Traditional methods for estimating energy usage have found form in the “degree day method”. The “bin” method lends itself to incorporating selected space temperatures and internal gains in a more encompassing manner. Manipulation of the bin method to incorporate variables such as space temperatures, internal gains, and ventilation rates is presented in this paper to provide a two-fold purpose. First, to provide an appropriate method to evaluate seasonal energy usage in livestock buildings in a simple, convenient manner using tabulated bin data. Second, to provide a technique to model livestock buildings for hourly computer simulation of energy usage.