Environmentalism in Ancient Rome

To modern tastes the Romans appear a backwards and bloodthirsty people whose influence we are glad to have shed.  The movie The Gladiator  reminds us of this.  Roman games are notorious for their butchery of animals, slaves, and religious radicals like the early Christians.  But in other ways the Romans were advanced and found solutions to problems we still wrestle with today.  One of these was the use of solar energy.  The Romans didn’t have the luxury of electric heating, so they developed efficient ways of holding on to the heat they derived from the sun.

It’s obvious that in the Northern Hemisphere it is the south side of a house or building that gets the most sun.  But how many of us live in buildings that take full advantage of this fact?  The Roman architect Vitruvius made this a fundamental design feature in his housing recommendations.[1] In developed centers like Rome, laws were passed that prevented anyone from erecting a new building that blocked an older structure’s access to the sun.

On several occasions the Romans planned entire suburbs in which every house faced the southwest, had few openings to the north or east, and included partial walls around the sun-exposed openings to allow the heated air within to circulate rather than to leak away.  These partial walls consisted of a short wall rising about one and a half feet up from the floor, and a short wall descending about a foot and a half from the ceiling directly above.  This pair of partial walls made the air turn corners and stay inside the room, rather than escaping into the outside air.  For example, warm air flowing in the ceiling area would bump into the upper partial wall and be forced to turn downward rather than escape so that the air in the room moved in a circle.  Floors were often made of dark flagstones to hold heat.  Some units had large basements filled loosely with rubble to act as heat storage systems, giving back at night the energy absorbed in the daytime.

The great public baths were designed with huge windows to trap solar heat and under-floor smokeways to capture energy from the fire gases that heated the baths.  Actually the baths had double floors with a gap in between through which the trapped gases could circulate.  Thanks to this feature, Romans could walk barefoot through public baths even in the winter.  At the famous city of Pompeii, the water for the bath, after emerging from the aqueduct, passes over a grooved, shallow channel made of black slate—an obvious solar pre-heater.  How do you think it worked?  Aqueducts were usually covered to keep debris out of the water.  So the water that flowed into these channels in the bath house was cool.  The channel was open to the sun, but for the most part, solar energy passes through water without being changed into heat.  The black slate would capture this solar energy and transform it into heat, which in turn radiated back up through the water, warming it up.   The grooves cut through the slate made this heat transfer more efficient.  The same sort of grooving appears on the bottoms of surviving bronze Roman cooking pots from all over the empire.  This feature helped transfer heat to the food more efficiently, like the cooling fins of a lawnmower engine, but working in reverse.

The private homes of the wealthy were usually built around one or more courtyards called atria.  Few doors and windows communicated with the outside, but light and air could enter through the hollow square cut from the roof.   Atria might contain a reservoir to trap rainwater, freeing the house from the local aqueduct system to some degree.  Or they might enclose a garden raised a few handspans above the floor to lengthen the growing season, for cold air sinks and warm air rises.  An elevated garden can extend the growing season for a week or two because the area will be too warm to be affected by the first frost.  With these features, the north side of an atrium  could be a pleasant place to sit even in winter, with the sun pouring down through the roof.

[1]To keep homes cooler in the hot season, Vitruvius specified that a porch be erected on the south side of a house to shield it from the summertime sun.

Environmentalism Today

Decades of cheap energy have encouraged modern civilization to sometimes use it in irresponsibly lavish ways.  Controversy occurs today over automobiles which are larger than is functionally needed, and architectural style sometimes results in houses whose design is far from suitable for the local climate.  The Romans in their time committed plenty of environmental sins.  They occasionally built straight roads up and down hills where curving and more level pavement would have helped forestall erosion.  Their skill in war often extended to deliberate deforestation, the slaughter of local herds, and in general a scorched-earth policy.  But at their best, they showed an awareness of the limits of their available energy supplies, and an attempt to live within their means through innovative designs that we would do well to copy.  Full solutions to today’s energy supply issues may require such things as more efficient photovoltaic cells, electric cars, or more efficient ways to produce and store hydrogen as a fuel to replace petroleum hydrocarbons.  But in many cases, we have overlooked such simple solutions as the Romans achieved and built into law.

by Vernard Foley, Associate Professor and Historian of Technology, Purdue University and a frequent contributor to Scientific American © NEXUS, 2001. Vernard Foley also wrote “Catapults, Roman War Machines” for Julius Caesar and Ancient Rome, from Republic to Empire (NEXUS), “The Wizard of Syracuse – Archimedes” for Antigone and Greek World (NEXUS), “Chariots of the Sky (Da Vinci’s flight research), Romeo and Juliet and the Renaissance (NEXUS), “Trebuchet, the Nightmare Weapon of the Middle Ages,” Macbeth and the Dark Ages (NEXUS), and “Physics of the Crossbow” (Da Vinci’s discoveries of several principals of physics from his studies of this weapon), The Lion in Winter and the Middle Ages (NEXUS).

QUESTIONS

1. Read Book V, Chapter X, pp. 157-159 of Vitruvius’ On Architecture – http://academics.triton.edu/faculty/fheitzman/Vitruvius__the_Ten_Books_on_Architecture.pdf – then discuss any suggestions Vitruvius makes regarding heat retention that are not covered in the essay.
2. What Roman law(s) were passed to guarantee that each home and building had optimal access to the sun?
3. Explain in your own words how “partial walls” promoted the circulation of heat in Roman structures?
4. Track down and discuss at least one other ancient Roman source (other than Vitruvius) that supports or refutes claims made in this essay.
5. The essay states that “Some units had large basements filled loosely with rubble to act as heat storage systems, giving back at night the energy absorbed in the daytime.” How would heat stored in a basement during the day help heat the floor(s) above it at night?
6. Why was the rubble in the basement (mentioned in question 5) packed loosely rather than tightly?
7. Why do you think the Romans used black slate channels to transfer aqueduct water to their bath houses?
8. Can you explain how the fins on a lawnmower engine help cool the engine (discussed in paragraph 4)?
9. Why do you think the Romans put grooves on the bottoms of bronze cooking pots instead of the tops?
10. How could Roman solar heating methods be utilized today to reduce fossil fuel consumption and lower heating bills in the winter?

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