- Example U Value Calculation -
Typical Cornish Houses
 
 
Construction Type
Element: Wall - Concrete
Exposure: Normal
Internal Surface Emissivity: High
External Surface Emissivity: High
Building Use: Domestic House / Flat


Prior to WBS system application
Thickness
Thermal Conductivity
Thermal Resistance
Vapour Resistivity
Vapour Resistance
 
(mm)
(W/m²K)
(m²K/W)
(MNs/gm)
(MNs/g)
Outside surface resistance
-
-
0.040
-
-
External concrete leaf
75.00
1.400
0.054
60.00
4.50
Cavity
-
-
0.180
-
-
Inner concrete leaf
75.00
1.400
0.054
60.00
4.50
Plaster, dense
16.00
0.500
0.032
60.00
0.96
Inside surface resistance
-
-
0.130
U-Value, Proportionate Area Method:
2.041 (W/m²K)


90mm Mineral Wool
Thickness
Thermal Conductivity
Thermal Resistance
Vapour Resistivity
Vapour Resistance
 
(mm)
(W/m²K)
(m²K/W)
(MNs/gm)
(MNs/g)
Outside surface resistance
-
-
0.040
-
-
WBS Polymer Cement Render
10.00
0.115
0.087
100.00
1.00
WBS Mineral Wool Insulation
90.00
0.036
2.500
0.00
0.00
External concrete leaf
75.00
1.400
0.054
60.00
4.50
Cavity
-
-
0.180
-
-
Inner concrete leaf
75.00
1.400
0.054
60.00
4.50
Plaster, dense
16.00
0.500
0.032
60.00
0.96
Inside surface resistance
-
-
0.130
U-Value, Proportionate Area Method:
0.325 (W/m²K)


50mm Phenolic
Thickness
Thermal Conductivity
Thermal Resistance
Vapour Resistivity
Vapour Resistance
 
(mm)
(W/m²K)
(m²K/W)
(MNs/gm)
(MNs/g)
Outside surface resistance
-
-
0.040
-
-
WBS Polymer Cement Render
10.00
0.115
0.087
100.00
1.00
WBS Phenolic Insulation
50.00
0.021
2.381
0.00
0.00
External concrete leaf
75.00
1.400
0.054
60.00
4.50
Cavity
-
-
0.180
-
-
Inner concrete leaf
75.00
1.400
0.054
60.00
4.50
Plaster, dense
16.00
0.500
0.032
60.00
0.96
Inside surface resistance
-
-
0.130
U-Value, Proportionate Area Method:
0.338 (W/m²K)



 

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Provided strictly for guidance purposes only. WBS accept no liability for errors or omissions.
For a full U-value calculation, including Condensation Risk Analysis and Temperature Profiles,
please contact WBS Technical Support on 08458 382380.