Thermally Active Surfaces in Architecture

Kiel Moe

Princeton Architectural Press New York

Published by Princeton Architectural Press 37 East 7th Street New York, NY 10003 For a free catalog of books, call 1-800-722-6657 Visit our website at www.papress.com © 2010 Princeton Architectural Press All rights reserved Printed and bound in China 13 12 11 10 4 3 2 1 First edition No part of this book may be used or reproduced in any manner without written permission from the publisher, except in the context of reviews.

Every reasonable attempt has been made to identify owners of copyright. Errors or omissions will be corrected in subsequent editions.

Editorial: Lauren Nelson Packard, Dan Simon Design: Paul Wagner Special thanks to: Nettie Aljian, Bree Anne Apperley, Sara Bader, Nicola Bednarek, Janet Behning, Becca Casbon, Carina Cha, Penny (Yuen Pik) Chu, Carolyn Deuschle, Russell Fernandez, Pete Fitzpatrick, Wendy Fuller, Jan Haux, Clare Jacobson, Erin Kim, Aileen Kwun, Linda Lee, Laurie Manfra, John Myers, Katharine Myers, Dan Simon, Andrew Stepanian, Joseph Weston, and Deb Wood of Princeton Architectural Press —Kevin C. Lippert, publisher Library of Congress Cataloging-in-Publication Data Moe, Kiel.

Thermally active surfaces in architecture / Kiel Moe. — 1st ed. p.

cm.

ISBN 978-1-56898-880-1 (alk. paper) 1. Building materials—Thermal properties. 2. Surfaces (Technology) 3. Buildings—Thermal properties. 4. Heat—Transmission.

5. Sustainable architecture. 6. Heating. I. Title.

TA418.52.M64 2010 720’.472—dc22 2009021871

Contents

22

24

27

35 42 54

68 84

Foreword D. Michelle Addington, D.Des., RA, P.E. Foreword / Tradition, Comfort, and Conservation Matthias Schuler, P.E. Preface Approaches to Technology and Human Comfort Theories, Techniques, and Technologies Conditioned Air Thermally Active Surfaces Principles and Practices of Thermally Active Surfaces What Your Body Already Knows Batiso (Constant Temperature Building)

94 118

132 146 156 170 178 188 198 210

222 230

237 238 239

Building Design Guide by Geoff McDonnell, P.E.

De-fragmentation of Buildings and Practices Thermodynamic Figures in Architecture Thermally Active Surface Case Studies Kunsthaus Bregenz, Peter Zumthor Zollverein School of Management and Design, SANAA S端dwestmetall Regional Headquarters, Dominik Dreiner Architekt Linked Hybrid, Steven Holl Architects Charles Hostler Student Recreation Center, VJAA Housing for Kripalu Center for Yoga and Health, Peter Rose and Partners The Fred Kaiser Building, University of British Columbia, architectsAlliance Terrence Donnelly Centre for Cellular and Biomolecular Research, architectsAlliance / Behnisch Architekten Klarchek Information Commons, Loyola University, Solomon Cordwell Buenz The Graham Resource Center, Crown Hall, Illinois Institute of Technology, Tom Brock Architect, P.C. Acknowledgments Sources Illustration Credits

Approaches to Technology and Human Comfort

WILLIS CARRIER’S PYSCHROMETRIC CHART

1950s & 60s FAILURE OF METAL TUBE HYDRONICS

HYDRONIC FLOOR SLABS AT LEVITTOWN, NY

GEORGE NELSON’S TOMORROW’S HOUSE

2000

2000

1000

0

1000

HEATING COOLING FIRES

METAL TUBE HYDRONICS

KUNSTHAUS BREGENZ (MEIERHANS & ZUMTHOR)

1950

TECHNOLOGICAL MOMENTUM

ICE & FAN COOLING

1937 “CRITTALL” SYSTEM IN SWITZERLAND

FRANK LLOYD WRIGHT’S USONIAN HOUSES

JOHANNES DUIKER’S OPEN AIR SCHOOL

A.H. BAKER HYDRONIC RADIANT CEILING PANELS

1900

1850

ROMAN HYPOCAUST

THOMAS ENGEL’S CROSSLINKED POLYETHYLENE TUBING (PEX) WIRSBO PRODUCTION OF CROSSLINKED POLYETHYLENE TUBING

Heat transfer points of transformation

AMMONIA REFRIGERANTS

DR. JOHN GORRIE’S ICE MAKER

Heat transfer technique points, periods, and paradigms

Paradigms of heat transfer

RADIANT TRANSFER

KOREAN ONDOL

MEDIEVAL HYPOCAUST

FIREPLACES

RADIANT HEATING

CONVECTIVE TRANSFER

RADIANT COOLING

“PASSIVE” COOLING

REFRIGERATION / HVAC

Heat transfer technique periods

DUCTED, FORCED HVAC

POLYETHYLENE TUBE HYDRONICS HIGH-VELOCITY, VENTILATION SPECIFIC DUCTS

Theories, Techniques, and Technologies

35

A Systemic View of Technology in Architecture

A primary premise of this book is that any coherent and reliable practice of sustainable architecture and urbanism can only emerge from a coherent understanding of our technics. Technics refers to the collective theories, techniques, and technologies that characterize different paradigms of human civilization. Given the current contingencies and obligations of architectural practice, it is critical to consider our technics as we pursue sustainable building and development techniques for the twenty-first century. Too often, in and outside of architecture, a technical determinism characterizes discourse about the role of technology today. Technological determinism is problematic in a number of ways, as Canadian philosopher George Grant noted: We can hold in our minds the enormous benefits of a technological society, but we cannot so easily hold the ways it may have deprived us, because technique is ourselves.1 In our rush toward more sustainable practices and perpetual innovation in architecture, Grant’s reflexive observation that “technique is ourselves” often escapes us in our technologically determined mode. This is certainly the case with the underwriting determinants of contemporary construction and energy practices. In this chapter I suggest that this collective oversight prescribes too much of these practices and that this is detrimental to the profession, our buildings, and our cities.

When architects view technology as a primary determinant of production and innovation, we perpetuate a blatant fiduciary irresponsibility. Despite the fact that technology dominates our buildings, our practices, and our lives, architects know relatively little about its operation, effects, and behaviors. We often unreflectively accept building technologies, energy practices, and “innovations.” In doing so, we collectively yield great momentum to techniques and technologies that may or may not serve our interests or the interests of our constituencies. Too often we limply accept the technological momentum thrust upon us by our adjacent industries and the habits of mind bestowed upon us by previous generations of building. This state of technological acquiescence is a product of a persistent, unexamined fallacy: the techniques and technologies of architecture are often taught and practiced as technologically determined rather than socially constructed.

This technological determinism is a fundamental problem of knowledge for architecture and bears directly on its efficacy in the new century. In contrast, adjacent disciplines, such as the history of science and technology, understand technology as a variable of social practice and progress rather than a determinant.

In architecture, technological determinism has deformed the relationship between architects, buildings, technologies, industries, and more strategic forms of innovation.

It presumes that architects merely implement larger technological forces rather than actively engage and swerve technology for social and architectural ends. It limits the role of the architect and contributes to a receding horizon of practice.

36

Thinkers in our adjacent disciplines—such as Lewis Mumford, Jacques Ellul, David Nye, Bruno Latour, and Merritt Roe Smith, to name a few—document the historical assemblages and multifarious exchanges that ultimately constitute technical practices.2 Eschewing technological determinism, these accounts describe the often non-linear, irrational relationship between research, practice, and technological change. Deepened engagement with our technics provides a more substantial connection with the factors and forces that underwrite our practices. As such, this engagement helps to identify more strategic forms of innovation and change.

This first chapter introduces a few assumptions, based in these sources, about the role of technology in architecture that helped shape the research for the book. These assumptions orient a view of technology that aims at a more systemic understanding of the agencies that underwrite a technology in architecture. These assumptions are: 1.

2.

3.

4.

Technology is socially constructed.

All technologies contain some form of risk.

