Economic Thickness & Payback

More insulation always saves more energy, but each added millimetre saves less than the last while costing the same to install. Somewhere between "not enough" and "wasteful excess" is an optimum, the economic thickness, and finding it is what separates an engineered specification from a guess. This lesson explains the principle of diminishing returns, how to locate the optimum, what shifts it, and why the practical constraints sometimes overrule the pure economics.