Punkah Louvres and the History of Ventilation and AC

Learning Objectives

In this lesson plan, students will learn about the history of Punkah Louvres, ventilation, and AC on ships. This can be used for history, technology, or engineering and features discussion questions as well as an experiment for Grades K-2 and 3-5.

National Education Standards

Grades K-2

NGSS – Appendix F – SEP.1.b – Ask and/or identify questions that can be answered by an investigation.
NGSS – Grade Level Disciplinary Core Ideas – 2-PS1.A.1 – Different kinds of matter exist and many of them can be either solid or liquid, depending on temperature. Matter can be described and classified by its observable properties.
College, Career, and Civic Life (C3) Framework (5) – D2.Eco.1.K-2 – Individually and with others, students: Explain how scarcity necessitates decision making.

Grades 3-5

Benchmarks for Science Literacy (1) – 4E/E2c – By the end of the fifth-grade students should know that: A warmer object can warm a cooler one by contact or at a distance; D2.Eco.1.3-5 – Individually and with others, students: Compare the benefits and costs of individual choices.

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You’re sitting in your seat, waiting for takeoff while people inevitably fumble around with getting hand luggage in the overhead compartments, and then it starts to get stuffy. You reach up and adjust that little nozzle above your seat and pray for a reprieve from the heat (and potential smells) caused by the crowded plane. Did you know those vents are called Punkah Louvres and have a history dating all the way back to the 6^th century? They have evolved over time from servants cooling the British in colonial India to slaves in the American South ensuring flies do not disturb their master’s dinner to their use on steamships to provide respite from the heat before central air conditioning.

Images from a Thermotank Brochure, 1931.

Many sources credit the first commercial air conditioning system to the American Willis Carrier in 1902, but the first workable machine was patented four years earlier by Alexander Stewart, a Scottish marine engineer, who called his invention the Thermotank – consisting of heating and ventilation or what we now know as HVAC (heating, ventilation, and air conditioning). The term air conditioning came about some years later. It offered a massive improvement in comfort for passengers and was rapidly adopted by the shipping industry, and by 1908, luxury liners like Cunard’s Mauretania and Lusitania, and later the White Star Line’s RMS Titanic, Olympic, and Britannic had complex mechanical ventilation systems.

Thermotank diagram from the patent application.

*Lusitania* at the Clydebank in Glasgow, Scotland.

Diagram of the Thermotanks on board the *Lusitania* and the *Mauretania*.

Learn more about Titanic‘s heating and cooling.Thermotanks are discussed at 12:00.

So where did the term punkah louvre come from? Punkah or pankah is a type of fan used since the early 6th century. The word pankha originated from paksa (a Hindi word), meaning wing. In its original sense, in the Indian subcontinent, pankha typically describes a handheld fan made from a single frond of palm or a woven square of bamboo strips, rattan, or other plant fiber, that can be rotated or fanned. From 1700 to 1900, the British Empire in India saw its beginnings and development. It evolved from trade to direct rule in what came to be known as the British Raj or Crown Rule, which began in 1858 when the East India Trading Company was transferred to Queen Victoria and lasted until 1947.

During the colonial period in British India and elsewhere in the tropical and subtropical world, the word came to be used for a large swinging fan, fixed to the ceiling, pulled by a punkah wallah or servant who operated the fan, often using a pulley system, during hot weather. It worked to keep the room cool but also kept flies away from the dining room tables. The ubiquity of the punkah in the British conquest of the Indian subcontinent made living conditions for the British more tolerable and signaled their dominance over the indigenous population. Similarly, the political conditions in the United States saw their introduction into Southern homes at a time when exported Indian goods were becoming fashionable in both the U.S. and Britain.

In many elite Southern homes, punkahs or ceiling-mounted fans that slaves manipulated, were an integral part of the architecture of the dining room in the antebellum United States. Planters enjoyed the cooling breezes, insect-free meals, and the opportunity to display their wealth. But as Historian Dana E. Byrd describes in her article “Motive Power: Fans, Punkahs, and Fly Brushes in the Antebellum South,” ‘enslaved workers likely used their proximity to elite whites to learn “genteel” codes of behavior, while gleaning information about the plantation world and beyond. The end of slavery did not mark the end of punkahs; rather, the fans were used to celebrate the “noble” history of the Old South while eliding any reference of slavery.’

Punkah in dining room, Melrose, Main House, 1 Melrose-Montebello Parkway, Natchez, Adams County, MS. Library of Congress.

How did fans that demonstrated the racial hierarchy of the past become a means of keeping cool on steamships in the 1920s? And what is a louvre? A louvre is a screen that allows air to pass through.

Enter, Alexander William Stewart (1865-1933) who was a Scottish naval architect, engineer, and inventor of international distinction. Alexander and his younger brother worked in the Clydebank shipyard of J&G Thomson & Co Ltd, soon to be known as John Brown & Company. He qualified as a member of the Institution of Naval Architects and was the top prizeman in Britain in his final year. He spent some time under the chief naval architect Sir John Biles, at the Clydebank yard, where as manager of the electrical department he had much to do with the first and early application of electricity to ships. During his time at the shipyard, he was involved in the construction of vessels such as the Inman Line’s City of New York and City of Paris.