Technology is not new or innovative.

We must question the “machine mentality.”

Technology Is Socially Constructed Technical development is first an expression of an immaterial need or desire and only later it becomes material and technical. As Gilles Deleuze states, “Tools always presuppose a machine, and the machine is always social before it is technical. There is always a social machine which selects or assigns the technical elements used.”3 Contrary to a few decades of architectural theory, architecture is not autonomous.

It is a highly contingent practice. Its disciplinary expertise involves the integration of multiple, necessary factors and contexts that often determine much of design practice. These factors are social in their origin. Social needs and desires predetermine technical systems in both rational and irrational ways. As David F. Noble, a historian of technology, stated: “There are no technological promises, only human ones, and social progress must not be reduced to, or confused with, mere technological progress.”4 In Technics and Civilization, Lewis Mumford developed a cogent summation of the parallel histories of technical and human development.5 While any culture can develop a particular technology, Mumford suggests that only a limited number of cultures are predisposed to take full advantage of them at any particular point. He suggests that fully developed technologies coincide with certain pervasive habits of mind. In this way, technological development is not seen as an autonomous agent.

Mumford writes: “The gains of technics are never registered automatically in society; they require equally adroit inventions and adaptations in politics...the machine itself makes no demands and holds out no promises: it is the human spirit that makes and keeps promises.”6

Theories, Techniques, and Technologies

37

Mumford also writes about the agency of choice within technical practices.

Acknowledging the social construction of architecture means recognizing the role of choice in technical systems. As they cycle from individual action up to collective paradigm, all choices in a technical system, in a building, are consequential. They are thus open to reflection, doubt, scrutiny, and responsibility. This is part of a technical practice and, as such, part of social practice.

In this book, it is important to acknowledge both the technical and social factors that determine the way that we build. Many aspects of our technical systems are determined by social need and desire and so will their alternatives. From the history of thermal conditioning systems to the role of human comfort to the prospect of more sustainable future practices, the social construction of technology should be a central concern today in architecture.

All Technologies Contain Some Form of Risk When a technology does become physical, it is not a benign reserve of technical solutions to social, ecological, or fabrication problems. Rather, it produces its own risks and problems as a constitutive fact of that technology. 7 All technologies contain some form of risk. Hazard increasingly characterizes our world. German sociologist Ulrich Beck calls this a “Risk Society.�8 At present, the sources, sites, and effects of low-probability yet high-consequence catastrophe have continental and global ramifications. Yet, we do not often cultivate proper technological management practices that would account for the constituent by-products of a world characterized by small and large-scale risk. Three Mile Island, Chernobyl, and Hurricane Katrina represent large-scale examples of failed technological management. In these cases, society demands of technology what it cannot reliably provide: assured protection from hazard. The difference between a vibrant community and its total destruction increasingly becomes a problem of risk management based upon calculations of what is just less than hazardous. We manage the risks of technology with outmoded, nineteenth-century methods that assign culpability to individuals and singular causes. The threats, sources, and effects of these hazards cannot be isolated to any single culprit or cause. Broader consumer, political, and industrial choices actually produce this context of risk, not individuals or individual technologies alone.

Technology is as likely to unintentionally annihilate the benefits of innovation as it is likely to engender it. Risk leaves no life, and no aspect of life, untouched.

In architecture, there is a precarious asymmetry between the capabilities and culpabilities of technology. It offers no automatic security or promise on its own. While technology is often associated with progress, it does not manage associated risks.

Presenting the culpabilities of technology alongside its capabilities would establish a more realistic, albeit less euphoric, relationship between innovation, its benefits, and its various costs. We will know very little about the capabilities and culpabilities of technology in respect to sustainability if we study technology only in terms of its

38

technical performance. One must engage the technics and context of sustainability— its theories, techniques, and technologies—to enable sustainable architectural practices.

Technology Is Not New or Innovative Our technics are pervasive; by now there is nothing more natural to us than technology. To understand technology at all, we must study and understand it as an uninterrupted and ubiquitous practice. As Technics and Civilization demonstrates, all technologies have a long period of social, cultural, technical, and practical preparation. In our mythical paradigms of progress and technical mastery, terms such as “new” and “innovative” are rhetorical escalations. The impossibility of “new” technologies or systems is evident when Gilles Deleuze and Felix Guattari state, “The principle behind all technology is to demonstrate that a technical element remains abstract, entirely undetermined, as long as one does not relate it to an assemblage it presupposes.”9 Specifying a technical system without a grasp of these systemic factors is a fiduciary irresponsibility. A more systemic understanding of our techniques and technologies is necessary. Thus the research of material and energy systems, including the thermally active surfaces discussed in this book, must necessarily emerge from and merge a range of research topics.

We Must Question the “Machine Mentality” The final characteristic of contemporary technology that helps orient the research in this book is known as the “machine mentality.” The machine mentality is at the center of the deterministic view that technologies will resolve any problem—be it social, ecological or economic. Noble describes it as the: Understandable perhaps but nevertheless self-serving belief that whatever the problem, a machine is the solution. This manifests itself in a preference for, and the tireless promotion of, capital-intensive methods and in the widespread but mistaken belief that the more capital intensive the process of production, the higher the productivity.10 The pervasive “machine mentality” causes problematic issues for architectural research and production. First, it obfuscates the assemblage of a technology and limits the agency of choice within architectural research. If sustainable design practices are socially constructed rather than technologically determined, then the “machine mentality” precludes sustainable solutions. A predetermined solution negates the role human choice will play in sustainable futures. A more reflective view of technology that expands the agency of choice is essential to the role of technology in future practices.

Theories, Techniques, and Technologies

39

Second, there is also an implication in the machine mentality that as social, ecological, economic, and political problems escalate, technology must also escalate.

However, it is apparent that as technology de-escalates, it becomes more appropriate and more applicable throughout a variety of social, economic, and ecological contexts.

High-performance, low-technology solutions typically are more durable, consume less, and are applicable in the developed and developing worlds. E. F. Schumacher’s concept of intermediate technology provides an alternative to the inveterate philosophy of the machine mentality: The idea of intermediate technology does not imply simply a “going back” in history to methods now out-dated, although systematic study of methods employed in the developed countries, say, a hundred years ago could indeed yield highly suggestive results. It is too often assumed that the achievement of western science, pure and applied, lies mainly in the apparatus and machinery that have been developed from it, and that a rejection of the apparatus and machinery would be tantamount to a rejection of science. This is an excessively superficial view. The real achievement lies in the accumulation of precise knowledge, and this knowledge can be applied in a great variety of ways, of which the current application of modern industry is only one. The development of intermediate technology, therefore, means a genuine forward movement into new territory.11 The conceptual shift regarding the role of technology that Noble and Schumacher describe can swerve architectural research and production toward more effective forms of research and innovation that can solve real problems in the building industry.

The following two sections of this book—one on the history of air conditioning and one on the history of thermally active surfaces—emerge from these principles and help establish the current context for thermally active surfaces in architecture. These narratives of air-based versus hydronic-based approaches to heating and cooling bodies in buildings illuminate a range of technical and social issues. A historical reading of air-based strategies for tempering buildings reveals that the enormous technological momentum of air-based convective strategies is related as much to the circumstances of individuals, such as Willis Haviland Carrier and his entrepreneurial ambitions as well as the widespread marketing of air conditioning after World War II, as it is to the technical and physiological efficacy of using air to heat and cool a building. The social, economic, marketing, and physiological history of air-conditioning technology further reveals that the entities that developed forced air-conditioning systems conditioned not only air but human comfort, energy practices, economic decisions, and construction systems in the twentieth century as it developed its technological momentum. Throughout this history, technical, economic, and social factors legitimated the gross inefficiencies of forced air systems. The history of air conditioning is an assemblage of rational and irrational developments. This

40

assemblage of factors in the development and use of this technique demonstrates that it was socially and technically constructed and so will their now necessary alternatives.

A parallel historical narrative focuses on twentieth-century hydronic systems.

