) 0.20 (1) 0.25 (1) (2) 0.25 (1) (2) 0.25 (2) 0.25 (2) 0.30
L 0.16 (3) (270 mm) (1) 0.18 (1) 0.18 (1) 0.18 (1) 0.18 0.18 -
M 0.15 (300mm) (1) 0.15 (1) 0.15 (1) 0.15 (1) 0.15 0.15 0.15
(a)
If the roof insulation is “none” use U = 2.3 (all roof types, except for thatched roofs); it takes into the account sheltering effect of unheated roof space.
(b)
Applies also to roof with sloping ceiling and “unheated space above the building part”. See also 2.14 .
(1)
The value from the table applies for unknown and as built.
(2)
0.20 W/m²K in Scotland
(3)
0.15 W/m²K in Scotland
(4)
Most lofts are insulated to at least 100 mm insulation
(c)
For thatched roofs if there is also retro-fitted insulation between the rafters reduce the U-value to U = 1 / (1/U_table + R_ins), where R_ins is 0.7 m²K/W for 50 mm, 1.4 m²K/W for 100 mm and 2.1 m²K/W for 150 mm.

In the case of roof rooms, the insulation thickness on the flat part of the ceiling should be measured where possible and the U-value taken from column (2) in Table 17.

The U-value of the remaining parts of the roof rooms, i.e. walls and sloping ceilings, is taken from Table 18 according to the age band of the roof rooms, unless evidence is available as to the insulation of these parts in which case column (1) in Table 17 applies.

There is no heat loss through the roof of a building part that has the same dwelling above or another dwelling above.

Note: These U-values take account of joists. They may differ from Elemental U-values in regulations applicable at the time of construction, where the Elemental U-values in regulations (up to age band H) were set on the basis of ignoring joists in U-value calculations.

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 18 (page 41).

The other element defaults

Age bands are the fallback of last resort. Where the assessor can measure something — the depth of loft insulation, say — RdSAP uses a better table instead, and those tables are indexed by thickness rather than by year. These are the rest of the defaults for an element that cannot be evidenced: party walls, roofs by measured thickness, rooms in roof, floors and the thermal bridging factor.

Table 15 — party walls

Party wall typeU-value (W/m²K)
Solid masonry / timber frame / system built0.00
Cavity masonry unfilled0.50
Cavity masonry filled0.20
Unable to determine, house or bungalow0.25
Unable to determine, flat or maisonette*0.00
*
In the case of flats and maisonettes it is assumed that the construction is such as to avoid a thermal bypass.

Table 16 — roof U-value when the loft insulation thickness is known

This is the table that applies whenever the insulation has actually been measured, which is why Table 18 above is headed “when Table 16 or Table 17 do not apply”. If joist and rafter insulation are both present, RdSAP records the joist insulation only.

Insulation thickness Insulation at joists at ceiling level and flat roofInsulation at rafters but U-value is attributed to the ceiling areaInsulation at joists (thatched roof only)
None 2.302.300.35
12 mm 1.501.750.32
25 mm 1.001.300.30
50 mm 0.680.880.25
75 mm 0.500.670.22
100 mm 0.400.540.20
125 mm 0.350.450.18
150 mm 0.300.390.17
175 mm 0.250.320.15
200 mm 0.210.290.14
225 mm 0.190.250.13
250 mm 0.170.230.12
270 mm 0.160.210.12
300 mm 0.140.190.11
350 mm 0.120.160.10
≥ 400 0.110.140.09

Table 17 — rooms in roof, where the insulation thickness is known

Insulation thickness Insulated slope – sloping ceiling U-valueInsulated slope - flat ceiling U-valueStud wall u-value For Room in Roof
Mineral wool or EPS slabPUR or PIR optionalMineral wool or EPS slabPUR or PIR OptionalMineral wool or EPS slabPUR or PIR optional
none 2.302.302.302.302.302.30
12 mm 1.501.251.751.500.950.85
25 mm 1.000.801.251.000.700.60
50 mm 0.680.520.880.690.520.45
75 mm 0.500.380.670.510.430.35
100 mm 0.400.300.540.410.360.29
125 mm 0.350.250.450.340.310.24
150 mm 0.300.210.390.290.270.21
175 mm 0.250.170.320.230.240.19
200 mm 0.210.150.290.200.220.17
225 mm 0.190.130.250.180.200.15
250 mm 0.170.110.230.150.180.14
270 mm 0.160.100.210.140.170.13
300 mm 0.140.090.190.130.160.12
350 mm 0.120.080.160.110.140.11
≥400 0.110.070.140.090.120.10

Table 19 — ground floors

Ground floor U-values are not tabulated: they are calculated to BS EN ISO 13370 from the floor’s area and exposed perimeter, so the same construction gives a different U-value in a different shape of building. What the age band supplies is the input — the assumed construction and the assumed insulation thickness.

