One of the least used aspects of BIM (Building Information Modeling) is the ability to obtain the energy model of the building using the BIM methodology known as BIM 6D. This digital information model allows simulating the real energy behavior of the building and the improvement in the building’s lighting systems, both natural and artificial, in particular daylighting. In this way, the BIM 6D simulation allows us to make design and operation decisions for the building, not only for new buildings that must be, in accordance with current legislation, NZEB (Nearly Zero-Energy Building) but also for the rehabilitation of existing buildings. Particularly in buildings for sanitary use, BIM 6D allows an exhaustive analysis of the energy impact of said rehabilitation, guiding it towards an improvement in energy and light efficiency, which in turn provides greater quality and comfort in the use of the sustainable building. This subject of study is especially important in public buildings for hospital use. Buildings where energy efficiency and comfort, oriented towards optimal and efficient lighting, are two fundamental criteria highly appreciated by patients and citizens in general. Once the energy model of the building has been obtained, it is possible to study and identify possible alternatives to improve energy efficiency and improve lighting, as well as to analyze the possibilities of incorporating other more efficient forms of renewable energy, such as the use of daylight. In this work we can see how applying a set of simulated improvement actions in BIM 6D achieves an energy saving of 50% in general and up to 13% only by acting on lighting systems, allowing the decarbonization of buildings with high energy consumption, such as hospitals, and in turn, will lead to an improvement in the energy certification of these buildings; thus achieving a better and higher quality of habitability, using more efficient forms of lighting and transforming buildings into more sustainable spaces.

The requirements concerning the energy certification of buildings established in Directive 2002/91/EC of the European Parliament and of the Council of 16 December 2002, which was in turn modified by Directive 2010/31/EU of the European Parliament and of the Council, of 19 May 2010, regarding the energy efficiency of buildings, were transposed into Spanish legislation through Royal Decree 47/2007, dated January 19, through which a Basic Procedure for certification was approved of energy efficiency of new buildings, which was consolidated by Royal Decree 235/2013, of April 5, which approves the basic procedure for the certification of the energy efficiency of buildings. In said Royal Decree, it is established that existing buildings or units of buildings occupied by a public authority, must obtain an energy efficiency certificate and will have the obligation to display their energy efficiency label, when their total useful area exceeds 250 m2, and are usually frequented by the public. The Basic Procedure is established that must comply with the methodology for calculating the energy efficiency rating, considering those factors that have the greatest impact on their energy consumption, as well as the technical and administrative conditions for the energy efficiency certifications of the buildings. For this purpose, three software programs were promoted from the competent Ministry, one corresponding to the general option (LIDER-CALENER “HULC” unified tool) and two others corresponding to the simplified option (simplified procedures CE3 and CE3X), which allow the energy qualification to be carried out of buildings according to three types of buildings (residential, small and medium-sized tertiary, and large tertiary) that are increasing the requirements of the energy certification of the building depending on the type of the same. This study identifies the possible alternatives for improving energy efficiency over the initial qualification of the building, within a context of technical and economic feasibility, optimizing energy demand, reducing CO2 emissions and building energy consumption, being The study also compares the results obtained in the energy rating, between the general option and the simplified procedures, on an Andalusian health center in 1957, which corresponds to the typology of the Grand Tertiary building (GT).