It reveals a flawed material history, misconceived building science, and a lack of widespread marketing. The failure of a mid-century solder joint in a copper tube, however, cannot be mistaken for a failure of the physiological or thermodynamic efficacy of thermally active surfaces as the optimal method of delivering thermal comfort to occupants of a building. The waxing and waning, the successes and failures, of the experimental physical and intellectual systems that have underwritten thermally active surfaces in the twentieth century explain its lack of technological momentum when contrasted with air conditioning.

Together, these parallel practices demonstrate the social, economic, and ecological consequences of conventional conditioning systems. They also inversely suggest social, economic, and ecological opportunities for thermally active surfaces as an alternate paradigm. While amended techniques and technologies will undoubtedly play a central role in more sane building and energy practices, these techniques and technologies will not determine the relative sustainability of our building, cities, and practices. Our decisions will. As Reyner Banham notes: The greatest of all environmental powers is thought, and the usefulness of thought, the very reason for applying radical intelligence to our problems, is precisely that it dissolves what architecture has been made of to date: customary forms.12 These histories are by no means exhaustive but rather are intended to help explain why we build the way we build today. As such, they are as much anthropological as they are historical, social as much as they are technical. The social construction of technology is not well understood, if not entirely absent in current approaches to the thermal conditioning of buildings. This has severely constrained the development of more physiologically, technically, and ecologically sound thermal conditioning systems. The aim here is to research and implement techniques and technologies that emerge from a broader conception of technology in architecture and aim toward more sound building practices.

Theories, Techniques, and Technologies

Notes 1 George Grant, “A Platitude,” in Technology and Empire (Toronto: Anansi, 1969), 137–143.

2 Lewis Mumford, Technics and Civilization (New York: Harcourt, Brace & World, 1934). For further examples see: Thomas Kuhn, The Structure of Scientific Revolutions (Chicago: University of Chicago Press, 1970). Bruno Latour, Science in Action: How to Follow Scientists and Engineers through Society (Cambridge: Harvard University Press, 1987). David F. Noble, America by Design: Science, Technology, and the Rise of Corporate Capitalism (Oxford: Oxford University Press, 1979).

3 Gilles Deleuze and Claire Parnet, Dialogues II (New York: Columbia University Press, 1987), 70.

4 David F. Noble, Forces of Production: A Social History of Industrial Automation (New York: Alfred A. Knopf, 1984), 351.

5 Lewis Mumford, Technics and Civilization (New York: Harcourt Brace & Company, 1963).

6 Ibid., 324.

7 Ulrich Beck, Risk Society: Towards a New Modernity (London: SAGE Publications, 1992).

8 Ulrich Beck, Ecological Politics in the Age of Risk (Cambridge: Polity Press, 1995).

9 Gilles Deleuze and Felix Guattari, “1227: Treatise on Nomadology,” in A Thousand Plateaus: Capitalism and Schizophrenia (Minneapolis: University of Minnesota Press, 1987), 397–8.

10 David F. Noble, “Statement of David F. Noble at Hearings on Industrial Sub-Committee of the 98th U.S. Congress,” in Progress Without People (Chicago: Charles H. Kerr Publishing, 1993), 100.

11 E. F. Schumacher, Small is Beautiful: Economics as if People Mattered (New York: Harper Perennial, 1989), 198.

12 Reyner Banham, The Architecture of the Well Tempered Environment (Chicago: University of Chicago Press, 1984), 312.

41

Conditioned Air How a Thermodynamically Irrational Mode of Heat Transfer Became the Dominant Mode of Heating and Cooling in the Twentieth Century

The emphasis on air conditioning in the twentieth century eventually conditioned not only the air in buildings but is part of a larger history of conditioning: the conditioning of human comfort, building industry, and energy practices. Building types, engineering and architectural practices, industries, levels of energy consumption, and expectations for human comfort developed alongside the technics that surround air conditioning technology.1 As such, air conditioning in the twentieth century is a prime example of what Thomas P. Hughes, a historian of technology, describes as “technological momentum.”2 Technological momentum is the notion that technologies are initially socially determined through needs and desires and then, through collective choice, acquire levels of technological determinism and come to dominate periods of technical work. It is important to understand that air conditioning technology did not determine this momentum; rather we collectively granted it through individual choice and enterprising industrial ambitions. These needs and desires granted air-based energy systems great technological momentum.

These social and economic factors likewise transformed the scientific development of air conditioning: marketing focused on consumer demand and profit rather than the efficacy of its science.3 This has had far-reaching effects for our building industry and energy resources—not to mention our health, comfort, and sustainability.

As part of this momentum, during the twentieth century we made buildings taller and deeper through air conditioning and electric illumination. We also made building envelopes more hermetically sealed and turned largely uninhabitable climates into sprawling metropolitan areas. Increasingly, we choose to live and work with the determinants of air-conditioned spaces. It quickly became an assumption of human comfort and engineering practice, ultimately structuring our energy habits and policies.

To fully understand the technological momentum of air conditioning, it is essential to explain the assemblage of factors that contributed to it. In what follows, I describe a social, economic, marketing, and physiological narrative of air conditioning technology that is central to this momentum. Again, this narrative is by no means exhaustive, but rather helps explain why we build the way we do and how this technological momentum can shift in the coming decades. This narrative ultimately focuses on the development and ubiquitous use of the psychrometric chart in the engineering practices. The psychrometric chart, as the primary basis of air-conditioning design, instrumentalized air-conditioning science and accelerated its use to multiple aspects of our cities. While the psychrometric chart is necessary for some factors of human comfort, the psychrometric chart has neglected significant aspects of human physiology. These oversights have been embedded in the basic assumptions of heating, cooling, and ventilation strategies from their origins and as they spread through the last century. These assumptions— professional and technical, consumer driven and social—about air conditioning led to enormously consumptive, wasteful practices. “The sum total of consumer

42

Conditioned Air

43

decisions,” states Gail Cooper, a historian of air conditioning, “created a huge public policy problem.”4 Throughout its history—from its origins to contemporary systems—the gross inefficiencies of forced air systems were legitimated by this assemblage of technical, economic, and social factors. Articulating this assemblage of factors of conventional conditioning systems inversely suggests opportunities for alternate systems.

Origins: The Birth of Hot Air The coupling of thermal comfort with convective air flows for human comfort is as old as fire. Often, radiant transfer is the dominant mode of heat distribution in a fire, but in many fireplace configurations, convective transfer plays an important role.

The history of fireplace design is a history of the mixture of these two modes of heat transfer. The fireplace underwent significant scientific developments during the eighteenth and nineteenth centuries, making its convective transfer increasingly effective.5 These fireplaces, with a burn chamber and increasingly convoluted channels of combustion exhaust air contained inside a box, were the prototypical logic for later centralized heating systems. Their miniaturized system of thermal source and ducted distribution systems in many ways prepared the logic of later HVAC systems.

A growing awareness in the medical field about the effects of foul air in the mideighteenth century spurred a series of experiments focused on adequate building ventilation in hospital and prison typologies. Natural ventilation systems were developed, initially using cross ventilation strategies and then later using fire to induce and amplify convective currents. The fire could also heat the ventilation air, a coupling that would come to unreflectively dominate our thermal strategies. It was soon apparent that machine-powered devices could force ventilation. These applications of poweroperated ventilation and heating systems date back to the early eighteenth century and were in widespread use by the beginning of the nineteenth century; particularly in the foul air of mill buildings in England.6 Centralized heating and ventilation systems, however, would not fully emerge until the late nineteenth century.

Once heating and ventilation were coupled and centralized in the same distribution system, it followed that the emerging technologies to cool air could use this same distribution system. Heating, however, is a relatively simple proposition compared with the more daunting task of cooling and humidity control. Once its techniques and technologies were devised, cooling eventually played a consequential role in the development of these air-based systems and their technological momentum.

