Windows, Baths, and Solar Energy in the Roman Empire Author(S): James W
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Windows, Baths, and Solar Energy in the Roman Empire Author(s): James W. Ring Source: American Journal of Archaeology, Vol. 100, No. 4 (Oct., 1996), pp. 717-724 Published by: Archaeological Institute of America Stable URL: http://www.jstor.org/stable/506675 . Accessed: 29/05/2014 17:32 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Archaeological Institute of America is collaborating with JSTOR to digitize, preserve and extend access to American Journal of Archaeology. http://www.jstor.org This content downloaded from 128.135.12.127 on Thu, 29 May 2014 17:32:48 PM All use subject to JSTOR Terms and Conditions Windows, Baths, and Solar Energy in the Roman Empire JAMES W. RING Abstract sea."' One can infer from his writings that Seneca Windows were a prominent feature of Roman archi- regrets this new style and, indeed, it is clear that he tecture and were especially important in the magnifi- looks back with nostalgia on the days of the Roman cent of the Roman A bath buildings Empire. growing when baths were and literature attests to the Romans' use of solar in Republic properly modestly energy dark. heating these large buildings. Edwin Thatcher claimed in 1956 that the windows in such baths did not require Roman baths of the Early Empire were in the fore- glazing. In this paper I refute this claim, drawing on front of developments both architecturally and tech- modern ideas about solar heat human energy, transfer, nologically and thus make a very interesting study comfort, and the effect of glazed windows to analyze in their own right. This point has been brought out one room in the Forum Baths at Ostia. This analysis and and Nielsen. is compared with that of Thatcher for the same room. ably developed by Yegul2 Vaults, In window size and solar orientation, this room is typ- domes, and large windows were first found in these ical of Roman baths in many parts of the empire. The baths, where Greek orders were also first combined solar science and of is thus technology today compared with Roman vaults. Hypocausts were developed and with that of the Romans and with that of Thatcher'sdayf* used to heat large rooms and, indeed, to heat the imposing ensembles of large rooms that the great INTRODUCTION imperial baths represented. According to Yegill, The importance of windows in architecture seems Seneca speaks of the recent invention of tubuli, or indisputable. But in its chronological development hollow walls, which maintain an even temperature Western architecture shows striking variation in in the lowest as well as the highest spaces. This in- its treatment of windows. For example, medieval vention also prevents condensation on the walls and churches of the Romanesque style were typically dark increases the area that radiates heat around the bath- and lit only by small windows that pierced massive ers. In these large evenly heated spaces, thousands masonry walls. One of the distinguishing features of bathers could be and often were accommodated. of later Gothic churches was the use of large win- To supply sufficient water, extensive aqueduct systems dows made possible by outside buttressing. The were developed. Furthermore, as Yegill maintains, Roman Empire prototypes, however, unlike their and is shown in a detailed fashion by D.B. Harden, Romanesque successors, were often lit by magnifi- the Romans by this time had developed glassblow- cently large windows. The Roman public baths of ing and were producing flat panes of window glass.4 the Early Empire are very good examples of this Thus, with all of these elements in hand, it is not anachronism. Seneca, writing in the first century A.D., surprising that the Romans would have utilized the says of these baths: "Nowadays... people regard baths radiant energy of the sun to help heat as well as light as fit only for moths if they have not been so arranged these magnificent buildings. that they receive the sun all day long through the Indeed, so obvious is the Romans' interest in so- of widest windows, if men can not bathe and get a lar heating through their use of large south-facing coat of tan at the same time, and if they can not look windows that in 1956 Edwin Thatcher published a out from their bath-tubs over stretches of land and paper in which he claimed that the large windows * I wish to thank the American Academy in Rome for a Faculty Fellowship in 1993 during which research lead- help in arranging visits to various Roman sites, including ing to this paper was completed. in the Museum of Glass and Ostia, 1985; Corning Rakow 1 Sen. Ep. 86, trans. R.M. Gummere, 1986, as quoted by for in Library help exploring Roman glass in 1991; Todd E Yegill, Baths and Bathing in Classical Antiquity (Cambridge, Moore of the Physics Department at Hamilton College for Mass. 1992) 40. his careful reading of the manuscript; Carl Rubino of the 