The cost of insulation (including application and any normal finish) and of the heat lost are tabulated for a range of thickness of insulation (see Table 1.16
). These costs are added for each thickness and the minimum total becomes apparent.
For the purpose of calculating the cost of heat lost, the surface coefficient can be taken to be 10.0 W/(m2.K), since likely variations from this figure do not significantly affect the result. The insulating effect of finishing materials is ignored. The cost of heat lost is as follows: