Losses due to lack of insulation and evaporation are not considered.
We have tried in vain to come up with something better than the various calculators from beer brewing sites. For example, we looked at specific heat capacities of different grains as a function of temperature and residual moisture, and then developed a formula from that, which is now not really different from the established formula.
This formula, like ours, generalizes a few complex relationships. It seems to us that at the price of a much more complicated operability only a hardly noticeable improvement would be possible. For example, one would have to enter the grain type and its residual moisture into the calculator, and then the calculator might calculate 71 instead of 70°C necessary water temperature. This seems unnecessary to us.
Therefore, our calculator is now based on the same formula as the calculators on beer brewing sites and, consequently, naturally calculates the same temperatures.