Origins: The Birth of Cool Various vernacular evaporative cooling techniques have been in use throughout the history of building in hot climates. Mechanized versions of evaporative cooling techniques were used in the nineteenth century. For example, by adding ice racks to forced ventilation systems, early engineers lowered the supply air temperature by

44

several degrees. But these applications were rare due to the infrastructure required as well as the limited availability and cost of ice. As such, rather extravagant residences and assembly spaces such as the Auditorium Theater in Chicago and Madison Square Theater in New York utilized such systems. Their infrequent employment was also a result of their unreliability. There were numerous problems with the ice and fan systems: they were difficult to control and consumed large amounts of space and ice.7 They were therefore not economically viable in the long term. Yet interest and demand increased driving the search for alternative “cooling” techniques suitable for broader applications.

The science of cooling air through refrigeration processes was developed in the nineteenth century, aided by developments in thermodynamics and the science behind the steam engine. During this time, a number of refrigeration experiments took place in Europe and the United States.8 The early forms of air refrigeration were trial and error attempts to modify the temperature or humidity levels of air. John Gorrie, a Floridian physician in the mid-nineteenth century, was the first American to conduct a set of such refrigeration experiments. In attempting this end, he was the earliest to envision modulating the air milieu with mechanical cooling by tempering its latent heat. In 1844, Gorrie produced his first refrigeration machine. With it he envisioned cooled houses and even cooled cities based on large district refrigeration networks. While his conception of mechanical refrigeration was available in the second half of the nineteenth century, the infrastructure necessary to construct his approach was not.

Progress continued toward the turn of the century. Alfred Wolff, an engineer in New York City, developed more calculated systems between 1893 and 1902.9 He identified several key variables necessary to construct engineered systems for human comfort: temperature, humidity, air borne contaminants, and air distribution. He also developed an early, albeit eventually inaccurate, method for sizing air system components. He derived a “heat-unit system” that calculated the size of radiators as a ratio of glazed wall to opaque wall. His work on the Cornell Medical College building in New York contained the first air conditioning system with components and operations similar to those of modern HVAC systems. This work prepared him for his most famous comfortcooling installation at the New York Stock Exchange. This system used steam-powered ammonia-absorption chillers to cool supply air.10 Concurrently, Stuart Cramer, an engineer from North Carolina, developed conditioning systems for machines in the textile industry.11 He was the first to use the term “air conditioning” in his explanation of the system. It was critical to control air humidity in industrial facilities that processed hygroscopic materials such as paper and textiles. Cramer used both wet and dry bulb thermometers to control the system aiming to maintain a constant difference between the two measurements.

His work is important in terms of increased control of conditioned air as opposed to merely the ability to cool or humidify it. These early technical experiments prepared

Conditioned Air

Wolff’s New York Stock Exchange system

brine

steam water ammonia brine

filtered air

ammonia pump brine pump

ammonia pump

fresh air chamber

cooling coils

fan

brine cooler condensers

brine

more precisely derived and more elaborately developed air cooling and humidity control systems. During this early period, air became increasingly systemized and quantitatively defined in Europe and in the United States. Consequently, so did the expectations of the people and machines it conditioned.

Willis Haviland Carrier While these early developments were important in terms of experimentation and scientific development, air conditioning gained real momentum in the first half of the twentieth century under Willis Haviland Carrier, the so-called “Father of Air Conditioning.”12 It is important to note that from the beginning, in his work with air-conditioning Carrier combined both the necessary quantitative capacities for technical development and the marketing acumen necessary for the dissemination and broad use of air conditioning technology.

Carrier’s efforts built-upon the nineteenth century work on air conditioning systems, advancing it into the twentieth century. Initially, his focus remained the heating, cooling, and ventilation problems inherent in the mechanization of many industries. The machines in newly mechanized industries generated new levels of internal heat gains, humidity, and exhaust air. All required more effective ventilation.

It should be noted that the impetus behind both Cramer and Carrier’s work focused initially on machines, not people. Carrier’s first professional engagement with humidity and the tempering of air was in a printing facility in New York City.

Carrier’s solution to ventilation problems in the factory launched his career and

45

46

consequently a mode of conditioning that still dominates approaches to human comfort today. One of Carrier’s most significant contributions to the technology was the derivation and quantification of the relationships between heat and humidity in the psychrometric chart.

At this time, though, Carrier was but one individual concerned with air and humidity relationships. Early in the twentieth century variations of diagrams describing the relationship between water vapor (humidity), temperature, air pressure, and enthalpy were independently developed by three individuals: Richard Mollier in Germany, Carrier in the United States, and Leonid Ramzin in Russia. There was little or no known contact between them.13 In the United States, Carrier’s psychrometric chart became the basis of all air-conditioning calculations in North America and a major enabler of its technological momentum. His enterprising ambition distinguishes him from his European counterparts, who made similar contributions to the theory of air conditioning but had more modest entrepreneurial ambitions.

In December of 1911, Carrier gave a paper entitled “Rational Psychrometric Formulae” to the American Society of Mechanical Engineers.14 The principles in this paper—and its psychrometric chart diagram—constitute the core of air-conditioning design and engineering practices. As Margaret Ingels noted, “His ‘Formulae’— translated into many foreign languages—became the authoritative basis for all fundamental calculations in the air-conditioning industry.”15 The Psychrometric Chart: Conceptualized in a Fog Carrier’s “Rational Psychrometric Formulae” paper was the result of a flash of insight that occurred nine years previously in a Pittsburgh winter while he stood on a railway platform engrossed in a fog. Margaret Ingels recorded this moment of insight as recounted by Carrier late in his life: Here is air approximately 100 percent saturated with moisture. The temperature is low so, even though saturated, there is not much actual moisture. There could not be at so low a temperature. Now, if I can saturate air and control its temperature at saturation, I can get air with any amount of moisture I want in it. I can do it, too, by drawing the air through a fine spray of water to create actual fog. By controlling the water temperature I can control the temperature at saturation. When very moist air is desired, I’ll heat the water. When very dry air is desired, I’ll heat the water.

When very dry is desired, that is, air with a small amount of moisture, I’ll use cold water to get low temperature saturation. The cold spray water will actually be the condensing surface.16 His formulae focused on the interactions of temperature, humidity, and the dew point. To help develop his insight Carrier based his “Rational Psychrometric Formulae” upon psychrometric charts from the National Weather Bureau.17 While such

Conditioned Air

below Psychrometric chart

47

calculations of gas and vapor mixtures provide insight to the behavior of air inside a building, meteorological processes do not account for the more discreet but pervasive radiant transfer processes of the human body within interior milieus. Consequently, these radiant transfer processes were absent from the resulting psychrometric chart that instrumentalized his insight on that train platform. While seemingly adequate for hygroscopic machines in the printing and textiles industries, the focus on the relationship between humidity and temperature in the “Rational Psychrometric Formulae”—and the eventual broad use of the psychrometric chart in engineering practices—did not fully account for human physiological processes, particularly the role of radiant transfer in thermal milieus. This oversight is evident in Carrier’s definition of air conditioning in later publications: Air-conditioning is the control of the humidity of air by either increasing or decreasing its moisture content. Added to the control of humidity are the control of temperature by either heating or cooling the air, the purification of the air by washing or filtering the air, and the control of the air motion and ventilation.18 In Modern Air-conditioning, Heating and Ventilating, an early textbook on airconditioning technology that he co-authored, Carrier expanded and codified his research on the “Rational Psychrometric Formulae” into practical applications.19 The book begins with a brief account of thermal conditioning practices throughout world history before proceeding into the procedures of conditioning the temperature and humidity levels of air.

