-
Appendix 4. Rooms in Roof – U-values applicable to room in roof insulation
The values should be used only in relation to Room in Roof when the “U-value” option is chosen in the extended data entry.
Insulation thickness at joists (mm)
Slope u-value
Flat ceiling u-value
Stud wall u-value
Mineral wool or EPS slab
PUR or PIR
Mineral wool or EPS slab
PUR or PIR
Mineral wool or EPS slab
PUR or PIR
Key:
none
If “none”, use values fron SAP-2012 Apepndix S, Table S10
EPS – expanded polystyrene slab
12
1.91
1.23
1.18
1.04
1.79
0.71
PUR – polyurethane rigid insulation
25
1.24
0.82
0.9
0.75
1.23
0.56
PIR – polyisocyanurate rigid foam
50
0.77
0.52
0.62
0.51
0.78
0.41
75
0.56
0.39
0.5
0.39
0.59
0.34
Assumptions used for calculating U-values:
100
0.45
0.31
0.41
0.32
0.48
0.29
Up to 150 mm, the insulation is between timber (rafters or studs)
150
0.33
0.24
0.33
0.26
0.29
0.24
Timber fraction is 12%
200
0.23
0.16
0.23
0.16
0.21
0.16
After 150mm, the next layer of insulation is continuous
250
0.18
0.12
0.18
0.12
0.17
0.12
0.04 W/mK – thermal conductivity of mineral wool slab or EPS slab
270
0.16
0.11
0.17
0.11
0.16
0.11
0.025 W/mK – thermal conductivity of PUR or PIR slab
300
0.15
0.1
0.15
0.1
0.14
0.1
350
0.13
0.08
0.13
0.09
0.12
0.08
>400
0.11
0.07
0.11
0.07
0.11
0.07
Notes:
U-values from this table can be used for elements of rooms in roof only when the type of insulation and its thickness are known (evidence required)
-
Use the actual thickness of insulation (do not double insulation thickness if thermal conductivity is 0.025 W/mK)