The difference lies in that in lightweight plaster, fillers of low bulk density are used to increase the productivity by reducing the amount of plaster used per square meter. With the use of lightweight fillers, ALPOL AG T31 shows very good thermal conductivity λ ≤ 0.25 W/(m•K). If your walls are built properly, with well maintained verticality and planes, it is recommended to use ALPOL AG T31 lightweight gypsum plaster for machine application. However, in case of large deviations of verticality and linearity, it is suggested to use “plain” gypsum plaster for machine application i.e. ALPOL AG T30. Using a more expensive lightweight plaster makes no economic sense, since the quality of the finished surface in both cases is identical.