Being highly insulated, low energy buildings are very sensitive to variable solar and internal gains. In this context, thermal mass is useful in storing surplus energy, reducing temperature variations and improving thermal comfort. Thus, conduction modelling is fundamental, but not sufficient: appropriate superficial heat transfer modelling is also needed. Therefore, several common simplifying assumptions have been investigated and adapted to the case of high performance buildings. These models are reassessed using the BESTEST numerical building simulations and compared to reference models.