Age band Floor construction All-over floor insulation
England & Wales Scotland Northern Ireland Park home
A, B suspended timber (4) none none none -
C to F solid none none none none
G solid none none none 25 mm
H solid none 25 mm 25 mm -
I solid 25 mm 50 mm 50 mm 50 mm
J solid 75 mm 75 mm - -
K solid 100 mm 100 mm 100 mm 70 mm
L solid 100 mm 120 mm 100 mm -
M solid 140 mm 180 mm 140 mm 100mm

Table 20 — exposed and semi-exposed floors

RdSAP makes no distinction between a floor over outside air and one over an enclosed unheated space — both take these values.

Age band Insulation unknown or as builtInsulated 50 mmInsulated 100 mmInsulated 150 mm
A to G 1.20 0.50 (1) 0.30 0.22
H or I 0.51 0.50 (1) 0.30 0.22
J 0.25 0.25 0.25 0.22
K 0.22 0.22 0.22 0.22
L 0.22 (2) 0.22 (2) 0.22 (2) 0.22 (2)
M 0.18 (3) 0.18 (3) 0.18 (3) 0.18 (3)

Table 21 — the thermal bridging factor

Where junctions are not calculated individually, RdSAP applies a whole-dwelling y-factor by age band. For a new dwelling being designed rather than assessed, calculating the junctions beats any default — see the SAP Table K1 and R2 reference.

Age band y, not park home (W/m²K) y, park home (W/m²K)
A to I 0.15 0.15
J 0.11 0.15
K, L, M 0.08 0.15

Source for this section: RdSAP10 Specification, BRE, 12 February 2024 — Table 15 (page 38), Table 16 (pages 38–39), Table 17 (page 39), Table 19 (page 42), Table 20 and Table 21 (page 43).

Where “see 6.6” and “see 6.7” lead

The stone and solid-brick cells in Tables 6–10 above do not carry a default: for those, RdSAP calculates from the wall’s measured thickness. These are the tables it calculates with — and Table 3 is the thickness it assumes when even that cannot be measured.

Table 3 — Wall thickness (mm)

Wall typeABCDEFGHIJ, K, L, M
Stone* 500500500500450420420420450450
Solid brick 220220220220240250270270300300
Cavity** 250250250250250260270270300300
Timber frame 150150150250270270270270300300
Cob 540540540540540540560560590590
System build 250250250250250300300300300300
Park home —————5050—75100
  • * If in Scotland add 200 mm for bands A and B, and 100 mm for other bands
  • ** If in Scotland add 50 mm

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 3 (page 17).

Table 12 — Default U-values of stone walls

Stone wall typeEquation
Sandstone or limestone U= 54.876×W-0.561
Granite or whinstone: U= 45.315×W-0.513

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 12 (page 36).

Table 13 — Default U-values of brick walls

Wall thickness, mmU-value, W/m2K
Up to 200 mm 2.5
200 to 280 mm 1.7
280 to 420 mm 1.4
More than 420mm 1.1

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 13 (page 36).

Table 11 — Default U-values for park home walls

Age bandFGIKLM
Park home as built 1.71.20.70.60.60.6
Park home with additional insulation Entered U-value (see section 2.19.1)Entered U-value (see section 2.19.1)Entered U-value (see section 2.19.1)Entered U-value (see section 2.19.1)Entered U-value (see section 2.19.1)Entered U-value (see section 2.19.1)

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 11 (page 36).

Table 4 — U-values of gable-end and other walls in a room in roof

DescriptionRR wall typeAssigned U-value
A RR_gable Exposed gableU-value as common wall
A RR_party PartyU-value = 0.25 W/m2K
A RR_sheltered ShelteredU-value as external wall with sheltering factor R = 0.5
A RR_connected Adjacent to heated spaceU-value = 0

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 4 (page 20).

The rest of the defaults

Insulation resistance, thermal mass, basements, windows, conservatories and doors — the remaining tables an assessment falls back on when a value cannot be evidenced.

