Book - School of Science and Technology

40 The building in winterSurfaceArea (A)(m 2 )U(W/m 2 K)AU(W/K)Floor ˆ 14.5 8.5 ˆ 1236.0 8.5 ˆ 51 174 0.40 ˆ 69.6Roof ˆ 6.0 8.5 ˆ 51 0.44 ˆ 22.4Windows ˆ 12.0 2.0 ˆ 24 3.1 ˆ 74.4Walls ˆ 48.5 4.0 ˆ 194less windows ˆ 24 170 0.43 ˆ 73.1419 239.5Thus, the conduction loss, air to air, is 240 22 ˆ 5:28 kW and (AU)/A ˆ240/419 ˆ 0:57 W/m 2 K.Selection of the means to be used in upgrading an existing structure or to produce anacceptable standard in a proposed building may follow the use of calculation routines whichhave been described earlier (p. 24). It may however be found convenient to make use ofTables 2.5 and 2.6 when selecting the type and thickness of insulation to be used. The firstof these lists U values and the corresponding resistances (1/U) for a limited selection ofTable 2.5 Transmission coefficients (U values) and resistances for a range of typical uninsulated constructionsfor `normal' exposure (for use in conjunction with Table 2.6)Construction (dimensions in mm) U (W/m 2 K) 1/U (m 2 K/W)1. 19 render, 220 no fines concrete block : & : 12 plasterboardon battens 2.05 0.4882. 19 render, 220 dense concrete block : & : 12 plasterboardon battens 2.40 0.4163. 80 dense concrete panel : & : 100 dense concrete block,13 dense plaster 2.68 0.3734. 80 dense concrete panel : & : 100 dense concrete block,13 dense plaster 3.09 0.3245. 220 solid brick : & : 13 dense plaster 2.14 0.4686. 220 solid brick : & : plasterboard on battens 1.93 0.5177. 105 brick : & : 105 brick, 13 lightweight plaster 1.82 0.5498. 105 brick : & : 105 brick, 13 dense plaster 2.0 0.4999. 105 brick : & : 100 dense concrete block, 13 dense plaster 2.55 0.39210. 105 brick : & : 100 lightweight concrete, 13 dense plaster 1.17 0.85711. 105 brick : & : 100 autoclaved aerated concrete,13 lightweight plaster 1.07 0.93612. 105 brick, air gap, plywood membrane, 95 stud : & :12plasterboard on stud 1.44 0.69613. 105 brick, air gap, plywood membrane, 140 stud : & :12plasterboard on stud 1.44 0.69614. Waterproof covering, 75 screed : & : 150 concrete roof, 13 denseplaster 2.05 0.48815. Tiles on battens, roofing felt and rafters : & : bare plaster ceilingbelow joists 2.6 0.385NoteIf a better performance be required, subject to investigation of the risk of condensation, insulation may be placed as shown by the symbol &.