  In many extensions of the Standard Model, finite temperature computations are
complicated by a hierarchy of zero temperature mass scales, in addition to the
usual thermal mass scales. We extend the standard thermal resummations to such
a situation, and discuss the 2-loop computations of the Higgs effective
potential, and an effective 3d field theory for the electroweak phase
transition, without carrying out high or low temperature expansions for the
heavy masses. We also estimate the accuracy of the temperature expansions
previously used for the MSSM electroweak phase transition in the presence of a
heavy left-handed stop. We find that the low temperature limit of dealing with
the left-handed stop is accurate up to surprisingly high temperatures.
