Book - School of Science and Technology

typical but wholly uninsulated constructions. It would, of course, be out of the question toprovide a fully comprehensive version of such a table in view of the wide and ever-changingavailability of composite constructions.The complementary table (Table 2.6) provides values of resistances for a variety ofinsulation materials of standard thickness, as manufactured. The method of use of thetwo tables is best illustrated by a simple example:The walls of a new building are to be constructed as Item 10 in Table 2.5. The resistanceis 0:857 m 2 K/W but Building Regulations require a U value of 0:35 W/m 2 K or a resistance(1/U) of 2:857 m 2 K/W.Resistance deficit ˆ (2:857 0:857) ˆ 2:000Deduct for an air gap (Table2:1) ˆ 0:181:82 m 2 K/WAtypical construction features 41Table 2.6 Resistances of insulation materials of standard thickness (m 2 K/W)Thickness (mm)Material 20 25 30 35 40 45 50 55 60 65 70 75A.1 Expanded polystyrene(board) 0.54 0.68 0.81 0.95 1.08 1.22 1.35 1.49 1.62 1.76 1.89 2.02A.2 Extruded polystyrene(board) 0.8 1.0 1.2 1.4 1.6 ± 2.0 ± 2.4 ± ± ±A.3 Glass fibre(rigid slab or batt) ± 0.81 0.97 ± 1.29 ± 1.61 ± 1.94 ± ± 2.42A.4 Glass fibre(flexible and mat) ± 0.63 ± ± 1.0 ± 1.25 ± 1.5 1.63 ± 1.88A.5 Mineral fibre(rigid slab or batt) ± 0.76 0.91 ± 1.21 ± 1.52 ± 1.82 ± ± 2.27A.6 Mineral fibre(flexible and mat) ± ± ± ± ± ± 1.35 ± 1.62 ± ± 2.02A.7 Phenolic foam(board) 1.11 1.39 1.67 1.94 2.22 2.5 2.78 3.06 3.33 3.61 3.88 4.17A.8 Polyurethane foam,CFC blown (board) 1.05 1.32 1.58 1.84 2.11 ± 2.63 ± 3.16 ± ± ±A.9 Polyurethane foam,PHA blown (board) 0.95 1.19 1.43 1.67 1.9 ± 2.38 ± 2.86 ± ± ±Thickness (mm)Material 50 55 60 65 70 75 80 100 150 200B.1 Blown mineral fibre(for existing cavity) 1.25 1.38 1.5 1.63 1.75 1.88 ± ± ± ±B.2 Urea formaldehyde foam(for existing cavity) 1.61 1.77 1.94 2.1 2.25 2.42 ± ± ± ±B.3 Glass fibre mat (in roll) ± ± 1.5 ± ± ± 2.0 2.5 3.75 5.0B.4 Mineral fibre mat(in roll) ± ± 1.62 ± ± ± 2.16 2.7 4.05 5.41B.5 Vermiculite granules(loose fill) ± ± ± ± ± ± 1.23 1.54 2.31 3.08