The idea of passive buildings can be broadly understood when understand how the building behaves in relation to energy consumption. All buildings have an energy balance, energy is lost and won every hour of the day and the difference is covered by the systems heating (boiler, radiators etc) and cooling (A/C). The energy energy losses and gains are the result of passive technologies have been applied to the building (insulation, frames, etc.), while the active technologies such as the heating and cooling system are those balance the energy27 balance.