- Example U Value Calculation -
Typical BISF Houses - Upper Floor
 
 
Construction Type
Element: Wall - Steel Panels
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
-
-
Steel
1.00
50.00
0.000
100000.00
100.00
Cavity
76.00
-
0.180
-
-
Softwood, dry
25.00
0.125
0.200
100.00
2.50
Plasterboard
12.50
0.167
0.075
45.00
0.56
Inside surface resistance
-
-
0.130
U-Value, Proportionate Area Method:
1.600 (W/m²K)


80mm Expanded Polystyrene
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 EPS Insulation
80.00
0.036
2.222
0.00
0.00
Plywood
18.00
0.143
0.126
450.00
8.10
Cavity
76.00
-
0.180
-
-
Softwood, dry
25.00
0.125
0.200
100.00
2.50
Plasterboard
12.50
0.167
0.075
45.00
0.56
Inside surface resistance
-
-
0.130
U-Value, Proportionate Area Method:
0.327 (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
Plywood
18.00
0.143
0.126
450.00
8.10
Cavity
76.00
-
0.180
-
-
Softwood, dry
25.00
0.125
0.200
100.00
2.50
Plasterboard
12.50
0.167
0.075
45.00
0.56
Inside surface resistance
-
-
0.130
U-Value, Proportionate Area Method:
0.311 (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.