Microclimate for Cultural Heritage

Conservation, Restoration, and Maintenance of Indoor and Outdoor Monuments

Dario Camuffo

• Publisher: Elsevier Science
• Year: 2013
• Print ISBN:
  9780444632968
• eBook ISBN:
  9780444632982
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Meteorology & Climatology

Microclimate for Cultural Heritage: Conservation and Restoration of Indoor and Outdoor Monuments, Second Edition, is a cutting-edge, theoretical, and practical handbook concerning microclimate, environmental factors, and conservation of cultural heritage. Although the focus is on cultural heritage objects, most of the theory and instrumental methodologies are common to other fields of application, such as atmospheric and environmental sciences. Microclimate for Cultural Heritage, Second Edition, is a useful treatise on microphysics and a practical handbook for conservators and specialists in physics, chemistry, architecture, engineering, geology, and biology who work in the multidisciplinary field of the environment, and, in particular, in the conservation of works of art. Part I, devoted to applied theory, is a concise treatise on microphysics, which includes a survey on the basic ideas of environmental diagnosis and conservation. The second part of the book focuses on practical utilization, and shows in detail how field surveys should be performed, with many suggestions and examples, as well as some common errors to avoid. - Presents updated scientific and technological findings based on the novel European standards on microclimate and cultural heritage - Includes the latest information on experimental research on environmental factors and their impact on materials, such as the behavior of water and its interactions with cultural heritage materials - Contains case studies of outdoor and indoor microclimate conditions and their effects, providing ideas for readers facing similar problems caused by heat, water, radiation, pollution, or air motions - Covers instruments and methods for practical applications to help readers understand, to observe and interpret observations, and avoid errors

Part I

Atmospheric Physics Applied to Microclimate Analysis and Conservation

Outline

Chapter 1 Microclimate, Air and Temperature

Chapter 2A Theoretical Grounds for Humidity

Chapter 2B Humidity and Conservation

Chapter 3 Parameters to Describe Air Masses and Vertical Motions

Chapter 4 Radiation and Light

Chapter 5 Physics of Drop Formation and Micropore Condensation

Chapter 6 Atmospheric Water and Stone Weathering

Chapter 7 Atmospheric Stability and Pollutant Dispersion

Chapter 8 Dry Deposition of Airborne Particulate Matter

Chapter 9 Consequences of the Maxwell–Boltzmann Distribution

Chapter 1

Microclimate, Air and Temperature

Abstract

The basic concepts of climate and microclimate are discussed in relationship with the different scales and the interactions with the cultural heritage. The differences between air, water vapour, perfect and real gases are clarified for a better understanding of the approximations used in thermodynamics and how much they may be relevant to the real world and the conservation practice. Most of the chapter is devoted to temperature: from the definition to practical consequences. The temperature is analysed as a key variable responsible for a number of physical, chemical and biological deterioration mechanisms; useful to study air–surface interactions and for environmental diagnostics. How temperature may change passing from outside to inside, in a building, a room or even a showcase. Heating a room requires to combine people comfort, conservation needs and sustainability; however, conservation and sustainability are not always compatible with people comfort and a compromise should be sought.

Keywords

Chemical kinetics; Environmental diagnostics; Microclimate; Perfect gases; Temperature; Thermal comfort

Outline

1.1. Microclimate

1.2. Air, Water Vapour, Perfect and Real Gases

1.3. Temperature

1.4. Mechanisms of Temperature Degradation

1.5. Temperature in a Building, a Room

1.6. Temperature in a Showcase

1.7. Is it Possible to Combine People Comfort, Conservation Needs and Sustainability?

1.8. Monitoring Air Temperature to Study Air–Surface Interactions and for Environmental Diagnostics

References

1.1 Microclimate

First of all, it may be useful to define the word ‘microclimate’ to which we refer, as in the everyday practice some terms such as ‘global climate’, ‘macroclimate’, ‘mesoclimate’, ‘climate’, ‘microclimate’, ‘nanoclimate’ and ‘picoclimate’ are used by people with different meaning, and the same is also true for specialists. It is clear that all these terms have been utilized to define the climate of a specific area, and the prefix is chosen to indicate the size of the area involved. However, we cannot proceed in the most apparently straightforward way, that is establishing a scale with the appropriate size unit, for example 1 km in diameter, and then apply the well-known definitions, that is milli = 10⁻³, micro = 10⁻⁶, nano = 10⁻⁹, pico = 10⁻¹², as in this case the ‘microclimate’ would apply to a site sized only 10⁻⁶ km = 1 mm, and this would be ridiculous. Somebody uses the term ‘microclimate’ for an urban area, ‘nanoclimate’ for a monument and ‘picoclimate’ for a very small portion of a monument, but this definition has not gained popularity. In principle, the prefix varies with the actual area size, as determined by geographic, topographic or other local factors, for example the requirement of reaching a basic homogeneity in some key parameters, but it may also vary with reference to the actual interest, in view of a peculiar application, and the list of the subjective elements that intervene in the choice of the appropriate word may continue.

