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Junction ψ-values and f-values (walls with partially filled cavities)

Thermal bridging ψ-values and f-values for walls partially filled with PU thermal insulation.

The models given in this document cover:

Ultralightweight aggregate blocks with λ not exceeding 0.28 W/mK
Lightweight aggregate blocks with λ not exceeding 0.60 W/mK
Dense aggregate blocks with λ not exceeding 1.33 W/mK

SAP 2012 approved and default ψ-values should be applied to each dwelling.

  • See individual CBA details for guidance on allocation of calculated ψ-values to dwellings at a junction.

SAP 2012 Table K1 ref: E2
Junction Detail: Other lintels (including other steel lintels)
SAP2012 Approved ψ-value (W/mK): 0.30
SAP2012 Default ψ-value (W/mK): 1.00
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.022 to 0.024
Lightweight: 0.017 to 0.022
Dense: 0.015 to 0.021
CBA detail ref: E2 PF CBA-213

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SAP 2012 Table K1 ref: E3
Junction Detail: Sill
SAP2012 Approved ψ-value (W/mK): 0.04
SAP2012 Default ψ-value (W/mK): 0.08
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.019 to 0.027
Lightweight: 0.018 to 0.027
Dense: 0.018 to 0.027
CBA detail ref: E3 PF CBA-214

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SAP 2012 Table K1 ref: E4
Junction Detail: Jamb
SAP2012 Approved ψ-value (W/mK): 0.05
SAP2012 Default ψ-value (W/mK): 0.10
Calculated CBA Full-fill ψ-value (W/mK):  Ultra-lightweight: 0.041 to 0.055
Lightweight: 0.013 to 0.021
Dense: 0.013 to 0.021

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SAP 2012 Table K1 ref: E5
Junction Detail: Ground Floor (Normal)
SAP2012 Approved ψ-value (W/mK): 0.16
SAP2012 Default ψ-value (W/mK): 0.32
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.055 to 0.064
Lightweight: 0.091 to 0.107
Dense: 0.144 to 0.177
CBA detail ref: E5 PF CBA-201 (Beam and Blick)

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E5 PF CB-202 (Slab on Ground)

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SAP 2012 Table K1 ref: E6
Junction Detail: Intermediate floor within a dwelling
SAP2012 Approved ψ-value (W/mK): 0.07
SAP2012 Default ψ-value (W/mK): 0.14
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.000
Lightweight: 0.000 to 0.001
Dense: 0.000 to 0.002
CBA detail ref: E6 PF CBA-203

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SAP 2012 Table K1 ref: E7
Junction Detail: Intermediate floor between dwellings*
SAP2012 Approved ψ-value (W/mK): 0.07
SAP2012 Default ψ-value (W/mK): 0.14
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.085 to 0.121
Lightweight: 0.086 to 0.124
Dense: 0.088 to 0.126
CBA detail ref: E7 PF CBA-204

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SAP 2012 Table K1 ref: E10
Junction Detail: Eaves (insulation at ceiling level)
SAP2012 Approved ψ-value (W/mK): 0.06
SAP2012 Default ψ-value (W/mK): 0.12
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.080 to 0.097
Lightweight: 0.086 to 0.105
Dense: 0.090 to 0.111
CBA detail ref: E10 PF CBA-208

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SAP 2012 Table K1 ref: E11
Junction Detail: Eaves (insulation at rafter level)
SAP2012 Approved ψ-value (W/mK): 0.04
SAP2012 Default ψ-value (W/mK): 0.08
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: -0.008 to 0.007
Lightweight: -0.009 to 0.007
Dense: -0.009 to 0.008
CBA detail ref: E11 PF CBA-209

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SAP 2012 Table K1 ref: E20
Junction Detail: Exposed Floor (Normal)
SAP2012 Default ψ-value (W/mK): 0.32
Calculated CBA Full-fill ψ-value (W/mK):

Ultra-lightweight: 0.135 to 0.158   Lightweight: 0.201 to 0.219   Dense: 0.307 to 0.318    CBA detail ref: E20-C-B1 Concrete floor over garage/side wall

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Ultra-lightweight: 0.223 to 0.238   Lightweight: 0.230 to 0.244   Dense: 0.239 to 0.252    CBA detail ref: E20-C-B2 Concrete floor over drive-through/side wall

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Ultra-lightweight: 0.086 to 0.172   Lightweight: 0.088 to 0.231   Dense: 0.090 to 0.291    CBA detail ref: E20-C-B3 Concrete floor over garage or drive through/opening

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Ultra-lightweight: 0.078 to 0.081   Lightweight: 0.131 to 0.139   Dense: 0.227 to 0.243    CBA detail ref: E20-T-B1 Timber floor over drive-through/side wall

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Ultra-lightweight: 0.100 to 0.107   Lightweight: 0.142 to 0.150   Dense: 0.189 to 0.200    CBA detail ref: E20-T-B2 Timber floor over drive-through/side wall

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Ultra-lightweight: 0.069 to 0.1050   Lightweight: 0.082 to 0.161   Dense: 0.094 to 0.244    CBA detail ref: E20-T-B3 Timber floor over garage or drive through/opening

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SAP 2012 Table K1 ref: E21
Junction Detail: Exposed floor (inverted)
SAP2012 Default ψ-value (W/mK): 0.32
Calculated CBA Full-fill ψ-value (W/mK):

Ultra-lightweight: 0.056 to 0.057   Lightweight: 0.136   Dense: 0.259    CBA detail ref: E21-C-B1 Concrete floor over garage/side wall

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Ultra-lightweight: 0.171 to 0.172  Lightweight: 0.170   Dense: 0.070 to 0.171   CBA detail ref: E21-C-B2 Concrete floor over drive-through/side wall

