In the last decades, increasing attention has been paid to the enhancement of energy performance and comfort conditions of historic buildings, where the necessity to preserve architectural heritage does not allow typical invasive retrofit interventions. The need for a replicable methodology for improving the sustainability of historic buildings based on the integration of energy efficiency solutions with renewable technologies is here addressed, by riding over the constraints imposed by architectural preservations, rather taking advantage of heritage architectural peculiarities. The case study is represented by Palazzo Gallenga Stuart, a historical university building located in central Italy. The optimization of the building energy efficiency has been pursued through two strategies specifically prototyped for application in historic buildings, i.e. innovative cool tiles with the same appearance of traditional historic tiles, and a geothermal heat pump system with water storage tanks positioned in the under-ground unoccupied areas of the building previously used as archives, also preventing the use of external units spoiling the building facade. Four retrofit scenarios were analyzed and compared from a both technical and economical point of view. The results showed that the application of the innovative cool tiles lead to a maximum cooling energy saving of 14.0% and 3.8% in the classrooms of the top floor and in the whole building, respectively. Furthermore, the installation of a more effective energy plant leads to an average energy saving of 64.3% and 67.0% in terms of heating and cooling demand, respectively. The combination of the two effects leads to an average energy saving of 64.0% for heating and 69.2% for cooling. Additionally, the cost-benefit analysis showed a payback time of 5 years. This work shows the important environmental benefit achievable by researching around smart and innovative integrated systems for energy saving in historic buildings having a great potential in reducing energy demand and carbon emissions, in ancient European countries in particular. (C) 2015 Elsevier Ltd. All rights reserved.