Microclimate for Cultural Heritage

Measurement, Risk Assessment, Conservation, Restoration, and Maintenance of Indoor and Outdoor Monuments

Dario Camuffo

• Publisher: Elsevier Science
• Year: 2019
• Print ISBN: 9780444641069
• eBook ISBN: 9780444641076
• Edition: 3
• Topic: Physical Sciences
• Subtopic: Meteorology & Climatology

Microclimate for Cultural Heritage: Measurement, Risk Assessment, Conservation, Restoration, and Maintenance of Indoor and Outdoor Monuments, Third Edition, presents the latest on microclimates, environmental issues and the conservation of cultural heritage. It is a useful treatise on microphysics, acting as a practical handbook for conservators and specialists in physics, chemistry, architecture, engineering, geology and biology who focus on environmental issues and the conservation of works of art. It fills a gap between the application of atmospheric sciences, like the thermodynamic processes of clouds and dynamics of planetary boundary layer, and their application to a monument surface or a room within a museum. Sections covers applied theory, environmental issues and conservation, practical utilization, along with suggestions, examples, common issues and errors. - Connects theory to practice with clear illustrations, useful examples, and case studies - Covers practical issues, e.g. rising damp, moulds, and pests, indoor heating, thermal comfort, green lighting technology, performing field surveys - Presents the latest standards for measuring cultural assets and their environment - Discusses climate change and indoor - outdoor potential scenarios, including sea-level rise

Part I

Theoretical Grounds, Key Variables, Main Deterioration Mechanisms

Chapter 1

Microclimate and Atmospheric Variables

Abstract

The basic concepts of climate and microclimate are discussed in relationship with their different scales and their interactions with cultural heritage. Internal boundary layers (either of thermic or dynamic origin) and the laminar, viscous layers are considered. 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 in the real world and conservation practice. Finally, the main concepts concerning atmospheric variables and parameters are discussed. Development and aims of the various sensors used for environmental investigations in the field of conservation are presented.

Keywords

Air, boundary layer; Coanda effect; Environmental diagnostics; Microclimate; Perfect and real gases; Variables and parameters; Viscous layer

Outline

• 1.1 Microclimate
• 1.2 Air, Water Vapour, Perfect and Real Gases
• 1.3 The Internal Boundary Layer and the Viscous Layer
• 1.4 Coanda Effect
• 1.5 Atmospheric Variables and Parameters
• References

1.1 Microclimate

Microclimate for cultural heritage is special: it includes temperature, humidity, ventilation etc., but is different from the everyday feeling of people. In the human body experience, hot weather may be countered with ventilation, because this increases evaporation, and the evaporating sweat takes up some heat from the skin. Cold weather may be countered with heavier clothing because the body produces heat and better insulation reduces the heat loss and gives a more comfortable feeling. These two examples are based on the fact that the body reacts to the environmental conditions to reach a convenient microclimate sensation. Objects and materials don’t have such a regulatory system, and these two remedies would be useless. However, objects and materials react to the environmental forcing with an on-going feedback, in order to reach a dynamic equilibrium with it. Microclimate affects materials, and materials affect microclimate: for instance, the temperature and relative humidity (RH) of the air surrounding a monument, a building, or an archaeological site, are strongly affected by the temperature that the material, e.g. bronze, brick or stone, attains. While trying to attain this equilibrium as a response to certain conditions, materials will suffer transformation, ageing, and other forms of deterioration. Conservation requires that the most important deterioration mechanisms are slowed down as far as possible, and the task of the conservator is to identify and apply the microclimate conditions that are better suited to this requirement.

It may be useful to clarify the word ‘climate’. A number of definitions can be found, e.g. ‘climate is a fluctuating aggregate of atmospheric conditions characterized by the states and developments of the weather of a given area’ (WMO, 1966); ‘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 characterized by the states and developments of weather in a given area’ (Maunder, 1994). The most recent is ‘climate in narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years’ (IPCC, 2014). In the case of cultural heritage, available environmental records generally cover short periods, or are missing. New indoor/outdoor monitoring may be reasonably carried out for one or two years before undertaking restorations. The conclusion is that interventions for conservation are often based on far too short monitoring periods.

It may be useful to define the word ‘micro’ to which we refer, as in the everyday practice, ‘global climate’, ‘macroclimate’, ‘mesoclimate’, ‘climate’, ‘microclimate’, ‘nanoclimate’ and ‘picoclimate’ are popularly used with different meanings and without a clear definition. These terms are employed to define the climate of a specific area, and the prefix is chosen to indicate the extension of the involved area. The most apparently straightforward way is to establish 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. However, in this case, ‘microclimate’ would apply to a site sized 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 atmospheric variables, but it may also vary with reference to the actual interest, or for 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 determined by the field of interest, e.g. 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, in conservation science, it is useful to use ‘regional climate’ for 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 to the Second Edition (2013)
• Preface to the Third Edition
• Acknowledgements
• Credits
• Author Biography
• Part I: Theoretical Grounds, Key Variables, Main Deterioration Mechanisms
• Part II: Atmospheric Stability, Pollutant Dispersion and Soiling of Paintings and Monuments
• Part III: Radiation, Light and Colours
• Part IV: Climate-Related Risks
• Part V: European Standards and Field Surveys
• Part VI: Measuring Instruments and Their Development
• 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