The quality of most buildings may be affected during the initial phase of architectural design. Therefore, it is important to optimize input parameters, which sig-nificantly influence energy efficiency. In principle, it is possible to speak of a deterministic approach, which considers input parameters to be fixed, or a stochastic approach, which takes a wider set of input parameters into account. A reference building is evaluated in terms of energy performance, where input parameters are changed in order to determine a correlation coefficient. Regressions were written to express the impact architectural design has on energy performance.