Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
The weather data may be hourly but they are then interpolated for use with shorter timesteps. So it is not really the case that the outside conditions stay the same over an hour when using shorter timesteps -- they will vary smoothly between weather data points.
One of the deep technical reasons for the existence of timestep dependence in the zone heat balance method in EnergyPlus is that it when predicting a new zone air temperature is uses the lagged zone air temperature for the temperature difference when calculating surface convection heat transfer. (It could go back and iterate with the new temperature but that would slow it down execution.)
For long timesteps and fast execution you want to use Conduction Transfer Function.
