The new complex selection strategy of low energy ventilating or air conditioning system (HVAC system) from a holistic perspective is presented in the paper. The strategy carries out the solution of the whole optimization problem that consists of the HVAC system model, optimization model and optimization procedure. The practical function is the starting point of the optimization problem, whereas the energy optimal variant of the HVAC system is the final stage. Universal sets of constant parameters, decision variables and limiting conditions of the HVAC system were formulated for the mathematical description of the problem. In optimization procedure, the sets of all variants and permissible variants of the HVAC system were defined based on the system analysis with the use of matrix calculation. The objective function was determined by the use of the simulation model of the HVAC system where the algorithms of energy optimal control is determined by dynamic optimization.