Independent fraction, located in Portalegre, intended to the provision of services with administrative character to the respective community, located in the first floor of the north corp of a building which also integrates another fraction of public service. This specific fraction is composed for the following installations: secretariat/public service; presidency office, work office, conference room, service cop, storage and sanitary facilities. In the inspection and analyze of the building was made an inventory of the constructive solutions which compounds the building envelope, as well the evaluation of the constructive weakness/pathologies. It was made the identification of the weak points at the thermal behavior level of the building envelope, supported with infrared technology technical. It was evaluated the inside air quality and the energetic consumption with the heating/cooling, (energetic auditing), and it was made the dynamic simulation of the building.  This building only consumes electrical energy in some uses (heating, illumination, informatics systems, power outlets, and so on). The main opportunity of improvement identified in energetic auditing are related with the reinforcement of thermal insulation in the constructive elements with worse performance; the shadowing of the façade by the exterior through fixed shadowing blades, blinds, among others solutions; introduction of a timing device in the feeding of the electrical water heaters; and the reduction of the hired power for the 20,7 kVA, having in consideration that the sum of the power of the main equipments doesn’t exceed the 20kVA. Through the results of the dynamic simulations it is possible to observe that, in the scenario where the building is painted with a white color which presents a solar absorption of 0,2, the heating needs will be of 42% superior than the initial solution. This result is owned to the fact that the reduction in the coefficient of solar absorption of the wall lead to a reduction of the heat gains by the envelope during the warming season. However, once, in the building in analyze, the needs of cooling are considerable superiors to the warming needs, the impact of this measure in the total consumption energy is significant, having obtained a reduction  in the annual consumption of 22%. The correspondent scenario of the green roof demonstrates good results, both in warming season (16% of reduction), both as in the cooling season (9% reduction), being the reduction in the annual consumption of annual energy of 10%. The scenario correspondent to the introduction of grids to air admission in the glazed areas is the lesser contribution for the reduction of the energetic needs, only performing a reduction of 2% in the annual consumption of energy.