30

25

20

15

10

5

T(°C)

5

10

15

20

25

30

35

40

45

50

48

This textbook reflects an understanding of thermal conditioning not fully based on physiology. The authors discuss heating systems based on radiant transfer, including the Korean Ondol, the Chinese Kang beds, and the Roman hypocaust (each of these are discussed in the next chapter).20 Yet in each circumstance, the focus is on the convective operation of these systems rather than the primary, radiant mode of transfer that heats the spaces and occupants in these precedents. In their discussion of human comfort factors in subsequent sections, the authors at once acknowledge the role of radiant heat transfer—about half of the body’s normal heat exchange—as a factor, but then dismiss turn-of-the-century radiant panel systems as defective.21 In their description of psychrometrics, the authors again acknowledge the role of surface temperatures and their effect on human comfort. But then, only a few sentences later, they fail to acknowledge the role of surface temperatures in their derivation of psychrometric factors by limiting their focus to air temperature, humidity, air motion, and air purity.22 This simultaneous acknowledgement and exclusion regarding radiant heat transfer in the derivation of the psychrometric chart led to what can be described as a radiant void in the history of air-conditioning practices as the use of the psychrometric chart became increasingly widespread. The exclusion of radiant transfer in the derivation of this thermal conditioning system is comparable to a structural engineer consciously ignoring all lateral loads in a region that has high seismic and wind loads. The design may nonetheless work, but its ultimate efficacy is dubiously in doubt. As instrumentalized psychrometric science expanded and air-conditioning systems continued to multiply and gather momentum throughout the twentieth century, so did this radiant void.

Carrier’s term for his work—“Man-Made Weather”—reveals the metaphorical fallacy and mechanistic basis of this thinking. This analogical approach to human comfort and interior climate control, while rhetorically compelling as a marketing tactic with its focus on the control of ever elusive weather, again lacks a full physiological basis of the human body: the Man in his “Man-Made Weather.” The reality is that the early psychrometric chart was developed in a context for the “comfort” and performance of the industrial machines of Carrier’s early practice rather than the more complicated and nuanced comfort and performance of human bodies. It was fundamentally a system of conditioning by machines, for machines. The early psychrometric chart and its resultant air systems were only later swerved toward human comfort applications as people realized its lucrative promise.

In the last century, nearly all approaches to human comfort in buildings relied upon the psychrometric chart as the core technique for determining human comfort.

Even most approaches to “environmental design” and “bioclimatic design” relied on the psychrometric chart. While the logic of the psychrometric chart for modulating the vapor properties of air is of course sound, the repeated and broad use of the psychrometric chart over the years conditioned human comfort practices. As such, when Carrier developed and codified his system for conditioning air through

Conditioned Air

49

psychrometric processes, he codified not only air but twentieth-century engineering, architectural, and energy practices as well. This in turn conditioned sustainable possibilities. One example exemplifies this narrowly interpreted approach to human comfort. Amidst the sprawling, post-war housing fervor, in 1952 the Carrier Corporation sponsored a house that featured a Carrier air-conditioning system. Carrier wrote: This house started a revolution. It need not depend on natural ventilation. Ells and wings wouldn’t be necessary. Only a few windows need have a movable sash.

The bathrooms needn’t require a window. Windows, doors, and even the rooms themselves could be placed to suit the convenience of the owner, not to catch a breeze.23 The history of Carrier’s early efforts to condition air and his use of the psychrometric chart reveals an understandable but nonetheless disproportionate emphasis on the role of air and humidity in human comfort. While, again, the role of humidity and convective transfer are important to human thermal comfort, it is not the only or most efficient means to achieve it.

Air was but the circumstantial starting point for an ambitious and enterprising Carrier. Reyner Banham characterized Carrier as “content to solve problems as they were put to him—often with startling ingenuity and depth of technical or intellectual resource—that one may doubt whether he had any general means of conception of the art he was founding until long after he had fathered it.” 24 The canonization of both air conditioning and Carrier himself were the product of his personal, intellectual, and business ambitions. Air conditioning for Carrier was a combination of work on humidity control for machines and an opportunity for industrial enterprise. The rapid development of his air-conditioning success has as much to do with the idiosyncratic trajectory of his professional career as it does with the efficacy of his science or the technologies that emerged from that science. Air conditioning, in this way, was socially determined as much as it was technically determined.

Social Choice and Energy Use As Gail Cooper demonstrated in Air-conditioning America, the marketing and social choices of air conditioning in the middle of the twentieth century determined as much about the development of air-conditioning systems as its engineers during this period.25 The large market share of small scale, inefficient, packaged air-conditioning window units is a prime example. As Cooper makes the case, the history of airconditioning marketing is more central to its widespread use than its efficacy to achieve human comfort. Another historian of air conditioning, Marsha Ackerman, has documented the incorporation of various air-conditioning technologies into daily life in America.26 In Ackerman’s social history of air conditioning, she focuses heavily on the exchanges between climatologists, mechanical engineers, and domestic consumers

50

through cases such as Levittown, but also through mid-century popular domestic journals, for example House Beautiful’s “Climate Control Project” that began in the late 1940s. This project aimed to evaluate the role of air conditioning in post-war housing. These projects emphasized the reliance on air conditioning rather than passive modes that dealt more with house orientation and configuration than power-operated technologies to fit a house to its climate; feeding the technological momentum of air conditioning.

While bottom-up consumer choice affected technological momentum, so did top-down business. Histories of American technology before and after World War II emphasize the confluence of science, technology, and the corporation as codeterminants in deciding which technologies were developed and adopted. A classical example of this process of adoption was the selection of refrigerators that utilized electric compression and their characteristic humming over nearly silent gasabsorption models. Absorption refrigerators, developed initially by Ferdinand Carre in the second half of the nineteenth century, did not require electro-mechanical compressors, the most energy-intensive process in now-typical refrigeration processes.27 Absorption units were more common initially, but electrical units soon became dominant. This happened largely through the agency of General Electric and their ability to expend greater capital on the research, development, and most significantly, marketing and promotion of a technology. This yielded greater profits for manufacturers and increased utility grid demand (i.e., more energy-intensive means): The case of the gas refrigerator appears, in many particulars, to be structurally similar to the cases of many other aborted or abandoned devices intended for the household....In an economy such as ours in the United States, the first question that gets asked about a new device is not, Will it be good for the household—or even—Will householders buy it? But, rather, Can we manufacture it and sell it for profit? Consumers do no get to choose among everything that they might like to have, but only among those things that manufacturers and financiers believe can be sold at a good profit....General Electric became interested in refrigerators because it was experiencing financial difficulties after the First World War and needed to develop a new and different line of goods.28 The interests of Willis Haviland Carrier and the Carrier Corporation followed a similar logic. Speaking in 1933 about the role air conditioning could play in stimulating the nation’s economy (and as a result, his economy), Carrier said: “The situation imposes a crying need for new industries, which will contribute wealth and employment in a degree comparable to that produced by the automobile, the radio, and the household refrigerator.”29 Elsewhere, Carrier makes his priorities equally clear: “Between a fundamental demand for a product and the scientific knowledge of its requirements, the former is the most essential...in fact, the all essential factor.”30

Conditioned Air

51

In a context of seemingly infinite energy resources, this confluence of consumer choice and corporate profit resulted in the widespread use of conditioning strategies based on fiscal promise rather than the technical or physiological efficacy. This also expanded the technological momentum of air conditioning.

Energy Crises, Sick Building Syndrome, Indoor Air Quality, Delta T As air-conditioning practices gained momentum, it led to the technological momentum in other areas of building production. The construction of hermetically sealed boxes, thin layers of dropped ceilings, thin curtain walls, deep floor plates, and extensive electrical illumination all contributed to the habits of mind and practice that play a major role in the crisis of resources in contemporary architecture.

William Braham wrote: First air-conditioning and efficient fluorescent lighting make it possible to fill larger areas with people and the equipment they use to work, but the people, lights, and equipment all produce heat, which requires even more conditioning.

As heat removal becomes ever more important, windows are sealed and were designed to exclude as much sunlight as possible, making the interior environment more efficient, but less and less pleasant.31 In this context of cheap and seemingly limitless energy resources, power-operated air-conditioning solutions dominated building systems. The social demand for air conditioning began to alter people’s perception of human comfort. The consumption of energy resources grew rapidly. These air-based strategies soon became a prime factor in the energy crisis during the 1970s.