Table 14 — Insulation thickness and corresponding resistance

Insulation thickness T, mmR (m2K/W) insulationR (m2K/W) insulationR (m2K/W) insulation
Insulation thickness T, mmλ =0.04 W/m∙Kλ =0.03 W/m∙K (optional)λ =0.025 W/m∙K
10mm 0.50.580.65
25mm 0.8751.081.25
50 mm 1.51.922.25
75mm 2.1252.753.25
100 mm 2.753.584.25
125mm 3.3754.425.25
150 mm 45.256.25
175mm 4.6256.087.25
200 mm 5.256.928.25
  • λ =0.04 W/m∙K is typical for mineral wool, rock wool, fibre glass or EPS (expanded polystyrene); λ =0.03 W/m∙K (optional) typical for XPS (extruded polystyrene), λ =0.025 W/m∙K is typical for PUR (polyurethane foam), PIR (polyisocyanurate), phenolic foam. For drylining including laths and plaster use R insulation = 0.17m2K/W. Thickness of render is included in the thickness of uninsulated wall.
  • If thickness of insulation is in between of the values given in this table, the resistance value can be interpolated by using equations: λ R= 0.04*T+0.25 when =0.025 W/m∙K λ R=0.0333*T+0.248 when =0.03 W/m∙K λ R=0.025*T+0.25 when =0.04 W/m∙K Where T is thickness of insulation in mm

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 14 (page 37).

Table 22 — Thermal mass parameter

Construction type of main buildingThermal mass parameter
Timber frame, cob and park home (the three types regardless of presence of internal insulation) or masonry including stone, solid brick, cavity walls and system built (all four types with internal insulation) 100 kJ/m²K
Masonry including stone, solid brick, cavity walls and system built (all four types without internal insulation) 250 kJ/m²K

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 22 (page 44).

Table 23 — Basement U-values

Age bandU-value (W/m²K)U-value (W/m²K)
Basement WallBasement Floor
A to E 0.70.50
F 0.70.50
G to H 0.60.5
I 0.450.5
J 0.350.25
K 0.30.22
L 0.280.22
M 0.260.18

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 23 (page 44).

Table 24 — Window characteristics

GlazingInstalledGlazing gap between panes of glassU-value (PVC or wooden frame)U- value (metal frame)U- value** (roof window)g- value
Single Any period-4.85.75.30.85
Double glazed* England/Wales: before 2002, Scotland: before 2003 N. Ireland: before 20066 mm3.13.73.40.76
Double glazed* England/Wales: before 2002, Scotland: before 2003 N. Ireland: before 200612 mm2.83.43.10.76
Double glazed* England/Wales: before 2002, Scotland: before 2003 N. Ireland: before 200616 mm or more2.73.33.00.76
Triple glazed England/Wales: before 2002, Scotland: before 2003 N. Ireland: before 20066 mm2.42.92.60.68
Triple glazed England/Wales: before 2002, Scotland: before 2003 N. Ireland: before 200612 mm2.12.62.30.68
Triple glazed England/Wales: before 2002, Scotland: before 2003 N. Ireland: before 200616 mm or more2.02.52.20.68
Double or triple glazed England/Wales: 2002 or later, Scotland: 2003 or later N. Ireland: 2006 or laterany2.02.22.30.72
Double or triple glazed England/Wales: 2022 or later Scotland: 2023 or later NI: 2022 or laterany1.4-1.60.72
Secondary glazing Any period16 mm or more Normal emissivity2.9--0.85
Secondary glazing Any period16 mm or more Low emissivity2.2--0.85
Any glazing- known data Any periodAnyAs providedAs providedAs providedAs provided
  • * Use this row for conservatories and for other double or triple glazing whose installation date is unknown. ** Roof pitch 45° (unless horizontal), wooden or PVC. Frame factor is 0.7 for wooden or PVC frame; 0.8 for metal frame (not applied if data source is BFRC) For curtains and blinds no additional adjustment is required as curtains and blinds already accounted in formula (2) §3.2 in SAP10.2 by adding resistance R=0.04 m2K/W , however: - If a window is fitted with uninsulated shutters use R=0.13 m2K/W in formula (2) §3.2 in SAP10.2 - If a window is fitted with insulated shutters use R=0.16 m2K/W in formula (2) §3.2 in SAP10.2

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 24 (page 46).

Table 25 — Default U-values for a non-separated conservatory

GlazingAge bandFrame (FF)U-value of windowU-value of roof windowg- value
Single AnyWood/PVC (FF=0.7)4.85.30.85
Double (6 mm gap) AnyWood/PVC (FF=0.7)3.13.40.76
Triple (6 mm gaps) AnyWood/PVC (FF=0.7)2.42.60.68
  • U-values are adjusted for curtains (section 3.2 of the SAP 10.2 specification).

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 25 (page 46).

