The Teatro Regio in Turin (1738-40) - radically altered between 1904 and 1906 and completely destroyed after the fire of 1936 - presented innovative and sophisticated building solutions. Heating system included four masonry stoves when the air flowed from the entrance porch underneath and was passing in iron pipes to the firebox sides. The heated air entered the channels from which it come out by four equally spaced openings in the base of the lower order of loges, toward the parterre. First time, it would seem, this system was introduced in a public building and maintenance costs, documented until the end of the eighteenth century show that the apparatus was long in service. The author, Count Benedetto Alfieri, First Architect of the King, dedicated to the Theatre in 1761 a book of engravings, funded by the Savoy government, which achieved great notoriety. French publications on the theatre’s architecture, since 1765, partially reproduced its etchings, and an important selection was included in the tenth volume of the Planches of the Encyclopédie (1772). The heating system was always reproduced in plants and described in the captions. On what previous example Benedetto Alfieri had based his project? The printed editions of Vitruvius show - in comments and illustrations - that the hypocaust operating principes was not well understood, it was not clear if hypocaust was acting on irradiation - the walls and floors heated by the smoke - or by convection, the injected hot air in the different rooms. The experiences on greenhouses (John Evelyn, 1683) and studies on improving the efficiency of fireplaces using the air passage around the fireplace, especially the "Mécanique du Feu" of Gauger (1713) from which Alfieri resumed regulating vents , they provided a practical response to the older literature, while the British excavation reports properly describe the hypocaust systems identified. The same Filippo Juvarra, Alfieri's predecessor as prime architect, has left the designs of a "turkish bath", which describes in detail a radiant system in the floor and wall. Some document, which is of uncertain interpretation, alluding between seventeenth and eighteenth centuries to the presence of similar recently made solutions. The Alfieri system therefore forms a renewed and gradually increasing interest to the Old and in a widespread search of comfort probably stimulated by the cold winters of the "little ice age".