As Michelle Addington pointed out, when the effects of the 1973 OPEC oil embargo occurred, air-conditioning engineers targeted ventilation as a conservation measure because “introducing outside air brings the dual penalty of requiring energy to condition it to the level of the inside air as well as requiring additional fan energy for its distribution.”32 This condition was exasperated by the significant swing in the temperature between the outside air and the inside air—invariably at odds with one another in the heating and cooling seasons. Thus to conserve energy in this period engineers began to dial back the required air changes, recirculating already conditioned, filtered air instead. Thus the response was to increase air exchanges back up in the 1980s, multiplying the thermal inefficiencies inherent in air-based systems. This logic also led to other problems such as sick building syndrome.

As awareness in indoor air quality issues grows in contemporary practice, air exchanges are popular once again. This is at odds with the need for reduced energy consumption. As discussed in more depth later in this book, air is simply a poor medium for moving thermal energy around a building and a poor medium for exchanging heat energy with a human body. However, when ventilation loads are

52

decoupled from thermal loads in air-based systems, the increased requirements for indoor air quality represent a far less significant energy penalty. This is one of many reasons that, in low-to-no energy buildings, thermal conditioning and air-quality conditioning will increasingly be decoupled.

Conclusion The path leading to our use of air to thermally condition buildings is a conflation of economic, social, and scientific concerns. It reflects a fervent mentality about machines rather than bodies that pervaded the twentieth century. It is evident in Carrier’s personal ambitions, corporate ambitions, his profound scientific achievements, and his equally significant scientific oversights. The dynamic assemblage of factors in the twentieth century that allowed Carrier’s psychrometrics to expand has begun to change, however. The dynamics of new building economics point toward an alternative to this air-based approach. Likewise, building ecologies based upon increasing energy demands coupled with decreasing energy resources demand a greater relationship between biology and design. Alternative thermal conditioning systems based on the thermodynamic and physiological processes of the human body, rather than a printing press, will become increasingly familiar. Where there was once logic for coupled ventilation, heating, and cooling systems, thermally active surface systems are more rational on a number of levels given the current obligations and contingencies of contemporary practice. The next chapter documents the history of the science, materials, and methods of these thermally active surfaces.

Conditioned Air

53

Notes 1 The development and adoption of these

13 Branislav B. Todorovic, “Occurrence of Humid

technologies is covered well by Reyner Banham,

Air Diagrams within a Short Period at Three Distant

Cecil Elliot, Bill Addis, Robert Bruegmann, Michelle

Places on a Globe,” ASHRAE Transactions 113,

Addington, and Gail Cooper. Michelle Addington,

no. 1 (2007).

“The History and future of ventilation,” in Indoor

14 Carrier derived and published his “Rational

Air Quality Handbook, eds. Samet Spengler

Psychrometric Formulae” in American Society of

and McCarthy (New York: McGraw-Hill, 2001),

Mechanical Engineers (ASME) Transactions 33

2.1–2.16. Bill Addis, Building: 3000 Years of Design,

(1911): 1005.

Engineering, and Construction (London: Phaidon

15 Ingels, 42.

Press, 2007). Reyner Banham, The Architecture of

16 Ibid., 20–1.

the Well-Tempered Environment (Chicago: University

17 Ibid., 15–7.

of Chicago Press, 1984). Robert Bruegmann,

18 Ibid., 17.

“Central Heating and Forced Ventilation: Origins

19 Willis H. Carrier, Realto E. Cherne, and

and Effects on Architectural Design,” in The Journal

Walter A. Grant, Modern Air Conditioning, Heating

of the Society of Architectural Historians 37, no.

and Ventilating (New York: Pitman Publishing

3 (1978): 143–60. Gail Cooper, Air-Conditioning

Corp., 1940).

America: Engineers and the Controlled Environment,

20 Ibid., 1.

1900–1960 (Baltimore, MD: Johns Hopkins

21 Ibid., 17.

University Press, 1998). Cecil D. Eliot, Technics and

22 Ibid., 6.

Architecture: The Development of Materials and

23 Carrier as quoted in Marsha A. Ackerman, Cool

Systems for Building (Cambridge, MA: MIT Press,

Comfort: America’s Romance with Air-Conditioning

1992).

(Washington, DC: Smithsonian Institution Press,

2 Thomas P. Hughes, “Technological Momentum,”

2002), 121.

in Merritt Roe Smith and Leo Marx, eds. Does

24 Banham, 171–2.

Technology Drive History? (Cambridge, MA: MIT

25 Cooper, 3.

Press, 1994).

26 Ackerman, 120–1, 135.

3 Cooper, 183–90.

27 Addis, 334.

4 Ibid., 165.

28 Ruth Schwartz Cowen, “How the Refrigerator got

5 Cecil Elliot and Reyner Banham both elaborate on

its Hum,” in Donald MacKenzie and Judy Wacjman,

the development of the fireplace in the eighteenth

eds. The Social Shaping of Technology (Philadelphia:

and nineteenth centuries. Eliot, “Heating and

Open University Press, 1985), 214–6.

Ventilation,” and “Air Conditioning,” 270–79.

29 Cooper, 118.

Banham, 29–50.

30 Ibid., 81.

6 Addis, 318.

31 William Braham, “Biotechniques: Remarks on

7 Eliot, “Heating and Ventilation,” and “Air

the Intensity of Conditioning,” in Branko Kolarevic

Conditioning,” 271–325.

and Ali M. Malkawi, Performative Architecture:

8 Addis, 333–35.

Beyond Instrumentality (New York: Spon Press,

9 Cooper, 9–17.

2005), 55–70.

10 Addis, 408–9.

32 Addington, 2.8.

11 Cooper, 9–17.

12 See Margaret Ingels, Willis Haviland Carrier: Father of Air Conditioning (Garden City, NJ: Country Life Press, 1952).

Thermally Active Surfaces A Minor Paradigm with Major Implications

The history of thermally active surfaces in architecture is a minor history of failed material systems and often misconceived or misconstrued building science.

The successes and failures of the various physical and intellectual experiments in thermally active surfaces during the last century ultimately account for the technique’s lack of technological momentum and widespread use. But the failure of a mid-century solder joint in a copper tube should not be confused as a failure of the physiological or thermodynamic basis of thermally active surfaces.

Thermally active surfaces are not new. The history of thermally active surfaces in architecture extends back thousands of years. Examples oscillate between techniques that utilize radiant and convective transfer methods. But only recently have their thermodynamic and physiological uses been understood. The early thermally active systems were archaic heat-recovery systems that captured heat energy into a surface mass by channeling the convective flow of combustion air under floor surfaces before it was finally exhausted through chimneys.

Thermally Active Surfaces in Northeast Asia A series of heating techniques used in Northeast Asia provide the earliest examples of thermally active surfaces in buildings. The Chinese Kang—a thermally active bed— and the Korean Ondol—a thermally active floor system—date back to 1,000 BCE. Ondol means “warm stone” in Korean. In this system, the living space of the house was a few feet above the level of the kitchen and fireplace in an adjacent room. Two construction techniques channeled hot air horizontally from the fire. In a subtractive mode, slots were dug under the finished floor from the fireplace to an exterior chimney. In an additive mode, masonry pedestals raised stone floor slabs, creating a plenum for exhaust air to run to a similar free-standing chimney outside the house.

In both cases, the floor slabs were stone and coated with clay. Atop this base were layers of oiled paper and floor mats. The impervious clay layer contained the noxious combustion gases within the convection channels while heat from the combustion exhaust air warmed the stone slabs. This in turn warmed the space above through primarily radiant transfer. Thus the surface of the floor mass was the heat transfer mechanism, even though secondary convection patterns are typically associated with thermally active systems.1 The Ondol system helped engender a number of cultural and social patterns.

The concentrated heat in the living space, adjacent to the fireplace, established a patriarchal spatial hierarchy in which the eldest occupied the warmest zones of the floor. Likewise, the tradition of not wearing shoes in a house and sleeping on the floor are also connected to these early thermally active floor systems. The Ondol technique and the customs it brought about will figure prominently in more recent periods of thermally active surfaces.