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Ultra-lightweight: 0.061 to 0.070   Lightweight: 0.121 to 0.132   Dense: 0.196 to 0.209    CBA detail ref: E21-T-B1 Timber floor over garage/side wall

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Ultra-lightweight: 0.143 to 0.154   Lightweight: 0.143 to 0.155   Dense: 0.144 to 0.155    CBA detail ref: E21-T-B2 Timber floor over drive-through/side wall

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SAP 2012 Table K1 ref: E24
Junction Detail: Eaves (Insulation at ceiling level – inverted)*
SAP2012 Default ψ-value (W/mK): 0.24
Calculated CBA Full-fill ψ-value (W/mK):

Ultra-lightweight: 0.094 to 0.111   Lightweight: 0.191 to 0.110   Dense: 0.091 to 0.110    CBA detail ref: E24-1-C-B Pitched roof over addition/concrete lintel

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Ultra-lightweight: 0.117 to 0.158   Lightweight: 0.116 to 0.158   Dense: 0.117 to 0.159    CBA detail ref: E24-1-S-B Pitched roof over addition/steel lintel

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Ultra-lightweight: 0.106 to 0.123   Lightweight: 0.103 to 0.122   Dense: 0.102 to 0.121    CBA detail ref: E24-2-C-B Pitched roof over bay/concrete lintel

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Ultra-lightweight: 0.173 to 0.175   Lightweight: 0.174 to 0.177   Dense: 0.176 to 0.180    CBA detail ref:E24-2-S-B Pitched roof over bay/steel lintel

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Ultra-lightweight: 0.194 to 0.224   Lightweight: 0.194 to 0.224   Dense: 0.194 to 0.224    CBA detail ref: E24-3-C-B Stepped apartment/concrete floor

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Ultra-lightweight: 0.186 to 0.211   Lightweight: 0.186 to 0.211   Dense: 0.187 to 0.212    CBA detail ref: E24-3-T-B Stepped apartment/timber floor

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SAP 2012 Table K1 ref: E12
Junction Detail: Gable (insulation at ceiling level)
SAP2012 Approved ψ-value (W/mK): 0.24
SAP2012 Default ψ-value (W/mK): 0.48
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.0049 to 0.0057
Lightweight: 0.076 to 0.087
Dense: 0.114 to 0.131
CBA detail ref: E12 PF CBA-210

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SAP 2012 Table K1 ref: E13
Junction Detail: Gable (insulation at rafter level)
SAP2012 Approved ψ-value (W/mK): 0.04
SAP2012 Default ψ-value (W/mK): 0.08
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.0053 to 0.055
Lightweight: 0.072 to 0.073
Dense: 0.086 to 0.088
CBA detail ref: E13 PF CBA-211

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SAP 2012 Table K1 ref: E16
Junction Detail: Corner (normal)
SAP2012 Approved ψ-value (W/mK): 0.09
SAP2012 Default ψ-value (W/mK): 0.18
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.041 to 0.055
Lightweight: 0.046 to 0.064
Dense: 0.048 to 0.069
CBA detail ref: E16 PF CBA-216

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SAP 2012 Table K1 ref: E17
Junction Detail: Corner (inverted – internal wall area greater than external area)
SAP2012 Approved ψ-value (W/mK): -0.09
SAP2012 Default ψ-value (W/mK): 0.00
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: -0.103 to -0.057
Lightweight: -0.110 to -0.059
Dense: -0.113 to -0.060
CBA detail ref: E17 PF CBA-217

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SAP 2012 Table K1 ref: E18
Junction Detail: Party (separating) wall between dwellings*
SAP2012 Approved ψ-value (W/mK): 0.06
SAP2012 Default ψ-value (W/mK): 0.12
Calculated CBA Full-fill ψ-value (W/mK): Ultra-lightweight: 0.072 to 0.100
Lightweight: 0.076 to 0.108
Dense: 0.078 to 0.113
CBA detail ref: E18 PF CBA-205

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SAP 2012 Table K1 ref: E25
Junction Detail: Staggered separating wall between dwellings*
SAP2012 Default ψ-value (W/mK): 0.12
Calculated CBA Full-fill ψ-value (W/mK):

Ultra-lightweight: 0.098 to 0.142   Lightweight: 0.0104 to 0.156   Dense: 0.107 to 0.165    CBA detail ref: E25-338-B 338mm stagger

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Ultra-lightweight: 0.091 to 0.148   Lightweight: 0.095 to 0.155   Dense: 0.104 to 0.159    CBA detail ref: E25-1038-B 1038mm stagger

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SAP 2012 Table K1 ref: P8
Junction Detail: Exposed floor (inverted)*
SAP2012 Default ψ-value (W/mK): 0.24
Calculated CBA Full-fill ψ-value (W/mK):

Ultra-lightweight: 0.095 to 0.107   Lightweight: 0.169 to 0.184   Dense: 0.279 to 0.298    CBA detail ref: P8-C-B1 Concrete floor over garage

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Ultra-lightweight: 0.201 to 0.217   Lightweight: 0.200 to 0.217   Dense: 0.171 to 0.217    CBA detail ref: P8-C-B2 Concrete floor over drive-through

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Ultra-lightweight: 0.144 to 0.203   Lightweight: 0.167 to 0.251   Dense: 0.185 to 0.294    CBA detail ref: P8-T-B1 Timber floor over garage

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Ultra-lightweight: 0.174 to 0.266   Lightweight: 0.173 to 0.265   Dense: 0.174 to 0.265    CBA detail ref: P8-T-B2 Timber floor over drive-through

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