After several batches, and some pretty careful note taking, I am getting more confident that there is a hidden temperature offset in the strike water calculator that can't be avoided. From the FAQ Section I can see that this was an intentional addition: NOTE: The strike calculator assumes your tun will absorb heat (a few degrees will be absorbed by the mash tun, this varies widely by the type of mash tun). Even if you 'pre-heat' the tun with a little boiling water, this may still be the case. Do not stabilize the tun at the calculated strike temperature, and then add grains, or you will probably overshoot. I had assumed that this was referring to the "Initial Heat Loss" offset that is part of the mash profile, but the consistency of my overshoot in a pre-heated tun makes me think that there is actually a background heat offset as well. The Request: Please allow negative values for the "Initial Heat Loss" field, or provide a mash option for BIAB which eliminates any background heat loss calculations. I do accept that there may be something in my equipment that does not correspond to the typical heat loss equations. The simplest solution would be to allow the negative value so that an equipment profile can more accurately reflect the strike temperature.