In Italy, historic buildings constitute 20% of the built environment. Although historic buildings are usually excluded from the obligation of adopting specific energy standard, energy related aspects should be nevertheless faced and managed in order to exploit the building "usability" potential, to attain indoor environmental quality and energy efficiency conditions. The energy refurbishment of this kind of building is, however, a very complex matter that leads to a number of question concerning buildings conservation and valorisation aspects. A non-invasive technique, that is, the application of thermal plaster to the internal side of a building envelope, has been investigated in this paper. Thanks to its relatively easy installation and reversibility, thermal insulating plaster seems to represent a very interesting solution as it is able to offer a good compromise between energy and conservation aspects. The aim of this work is to present a thermal, vegetal based, insulating plaster, which has recently been developed within a research project, and to investigate its potential to reduce the heat flux exchanged through the vertical envelope of historic buildings, by means of measurements carried out in both the laboratory and in the field, for a real case application. (C) 2014 Elsevier B.V. All rights reserved.