2Yegiil (supra n. 1). ClassicsDepartment at Hamilton for his advice;Fikret Yegiil 3 I. Nielsen, Thermaeand Balnea: The Architectureand Cul- of the Universityof California at Santa Barbaraand Ingrid tural History of Roman Public Baths (Aarhus 1990). E.M. Edlund-Berryof the University of Texas at Austin for 4Yegiil (supra n. 1) 363-65; and D.B. Harden, "Domes- reading an earlier version of this manuscript and advising tic Window Glass:Roman, Saxon and Medieval Studies in about publication; and Richard de Dear of MacquarieUni- Building History,"in E.M.Jope ed., Studiesin BuildingHis- versity,Sydney, for his advice about thermal comfort con- tory. Essays in Recognition of B.H. St.J. O'Neil (London 1961) ditions in these baths. Finally,Hamilton College provided 39-63. 717 American Journal of Archaeology 100 (1996) 717-24 This content downloaded from 128.135.12.127 on Thu, 29 May 2014 17:32:48 PM All use subject to JSTOR Terms and Conditions 718 JAMES W. RING [AJA 100 of the second-century Forum Baths at Ostia, which ing shortages and expense, the Romans, like the he took to be unglazed, provide "a striking demon- Greeks before them, turned to solar heat."8 stration of the potentialities of the Roman heating method and, in extension, of the principles of ra- DID THE ROMANS USE GLAZING? diant It was this method that made the heating. open The Forum Baths in Ostia were constructed early rooms to we have not matched possible and, date, in the second century A.D. There is no controversy them in a modern It is evident that the building. about the existence of large windows in several of Roman engineers had a greater confidence in ra- the rooms of these baths. These windows faced the diant than we have and a heating greater knowledge south and hence would intercept the sun's beam ra- of what it could accomplish." diation most of the day,particularly from early after- This sets out to this claim. Is paper investigate noon to near sunset, which were the most popular Thatcher's confidence in radiant heating justified? hours for Romans to bathe. These rooms indeed are Could there be the sun enough heating provided by typical of baths built during this period in many parts and the to allow nude bathers to be com- hypocaust of the empire. fortable even the windows of the baths though large Thatcher gives attention to the whole set of large- were and What do the modern open unglazed? prin- windowed rooms but for our purposes let us con- ciples of passive solar heating and the physics and centrate on one, room 4, which seems to have been of heat transfer tell us about the Forum physiology a warm room, or tepidarium.Figures 1 and 2 show Baths and Thatcher's claim? the southern elevation and north-south section, re- I take a raised He In addition, up point by Yegiul. spectively, of this room and its window. The dimen- that Thatcher has too far in his claims suggests gone sions are those given by Thatcher. for radiant heating: The question is whether or not the walls, vault, In full admiration of the system'spotential, I still and floor surrounding the nude bather on all but doubt if the implications of radiantheating should the window side can be maintained at a high-enough be stretchedthat far.Not only is the evidencefor win- temperatureto ensure comfort.Thatcher approaches dow glass and window frames (both in wood and the issue from the of the nude bather from the heatedrooms of Romanbaths across standpoint metal) both to the radiant of the sun and the Mediterraneanoverwhelming, but Thatcher'sthe- exposed energy sis, despite its theoretical possibility,seems to refute that given off by the surrounding heated room sur- the preceptsof simple economic logic.It maybe that faces, holding that radiant energy, if the walls are by heating the floor, the walls,and the vaultto a high maintained at close to skin temperature, can by it- degree, sufficient radiant energy could be released self establish a comfortable to offset the effects of low air on a cold temperature. My ap- temperature on the other hand, is to assume that com- winterday, but whyshould fuel and energybe wasted proach, in order to makean open-airhot bath possible when fort will be determined by conditions in the room, the same degree of warmth and comfort could be both the air temperature and the radiant temper- achieved with much lower furnace activity and fuel ature being considered along with air currents, or in a and well-insulatedroom?6 consumption glazed convective flows, and the relative humidity of the This question is also raised byJordan and Perlin in air as prescribed by the American Society of Heat- an article about the use of solar energy in ancient ing, Refrigerating, and Air Conditioning Engineers times.7 They claim that by the first century B.C., (ASHRAE).9Comfortable conditions for nude sub- Rome had to import timber from the fringes of its jects have been studied carefully in climate cham- domains, such as the Alpine regions, in part because bers.