Alexander Stewart began working on a device called the Thermotank that would revolutionize ventilation and heating on board ships. This mechanical system could deliver either warm or cold air to a ship’s compartments. It drew air in, circulated it around steam heated pipes to warm it, or conversely, refrigeration plant cooled water pipes, and delivered it by using fans thus warming or cooling a compartment. The Russian gunboat Kostroma entered the Cyldebank for a major refit, and on September 17, 1898, she left the shipyard fitted with Stewart’s invention. He patented the Thermotank in 1898 that same year.

Punkah louver / louvre salvaged from Cunard Line’s RMS *Ivernia* / *Franconia* (1955) by donor Peter Knego while ship was being broken up at Alang, India, c. 2004. SSHSA Archives.

In 1900, he and his brothers set up their own firm, Thermotank, based in Glasgow. He became a leading member of the Institution of Electrical Engineers, and the Institution of Shipbuilders and Engineers in Scotland. In 1901, NYK Line’s Kumano Maru was fitted with a Thermotank system and fulfilled the promise of the patent for his invention. BY 1908, Themotanks had been fitted to ships from the following lines: Cunard, Allan Line, Canadian Pacific Steamship Co, Llyod Sabaudo, Navigazione Generale Italia, Egyptian Mail Steamship Co, Nipon Yuson Steamship Co, Red Star Line, Holland American Line, White Star Line, Compagnie Générale Transatlantique, and others. In addition to merchant ships, the system was also fitted to warships for the British, Japanese, Russia, Italian, Brazilian, Portuguese, and Argentine navies.

During World War I, Alexander Stewart also designed the Thermotank inductor, which enabled large volumes of poison-laden air to be dealt with without danger, particularly saving many lives in munitions factories. In 1922, he became a Freeman of the City of London. He received from the King of Italy the honor of Knight of the Crown of Italy, in recognition of his services to Italian shipbuilding.

Another invention was the Punkah Louvre ventilator, which found application in both naval and mercantile ships for many countries, luxury liners, and in the ventilation of public buildings including the Chrysler Building in New York, railway carriages, and airplanes. Steward applied for a patent for what was then called “Improved Ventilation Fitting” in two parts in July 1922 and February 1923. The first application stated that: “With ordinary fixed louvres at present in use, the air is usually delivered in one direction only. The improved fitting is constructed on the well-known ball and socket principle… The described arrangement makes it possible to project a stream of air in any direction from the air duct covering a spherical radius of 180°.” The second part of the application stated that the new system made it possible to transmit air at a higher velocity, requiring ducting of much smaller dimensions. The existing fan driven ventilation systems delivered air at 4 to 8 feet per second and the updated invention could do the same at 30 to 50 feet per second.

A Thermotank brochure from the 1930s states: “When we introduced Louvres involving this principles a few years ago, their success was immediate and their benefits are confirmed by the extent to which our systems were adopted, especially for first class passenger ships, where the necessity of successful ventilation is of paramount importance.”

Primary Sources

Thermotank, Ltd. Brochure, c. 1931.

Home Lines Cruises Brochure, Advertising fully air conditioned ships, SSHSA Archives.

Experiment: Make your Own Ice Air Conditioner

Materials Needed:

bowl of ice
desktop fan

Without the technicalities of refrigerant and a high-pressure system, you can mimic this process in your classroom with a bowl of ice and a simple fan. Even if your classroom is at a comfortable or cool ambient temperature, ask students to feel the temperature difference created by fast moving air from the fan. Then, place the bowl of ice in front of the fan and let it run for several minutes. Now, ask students to feel the temperature difference created by the melting ice. Depending on your ambient temperature, it might be a very slight change. If possible, repeat this activity outside on a warm day. Do your students feel the change now?

Questions for Further Thought

What would traveling on a steamship be like before air conditioning?
How do you think this differed between first-class and steerage-class passengers? Was ventilation accessible to all?
How did the technology of air conditioning affect cruise travel?

Additional Resources

Dana E. Byrd, “Motive Power: Fans, Punkahs, and Fly Brushes in the Antebellum South” in Buildings & Landscapes: Journal of the Vernacular Architecture Forum, Vol. 23, No. 1 (Spring 2016), pp. 29-51.

Ian Johnston, Blowing Hot & Cold: Thermotank and the Story of Air Conditioning at Sea (Seaforth Publishing, Great Britain: 2024).

United States Navy Training Film. 1952. Learn basic principles which commonly operational on shipboard ventilating, heating and cooling system; What factors influence the condition of the air, like – temperature, relative humidity, air motion, etc.; Elements of ventilating, heating and cooling system, and how they operate; And the importance of ship maintenance schedule which must be observed for best results.