54

top right Vernacular Ondol example

below Ondol variations

Thermally Active Surfaces

55

56

Ancient Roman Thermally Active Surfaces In the West, the Romans were early adopters of thermally active systems. The Roman hypocaust system (hypo: below, and kaiein: to burn) is perhaps the most well-known historical thermally active surface system. While its origins are not as clear as once thought, its organization and use in the Roman era were well documented.2 Vitruvius recorded the system in The Ten Books on Architecture: The hanging suspensurae of the hot bath rooms are to be constructed as follows. First the surface of the ground should be laid with tiles a foot and a half square, sloping towards the furnace in such a way that, if a ball is thrown in, it cannot stop inside but must return of itself to the furnace room; thus the heat of the fire will more readily spread under the hanging flooring. Upon them, pillars made of eight-inch bricks are built, and set at such a distance apart that twofoot tiles may be used to cover them. These pillars should be two feet in height, laid with clay mixed with hair, and covered with the two-foot tiles which support the floor.3 In the hypocaust, much like the Ondol, hot air from the praefurnium, or furnace fires, was drawn through the floor plenums and exhausted through flues embedded in the warmed masonry envelope. In some cases the praefurnium was located below the bath level and in others it was level with the baths. The warmed thermal mass of the floor and walls became the primary mechanism for heat transfer and human comfort, at times reaching one hundred degrees centigrade. These temperatures were common in the laconium sweating room. Radiant transfer with thermally active surfaces made sense in attempting to temper the monumental scale of the baths’ interior spaces.

Like the Ondol, the floor assembly consisted of stone pavers—a stone antecedent to our own raised access floors—covered with a layer of plaster grout as a containment barrier and setting bed for mosaics. The hypocaust was an early heat recovery system that used waste heat energy from heating water to temper the large volume of the baths. Vitruvius wrote about this distinction: Three bronze cauldrons are to be set over the furnace, one for hot, another for tepid, and the third for cold water, placed in such positions that the amount of water which flows out of the hot water cauldron may be replaced from that for tepid water, and in the same way the cauldron for tepid water may be supplied from that for cold. The arrangement must allow the semi-cylinders for the bath basins to be heated form the same furnace.4 The hypocaust captures and channels heat energy, otherwise wasted, for the monumental domestic hot water system of the baths. The fires primarily heated water for the various pools in the bath and created the exhaust air that flows through the

left, right, bottom Hypocaust diagram and flue types

Thermally Active Surfaces

57

below Floor diffusers in Winter Refectory

hypocaust system. The cauldrons, hypocaust, and pools were tightly interlinked from an energy point of view, albeit in an inefficient and characteristically Roman manner. In addition, many of the baths have elaborate rain harvesting systems that further integrate the thermal and water cycles of the buildings.

Like the Ondol, the thermodynamic logic of the hypocaust dictated the arrangement of the program.5 The caldarium, or hot pool, was located closest to the heat source while the frigidarium was located furthest from the heat source. Isolated examples of these baths continued well into the Middle Ages. However, like many Roman techniques and technologies, the hypocaust system largely faded out of existence as the Roman Empire dissipated.6 Thermally Active Surfaces in the Middle Ages The principles of heating a thermal mass with hot air to condition spaces were used by other cultures during various periods. A range of heating systems and building typologies developed around large fireplaces and masonry heaters in Northern Europe during the Middle Ages. One notable example is the Malbork Castle in northern Poland. The castle incorporated a medieval version of a hypocaust. The best example is the Winter Refectory, located in the west wing of the Middle Castle. In this system, a subterranean double chamber stove generated heat for the large refectory space above. The lower fire-box chamber, with an isolated combustion box and exhaust air chimneys, heated a large pile of stones directly above the combustion chamber.

Air was drawn through the stones, exchanged its heat energy with this thermal mass, and rose to the refectory above through small-scale masonry ducts. Atop these ducts, the refectory had cast metal adjustable diffusers integrated into the floor.

This modulated the amount of convective heat energy that entered the space. While primarily a convective technique, the thermal mass of the refectory surfaces and the thermal mass of the stones captured and channeled heat by convective and radiant means.7 Once again, the limited thermally active surface behavior of the

58

left, right Section through heat source at Winter Refectory

Thermally Active Surfaces

59

system was a by-product of the air-based convective system. Given the relative complexity of this masonry system, it remained unusual. Its principles, however, were more frequently applied on a smaller scale pervasively throughout Europe.

The Austrian kachelofen, Finish kaakeliuuni, Swedish kakelugn, and other variations of masonry heaters also used low-temperature radiant heat to temper the long winters in these northern climates. A masonry heater is a massive masonry box with a fire chamber that is heated intermittently to charge the masonry mass. This then reradiates the energy to adjacent spaces. They are substantial constructions and often determine much of the spatial arrangements in a building. Martin Rausch, a contemporary German rammed-earth specialist, uses pre-cast rammed-earth panels with formed flues as hot air mass heaters. While examples of these air-based methods cut across the centuries, hydronic radiant systems are relatively recent, technically superior developments compared to other systems.

Thermally Active Surfaces in the Eighteenth and Nineteenth Centuries As metallurgical practices and processes expanded in the Enlightenment and beyond, especially after the development of the steam engine, piped steam and hot water were increasingly used in Europe throughout the eighteenth and nineteenth centuries as heating implements.8 This was essentially an expansion of industrial steam power. The steam system was used to distribute heat energy to spaces through radiators and convectors, with convective transfer as the primary method of heat transfer. When thermal energy was distributed via radiators, it was conceptually limited to being a replacement of a fireplace in a space. In certain cases the thermal energy was distributed in the thickness of a surface. An early example of a thermal surface strategy, rather than thermally active object strategies, was in a mill building

by Neil Snodgrass, located in Dornoch, Scotland, built in 1800. 9 In this case, steam circulated through vertical runs of tubes is placed in the walls of the mill to condition the interior space. This type of installation comes closer than any other precedent to the operation of a contemporary thermally active surface. The Armley Mill in Leeds,

60

another mill building in England, used cast iron columns to distribute radiant energy, an early integration of structural and thermal conditioning systems. This made sense given the even distribution of columns in the space.

Sir John Soane integrated a number of novel hot water strategies, steam strategies, and hypocaust-style thermally active surfaces into his projects during this period.10 At his house, high-pressure steam was ingeniously integrated in sculpture bases, furniture, and around the bases of its many skylights to offset thermal losses in these single pane glazing and iron thermal sinks.11 A particularly innovative example is Soane’s Bank of England Stock Office, completed in 1793.

It includes an under-floor hypocaust system, designed to recover heat energy in the form of combustion air to heat the thermally active floor surface. This design reflects his interest in Roman precedent.12 In this case, the design of the Stock Office foundation and the convoluted route of the combustion exhaust channels are tightly integrated. The Register Office in Edinburgh (1837) by Charles Richardson is an example of a different course. A pupil of Soane, Richardson used hot water rather than steam as its thermal conditioning system.13 While these examples show that progress was made in the application of radiant transfer, interest lagged behind that of conductive and convective modes of heat transfer. A quantitative understanding of radiant transfer did not occur until the twentieth century.

Thermally Active Surfaces in the Twentieth Century In 1908, an Englishman, Professor Arthur H. Barker, manufactured a commercially available hydronic thermally active surface.14 Barker’s system embedded small metal pipes in concrete and plaster in floor and ceiling surfaces as the source of heat transfer. Although effective and popular, the understanding of the building science and physiological responses to the system were not well understood and further development was interrupted by World War I. In 1916 Frank Lloyd Wright left the United States to work on the Imperial Palace Hotel in Japan. While in Japan, Wright visited a home built on the Korean Ondol model. The experience and logic impressed Wright. He in turn incorporated hydronic thermally active surfaces in the Imperial Hotel. He then brought the technique back with him when he returned to the United States and tested various hydronic systems in many of his projects. By the 1930s, thermally active floor slabs were a standard system in his Usonian Houses, including the Jacobs House built in 1936. The system Wright used consisted of cast iron or copper pipes embedded in sand and crushed rock located under, and sometimes in, a concrete floor slab.