Table 26 — Default U-values for doors

Door opens toAge bandDoor U-value, W/m2K
Outside A to JU-value =3.0 W/(m2·K)
Outside KU-value =2.0 W/(m2·K)
Outside LE/W and N.I: U-value =1.8 Scotland: U-value =1.6 W/(m2·K)
Outside M1.4 W/(m2·K)
Unheated corridor or stairwell anyU-value =1.4 W/(m2·K)
Heated corridor or stairwell any(omitted from data collection)

Source: RdSAP10 Specification, BRE, 12 February 2024, Table 26 (page 47).

Download it

All 1,885 wall cells as CSV or JSON — one row per country, wall type and band, with the footnote markers and cross-references kept as their own columns. Table 1 as CSV / JSON, Table 18 as CSV / JSON. The 224 element defaults from Tables 15, 16, 17, 19, 20 and 21 as CSV / JSON, and the 234 values from Tables 3, 4, 11–14 and 22–26 as CSV / JSON — both in long format, one row per table, row and column, so the differing table shapes sit in one file each.

Source, version and how this page was made

RdSAP10 Specification, BRE, 12 February 2024. Tables 1, 3, 4, 6–26 are reproduced here in full, with attribution. The specification is the authority: if you are producing an EPC for lodgement, work from it. The document carries no copyright, licence or reuse statement on any of its 106 pages.

The tables were read out of the PDF by table geometry rather than text order, because merged cells and year ranges containing spaces are silently mangled by a text read — and then every one of the 1,885 wall cells was compared back against the printed page, footnote markers included, and then every cell of the rendered page was compared back against that data — 2,280 in all. Every U-value table in the specification is now here. The tables deliberately left out are the ones that are not U-value lookups at all: ventilation parameters, cylinder sizes, heating and hot water parameters, living area fractions, fuel prices and the improvement measures.

What to do with the number

An age-band default is a fallback, not a target. It is what the assessment assumes when nobody can show what the wall is made of, and it is usually pessimistic — which is the point, but it costs the property points it might not deserve. Where the construction can be evidenced, a calculated U-value almost always beats the default. U-Monkey does that calculation free, layer by layer, with the λ values behind it shown and sourced. RenoMonkey takes the before-and-after pair and shows what a retrofit moves. For the junction losses that sit alongside the plane elements, see the SAP Table K1 defaults.

To be clear about what we do and don't do: this page is a reference, not a service pitch. Energycount does not carry out RdSAP assessments or EPCs on existing homes — that needs a domestic energy assessor who surveys the property, which is a different accreditation. Our EPC work is the new-build kind, lodged from the as-built SAP calculation by an accredited on-construction assessor. The tools above are free to anyone, assessors included.

Frequently asked questions

What is an RdSAP age band?

A letter, A to M, standing for a span of construction years. RdSAP uses it to assign a default U-value to any element the assessor cannot inspect or evidence — most walls, most roofs. The spans differ by country because they track changes to that country’s building regulations, and they are generally set one year after a regulation change to allow for dwellings approved under the previous rules. The band applies to each building part, so an extension can sit in a later band than the house it is attached to.

My house is 1965 — which band is it?

It depends where it is. 1965 is band D in England and Wales (1950–1966), band E in Scotland (1965–1975) and band D in Northern Ireland (1950–1973). That single year gives a cavity wall 1.5 W/m²K in England and 1.5 in Scotland, but the divergence matters at other dates — which is why the lookup at the top of this page asks for the country.

Why does the table say “see 6.6” instead of a U-value?

For stone and solid brick in the earliest bands, RdSAP does not use a fixed default. It calculates the U-value from the measured wall thickness using the equations in sections 6.6 (stone), 6.7 (solid brick) and 6.8 (insulated stone or solid brick) of the specification. A flat default would be badly wrong across the range of thicknesses those walls come in.

What does the asterisk on a value mean?

It marks a wall that may have been insulated when it was originally built. The starred value applies only where the insulation is known to have been increased since; otherwise the “as built” row is the one to use. The dagger means the value is the as-built figure. Both change the answer, so neither is decoration.

Can I use these for a SAP calculation on a new build?

No. These are RdSAP defaults for existing dwellings where the construction is unknown. A new dwelling is assessed under full SAP with U-values calculated from the actual build-up, layer by layer. Our U-value calculator does that calculation free.

Is this the current version?

This is the RdSAP10 Specification dated 12 February 2024, which is the version in force for RdSAP 10 assessments. The specification itself is the authority — if you are producing a lodged EPC, work from the PDF, not from a web page. This one is here so you can find the number quickly and check it.

Calculating a U-value rather than looking one up?

U-Monkey does the layer-by-layer calculation free, with every λ it uses shown and sourced. If it is a new dwelling, an extension or material works you are assessing, that is the calculation Building Control wants — and the one we do every day.

Try the free U-value calculator or call 01202 623236