An indoor climate is, in the broadest sense of the word, the total, physical effect a person can be subject to when they are inside a building. A building can be considered as a local micro climate separated from the surroundings but still affected by them. As every other well functioning system, functionality will be achieved through equilibrium. If the equilibrium is upset by an unintentional load which exceeds the capacity of the system, then the functionality of the system will be broken down. It is therefore essential that the building is designed and dimensioned in accordance with the proposed purpose and load as the unique system the building represents.