He completed a number of significant thermally active surface projects including Herbert Fisk Johnson’s 14,000-square-foot Wingspread house. He also used radiant panels in the Johnson Wax headquarters in Racine, Wisconsin. Wright referred to this system as “gravity heat.” In these projects he focused on the buoyancy of the air

top Open Air School, Amsterdam, 1930

Thermally Active Surfaces

61

bottom Mid-century human comfort metrics

caused by the radiant floor—this caused the warmed air to rise, drawing cooler air down to the slab in a convective current.

In Europe, during the second quarter of the twentieth century, an English firm, Richard Crittall & Co., developed hydronic radiant systems for schools and sanatorium projects. The Crittall Ceiling became a common method of installation for thermally active surfaces.15 One of the most famous examples of this system is Bernard Bijvoet and Johannes Duiker’s Open Air School in Amsterdam built in 1928. The school reflects the debate in the early twentieth century regarding indoor air quality.16 One outcome of this debate was the Open-Air School Movement in the United States and Europe. In the United States, the poor quality of urban air, the increasing size of urban schools, and poor student performance prompted experimentation with openair classrooms. During this time, open-air classrooms were supported as a medical approach to eradicate tuberculosis. As such, open-air classrooms were also an extension to the benefits of fresh air and sun prescribed as the primary tuberculosis treatment. Bijvoet and Duiker’s work on the Zonnestraal Sanatorium prepared their work on the Open Air School in Amsterdam.17 In their Open Air School, the benefits of open-air and sunlit classrooms were engendered by a hydronic radiant system embedded in the concrete ceilings and structure of the outdoor classrooms. The hydronic system extends the open-air teaching season by modulating the operative temperature of the outdoor classrooms shared by the two classrooms on each floor.

Duiker continued working on thermally active surfaces in subsequent projects, including his final project: the 1934 Grand Hotel in Gooiland, Hilversum. In a system developed and patented with de Ridder, the hotel used an air-based thermally active concrete ceiling structure to condition interior and exterior spaces.18 Throughout this period, the application of thermally active surfaces remained largely as idiosyncratic as its architects.

In the years before and after World War II, the Industrial Health Research Board of the Medical Research Council and the Department of Scientific and Industrial Research at the Building Research Station, both in Great Britain, independently worked on radiant heating systems, and more specifically, methods of measuring radiant transfer and its effects on human comfort.19 There was a particular emphasis on the role of radiant heating for the comfort and productivity of children in schools.

This work was a major contribution to research on the means and methods of radiant transfer.

Mid-Century Hydronic Systems Following World War II, interest in thermally active surfaces became more popular and their use more widespread in the United States. A group of publications about the use of concrete slabs and radiant heating were written in the United States after World War II, reflecting the penchant for thermally active surface building science and a renewed interest in the possibilities of hydronic and electric radiant

top left Field fabrication of metallic tubing for mid-century hydronic systems top right Field welding of metallic tubing

bottom left Prefabricated metallic tubing loops bottom right Installation of prefabricated metallic tubing loops

heating.20 At this same time, in his book American Building: The Environmental Forces that Shaped It, James Marston Fitch identified the benefits of radiant heating and proposed six-sided thermally active surface heating as the optimal thermal comfort technique.21 By this point, the science behind radiant transfer was catching up with the research on convective and psychrometric processes.

This literature and its audience expanded the implementation of radiant systems from idiosyncratic customized installations to more systemic installations on a larger scale. A large scale example of this post-war rise and fall of thermally active surfaces occurred in Levittown, New York. Irwan Jalonack developed a hydronic heating system with copper tubing for slab-on-grade homes.

In the decades after the war, however, the development of hydronic radiant systems was beset by several technical problems, largely due to material and labor deficiencies. For example, constructability issues negatively affected the Levittown system. The Levittown system was indicative of the systems available at this time and these systems eventually failed in the following two decades. The failure was a combination of two factors: they failed in their materials and their methods.

62

below Mid-century hydronic installation types

Thermally Active Surfaces

63

For the first two-thirds of the twentieth century, hydronic thermally active surface systems were fabricated from metal tubing: either steel, wrought iron, or copper embedded in either sand or a concrete slab. This led to several problems.

First, this system was an intensive proposition in terms of labor and material because it was fabricated almost entirely on site. This limited quality control. The pipe stock was cut and bent for all the loops and all the joints were soldered or welded into somewhat delicate hydronic loops. This led to a second problem: the fused joints had to be complete or the loop would leak, as often happened, after pouring the concrete slab. To amend this problem, prefabricated loops were built in shops and delivered to the site. But on-site joints remained as problematic as they were inevitable. Thus the systems were often too expensive, slow, and leaky. As such, hydronic radiant systems had a poor reputation in the building industry. This all but ceased its development in the subsequent decades. These problems contributed significantly to the demise of post-war interest in thermally active surfaces, just as the building science behind the system was beginning to be understood. As building industry confidence in radiant systems sank, air-based conditioning continued to acquire more momentum and better marketing compared with hydronic systems.

This would change. Developments in the post-war plastics industry soon improved the prospects for thermally active surfaces. In the 1950s, Wirsbo, a Swedish company, developed an early polyethylene tube for use in radiant systems.

As a supple, extruded product, Wirsbo tubing reduced the number of joints in its looped hydronic installation. Its advantages apparent, Wirsbo developed optimal compositions of the tubing. In 1968, Thomas Engel, a German engineer, developed cross-linked polyethylene tubing, known as PEX. In 1969 Wirsbo refined the manufacture process for PEX and made the tubing commercially available.22 This tubing resolved the mid-century material and methods issues with hydronic systems; it was a product that could outlast the life of the concrete that typically

64

encases it. This development continues today. PEX tubing advancements include oxygen-proof exterior barriers that improve durability and tubing profiles, maximizing thermal transfer.

PEX tubing, systematized fittings, and related technologies vastly increase installation speed, quality, and reliability. As a result hydronic systems are being used with greater regularity in both heating and cooling applications. Yet, as Lewis Mumford stated, the habits of mind in this industry do not align with the physiological basis of these systems. The recent growth in the discourse and practice of sustainability is shifting these habits of mind.

During the 1970s and 80s, Dr. Bruno Keller worked on the development and integration of techniques for low energy buildings. By the late 1980s he focused his efforts on high performance building envelopes, displacement ventilation, and thermally active surfaces in a number of projects. The Messerli Ltd. building in Wetzikon, Switzerland, for instance, was the first of many buildings to decouple thermal conditioning and fresh air ventilation. The building uses an all glazed building with optimal U-values and an early cooled ceiling using panel radiators. The Saniport building in Fribourg was the first building integrating hydronics into a concrete slab, in conjunction with displacement ventilation and a high performance building envelope.

In a house near Zurich built in the mid-1980s, architect Otto Kolb used plastic hydronic tubing behind stone walls as a thermally active wall surface, as well as a hydronic floor system to help heat the circular solar house.23 Roof mounted solar collectors heat a pool on the south side of the house. They reflect light into the house storing heat energy accumulated during the day.

In the early 1990s, other practices in Switzerland further developed these components of thermally active surface systems. Robert Meierhans, a Swiss engineer, developed a number of buildings and published important research papers about ground source radiant cooling and the night purge of concrete slabs.24 His collaborative work with architect Peter Zumthor on the Thermal Baths at Vals and the Kunsthaus Bregenz (a case study in this book) are both noteworthy examples. By the beginning of this century, the technique is gaining more technological momentum, with significant applications in Central Europe, China, and British Columbia.

In a wider context, however, thermally active surfaces remain a minor technique today for heating and cooling buildings. This is primarily on account of their troubled constructability issues that beset the practice in the middle of the twentieth century.

But with those issues resolved, the full efficacy of radiant transfer as the means to heat and cool a building means that it can be a more widespread practice of building design. In order to do so, however, it is important to grasp the thermodynamic and physiological basis of thermally active surfaces. This is the content of the next chapter.