Due to the thermal tempering process elastic energy is stored in glass panes. After breakage of thermally tempered glass, this energy is partly or fully released. The broken glazing measurably expands with noise and kinetic movement. The determination of elastic strain energy bases on the theory of glass fracture and its further extension. The distinction into elastic and kinetic parts of the stored energy was shown on the molecular dimension by Kerkhof 1970. The authors of this paper have developed an approach to transfer the molecular level into macro dimensions. An experimental study was performed to verify the elastic energy approach. A series of fully tempered glass put under constraint and in-plane force was measured at the moment of failure. This generated in plane force causes a membrane situation of the glasses. The gained experimental data were statistically analysed and support the new approach. Practical relevance of the investigation is given by a significantly increasing residual strength of the broken glasses and therefore, a reduction of glazing thickness and dead load.