In climate research, meteorology and physical geography, the distinction is rather clear and is determined by the field of interest, that is, the ‘global climate’ refers to our planet, the ‘regional climate’ to a geographical homogeneous area and the ‘local climate’ to a small limited area like a mountain, a valley or a city. Similarly, for conservation, it is useful to use clear terms, derived from the above-mentioned sciences, for example ‘regional climate’ for the main characteristics of the geographic area where the monument is found, ‘urban’, ‘rural’, ‘mountain’, ‘valley’, ‘coastal’ and so on for the next dimensional step, and ‘microclimate’ relating to the small location, for example a corner of the street, a square, a room, a corner of the room near a painting, where a monument or an object is located. This definition does not imply a precise size, but focuses the attention on a specific artefact (e.g. a historic building, a statue, a small exhibit) and its surrounding, so that the same term can also be applied when studying the interactions between a portion of a monument and the air nearby. In practice, it refers to the whole ambience which is necessary to study in order to know the factors which have a direct influence on the physical state of the monument and the interactions with the air and the surrounding objects.

Now that the prefix ‘micro’ has been explained, it might be useful to clarify the word ‘climate’. The following definitions can be found: ‘climate is the synthesis of the day-to-day weather conditions in a given area’, ‘climate is the statistical description of weather and atmospheric conditions as exhibited by the patterns of such conditions, in a given region, over a specified period of time long enough to be representative (usually a number of decades) ’, ‘climate is the fluctuating aggregate of atmospheric conditions characterised by the states and developments of weather in a given area’ (Maunder, 1994). It is evident that in our case the word ‘weather’ is inappropriate; only in exceptional cases, observations exist over a number of decades, and in general, new observations should be taken in the short term, for example 1 year or 2, before undertaking restorations; the same definition should be applied to either indoor or outdoor environments.

By adapting the above definitions to our aims, the following interpretation can be given: ‘microclimate is the synthesis of the ambient physical conditions (e.g. time and space distributions, fluctuating values and trends, average and extreme values, space gradients and frequency of oscillations) due to either atmospheric variables (e.g. temperature, humidity, sunshine, airspeed) or exchanges with other bodies (e.g. infrared emission, heating, lighting, ventilating) over a period of time representative of all the conditions determined by the natural and artificial forcing factors’. When a survey cannot continue for a time interval that is statistically representative of all the conditions, it should at least document one, or a few examples, of key different conditions, just to understand the type of problems we are dealing with.

Another key question is whether meteorological data, taken from a standard weather station located a few kilometres (or less) far from a monument, can be used for the estimation or interpretation of microclimatic situations, or is it always necessary to carry out specific and expensive field tests. It is clear that the recovery of existing data is helpful for a more complete interpretation of the phenomena, but we will see in the following chapter (Chapter 10) that standard weather stations operate by measuring parameters with some specific criteria and methodologies; in conclusion, some measurements will be useful to our aims, others of scarce relevance, and others useless.

In addition, several parameters needed for the science of conservation are not considered in weather stations. For this reason, special field surveys are needed. Only a few parameters, measured by weather stations in a compatible way, might be duplicates and could be omitted.

Generally speaking, it is convenient to record in the same data acquisition system and with the same criteria the whole set of data useful for a specific study and then add or compare further observations, if any. In the field of conservation or in other environmental purposes, observations are made to study certain individual problems, so that the instrumental apparatus as well as the operative methodologies should be specifically tailored to fit the actual problem. On the other hand, it is evident that weather stations are planned and standardized for meteorological measurements as defined by international protocols, so that the...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface to the First Edition (1998)
• Preface to the Second Edition (2014)
• Foreword to the First Edition (1998)
• Reviews to the First Edition (1998)
• Foreword
• Acknowledgments
• Credits
• The Author
• Part I: Atmospheric Physics Applied to Microclimate Analysis and Conservation
• Part II: Performing Microclimate Field Surveys
• Appendix 1. List of Fundamental Constants Met in This Book
• Appendix 2. Summary of Key Equations to Calculate Humidity Variables
• Appendix 3. Essential Glossary
• Relevant Objects, Museums, Monuments etc Exemplified in Figures
• Index